CYP51 clan

Arthropods are lacking the conserved CYP51 clan (sterol 14-demethylase) and are known to be sterol auxotrophs (they cannot synthesize sterols de novo), but CYP51 is present in Onychophora, the sister clade of arthropods (Nelson, 2018).

A CYP51 transcript sequence found in the collembolan Folsomia candida (GASX02003270.1) appears to be an algal contaminant (Helicosporidium sp. ATCC 50920 KDD76879.1, 100% identity)(Dermauw et al., 2020).

However, some Collembola carry genomic copies of CYP51-like genes that are apparently mimivirus-derived. In the Amsterdam assembly of Folsomia candida, CYP5253D1 is found as a single copy gene, with one phase two intron (see sequence below). This gene is a fusion between a CYP51-like gene and a AlkB-like Fe(II) oxoglutarate dioxygenase domain. It appears to result from a horizontal gene transfer (HGT) from Amoeba carrying giant viruses (see Acanthamoeba polyphaga mimivirus sequence of CYP5253A1). In the Shanghai assembly (said to be a different species), there are three copies of the gene. The CYP5253D1 fusion protein is found in four species of Collembola. The genomic region in the Amsterdam assembly (see figure) is conserved in the Shanghai assembly and in Folsomia manolachei. The flanking genes are eukaryotic genes.

The four species in which the fusion protein was found belong to Poduroidea (Xenylla mediterranea and Anurida granaria) and to Isotomoidea (Folsomia), so it is likely that the HGT occurred in the early Carboniferous.

It seems that following the HGT event, the fused OG dioxygenase domain was lost, and the P450 gene duplicated several times, so that the Folsomia candida CYPome now carries 9 such genes (including one apparent pseudogene. These CYP51-like genes are found in at least 15 species of Collembola.

Folsomia_candida-CYP5253D1 MEQKILSAVEEQW(2)LKLLILFALSVTFIWKKIWPTTHSAIPPNLKTVPIVSGALPFVGHGIAFSKDIVGFISNCYEKYGKIFRIKIFRVDMVVICDRTMNNEFFKATEDKMSLYDVLTRLYFADAFSDEPTSLPRIINVVKKSIAVRYDTFAPKIEHEARKMIARLRTEVSSGKKIDLIKEMTRFVATTSASCFISVELTDQLFAVLLKFTHLLNSVVVLTYFLPKWLLRLLVNPFLARLRKQITSVLSPEIEKYRENLDKSDSLILRAAVDYIDEESGANLTNQEIGDIVVCLLYVSSENTALGLTNTVTDLACNTTYWEKCKREAGLYLGGDSTDIKGLFASPLINACVMESARLNSHIFALNRKPLDKLASIGGYHVGHAETIAMCEPMLMVHASAQEIFSNPKIYNPDRFLGPAKESMAPLSVMTWGAGVHLCPGKMFSIYEIKMALGLILLNFEFELEKGSISKIDYFSPSAFAERKVQASLKVLVEESSSSPQNKGDLANVIVLKNGQKCHYYRGESTTGSQDGWLLRDFISREEQISLYQNIFELSKNSKEHDEIWKIPSDKVYPFAYHNLVYTGESNCPPPTAWYEWAANLWQLLESDKKLVSFSGPEIKGFNSLYAQLYGVGGSMKLHKDEHVSWGISVNLGASTTFVFGGEKILLHSGDVFIADFSQVEHGVEAVHETSMPDWFSKESGIVENFDRVRCSVQIRDISNLSERNFITREEFTKLLK

AAV51068.1 CYP5253A1-fusion with 2OG dioxygenase[Acanthamoeba polyphaga mimivirus] MLFELSIGAIIGFLTLYLLKRFNESKNFITPDNLKKIPIVEGAVPVLGHGPAFSKDIMQFMKNCYKKYGSVFQLKIFRTNMVVLCDRKLSEEFFKSRENDMSLYDVLNRLFFGLAFSDKPDSLEFIIKMVKKTITIRYDDFAPKIMDEAQRLTKIMRESHSGKKLDMIPEIIKFVSRTSARCFIAMDIDDEFYDALNKFTNLLNKIVVLTYFVPHWLLNATLNRFMLRKYRMRMTKLLENEIEKYRTDLNKSDSLLFRKCVDHIDPETGATLTNQDIGDIVVCLLYVSSENTSLLATNCLIDLTLNPKYWDLIKSECSAMIALGDYKNLFKAPLLNSIVMESARLNSHVFALARKPKTVNRIGDYFVADNVDTISLCEPALMKFEIASDVYANPNSYDPVRFMAPRNEPKDSGHVMNWGKGVHECPGKQFAIYEVKAAIAYIVTNFERFEFNHNDLKINYFSPSAMCEKNISVEFIPSQQNIHNIVYKDRTYIVEHIKCNETSAWLIYNALDRQQQREYYQYTYEISTDSQEHKLIEKAGPHKPFPIAYDKLVYTGQSNCMTPTKWYDFASDIWELLTENYAELGFPIYDDKIRNFVPNSFYGQLYSVESIMPTHRDQHVDYGLSISIGSNCEFVIEDKTILLPSGSVLIGDFSKISHSVSKIFHEKPDHLSDFEFFNRVRFSAQIRSIDPDVQPLMTTQEFLDMISEY