Halary Sébastien, Daubois Laurence, Terrat Yves, Ellenberger Sabrina, Wöstemeyer Johannes, Hijri Mohamed
Département de Sciences Biologiques, Institut de Recherche en Biologie Végétale (IRBV), Université de Montréal, Montréal, Québec, Canada.
PLoS One. 2013 Nov 19;8(11):e80729. doi: 10.1371/journal.pone.0080729. eCollection 2013.
The fungal kingdom displays a fascinating diversity of sex-determination systems. Recent advances in genomics provide insights into the molecular mechanisms of sex, mating type determination, and evolution of sexual reproduction in many fungal species in both ancient and modern phylogenetic lineages. All major fungal groups have evolved sexual differentiation and recombination pathways. However, sexuality is unknown in arbuscular mycorrhizal fungi (AMF) of the phylum Glomeromycota, an ecologically vital group of obligate plant root symbionts. AMF are commonly considered an ancient asexual lineage dating back to the Ordovician, approximately 460 M years ago. In this study, we used genomic and transcriptomic surveys of several AMF species to demonstrate the presence of conserved putative sex pheromone-sensing mitogen-activated protein (MAP) kinases, comparable to those described in Ascomycota and Basidiomycota. We also find genes for high mobility group (HMG) transcription factors, homologous to SexM and SexP genes in the Mucorales. The SexM genes show a remarkable sequence diversity among multiple copies in the genome, while only a single SexP sequence was detected in some isolates of Rhizophagus irregularis. In the Mucorales and Microsporidia, the sexM gene is flanked by genes for a triosephosphate transporter (TPT) and a RNA helicase, but we find no evidence for synteny in the vicinity of the Sex locus in AMF. Nonetheless, our results, together with previous observations on meiotic machinery, suggest that AMF could undergo a complete sexual reproduction cycle.
真菌界展现出了令人着迷的性别决定系统多样性。基因组学的最新进展为许多古代和现代系统发育谱系中的真菌物种的性别分子机制、交配型决定及有性生殖进化提供了见解。所有主要的真菌类群都进化出了性别分化和重组途径。然而，球囊菌门的丛枝菌根真菌（AMF）的有性生殖情况尚不清楚，AMF是一类对生态至关重要的专性植物根共生体。AMF通常被认为是一个古老的无性谱系，可追溯到约4.6亿年前的奥陶纪。在本研究中，我们对几种AMF物种进行了基因组和转录组调查，以证明存在保守的假定性信息素感应丝裂原活化蛋白（MAP）激酶，这与子囊菌门和担子菌门中描述的类似。我们还发现了高迁移率族（HMG）转录因子的基因，与毛霉目中的SexM和SexP基因同源。SexM基因在基因组中的多个拷贝间表现出显著的序列多样性，而在不规则球囊霉的一些分离株中仅检测到单个SexP序列。在毛霉目和微孢子虫中，sexM基因两侧是磷酸丙糖转运蛋白（TPT）和RNA解旋酶的基因，但我们在AMF的性位点附近未发现共线性的证据。尽管如此，我们的结果以及之前关于减数分裂机制的观察结果表明，AMF可能经历完整的有性生殖周期。
