Extreme diversification of the mating type-high-mobility group (MATA-HMG) gene family in a plant-associated arbuscular mycorrhizal fungus
Rohan Riley,Philippe Charron,Alexander Idnurm,Laurent Farinelli,Yolande Dalpé,Francis Martin,Nicolas Corradi
2014 January 01 New Phytologist, 201: 254-268. doi: 10.1111/nph.12462
Arbuscular mycorrhizal fungi (AMF) are important plant symbionts that have long been considered evolutionary anomalies because of their apparent long-term lack of sexuality, but recent explorations of available DNA sequence have challenged this notion by revealing the presence of homologues of fungal mating typeâhigh-mobility group (MATA-HMG) and core meiotic genes in these organisms.
To obtain more insights into the sexual potential of AMF, homologues of MATA-HMGs were sought in the transcriptome of three AMF isolates, and their functional and evolutionary trajectories were studied in genetically divergent strains of Rhizophagus irregularis using conventional and quantitative PCR procedures.
Our analyses revealed the presence of at least 76 homologues of MATA-HMGs in R. irregularis isolates. None of these was found to be surrounded by genes generally found near other known fungal mating type loci, but here we report the presence of a 9-kb-long region in the AMF R. irregularis harbouring a total of four tandem-repeated MATA-HMGs; a feature that highlights a potentially elevated intragenomic diversity in this AMF species.
The present study provides intriguing insights into the genome evolution of R. irregularis, and represents a stepping stone for understanding the potential of these fungi to undergo cryptic sex.
Figure 1. Drawing
of the standalone (a) and crossing (b) cultures. Smaller circles within
the larger circle are 70-mm plates inside the 120-mm plates. Gaps in
small circles are exit points. Brown lines inside the 70-mm plates
represent carrot roots. Finer black lines coming out of the carrot roots
Figure 2. Number of mating type–high-mobility group (MATA-HMG) domain-containing genes identified in the genomes of several Rhizophagus irregularis
strains, and the genomes of representative species of the Ascomycota,
Basidiomycota, Zygomycota and Chytridiomycota. The schematic
phylogenetic representation is based on rRNA sequences.
Figure 5. Schematic representation of an 8572-bp region of the Rhizophagus irregularis genome harbouring four tandem-repeated mating type–high-mobility group (MATA-HMG) genes obtained using inverse PCR and bioinformatics approaches.
Riley, R., Charron, P., Idnurm, A., Farinelli, L., Dalpé, Y., Martin, F. and Corradi, N. (2014), Extreme diversification of the mating typeâhigh-mobility group (MATA-HMG) gene family in a plant-associated arbuscular mycorrhizal fungus. New Phytologist, 201: 254â-268. doi: 10.1111/nph.12462