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Juyin halittar ƙwayoyin cuta ya ƙunshi magancewa tsakanin zaɓin halitta, wanda ke sa ƙwayoyin cuta su inganta, da kuma sauye-sauyen kwayoyin halitta, wanda ke sa ƙwayoyin cuta su rasa kwayoyin halitta da kuma tara sauye-sauye masu illa. A nan, domin fahimtar yadda wannan sauye-sauyen ke faruwa a kan sikelin macromolecule guda ɗaya, mun bayyana tsarin cryo-EM na ribosome na Encephalitozoon cuniculi, wani kwayar halitta mai suna eukaryotic tare da ɗaya daga cikin ƙananan kwayoyin halitta a yanayi. Ragewar rRNA mai yawa a cikin ribosomes na E. cuniculi yana tare da canje-canjen tsarin da ba a taɓa gani ba, kamar juyin halittar mahaɗan rRNA da aka haɗa da rRNA ba tare da ɓullo ba. Bugu da ƙari, ribosome na E. cuniculi ya tsira daga asarar gutsuttsuran rRNA da sunadarai ta hanyar haɓaka ikon amfani da ƙananan ƙwayoyin halitta azaman kwaikwayon tsarin gutsuttsuran rRNA da suka lalace da sunadarai. Gabaɗaya, mun nuna cewa tsarin kwayoyin halitta da aka daɗe ana tunanin suna raguwa, suna lalacewa, kuma suna fuskantar sauye-sauye masu rauni suna da hanyoyi da yawa na ramawa waɗanda ke sa su aiki duk da matsanancin matsewar kwayoyin halitta.
Saboda yawancin ƙungiyoyin ƙwayoyin cuta masu ƙwayoyin cuta suna da kayan aikin ƙwayoyin cuta na musamman don amfani da masu masaukinsu, sau da yawa dole ne mu ƙirƙiri hanyoyin magance cututtuka daban-daban ga ƙungiyoyin ƙwayoyin cuta daban-daban1,2. Duk da haka, sabbin shaidu sun nuna cewa wasu fannoni na juyin halittar ƙwayoyin cuta suna haɗuwa kuma galibi ana iya faɗi, wanda ke nuna yuwuwar tushen hanyoyin magancewa mai faɗi a cikin ƙwayoyin cuta masu ƙwayoyin cuta3,4,5,6,7,8,9.
Aikin da aka yi a baya ya gano wani yanayi na juyin halitta na yau da kullun a cikin ƙwayoyin cuta masu ƙwayoyin cuta da ake kira raguwar kwayoyin halitta ko lalata kwayoyin halitta10,11,12,13. Binciken da aka yi a yanzu ya nuna cewa lokacin da ƙwayoyin cuta suka daina salon rayuwarsu na 'yanci suka zama ƙwayoyin cuta masu ƙwayoyin cuta a cikin ƙwayoyin halitta (ko endosymbionts), ƙwayoyin halittarsu suna fuskantar canje-canje masu ban mamaki a hankali amma masu ban mamaki tsawon miliyoyin shekaru9,11. A cikin wani tsari da aka sani da lalata kwayoyin halitta, ƙwayoyin cuta masu ƙwayoyin cuta suna tara maye gurbi masu illa waɗanda ke mayar da kwayoyin halitta masu mahimmanci da yawa a baya zuwa kwayoyin halitta masu kama da juna, wanda ke haifar da asarar kwayoyin halitta a hankali da rushewar maye gurbi14,15. Wannan rushewa na iya lalata har zuwa kashi 95% na kwayoyin halitta a cikin tsoffin kwayoyin halitta na cikin ƙwayoyin halitta idan aka kwatanta da nau'ikan halittu masu rai masu 'yanci da ke da alaƙa. Don haka, juyin halittar ƙwayoyin cuta masu ƙwayoyin halitta wani abu ne da ke tsakanin ƙarfi biyu masu adawa: zaɓin halitta na Darwin, wanda ke haifar da inganta ƙwayoyin cuta, da kuma rugujewar kwayoyin halitta, yana jefa ƙwayoyin cuta cikin matuƙa. Yadda ƙwayar cuta ta sami damar fitowa daga wannan ja-in-yaƙi da kuma riƙe ayyukan tsarin kwayoyin halittarta har yanzu ba a fayyace ba.
Duk da cewa ba a fahimci yadda tsarin ruɓewar kwayoyin halitta yake ba sosai, da alama yana faruwa ne saboda yawan sauye-sauyen kwayoyin halitta. Saboda ƙwayoyin cuta suna rayuwa ne a cikin ƙananan al'ummomi, marasa jinsi, da kuma waɗanda ke da iyaka ga kwayoyin halitta, ba za su iya kawar da sauye-sauye masu illa da ke faruwa a lokacin kwafi na DNA ba. Wannan yana haifar da tarin sauye-sauye masu cutarwa da kuma rage kwayar halittar ƙwayoyin cuta. Sakamakon haka, ƙwayar cuta ba wai kawai tana rasa kwayoyin halittar da ba su da mahimmanci don rayuwa a cikin muhallin ƙwayoyin halitta ba. Rashin iyawar ƙwayoyin cuta wajen kawar da sauye-sauye masu illa lokaci-lokaci ne ke sa waɗannan sauye-sauye su taru a cikin kwayar halittar, gami da mafi mahimmancin kwayoyin halittarsu.
Yawancin fahimtarmu ta yanzu game da rage kwayoyin halitta ta dogara ne kawai akan kwatanta jerin kwayoyin halitta, ba tare da kulawa sosai ga canje-canje a cikin ainihin kwayoyin halitta waɗanda ke yin ayyukan kula da gida ba kuma suna aiki azaman maƙasudin magunguna. Nazarin kwatancen ya nuna cewa nauyin maye gurbi na ƙwayoyin cuta masu illa a cikin ƙwayoyin halitta yana sa sunadaran da nucleic acid su ninku da taruwa, yana sa su dogara da chaperone kuma su fi saurin amsawa ga zafi19,20,21,22,23. Bugu da ƙari, ƙwayoyin cuta daban-daban - juyin halitta mai zaman kansa wanda wani lokacin ke raba shi da kusan shekaru biliyan 2.5 - sun fuskanci irin wannan asarar cibiyoyin kula da inganci a cikin tsarin haɗin furotin su5,6 da hanyoyin gyaran DNA24. Duk da haka, ba a san komai game da tasirin salon rayuwar ƙwayoyin halitta akan duk wasu kaddarorin ƙwayoyin halitta ba, gami da daidaitawar ƙwayoyin halitta zuwa ƙaruwar nauyin maye gurbi masu illa.
A cikin wannan aikin, domin mu fahimci yadda furotin da nucleic acid na ƙwayoyin cuta ke yaduwa, mun tantance tsarin ribosomes na kwayar halittar da ke cikin ƙwayoyin halitta Encephalitozoon cuniculi. E. cuniculi wata halitta ce mai kama da fungi wacce ke cikin ƙungiyar microsporidia masu ɓarna waɗanda ke da ƙananan kwayoyin halittar eukaryotic waɗanda ba a saba gani ba kuma saboda haka ana amfani da su azaman samfuran halittu don nazarin ruɓewar kwayoyin halitta25,26,27,28,29,30. Kwanan nan, an tantance tsarin ribosome na cryo-EM don rage yawan kwayoyin halittar Microsporidia, Paranosema locustae, da Vairimorpha necatrix31,32 (~3.2 Mb genome). Waɗannan tsarin suna nuna cewa ana rama wasu asarar haɓaka rRNA ta hanyar haɓaka sabbin hulɗa tsakanin sunadaran ribosomal maƙwabta ko kuma samun sabbin sunadaran ribosomal msL131,32. Nau'in Encephalitozoon (ƙwayar halitta ~ miliyan 2.5 bp), tare da danginsu mafi kusa Ordospora, suna nuna matakin ƙarshe na raguwar kwayar halitta a cikin eukaryotes - suna da ƙasa da kwayoyin halittar da ke samar da sunadaran 2000, kuma ana sa ran cewa ribosomes ɗinsu ba wai kawai ba su da gutsuttsuran faɗaɗa rRNA (gutsuttsuran rRNA waɗanda ke bambanta ribosomes na eukaryotic daga ribosomes na ƙwayoyin cuta) suma suna da sunadaran ribosomal guda huɗu saboda rashin homologues a cikin E. cuniculi genome26,27,28. Saboda haka, mun kammala da cewa ribosome na E. cuniculi na iya bayyana dabarun da ba a sani ba a baya don daidaitawar kwayoyin halitta zuwa lalacewar kwayoyin halitta.
Tsarin cryo-EM ɗinmu yana wakiltar ƙaramin ribosome na cytoplasmic eukaryotic da za a iya siffanta shi kuma yana ba da haske game da yadda matakin ƙarshe na rage kwayar halitta ke shafar tsari, haɗuwa, da juyin halittar injunan kwayoyin halitta waɗanda ke da alaƙa da tantanin halitta. Mun gano cewa ribosome na E. cuniculi ya karya ƙa'idodin da aka kiyaye sosai na haɗakar RNA da ribosome, kuma mun gano sabon furotin ribosomal, wanda ba a san shi ba a da. Ba zato ba tsammani, mun nuna cewa ribosomes na microsporidia sun haɓaka ikon ɗaure ƙananan ƙwayoyin halitta, kuma muna tsammanin cewa raguwar rRNA da sunadarai suna haifar da sabbin abubuwa na juyin halitta waɗanda a ƙarshe za su iya ba da halaye masu amfani ga ribosome.
Domin inganta fahimtarmu game da juyin halittar sunadarai da nucleic acid a cikin kwayoyin halitta na cikin jiki, mun yanke shawarar ware E. cuniculi spores daga al'adun ƙwayoyin dabbobi masu shayarwa da suka kamu da cutar domin tsarkake ribosomes ɗinsu da kuma tantance tsarin waɗannan ribosomes. Yana da wuya a sami adadi mai yawa na microsporidia masu cutarwa saboda ba za a iya shuka microsporidia a cikin wani sinadari mai gina jiki ba. Madadin haka, suna girma da haifuwa ne kawai a cikin ƙwayar mai masaukin baki. Saboda haka, don samun E. cuniculi biomass don tsarkake ribosome, mun kamu da layin ƙwayar koda mai shayarwa RK13 da E. cuniculi spores kuma muka haɓaka waɗannan ƙwayoyin da suka kamu na tsawon makonni da yawa don ba da damar E. cuniculi su girma da haɓaka. Ta amfani da wani Layer na ƙwayar halitta mai kamuwa da cuta na kusan rabin murabba'in mita, mun sami damar tsarkake kusan 300 MG na ƙwayoyin Microsporidia kuma muka yi amfani da su don ware ribosomes. Sannan muka wargaza ƙwayoyin da aka tsarkake da beads na gilashi kuma muka ware ƙananan ribosomes ta amfani da raba polyethylene glycol na lysates. Wannan ya ba mu damar samun kimanin 300 µg na ribosomes na E. cuniculi don nazarin tsarin.
Daga nan muka tattara hotunan cryo-EM ta amfani da samfuran ribosome da suka fito kuma muka sarrafa waɗannan hotunan ta amfani da abin rufe fuska wanda ya dace da babban ribosomal subunit, ƙaramin kan subunit, da ƙaramin subunit. A yayin wannan aikin, mun tattara hotunan kusan barbashi ribosomal 108,000 da hotunan cryo-EM da aka ƙididdige tare da ƙudurin 2.7 Å (Karin Hotuna 1-3). Sannan muka yi amfani da hotunan cryoEM don yin samfurin rRNA, furotin ribosomal, da kuma yanayin bacci Mdf1 da ke da alaƙa da ribosomes na E. cuniculi (Hoto na 1a, b).
Tsarin ribosome na E. cuniculi a cikin hadaddun tare da factor na hutu Mdf1 (pdb id 7QEP). b Taswirar factor na hutu Mdf1 da ke da alaƙa da E. cuniculi ribosome. c Taswirar tsari ta biyu tana kwatanta rRNA da aka dawo da ita a cikin nau'in Microsporidian da tsarin ribosomal da aka sani. Faifan suna nuna wurin da aka ƙara girman gutsuttsuran rRNA (ES) da wuraren aiki na ribosome, gami da wurin decoding (DC), madauki na sarcinicin (SRL), da kuma cibiyar peptidyl transferase (PTC). d Yawan electron da ya dace da cibiyar peptidyl transferase na E. cuniculi ribosome yana nuna cewa wannan wurin catalytic yana da tsari iri ɗaya a cikin kwayar cutar E. cuniculi da masu masaukin ta, gami da H. sapiens. e, f Yawan electron da ya dace na cibiyar dikodi (e) da tsarin tsarin cibiyar dikodi (f) suna nuna cewa E. cuniculi yana da ragowar U1491 maimakon A1491 (lambar E. coli) a cikin wasu eukaryotes da yawa. Wannan canjin yana nuna cewa E. cuniculi na iya zama mai saurin kamuwa da maganin rigakafi da ke kai hari ga wannan wurin aiki.
Sabanin tsarin da aka kafa a baya na ribosomes na V. necatrix da P. locustae (duka sifofi suna wakiltar dangin microsporidia iri ɗaya kuma suna kama da juna), 31,32 E. cuniculi ribosomes suna fuskantar matakai da yawa na rRNA da rarrabuwar furotin. Ƙarin denaturation (Karin Sifofi 4-6). A cikin rRNA, canje-canje mafi ban mamaki sun haɗa da asarar cikakken ɓangaren 25S rRNA ES12L da aka haɓaka da kuma raguwar ɓangaren helices na h39, h41, da H18 (Hoto na 1c, Ƙarin Siffa 4). Daga cikin sunadaran ribosomal, canje-canje mafi ban mamaki sun haɗa da asarar cikakken furotin na eS30 da rage sunadaran eL8, eL13, eL18, eL22, eL29, eL40, uS3, uS9, uS14, uS17, da eS7 (Karin Sifofi 4, 5).
Saboda haka, raguwar kwayoyin halittar nau'in Encephalotozoon/Ordospora ya bayyana a cikin tsarin ribosome ɗinsu: E. cuniculi ribosomes suna fuskantar asarar furotin mafi girma a cikin ribosomes na cytoplasmic eukaryotic waɗanda ke ƙarƙashin siffa ta tsari, kuma ba su ma da waɗancan gutsuttsuran rRNA da furotin waɗanda aka kiyaye su sosai ba kawai a cikin eukaryotes ba, har ma a cikin fannoni uku na rayuwa. Tsarin ribosome na E. cuniculi yana ba da samfurin kwayoyin halitta na farko don waɗannan canje-canje kuma yana bayyana abubuwan da suka faru na juyin halitta waɗanda aka yi watsi da su ta hanyar kwatanta kwayoyin halitta da nazarin tsarin kwayoyin halitta na cikin ƙwayoyin halitta (Hoto na Ƙari na 7). A ƙasa, mun bayyana kowanne daga cikin waɗannan abubuwan tare da yiwuwar asalin juyin halitta da tasirinsu ga aikin ribosome.
Daga nan muka gano cewa, ban da manyan raguwar rRNA, ribosomes na E. cuniculi suna da bambancin rRNA a ɗaya daga cikin wuraren aikinsu. Duk da cewa cibiyar peptidyl transferase ta E. cuniculi ribosome tana da tsari iri ɗaya da sauran ribosomes na eukaryotic (Hoto na 1d), cibiyar decoding ta bambanta saboda bambancin jeri a nucleotide 1491 (lambar E. coli, Hoto na 1e, f). Wannan lura yana da mahimmanci saboda wurin decoding na ribosomes na eukaryotic yawanci yana ɗauke da ragowar G1408 da A1491 idan aka kwatanta da ragowar nau'in ƙwayoyin cuta A1408 da G1491. Wannan bambancin yana da alaƙa da bambancin yanayin ribosomes na ƙwayoyin cuta da eukaryotic ga dangin aminoglycoside na ribosomal antibiotics da sauran ƙananan ƙwayoyin cuta waɗanda ke kai hari ga wurin decoding. A wurin decoding na E. cuniculi ribosome, an maye gurbin residue A1491 da U1491, wanda ke iya ƙirƙirar hanyar haɗin gwiwa ta musamman ga ƙananan ƙwayoyin da ke kai hari ga wannan wurin aiki. Haka kuma akwai nau'in A14901 iri ɗaya a cikin wasu microsporidia kamar P. locustae da V. necatrix, wanda ke nuna cewa ya yaɗu a tsakanin nau'ikan microsporidia (Hoto na 1f).
Saboda an ware samfuran ribosome na E. cuniculi daga ƙwayoyin halittar da ba sa aiki yadda ya kamata, mun gwada taswirar cryo-EM na E. cuniculi don ɗaure ribosome da aka bayyana a baya a ƙarƙashin damuwa ko yanayin yunwa. Abubuwan da ke haifar da rashin barci 31,32,36,37, 38. Mun daidaita tsarin ribosome na hibernating da aka kafa a baya tare da taswirar cryo-EM na ribosome na E. cuniculi. Don docking, an yi amfani da ribosomes na S. cerevisiae a cikin hadaddun tare da factor na rashin barci Stm138, ribosomes na locust a cikin hadaddun tare da factor Lso232, da kuma ribosomes na V. necatrix a cikin hadaddun tare da factors na Mdf1 da Mdf231. A lokaci guda, mun sami yawan cryo-EM wanda ya dace da sauran factor Mdf1. Kamar yadda Mdf1 ke ɗaurewa da ribosome na V. necatrix, Mdf1 kuma yana ɗaurewa da ribosome na E. cuniculi, inda yake toshe wurin E na ribosome, mai yiwuwa yana taimakawa wajen samar da ribosomes lokacin da ƙwayoyin cuta suka zama marasa aiki yayin da jiki ya daina aiki (Hoto na 2).
Mdf1 yana toshe wurin ribosome na E, wanda da alama yana taimakawa wajen dakatar da ribosome lokacin da ƙwayoyin cuta suka zama marasa aiki ta hanyar metabolism. A cikin tsarin ribosome na E. cuniculi, mun gano cewa Mdf1 yana yin hulɗa da tushen ribosome na L1 wanda ba a san shi ba a da, ɓangaren ribosome wanda ke sauƙaƙe sakin deacylated tRNA daga ribosome yayin haɗa furotin. Waɗannan hulɗar sun nuna cewa Mdf1 yana rabuwa da ribosome ta amfani da irin wannan tsari kamar deacetylated tRNA, yana ba da bayani mai yiwuwa game da yadda ribosome ke cire Mdf1 don sake kunna haɗin furotin.
Duk da haka, tsarinmu ya bayyana wani abu da ba a sani ba tsakanin Mdf1 da ƙafar ribosome ta L1 (wani ɓangare na ribosome wanda ke taimakawa wajen sakin deacylated tRNA daga ribosome yayin haɗa furotin). Musamman ma, Mdf1 yana amfani da irin wannan hulɗar kamar ɓangaren gwiwar hannu na deacylated tRNA molecule (Hoto na 2). Wannan ƙirar kwayoyin halitta da ba a san ta ba a baya ya nuna cewa Mdf1 yana rabuwa da ribosome ta amfani da irin wannan tsari kamar deacetylated tRNA, wanda ke bayyana yadda ribosome ke cire wannan yanayin rashin barci don sake kunna haɗin furotin.
Lokacin gina samfurin rRNA, mun gano cewa ribosome na E. cuniculi yana da gutsuttsuran rRNA da ba a naɗe su ba, wanda muka kira fused rRNA (Hoto na 3). A cikin ribosomes ɗin da suka mamaye fannoni uku na rayuwa, rRNA yana naɗewa zuwa tsarin da yawancin rRNA ke kafawa ko dai tushe biyu da naɗewa tare da juna ko kuma yana hulɗa da sunadaran ribosomal38,39,40. Duk da haka, a cikin ribosomes na E. cuniculi, rRNAs suna kama da sun karya wannan ƙa'idar naɗewa ta hanyar canza wasu daga cikin helices ɗinsu zuwa yankunan rRNA da ba a buɗe ba.
Tsarin helix na H18 25S rRNA a cikin S. cerevisiae, V. necatrix, da E. cuniculi. Yawanci, a cikin ribosomes da ke kewaye da sassan rayuwa guda uku, wannan mahaɗin yana naɗewa zuwa helix na RNA wanda ya ƙunshi ragowar 24 zuwa 34. A cikin Microsporidia, akasin haka, wannan mahaɗin rRNA yana raguwa a hankali zuwa mahaɗin uridine guda biyu masu siffa ɗaya waɗanda ke ɗauke da ragowar 12 kawai. Yawancin waɗannan ragowar suna fallasa ga abubuwan narkewa. Hotunan sun nuna cewa microsporidia masu ɓarna suna bayyana sun karya ƙa'idodin gabaɗaya na naɗewar rRNA, inda tushen rRNA galibi ana haɗa su da wasu tushe ko kuma suna shiga cikin hulɗar rRNA-protein. A cikin microsporidia, wasu gutsuttsuran rRNA suna ɗaukar ninki mara kyau, wanda tsohon helix na rRNA ya zama gutsuttsuran da aka daɗe kusan a cikin layi madaidaiciya. Kasancewar waɗannan yankuna marasa ban mamaki yana ba microsporidia rRNA damar ɗaure gutsuttsuran rRNA masu nisa ta amfani da ƙaramin adadin tushen RNA.
Misali mafi ban mamaki na wannan sauyin juyin halitta ana iya gani a cikin helix na H18 25S rRNA (Hoto na 3). A cikin nau'ikan halittu daga E. coli zuwa ga mutane, tushen wannan helix na rRNA ya ƙunshi nucleotides 24-32, suna samar da helix mara daidaituwa. A cikin tsarin ribosomal da aka gano a baya daga V. necatrix da P. locusthae,31,32 tushen helix na H18 an cire shi kaɗan, amma haɗin tushen nucleotide yana kiyayewa. Duk da haka, a cikin E. cunicili wannan guntu na rRNA ya zama mafi guntu mahaɗi 228UUUGU232 da 301UUUUUUUU307. Ba kamar gutsuttsuran rRNA na yau da kullun ba, waɗannan mahaɗin uridine masu wadataccen uridine ba sa naɗewa ko yin hulɗa mai yawa da sunadaran ribosomal. Madadin haka, suna ɗaukar tsarin da ba a buɗe ba kuma cikakke wanda aka shimfiɗa zaren rRNA kusan madaidaiciya. Wannan tsari mai faɗi ya bayyana yadda E. cuniculi ke amfani da tushen RNA guda 12 kacal don cike gibin 33 Å tsakanin helices na H16 da H18 rRNA, yayin da wasu nau'ikan halittu ke buƙatar aƙalla tushen rRNA sau biyu don cike gibin.
Saboda haka, za mu iya nuna cewa, ta hanyar naɗewa mai ƙarfi wanda ba shi da kyau, ƙwayoyin cuta masu kama da ƙwayoyin cuta sun ƙirƙiro dabarun da za su ɗaure ko da waɗancan sassan rRNA waɗanda ke ci gaba da kasancewa a cikin yanayi daban-daban a cikin fannoni uku na rayuwa. A bayyane yake, ta hanyar tara maye gurbi waɗanda ke canza helices na rRNA zuwa gajerun mahaɗin poly-U, E. cuniculi na iya samar da gutsuttsuran rRNA marasa ban mamaki waɗanda ke ɗauke da ƙarancin nucleotides gwargwadon yiwuwa don haɗa gutsuttsuran rRNA na nesa. Wannan yana taimakawa wajen bayyana yadda microsporidia ya sami raguwa mai ban mamaki a cikin tsarin ƙwayoyin halittarsu na asali ba tare da rasa amincin tsarinsu da aikinsu ba.
Wani abu na musamman na E. cuniculi rRNA shine bayyanar rRNA ba tare da kauri ba (Hoto na 4). Bututu sune nucleotides ba tare da nau'ikan tushe ba waɗanda ke juyawa daga helix na RNA maimakon ɓoyewa a ciki. Yawancin abubuwan da suka fito daga rRNA suna aiki azaman manne na kwayoyin halitta, suna taimakawa wajen ɗaure sunadaran ribosomal da ke kusa ko wasu gutsuttsuran rRNA. Wasu daga cikin bututun suna aiki azaman hinges, suna bawa helix na rRNA damar lanƙwasawa da ninkawa yadda ya kamata don samar da sunadaran 41.
a An rRNA protrusion (S. cerevisiae numbering) ba ya cikin tsarin ribosome na E. cunculi, amma yana nan a cikin mafi yawan sauran eukaryotes b E. coli, S. cerevisiae, H. sapiens, da E. cuniculi internal ribosomes. ƙwayoyin cuta ba su da daɗaɗɗen rRNA bulges da aka kiyaye sosai. Waɗannan kauri suna daidaita tsarin ribosome; saboda haka, rashin su a cikin microsporidia yana nuna raguwar kwanciyar hankali na naɗewar rRNA a cikin ƙwayoyin cuta na microsporidia. Kwatanta da tushen P (tushen L7/L12 a cikin ƙwayoyin cuta) yana nuna cewa asarar kumburan rRNA wani lokacin yana daidai da bayyanar sabbin kumbura kusa da kumburan da suka ɓace. Helix na H42 a cikin rRNA 23S/28S yana da tsohon kumburi (U1206 a cikin Saccharomyces cerevisiae) wanda aka kiyasta ya kai akalla shekaru biliyan 3.5 saboda kariyar sa a fannoni uku na rayuwa. A cikin microsporidia, an kawar da wannan kumburin. Duk da haka, wani sabon kumburi ya bayyana kusa da kumburin da ya ɓace (A1306 a cikin E. cuniculi).
Abin mamaki, mun gano cewa ribosomes na E. cuniculi ba su da yawancin ƙwanƙwasa rRNA da aka samu a wasu nau'ikan halittu, gami da ƙwanƙwasa sama da 30 da aka adana a cikin wasu eukaryotes (Hoto na 4a). Wannan asarar tana kawar da hulɗa da yawa tsakanin ƙananan ribosomal da helices na rRNA da ke kusa, wani lokacin tana haifar da manyan ramuka a cikin ribosome, wanda ke sa ribosome na E. cuniculi ya fi rami idan aka kwatanta da ribosomes na gargajiya (Hoto na 4b). Abin lura, mun gano cewa yawancin waɗannan ƙwanƙwasa suma sun ɓace a cikin tsarin ribosome na V. necatrix da P. locustae da aka gano a baya, waɗanda nazarin tsarin da aka yi a baya ya yi watsi da su31,32.
Wani lokaci asarar rRNA bulges yana tare da ci gaban sabbin bulges kusa da bulges ɗin da ya ɓace. Misali, ribosomal P-stem yana ɗauke da bulges na U1208 (a cikin Saccharomyces cerevisiae) wanda ya tsira daga E. coli zuwa ga mutane kuma saboda haka ana kiyasta cewa yana da shekaru biliyan 3.5. A lokacin haɗa furotin, wannan bulges yana taimaka wa bulges na P motsawa tsakanin buɗaɗɗen da rufewa don ribosome ya iya ɗaukar abubuwan fassara ya kai su wurin aiki. A cikin E. cuniculi ribosomes, wannan bulges ɗin ba ya nan; duk da haka, sabon bulges (G883) wanda ke cikin nau'i-nau'i uku kawai zai iya taimakawa wajen dawo da mafi kyawun sassauci na bulges na P (Hoto na 4c).
Bayananmu game da rRNA ba tare da kumburi ba sun nuna cewa rage rRNA ba ta takaita ga asarar abubuwan rRNA a saman ribosome ba, amma kuma yana iya haɗawa da ribosome nucleus, yana haifar da lahani na ƙwayoyin cuta waɗanda ba a bayyana su a cikin ƙwayoyin halitta masu rai ba. Ana lura da nau'ikan halittu masu rai.
Bayan mun yi koyi da sunadaran ribosomal masu canonical da rRNA, mun gano cewa sassan ribosomal na gargajiya ba za su iya bayyana sassa uku na hoton cryo-EM ba. Biyu daga cikin waɗannan gutsuttsuran ƙananan ƙwayoyin halitta ne a girma (Hoto na 5, Hoto na Ƙarin 8). An haɗa ɓangaren farko tsakanin sunadaran ribosomal uL15 da eL18 a matsayin da C-terminus na eL18 ke mamaye shi, wanda aka gajarta a cikin E. cuniculi. Kodayake ba za mu iya tantance asalin wannan ƙwayar ba, girman da siffar wannan tsibiri mai yawa an bayyana shi sosai ta hanyar kasancewar ƙwayoyin spermidine. Haɗinsa da ribosome yana da ƙarfi ta hanyar maye gurbi na musamman na microsporidia a cikin sunadaran uL15 (Asp51 da Arg56), waɗanda da alama suna ƙara kusancin ribosome ga wannan ƙaramin ƙwayar, kamar yadda suke ba uL15 damar naɗe ƙaramin ƙwayar cikin tsarin ribosomal. Hoto na Ƙarin 2). 8, ƙarin bayanai 1, 2).
Hoton Cryo-EM yana nuna kasancewar nucleotides a wajen ribose da aka haɗa da ribosome na E. cuniculi. A cikin ribosome na E. cuniculi, wannan nucleotide yana zaune a wuri ɗaya da nucleotide na 25S rRNA A3186 (Saccharomyces cerevisiae numbering) a cikin mafi yawan sauran ribosomes na eukaryotic. b A cikin tsarin ribosomal na E. cuniculi, wannan nucleotide yana tsakanin sunadaran ribosomal uL9 da eL20, don haka yana daidaita hulɗar tsakanin sunadaran biyu. Binciken kiyaye jerin cd eL20 tsakanin nau'in microsporidia. Bishiyar phylogenetic na nau'in Microsporidia (c) da daidaitawar jerin abubuwa da yawa na furotin eL20 (d) sun nuna cewa ragowar nucleotide-binding F170 da K172 suna cikin mafi yawan Microsporidia na yau da kullun, ban da S. lophii, ban da farkon reshe na Microsporidia, wanda ya riƙe faɗaɗa ES39L rRNA. e Wannan adadi ya nuna cewa ragowar nucleotide-binding F170 da K172 suna nan ne kawai a cikin eL20 na kwayar halittar microsporidia da aka rage sosai, amma ba a cikin wasu eukaryotes ba. Gabaɗaya, waɗannan bayanai sun nuna cewa ribosomes na Microsporidian sun haɓaka wurin ɗaure nucleotide wanda ya bayyana yana ɗaure ƙwayoyin AMP kuma yana amfani da su don daidaita hulɗar furotin-protein a cikin tsarin ribosomal. Babban kiyaye wannan wurin ɗaurewa a cikin Microsporidia da rashinsa a cikin wasu eukaryotes yana nuna cewa wannan wurin na iya samar da fa'idar rayuwa mai zaɓi ga Microsporidia. Don haka, aljihun ɗaure nucleotide a cikin ribosome na microsporidia ba ya bayyana a matsayin siffa mai lalacewa ko nau'in ƙarshen lalacewar rRNA kamar yadda aka bayyana a baya ba, amma a maimakon haka sabuwar ƙirƙira mai amfani wacce ke ba da damar microsporidia ribosome ya ɗaure ƙananan ƙwayoyin kai tsaye, yana amfani da su azaman tubalan ginin kwayoyin halitta. tubalan gini don ribosomes. Wannan gano ya sa microsporidia ribosome shine kawai ribosome da aka sani don amfani da nucleotide guda ɗaya a matsayin tubalan gininsa. f Hanyar juyin halitta mai hasashe da aka samo daga ɗaure nucleotide.
Na biyu mai ƙarancin nauyin kwayoyin halitta yana nan a mahaɗin da ke tsakanin sunadaran ribosomal uL9 da eL30 (Hoto na 5a). An riga an bayyana wannan mahaɗin a cikin tsarin ribosome na Saccharomyces cerevisiae a matsayin wurin ɗaurewa don nucleotide na 25S na rRNA A3186 (wani ɓangare na faɗaɗawar ES39L rRNA)38. An nuna cewa a cikin ribosomes na P. locustae ES39L masu lalacewa, wannan mahaɗin yana ɗaure nucleotide guda ɗaya da ba a sani ba 31, kuma ana ɗauka cewa wannan nucleotide nau'i ne na ƙarshe na rRNA, wanda tsawon rRNA shine ~130-230 tushe. An rage ES39L zuwa nucleotide guda ɗaya 32.43. Hotunan cryo-EM ɗinmu suna goyon bayan ra'ayin cewa nucleotides za a iya bayyana yawan da yawa. Duk da haka, ƙudurin tsarinmu mafi girma ya nuna cewa wannan nucleotide ƙwayar extraribosomal ce, wataƙila AMP (Hoto na 5a, b).
Sai muka tambaya ko wurin ɗaure nucleotide ya bayyana a cikin ribosome na E. cuniculi ko kuma ya wanzu a da. Tunda haɗin nucleotide galibi yana da alaƙa da ragowar Phe170 da Lys172 a cikin furotin ribosomal na eL30, mun tantance kiyaye waɗannan ragowar a cikin eukaryotes masu wakiltar 4396. Kamar yadda yake a yanayin uL15 da ke sama, mun gano cewa ragowar Phe170 da Lys172 suna da matuƙar kiyayewa ne kawai a cikin Microsporidia na yau da kullun, amma babu su a cikin wasu eukaryotes, gami da Microsporidia Mitosporidium da Amphiamblys marasa tsari, inda ɓangaren ES39L rRNA bai ragu da 44, 45, 46 ba (Hoto na 5c). -e).
Idan aka haɗa waɗannan bayanai, waɗannan bayanai suna goyon bayan ra'ayin cewa E. cuniculi da wataƙila wasu ƙananan microsporidia sun haɓaka ikon kama adadi mai yawa na ƙananan metabolites a cikin tsarin ribosome don rama raguwar matakan rRNA da furotin. Ta yin hakan, sun haɓaka wata ƙwarewa ta musamman ta ɗaure nucleotides a wajen ribosome, wanda ke nuna cewa tsarin ƙwayoyin cuta na parasitic yana ramawa ta hanyar kama ƙananan metabolites masu yawa da amfani da su azaman kwaikwayon tsarin RNA da gutsuttsuran furotin da suka lalace.
Sashe na uku wanda ba a kwatanta shi ba na taswirar cryo-EM ɗinmu, wanda aka samo a cikin babban sashin ribosomal. Babban ƙuduri (2.6 Å) na taswirarmu yana nuna cewa wannan yawan yana cikin furotin tare da haɗuwa ta musamman na manyan ragowar sarkar gefe, wanda ya ba mu damar gano wannan yawan a matsayin furotin ribosomal da ba a san shi ba wanda muka gano a matsayin An sanya masa suna msL2 (Microsporidia-specific protein L2) (hanyoyi, hoto na 6). Bincikenmu na homology ya nuna cewa msL2 yana cikin Microsporidia clade na halittar Encephaliter da Orosporidium, amma babu shi a cikin wasu nau'ikan, gami da wasu Microsporidia. A cikin tsarin ribosomal, msL2 yana mamaye wani gibi da asarar ES31L rRNA mai tsawo ta samar. A cikin wannan fanko, msL2 yana taimakawa wajen daidaita naɗewar rRNA kuma yana iya rama asarar ES31L (Hoto na 6).
a Yawan Electron da samfurin furotin ribosomal msL2 na musamman na Microsporidia da aka samu a cikin ribosomes na E. cuniculi. b Yawancin ribosomes na eukaryotic, gami da ribosome na 80S na Saccharomyces cerevisiae, sun rasa haɓakar ES19L rRNA a cikin yawancin nau'ikan Microsporidian. Tsarin da aka kafa a baya na ribosome na V. necatrix microsporidia ya nuna cewa asarar ES19L a cikin waɗannan ƙwayoyin cuta ana rama shi ta hanyar juyin halittar sabon furotin ribosomal msL1. A cikin wannan binciken, mun gano cewa ribosome na E. cuniculi shi ma ya haɓaka ƙarin furotin mai kama da ribosomal RNA a matsayin diyya a bayyane don asarar ES19L. Duk da haka, msL2 (wanda a halin yanzu aka ambata a matsayin furotin ECU06_1135 na hasashe) da msL1 suna da asali daban-daban na tsari da juyin halitta. c Wannan ganowar samar da sunadaran ribosomal msL1 da msL2 waɗanda ba su da alaƙa da juyin halitta ya nuna cewa idan ribosomes suka tara sauye-sauye masu illa a cikin rRNA ɗinsu, za su iya cimma matakan bambancin tsari wanda ba a taɓa gani ba a cikin ƙaramin rukuni na nau'ikan halittu masu alaƙa da juna. Wannan gano zai iya taimakawa wajen fayyace asali da juyin halittar ribosome na mitochondrial, wanda aka san shi da raguwar rRNA da rashin daidaituwa a cikin abubuwan da ke cikin furotin a cikin nau'ikan halittu.
Sai muka kwatanta furotin msL2 da furotin msL1 da aka bayyana a baya, furotin ribosomal guda ɗaya da aka sani da microsporidia-specific microsporidia da aka samu a cikin ribosome V. necatrix. Mun so mu gwada ko msL1 da msL2 suna da alaƙa da juyin halitta. Bincikenmu ya nuna cewa msL1 da msL2 suna zaune a cikin rami ɗaya a cikin tsarin ribosomal, amma suna da tsarin farko da na uku daban-daban, wanda ke nuna asalin juyin halittarsu mai zaman kansa (Hoto na 6). Don haka, ganowar msL2 da muka yi ya ba da shaida cewa ƙungiyoyin ƙananan nau'ikan eukaryotic za su iya haɓaka furotin ribosomal daban-daban don rama asarar gutsuttsuran rRNA. Wannan binciken ya shahara saboda yawancin ribosomes na eukaryotic na cytoplasmic suna ɗauke da furotin mara canzawa, gami da iyali ɗaya na furotin ribosomal 81. Bayyanar msL1 da msL2 a cikin nau'ikan microsporidia daban-daban dangane da asarar sassan rRNA masu tsawo yana nuna cewa lalacewar tsarin kwayoyin halittar kwayar cutar yana sa ƙwayoyin cuta su nemi maye gurbi, wanda daga ƙarshe zai iya haifar da kamuwa da su a cikin nau'ikan ƙwayoyin cuta daban-daban.
A ƙarshe, lokacin da aka kammala samfurinmu, mun kwatanta tsarin ribosome na E. cuniculi da wanda aka annabta daga jerin kwayoyin halitta. An yi zaton cewa akwai wasu sunadaran ribosomal da dama, ciki har da eL14, eL38, eL41, da eS30, a baya sun ɓace daga tsarin E. cuniculi saboda rashin daidaiton su daga tsarin E. cuniculi. Haka kuma ana hasashen asarar sunadaran ribosomal da yawa a cikin mafi yawan sauran ƙwayoyin cuta masu raguwar ƙwayoyin halitta da endosymbionts. Misali, kodayake yawancin ƙwayoyin cuta masu rai suna ɗauke da iyali ɗaya na sunadaran ribosomal 54, 11 kawai daga cikin waɗannan iyalan sunadaran suna da homologues da za a iya gano su a cikin kowane tsarin kwayoyin halitta da aka bincika na ƙwayoyin cuta masu ƙuntatawa. Don tallafawa wannan ra'ayi, an lura da asarar sunadaran ribosomal ta hanyar gwaji a cikin V. necatrix da P. locustae microsporidia, waɗanda ba su da sunadaran eL38 da eL4131,32.
Duk da haka, tsarinmu ya nuna cewa eL38, eL41, da eS30 ne kawai suka ɓace a cikin ribosome na E. cuniculi. An kiyaye furotin na eL14 kuma tsarinmu ya nuna dalilin da yasa ba za a iya samun wannan furotin a cikin binciken homology ba (Hoto na 7). A cikin ribosomes na E. cuniculi, yawancin wurin ɗaure eL14 ya ɓace saboda lalacewar ES39L mai ƙarfin rRNA. Idan babu ES39L, eL14 ya rasa yawancin tsarinsa na biyu, kuma kashi 18% kawai na jerin eL14 iri ɗaya ne a cikin E. cuniculi da S. cerevisiae. Wannan rashin kiyaye jerin abubuwa abin mamaki ne domin har ma da Saccharomyces cerevisiae da Homo sapiens—halittu waɗanda suka samo asali shekaru biliyan 1.5 a tsakaninsu—suna raba fiye da kashi 51% na ragowar iri ɗaya a cikin eL14. Wannan rashin kiyayewa mai ban mamaki ya bayyana dalilin da yasa aka sanya E. cuniculi eL14 a matsayin furotin M970_061160 ba kamar furotin ribosomal na eL1427 ba.
kuma ribosome na Microsporidia ya rasa faɗaɗawar ES39L rRNA, wanda ya kawar da wani ɓangare na wurin ɗaure furotin na eL14. Idan babu ES39L, furotin microspore na eL14 yana fuskantar asarar tsarin sakandare, wanda tsohon α-helix mai ɗaure rRNA ya lalace zuwa ƙaramin madauki na tsawon lokaci. b Daidaito da yawa na jerin suna nuna cewa furotin na eL14 yana da matuƙar kiyayewa a cikin nau'in eukaryotic (kashi 57% na asalin jerin tsakanin yisti da homologues na ɗan adam), amma ba a kiyaye shi sosai kuma ba ya bambanta a cikin microsporidia (wanda ba fiye da 24% na ragowar iri ɗaya ne da homologue na eL14 ba). daga S. cerevisiae ko H. sapiens). Wannan rashin kyawun kiyaye jerin da bambancin tsarin sakandare ya bayyana dalilin da yasa ba a taɓa samun homologue na eL14 a cikin E. cuniculi ba kuma me yasa ake tunanin an rasa wannan furotin a cikin E. cuniculi. Sabanin haka, an riga an ambaci E. cuniculi eL14 a matsayin furotin M970_061160. Wannan lura ya nuna cewa bambancin kwayoyin halittar microsporidia a halin yanzu an yi kiyasin ya wuce gona da iri: wasu kwayoyin halittar da ake tunanin sun ɓace a cikin microsporidia a zahiri ana kiyaye su, kodayake a cikin nau'ikan da suka bambanta sosai; maimakon haka, ana tsammanin wasu suna wakiltar kwayoyin halittar microsporidia don sunadarai na musamman ga tsutsotsi (misali, furotin na hasashen M970_061160) a zahiri suna wakiltar sunadaran da ke cikin sauran eukaryotes.
Wannan binciken ya nuna cewa rRNA denaturation na iya haifar da asarar kiyaye jerin sunadaran ribosomal da ke kusa, wanda hakan ke sa ba za a iya gano waɗannan sunadaran ba don binciken homology. Don haka, za mu iya kimanta ainihin matakin lalacewar kwayoyin halitta a cikin ƙananan kwayoyin halitta, tunda wasu sunadaran da ake tunanin sun ɓace a zahiri suna ci gaba, kodayake a cikin nau'ikan da aka canza sosai.
Ta yaya ƙwayoyin cuta za su iya riƙe aikin injunan ƙwayoyin halittarsu a ƙarƙashin yanayin raguwar kwayar halitta mai tsanani? Bincikenmu ya amsa wannan tambayar ta hanyar bayyana tsarin ƙwayoyin halitta mai rikitarwa (ribosome) na E. cuniculi, wani halitta mai ɗaya daga cikin ƙananan kwayoyin halittar eukaryotic.
An san cewa kusan shekaru ashirin da suka gabata cewa ƙwayoyin furotin da RNA a cikin ƙwayoyin cuta masu ƙwayoyin cuta galibi sun bambanta da ƙwayoyin halittarsu masu kama da juna a cikin nau'ikan halittu masu rai saboda ba su da cibiyoyin kula da inganci, an rage su zuwa kashi 50% na girmansu a cikin ƙwayoyin cuta masu rai, da sauransu. sauye-sauye masu yawa masu rauni waɗanda ke lalata naɗewa da aiki. Misali, ana sa ran ribosomes na ƙananan ƙwayoyin halitta, gami da ƙwayoyin cuta masu rai da endosymbionts da yawa, ba su da sunadaran ribosomal da yawa da kuma har zuwa kashi ɗaya bisa uku na nucleotides na rRNA idan aka kwatanta da nau'ikan halittu masu rai 27, 29, 30, 49. Duk da haka, yadda waɗannan ƙwayoyin cuta ke aiki a cikin ƙwayoyin cuta ya kasance babban asiri, wanda aka yi nazari akai-akai ta hanyar kwatanta kwayoyin halitta.
Bincikenmu ya nuna cewa tsarin macromolecules na iya bayyana fannoni da yawa na juyin halitta waɗanda ke da wahalar cirewa daga nazarin kwayoyin halitta na gargajiya na ƙwayoyin cuta na cikin ƙwayoyin halitta da sauran halittu masu ƙuntatawa (Hoto na 7). Misali, misalin furotin eL14 ya nuna cewa za mu iya kimanta ainihin matakin lalacewar na'urar kwayoyin halitta a cikin nau'ikan ƙwayoyin cuta. Yanzu ana kyautata zaton ƙwayoyin cuta na encephalitic suna da ɗaruruwan kwayoyin halitta na musamman na microsporidia. Duk da haka, sakamakonmu ya nuna cewa wasu daga cikin waɗannan kwayoyin halitta da alama takamaiman ne kawai bambance-bambancen kwayoyin halitta ne da suka zama ruwan dare a cikin wasu eukaryotes. Bugu da ƙari, misalin furotin msL2 yana nuna yadda muke yin watsi da sabbin sunadaran ribosomal da kuma raina abubuwan da ke cikin injunan kwayoyin cuta. Misalin ƙananan ƙwayoyin cuta yana nuna yadda za mu iya yin watsi da sabbin abubuwa masu ban mamaki a cikin tsarin kwayoyin halitta masu ɓarna waɗanda za su iya ba su sabbin ayyukan halittu.
Idan aka haɗa waɗannan sakamakon, muna inganta fahimtarmu game da bambance-bambancen da ke tsakanin tsarin kwayoyin halitta na ƙwayoyin halitta da aka takaita da kuma takwarorinsu a cikin halittu masu rai. Mun nuna cewa injunan kwayoyin halitta, waɗanda aka daɗe ana tunanin suna raguwa, suna lalacewa, kuma suna fuskantar sauye-sauye daban-daban masu raunana jiki, suna da wasu siffofi na tsarin da ba a saba gani ba a tsarin.
A gefe guda kuma, gutsuttsuran rRNA marasa girma da gutsuttsuran da muka samu a cikin ribosomes na E. cuniculi sun nuna cewa rage kwayar halitta na iya canza ko da waɗancan sassan injunan kwayoyin halitta na asali waɗanda aka adana a cikin fannoni uku na rayuwa - bayan kusan shekaru biliyan 3.5. juyin halittar nau'ikan halittu masu zaman kansu.
Gutsuttsuran rRNA marasa ƙwanƙwasa da kuma waɗanda aka haɗa a cikin ribosomes na E. cuniculi suna da sha'awa musamman dangane da binciken da aka yi a baya game da ƙwayoyin RNA a cikin ƙwayoyin endosymbiotic. Misali, a cikin aphid endosymbiont Buchnera aphidicola, an nuna cewa ƙwayoyin rRNA da tRNA suna da tsarin da ke da saurin amsawa ga yanayin zafi saboda bambancin abun ciki na A+T da kuma babban rabo na nau'ikan tushe marasa canonical20,50. Waɗannan canje-canje a cikin RNA, da kuma canje-canje a cikin ƙwayoyin furotin, yanzu ana tsammanin su ne ke da alhakin dogaro da endosymbionts fiye da kima ga abokan hulɗa da kuma rashin iyawar endosymbionts don canja wurin zafi 21, 23. Kodayake parasitic microsporidia rRNA yana da canje-canje daban-daban a tsarin, yanayin waɗannan canje-canjen yana nuna cewa rage kwanciyar hankali na zafi da kuma dogaro mafi girma akan sunadaran chaperone na iya zama sifofi gama gari na ƙwayoyin RNA a cikin ƙwayoyin halitta masu ƙarancin kwayoyin halitta.
A gefe guda kuma, tsarinmu ya nuna cewa ƙwayoyin cuta na microsporidia sun samo asali ne daga wata baiwa ta musamman ta juriya ga gutsuttsuran rRNA da furotin da aka adana sosai, suna haɓaka ikon amfani da ƙananan metabolites masu yawa da ake samu a matsayin kwaikwayon tsarin rRNA da gutsuttsuran furotin da suka lalace. Rushewar tsarin kwayoyin halitta. . Wannan ra'ayi yana da goyon bayan gaskiyar cewa ƙananan ƙwayoyin halitta waɗanda ke rama asarar gutsuttsuran furotin a cikin rRNA da ribosomes na E. cuniculi suna ɗaure zuwa ga ragowar microsporidia na musamman a cikin sunadaran uL15 da eL30. Wannan yana nuna cewa ɗaure ƙananan ƙwayoyin halitta ga ribosomes na iya zama samfurin zaɓi mai kyau, inda aka zaɓi maye gurbi na musamman na Microsporidia a cikin sunadaran ribosomal saboda ikonsu na ƙara kusancin ribosomes ga ƙananan ƙwayoyin halitta, wanda zai iya haifar da ƙwayoyin ribosomal masu inganci. Binciken ya bayyana wani sabon abu mai wayo a cikin tsarin kwayoyin halitta na ƙwayoyin cuta kuma yana ba mu fahimtar yadda tsarin kwayoyin halitta na ƙwayoyin cuta ke kula da aikinsu duk da juyin halittar ragewa.
A halin yanzu, gano waɗannan ƙananan ƙwayoyin har yanzu ba a fayyace su ba. Ba a fayyace dalilin da ya sa bayyanar waɗannan ƙananan ƙwayoyin a cikin tsarin ribosomal ya bambanta tsakanin nau'in microsporidia ba. Musamman ma, ba a fayyace dalilin da yasa ake ganin ɗaurewar nucleotide a cikin ribosomes na E. cuniculi da P. locustae ba, kuma ba a cikin ribosomes na V. necatrix ba, duk da kasancewar ragowar F170 a cikin sunadaran eL20 da K172 na V. necatrix. Wannan gogewa na iya faruwa ne ta hanyar residue 43 uL6 (wanda ke kusa da aljihun ɗaurewar nucleotide), wanda shine tyrosine a cikin V. necatrix kuma ba threonine a cikin E. cuniculi da P. locustae ba. Babban sarkar gefen aromatic na Tyr43 na iya tsoma baki tare da ɗaurewar nucleotide saboda haɗuwar steric. A madadin haka, gogewar nucleotide da ke bayyane na iya kasancewa saboda ƙarancin ƙudurin hoton cryo-EM, wanda ke hana ƙirar gutsuttsuran ribosomal na V. necatrix.
A gefe guda kuma, aikinmu ya nuna cewa tsarin ruɓewar kwayoyin halitta na iya zama ƙarfin ƙirƙira. Musamman ma, tsarin ribosome na E. cuniculi yana nuna cewa asarar rRNA da gutsuttsuran furotin a cikin ribosome na microsporidia yana haifar da matsin lamba na juyin halitta wanda ke haɓaka canje-canje a cikin tsarin ribosome. Waɗannan bambance-bambancen suna faruwa nesa da wurin aiki na ribosome kuma suna kama da suna taimakawa wajen kiyaye (ko dawo da) haɗuwa mafi kyau na ribosome wanda in ba haka ba zai lalace ta hanyar raguwar rRNA. Wannan yana nuna cewa babban ƙirƙira na ribosome na microsporidia ya bayyana ya zama buƙatar rage guduwar kwayoyin halitta.
Wataƙila wannan ya fi kyau a kwatanta shi da ɗaurewar nucleotide, wanda ba a taɓa ganinsa a cikin wasu halittu ba zuwa yanzu. Gaskiyar cewa ragowar ɗaurewar nucleotide suna nan a cikin microsporidia na yau da kullun, amma ba a cikin wasu eukaryotes ba, yana nuna cewa wuraren ɗaurewar nucleotide ba kawai kayan tarihi bane da ke jiran ɓacewa, ko wurin ƙarshe don a mayar da rRNA zuwa siffar nucleotides na mutum ɗaya. Madadin haka, wannan rukunin yanar gizon yana kama da siffa mai amfani wanda da zai iya canzawa a cikin zagaye da yawa na zaɓi mai kyau. Wuraren ɗaurewar nucleotide na iya zama samfurin zaɓin halitta: da zarar ES39L ya lalace, ana tilasta wa microsporidia neman diyya don dawo da mafi kyawun biogenesis na ribosome idan babu ES39L. Tunda wannan nucleotide zai iya kwaikwayon hulɗar kwayoyin halitta na nucleotide A3186 a cikin ES39L, ƙwayar nucleotide ta zama tubalin ginin ribosome, wanda ɗaurewar ta ƙara inganta ta hanyar maye gurbin jerin eL30.
Dangane da juyin halittar ƙwayoyin cuta na ƙwayoyin cuta na cikin ƙwayoyin halitta, bincikenmu ya nuna cewa ƙarfin zaɓin halitta na Darwin da kuma rugujewar kwayoyin halitta na ruɓewar kwayoyin halitta ba sa aiki a layi ɗaya, amma suna juyawa. Da farko, rugujewar kwayoyin halitta yana kawar da muhimman fasalulluka na ƙwayoyin halitta, yana sa diyya ta zama da matuƙar muhimmanci. Sai lokacin da ƙwayoyin cuta suka biya wannan buƙata ta hanyar zaɓin halitta na Darwin ne kawai ƙwayoyin cuta nasu za su sami damar haɓaka halayensu mafi ban sha'awa da sabbin abubuwa. Abu mafi mahimmanci, juyin halittar wuraren ɗaure nucleotide a cikin ribosome na E. cuniculi ya nuna cewa wannan tsarin asarar da za a samu na juyin halittar kwayoyin halitta ba wai kawai yana rage maye gurbi masu illa ba, har ma wani lokacin yana ba da sabbin ayyuka gaba ɗaya akan ƙwayoyin cuta masu ɓarna.
Wannan ra'ayin ya yi daidai da ka'idar daidaiton motsi na Sewell Wright, wanda ya bayyana cewa tsarin zaɓen halitta mai tsauri yana iyakance ikon halittu don ƙirƙira51,52,53. Duk da haka, idan karkatar kwayoyin halitta ta wargaza zaɓin halitta, waɗannan karkatarwar na iya haifar da canje-canje waɗanda ba sa daidaitawa (ko ma cutarwa) amma suna haifar da ƙarin canje-canje waɗanda ke samar da mafi kyawun dacewa ko sabbin ayyukan halittu. Tsarinmu yana goyan bayan wannan ra'ayin ta hanyar kwatanta cewa irin wannan maye gurbi wanda ke rage ninki da aikin biomolecule ya zama babban abin da ke haifar da ci gabansa. Dangane da tsarin juyin halitta mai nasara-nasara, bincikenmu ya nuna cewa lalacewar kwayoyin halitta, wanda aka saba gani a matsayin tsari mai lalacewa, shi ma babban abin da ke haifar da ƙirƙira, wani lokacin kuma wataƙila ma sau da yawa yana ba da damar macromolecules su sami sabbin ayyukan parasites. na iya amfani da su.