Rukunin al'ada na rayuwa ya zama prokaryotes da eukaryotes a cikin 1977 lokacin da tsarin rRNA ya bayyana cewa archaea (wanda ake kira 'archaebacteria') suna da alaƙa da ƙwayoyin cuta kamar yadda ƙwayoyin cuta suke da eukaryotes. cikin eubacteria (wanda ya ƙunshi dukkanin kwayoyin cuta), archaea, da eukaryotes. Tambayar asalin eukaryotes ya kasance. A lokacin da ya dace, shaidu sun fara ginawa don goyon bayan zuriyar archaeal na eukaryotes. Wani abin sha'awa shi ne gano cewa Asgard archaea yana da ɗaruruwan furotin sa hannu na eukaryotic (ESPs) a cikin kwayoyin halittarsu. ESPs suna taka muhimmiyar rawa wajen haɓaka cytoskeleton da hadadden tsarin salon salula halayen eukaryotes. A cikin wani bincike na ci gaba da aka buga a ranar 21 ga Disamba, 2022, masu bincike sun ba da rahoton cin nasarar noman ingantacciyar al'adun gargajiya na Asgard archaea wanda suka zana ta amfani da hoton cryo-electron. Sun lura cewa ƙwayoyin Asgard suna da hadaddun cytoskeleton na tushen actin. Wannan ita ce shaidar gani ta farko kai tsaye na zuriyar archaeal na eukaryotes, wani muhimmin mataki a fahimtar asalin eukaryotes.
Har zuwa 1977, an haɗa nau'ikan rayuwa a duniya eukaryotes (rikitattun siffofin da aka kwatanta da hada kayan kwayoyin halitta na tantanin halitta a cikin madaidaicin tsakiya da kuma kasancewar cytoskeleton) da kuma prokaryotes (sauƙaƙan rayuwa tare da kwayoyin halitta a cikin cytoplasm ba tare da ƙayyadadden ƙwayar cuta ba, ciki har da kwayoyin cuta da archaebacteria). An yi tunanin cewa salula eukaryotes ya samo asali kimanin shekaru biliyan 2 da suka wuce, mai yiwuwa daga prokaryotes. Amma, ta yaya ainihin eukaryotes suka samo asali? Yaya hadaddun tsarin rayuwar salula, ke da alaƙa da mafi sauƙin sifofin rayuwar salula? Wannan babbar tambaya ce a cikin ilmin halitta.
Ci gaban fasaha a cikin ilmin kwayoyin halitta na kwayoyin halitta da furotin ya taimaka wajen zurfafa cikin ainihin lamarin lokacin da, a cikin 1977, an gano archaea (wanda ake kira 'archaebacteria') ""kamar yadda suke da alaƙa da ƙwayoyin cuta kamar yadda ƙwayoyin cuta suke eukaryotes. 'Bambancin farko na nau'ikan rayuwa zuwa prokaryotes da eukaryotes ya dogara ne akan bambance-bambancen dabi'a a matakin kwayoyin halitta. Dangantakar phylogenetic yakamata, a maimakon haka, ta dogara akan kwayoyin da aka rarraba a ko'ina. Ribosomal RNA (rRNA) shine nau'in kwayoyin halitta wanda ke samuwa a cikin duk tsarin da ke yin kwafin kansa kuma jerin sa suna canzawa kadan da lokaci. Binciken da ya danganta da siffanta jerin rRNA ya wajabta tara rayayyun halittu zuwa cikin eubacteria (wanda ya ƙunshi dukkan ƙwayoyin cuta na yau da kullun), archea, da eukaryotes1.
Bayan haka, alamun kusanci tsakanin archaea da eukaryotes suna farawa. A cikin 1983, an gano cewa DNA-dogara RNA polymerases na archaea da eukaryotes iri ɗaya ne; Dukansu suna nuna kamanceceniya da sifofin rigakafi na rigakafi kuma duka biyun an samo su ne daga tsarin kakanni na gama gari2. Dangane da bishiyar phylogenetic da aka kwatanta ta nau'in furotin, wani binciken da aka buga a 1989, ya bayyana kusancin archaea da eukaryotes fiye da eubacteria.3. A wannan lokacin, asalin archaeal na eukaryotes an kafa amma ainihin nau'in archaeal ya kasance don ganowa da kuma nazarin su.
Ci gaba a cikin karatun genomic bayan nasara a aikin genome, ya samar da abin cika da ake buƙata sosai ga wannan yanki. Tsakanin 2015-2020, bincike da yawa sun gano cewa Asgard archea dauke da takamaiman kwayoyin halittar eukaryote. Kwayoyin halittarsu an wadatar da su don sunadaran da aka yi la’akari da su musamman ga eukaryotes. Wadannan binciken sun bayyana a fili cewa Asgard archaea yana da kusancin kwayoyin halitta zuwa eukaryote ta hanyar kasancewar ɗaruruwan furotin sa hannu na eukaryotic (ESPs) a cikin kwayoyin halittarsu.
Mataki na gaba shine a hango yanayin tsarin cellar cikin gida na Asgard archaea don tabbatar da matsayin ESPs kamar yadda ake ɗauka cewa ESPs suna taka muhimmiyar rawa wajen samar da hadadden tsarin salula. Don wannan, ana buƙatar wadatattun al'adu na wannan archaea amma an san Asgard yana da ban tsoro da ban mamaki. yana haifar da wahalar noma a cikin adadi mai yawa don nazarin su a cikin dakin gwaje-gwaje. Kamar yadda wani bincike da aka bayar kwanan nan akan 21 Disamba 2022, an shawo kan wannan wahala.
Masu binciken sun yi, bayan shekaru shida na aiki tuƙuru, ingantattun dabaru kuma sun sami nasarar haɓaka a cikin dakin gwaje-gwaje, al'adun da aka wadatar sosai.Candidatus Lokiarchaeum ossiferum', memba na Asgard phylum. Wannan babbar nasara ce, kuma saboda wannan ya baiwa masu bincike damar hangowa da kuma nazarin tsarin salula na ciki na Asgard.
An yi amfani da hoto na Cryo-electron don kwatanta al'adun haɓakawa. Kwayoyin Asgard suna da jikin kwayoyin halittar coccoid da kuma hanyar sadarwa na protrusions masu reshe. Tsarin saman salula ya kasance mai rikitarwa. Cytoskeleton ya fadada ko'ina cikin jikin tantanin halitta. Filayen murɗaɗɗen madauri biyu sun ƙunshi Lokiactin (wato actin homologues wanda Lokiarchaeota ya yi rikodin). Don haka, Kwayoyin Asgard suna da cytoskeleton na tushen actin, wanda masu binciken suka ba da shawarar, sun riga sun yi juyin halittar farko. eukaryotes.
A matsayin shaida na farko na zahiri/gani na asalin kakannin eukaryotes, wannan babban ci gaba ne a ilmin halitta.
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References:
- Woese CR da Fox GE, 1977. Tsarin phylogenetic na yankin prokaryotic: Masarautun farko. An buga Nuwamba 1977. PNAS. 74 (11) 5088-5090. DOI: https://doi.org/10.1073/pnas.74.11.5088
- Hutu, J., et al 1983. Archaebacteria da eukaryotes sun mallaki RNA polymerases masu dogaro da DNA na nau'in gama gari. EMBO J. 2, 1291-1294 (1983). DOI: https://doi.org/10.1002/j.1460-2075.1983.tb01583.x
- Iwabe, N., et al 1989. Dangantakar juyin halitta na archaebacteria, eubacteria, da eukaryotes da aka samo daga bishiyoyin phylogenetic na kwayoyin halitta. Proc. Natl Acad. Sci. Amurka 86, 9355-9359. DOI: https://doi.org/10.1073/pnas.86.23.9355
- Rodrigues-Oliveira, T., et al. 2022. Actin cytoskeleton da hadadden tsarin gine-gine a cikin Archaeon Asgard. An buga: 21 Disamba 2022. Nature (2022). DOI: https://doi.org/10.1038/s41586-022-05550-y
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