Preliminary Study On Genome Evolution And Mating Gene In Tolypocladium Inflatum

The hypocrealean fungus Tolypocladium inflatum W.Gams,a pathogen of beetle larvae,is the type species of genus Tolypocladium.It is best known as the producer of cyclosporin that is used medically as a key immunosuppressive drug to prevent the rejection of transplanted organs as well as to treat autoimmune diseases.The previous study of Tolypocladium inflatum focus on how to optimize the production conditions of cyclosporine rather than how to enrich the molecular biology information.Therefore,molecular studies of the fungus remain limited.For the first time,we assembled and annotated the mitochondrial genome of Tolypocladium inflatum,which is to date the smallest mitogenome in the fungal family Ophiocordycipitaceae.The circular DNA molecule is 25 kp in length,and it includes all fungal mitochondrial genes as well as one intron.Transcription analyses using RNA-Seq validated that the expression of most conserved genes.We also found evidence of gene transfer from the mitochondrion to the nucleus.Generally,mtDNA evolve faster than nrDNA in animals,whereas if this is also true in fungi remains uncertain.We first assemble the complete mitochondrial genome of the ascomycete fungus Tolypocladium inflatum and analyze the genome sequence variations among five isolates originating from distantly separated localities.The alignment of the five genome-wide show that only 30 SNP sites(SNP frequency 0.12%)in mtDNA and that in nrDNA is 304,901(SNP frequency 0.97%).The SNP frequency of nucles genome is more higher than that of mitochondrial genome.Phylogenetic analyses based on mitogenome is consistent with that based on the nuclear genome.Efforts to cultivate the sexual fruiting body have also been hampered due to the lack of knowledge of the mating-type gene and the conditions required for fruiting body.In this study,Screening of 22 single spore isolates derived from the same fruiting body,plus 5 non-monospora strains,thendesigned specific primer pairs to demonstrate that either MAT1-1 idiomorph or MAT1-2 idiomorph occurred within the isolates.The result will lay a foundation for research of other ascomycetes fungus as well as cultivation of fruiting body.