Functional Analysis Of Chitinase Gene Pst₂3943 In Puccinia Striiformis F.sp.Tritici

Triticum aestivum L.is one of the largest grain crop in China.Wheat stripe rust（Puccinia striiformis f.sp.tritici）is a nutrition-specific parasitic fungus in vivo,which can cause destructive losses of wheat production.The frequent and rapid variability of wheat stripe rust is the main reason that the continuous loss of resistance to disease-resistant varieties and the prevalence of diseases.Because it can not be cultured in vitro,the lack of reliable transformation system makes the research on the pathogenic function of stripe rust fungi relatively lagging.Chitin is the main substance and key component of fungal cell wall.It is mainly abundant in nature,also found in cellulose and has many functions,including maintaining the mechanical stability of cells during cell division and polar growth and initially contact with host during fungal infection.Most fungal chitinases belong to the GH18 glycoside hydrolase superfamily and play an important role in different growth stages,including cell wall degradation and modification,such as spore germination,tip growth and mycelial branching,spore differentiation,autolysis and mycoparasitism.To resist pathogens,plants have developed complex immune systems,including plasmalemma receptors that recognize pathogen-related molecular patterns,such as chitin from fungal cell walls,and induce defense responses.Therefore,the identification of pathogen-related molecular patterns in wheat can play an important role in the pathogenesis of wheat stripe rust.According to the genome and transcriptome data from our laboratory,it was found that chitinase gene Pst₂3943 was up-regulated during germination of germ tube and formation of haustorial mother cells of wheat stripe rust.A complete sequence of Pst₂3943 was obtained by PCR amplification and it was projected that Pst₂3943 belong to GH18 glycoside hydrolase superfamily by NCBI blast.Subcellular localization indicated that Pst₂3943 localized in cytoplasm.Silencing the expression of Pst₂3943 decreased sporulation rate significantly.Quantitative analysis of qRT-PCR showed that a large number of defense related genes were expressed in silenced plant.It was confirmed by the DNS method that the active protein expressed by the gene Pst₂3943 can effectively degrade chitin.In summary,Active protein expressed by gene Pst₂3943 can effectively bind to chitinase and degrade chitin,and participate in the pathogenesis of wheat stripe rust to help the stripe rust infestation.It provides a new idea for studying the mechanism of wheat stripe rust infection and wheat disease resistance,and provides some new foundations for future research to improve the resistance of wheat to wheat stripe rust.