Functional Analysis Of Yeast CTS2Homologs In Magnaporthe Oryzae

Chitinase, one of cell wall degradation enzymes, can specially degrade chitinwhich is the major composition of fungal cell wall. Fungal chitinase genes alwaysexist as gene family, and function together in order to maintain cell wall degradationand restoration, such as conidia differentiation and mycelium autophagy.Furthermore, as a type of secretion proteins, chitinase can also involve in interactionbetween fungus and its host. Consequently, chitinases in Magnaporthe oryzae may beconcerned with its morphogenesis and infection processes.11homologous genes of Saccharomyces cerevisiae CTS2were identified inM. oryzae genome （version6） by bioinformatics, and these11genes can be furtherclassified into5classes according to their phylogenetic relationship. Previous analysisindicated that functional redundancy exist among Class I members, therefore, RNAinterference was used to simultaneously knockdown all genes in Class I, and resultsshowed that mutants exhibited different degree of defects in mycelium growth,conidiophore formation, conidiation and pathogenicity.Genes in the other4classes were analyzed through gene knock-out.Comparedwith the wild type strain, mutants which lost ClassⅡgenes showed no obviousphenotype difference in growth, development and pathogenicity; the loss ofMGG₀4732could cause the reduction of aerial mycelium, conidiophore andconidium, increased sensitivity to SDS, Congo red and H2O2; MGG₀6594mutantsdisplayed decrease in aerial mycelium, colony melanin, conidiophore and conidium,and the double deletion mutants of MGG₀6594and MGG₀8054resulted in thedeficiency of pathogenicity on rice cultivar CO39; the loss of MGG₀4534showed noobvious phenotype difference, while the double deletion mutants of MGG₀4534andMGG₀1336exhibited slight defect in colony growth, decrease in colony melanin,conidiophore and conidium, and obvious abnormality in the shape of partial conidia.In conclusion, dramatic functional redundancy exists among CTS2homologs inM. oryzae, while MGG₀4732, MGG₀6594, MGG₀8054and MGG₀1336playrelatively important roles in the growth, development and pathogenicity. Our researchresluts will not only be conductive to clarify the biologial functions of chitiniase genefamily in M. oryzae, but also can provide more reliable theoretical references fordeeply understanding of pathogenesis and molecular mechanism of interactions between M. oryzae and rice.