| Rice blast,caused by Magnaporthe oryzae,is a serious threat to worldwide rice production.In recent years,the pathogenic genes of M.oryzae have been widely identified,but the pathogenic mechanism of M.oryzae still needs further analysis.As an important organelle in eukaryotic cells,mitochondria not only provide energy but also participate in signal transduction,cell differentiation,senescence,cell death,maintaining the control of cell cycle and cell growth.These functions make mitochondria a target site for effective disease control.In this study,the functions of three mitochondrial proteins,including Mo Uth1,Mo BI-1,and Mo BI-1b in the pathogenesis of rice blast were analyzed.In previous studies,we found that Mo Whi2 is necessary for the pathogenicity of M.oryzae.In order to further analyze the function of Mo Whi2,we screened the c DNA library of M.oryzae by yeast two hybrid assays with Mo Whi2 as bait and identified a SUN family protein Mo Uth1.In Saccharomyces cerevisiae,Uth1 regulates the mitochondrial activity and participates in a variety of cellular processes.Knockout of Mo UTH1 resulted in reduced growth of vegetative hyphae,white aerial hyphae,significantly reduced conidiation,and defected conidia.The rice seeding infection assay showed that the pathogenicity of M.oryzae decreased significantly in the Mo UTH1 deletion mutant.Rice sheath infection assays and microscopic observation showed that the infected hyphae of the Mo UTH1 deletion mutant were limited in the first infected host cell and did not extend to adjacent cells.In addition,this study showed that the Mo UTH1 deletion mutant was sensitive to oxidative stress and osmotic stress,suggesting that Mo UTH1 was involved in oxidative stress,and cell wall integrity.All these results indicated that Mo UTH1 played an important role in the growth,sporulation,pathogenicity,stress response and cell wall integrity of M.oryzae.In addition,we also analyzed the function of Bax-inhibitor-1 family proteins Mo BI-1and Mo BI-1b in the pathogenesis of M.oryzae.BI-1 is an inhibitor of the pro-apoptotic protein Bax,which can inhibit cell apoptosis in animals and plants.In filamentous fungi,BI-1 homologous genes are widely distributed,but their biological functions are still unknown.In this study,we identified two Bax-inhibitor-1 paralogs proteins,Mo BI-1 and Mo BI-1b in M.oryzae.Knockout of Mo BI-1 and Mo BI-1b genes decreased the conidiation and pathogenicity of M.oryzae,and most of the appressoria of the knockout mutants could only differentiate into primary infected hyphae.Subcellular localization showed that Mo BI-1 and Mo BI-1b were located in mitochondria.Further analysis showed that Mo BI-1and Mo BI-1b were involved in intracellular ATP synthesis.The functional analysis of Mo BI-1 and Mo BI-1b provides a new understanding of the pathogenic mechanism of plant fungi.In the future,we will focus on elucidating the exact role and molecular mechanism of Mo UTH1,Mo BI-1 and Mo BI-1b during M.oryzae infection. |
