Function Analysis Of MoPEX20 Genes In Magnaporthe Oryzae

Magnaporthe oryzae caused rice blast,the most distructive disase rise.Magnaporthe oryzae is the model fungus in the study on pathogenic fungi interactions.The pathogenesis of M.oryzae is an important part of plant pathology.Along with the advances in research on gene function in the fungus,the roles played by various organelles,such as peroxisome,mitochondria and endoplasmic reticulum,in fungal infection were paid more attention,Peroxisomes,single membrane bound organelles,are ubiquitously present and participate in a variety of important biochemical metabolism in eukaryotes,and were demonstrated to play vital roles in the pathogenicity of plant pathogenic fungi.Peroxisomes originate from the endoplasmic reticulum.Since peroxisomes do not contain their own DNA,their matrix enzymes and membrane proteins are encoded by nuclear genes,synthesized in the cytoplasm,and then recognized and transported into the organelles relying on peroxisomal targeting signal(PTS).Proteins involved in peroxisome biogenesis are designated as peroxins and encoded by PEX genes.More than 30 PEX genes have identified in filamentous fungi so far.Our previous study showed that the receptors of PTS1(Pex5p)and PTS2(Pex7p)play shared and distinct roles in the infection process of the rice blast fungus.However,the functions of the PTS2 co-receptor(Pex20p)in peroxisome biogenesis and its roles in fungal pathogenicity were kept unclear yet.In present work the PEX20 gene in M.oryzae(MoPEX20)was functionally characterized.The results are as follows:1.Thirty hygromycin resistant transformants of MoPEX20 were selected via Agrobacterium mediated transformation.From them,25 gene deletion mutants were obtained and confirmed by PCR.2.The virulence of MoPEX20 deletion mutants was remarkably reduced on rice and barley leaves,compared with that of the wild type3.The PTS2 peroxisome import pathway,other than PTS1,was disordered in the MoPEX20 deletion mutants.4.The radial growth of the MoPEX20 deletion mutants on complete medium was unchanged.But the colony of the mutants generated much fewer aerial hyphae than that of the wild type.5.The growth on media with various lipids showed that the ability of lipid utilization of MoPEX20 deletion mutants was reduced significantly.6.The growth of MoPEX20 deletion mutant was inhibited in greater levels than that of the wild type on media with Congo red or calcofluor white,indicating the deletion of MoPEX20 led to deficient cell wall of the fungus.7.On the media containing hydrogen peroxide or methyl viologen the growth of MoPEX20 deletion mutants was nhabited in greater levels than the wild type indicating that the MoPEX20 gene deletion reduced the tolerance of fungus to reactive oxygen species(ROSs).8.Conidia were allowed to germinate and form appressoria on the surface of Terylene.The MoPEX20 deletion mutants kept the unchanged capacity to germinate and differentiate appressoria.9.The appressoria generated by MoPEX20 deletion mutants were in a lighter color that those of the wild type.Lots of lipid droplets were found undegraded and remained in conidia and germtubes of the mutants which formed the appressoria.Meanwhile,the appressorial turgor of the mutants was significantly decreased,compared with that of the wild type.In summary,our results indicated that MoPEX20 gene participate PTS2 peroxisomal import pathway,are required in the peroxisomal metabolism,and full virulence of the rice blast fungus.