| Maize dwarf mosaic disease(MDMD)is widely distributed in global maize producting areas.Sugarcane mosaic virus(SCMV)is the most important pathogen of MDMD in Europe and China.Studuies on the SCMV infection-regulated maized proteins and their roles in SCMV multireplication will contribute to dissecting the pathogenesis of SCMV and exploring new strategies to control MDMD.To identify maize proteins regulated by SCMV infection and to find proteins involved in SCMV multireplication,a comparative proteomic analysis was performed with the first(source leaf)and second(sink leaf)systemically-infected leaves(termed 1 SL and 2 SL,respectively)of the model maize line B73.Totally,71 significantly different expressed proteins(DEPs)were identified,among which eight were common regulated in both 1 SL and 2 SL in similar changing patterns.GO analysis showed that DEPs in 1 SL mainly were involved in phytosynthesis(28%),carbon metabolism(16%),stress and defense(14%),and amino acid metabolism(12%),while in 2 SL were mainly in redox processes(23%),amino acid metabolism(16%),carbon metabolism(13%),protein metabolic and modification(13%)and signal transduction(13%).Subcellular location analysis shwed that DEPs in 1 SL mainly located at chloroplast(47%),cytoplasm(31%),endoplasmic reticulum(ER)(6%)and mitochondria(6%),while in 2 SL mainly at cytoplasm(45%),chloroplast(29%),ER(10%)and mitochondria(7%).Western blot confirmed the proteomic data.Furthermore,reverse transcript-quantitative PCR showed most of DEPs were regulated at transcriptional level and minor DEPs were regulated at post-transcriptional level.Analyses of photosynthesis-associated proteins showed there were 12 DEPs down-regulated by SCMV infection in 1 SL,while only two proteins(which were also identified in 1 SL)were regulated in 2 SL.Measurement of photosynthesis parameters indicated that SCMV infection decreased the photosynthesis of 1 SL while no similar effects were observed in 2 SL.Ananlysis of DEPs involved in redox process showed that in 1 SL,SCMV infection upregulated proteins responsible for ROS production and downregulated proteins for ROS scavenging,while in 2 SL the accumulation levels of proteins for ROS production and proteins for scavenging ROS were both significantly increased.Measurement of H2O2 accumulation indicated that SCMV infection significantly up-regulated H2O2 production in 1 SL but not in 2 SL.Protein disulfide isomerase-like(ZmPDIL),phosphoglycerate kinase(ZmPGK)and polyamine oxidase(ZmPAO)were up-regulated both in mRNA and protein levels in 1 SL and 2 SL following SCMV infection.To investigate the potential functions of ZmPDIL,ZmPGK and ZmPAO during SCMV infection,knockdown of these three genes using a brome mosaic virus-based VIGS system was performed.Silencing of ZmPDIL and ZmPGK decreased SCMV accumulation,indicating that ZmPDIL and ZmPGK are essential host factors for SCMV multireplication.In contrast,knockdown of ZmPAO significantly increased SCMV accumulation,implying that ZmPAO might contribute to resistance or tolerance.Moreover,the role of phenylalanine ammonia lyase(ZmPALs)and salicylic acid(SA)during SCMV infection were studied.SCMV infection induced SA accumulation in maize leaves,while SA treatment significantly enhanced maize resistance to SCMV infection.Silencing of ZmPALs reduced SA accumulation and contributed to SCMV accumulation in systemically infected leaves.However,exogenous SA application partially recovered PAL-mediated resistance to SCMV in the ZmPALs-silencing maize plants.To our knowledge,this is the first time illustration about the function of ZmPALs in maize plants resistance to SCMV infection.These results revealed that ZmPALs played a vital role in SA-dependent signalling of defence response to SCMV infection.These data provide molecular reference for anti-SCMV breeding. |
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