Identificaiton Of Biocontrol Genes In Trichoderma Through Comparative Analysis Of Gene Families

Trichoderma is a fungal species in Deuteromycotina,which is capable of adapting to a variety of environments in different climatic zones. Because Trichoderma species have a competitive advantage over many other fungal species, they have been widely used as microbicide to control the growth of other fungal species. Thus, it is of economic importance to search for Trichoderma species with competitive strength in growth and in biological control.YYH13 and YYH16 are two Trichoderma hamatum strains that were isolated from soil in the Hunan Province in China. Experiments revealed that the strain YYH13 has stronger activities in biological control than YYH16 does. We hypothesize that YYH13 acquired these stronger activities through expansion of certain gene families in the YYH13 genome in evolution. In this thesis work, we analyzed gene families that have functions in biocontrol, including CAZyme gene families, Peptidase, and gene families that produces secondary metabolites.By analyzing the difference in these important families in these two genomes, we found that many gene families expanded in the genome of YYH13. In the CAZyme gene families, we found that YYH13 has more genes encoding chitinase and β-1,3-glucanase, which are important enzymes for cell wall degradation, than YYH16 does. In peptidase gene families, we found that YYH13 has many more genes in S08 and S10 gene families that have been experimental demonstrated to be important in biocontrol. Using the program antiSMASH, we found seven secondary metabolite gene clusters in YYH13, while there are only three gene clusters in YYH16. These genes play a role in biocontrol. Taken together, differences in these gene families may enhance the ability of YYH13 in biocontrol.Through comparative analysis of gene families in two Trichoderma hamatum strains YYH13 and YYH16, we have found candidate genes that play an important role in biocontrol. Further molecular and functional work on these genes is of primary importance for identifying important genes for biocontrol, understanding the mechanisms underlying biocontrol, which will further contribute to constructing Trichoderma hamatum strains with improved activities in biocontrol.