Metabolomic And Transcriptomic Analyses Of OsWRKY62 And OsWRKY76 Transgenic Rice Plants

There are about 0.2-1 million metabolic compounds in plant kingdom.Primary metabolites,such as sugar,amino acids,and phenoles,are important for the biosynthesis of protein,starch,and cell wall.These compounds are related to the agricultural production.Plants must arise proper responses to overcome the biotic and abiotic stresses.When the constitutive resistance fails to prevent entry of pathogens,plants are able to activate series of defense responses including the formation of secondary metabolites,such as phenolics,terpenoids,and glucosinolates.Many of these metabolites play a key role in plant disease resistance.WRKY transcription factors are involved in regulating plant response to biotic and abiotic stress.RNA interfering OsWRKY62 and Os WRKY76 transgenetic plants(dsOW62/76)significantly enhanced the disease resistance of Magnaporche oryzae SZ and Xanthomonas oryzae pv.oyzae J18.In order to make the research in metabolites and metabolic pathways involved with plant disease resistance,we analysed the differently accumulated metabolites in dsOW62/76 and wild-type(ZH17)plants,611 compounds in rice and 41 standards were qualified by using LC-TOF-MS/MS,265 compouds were annotated.They were including amino acid and its derivetives,phenylaprapanoid,phenolamides,flavonoids,and terpepoids.We qualitated 13 phytoalexines and 56 phenolamides in rice,34 phenolamides were the first time to be structured in rice.The primary metabolic pathways were activated in dsOW62/76 compared with ZH17,revealed by increased accumulation of amino acids and constituents of citric acid cycle etc.Contents of phenolic acids derived from phenylpropanoid pathway were elevated in dsOW62/76 plants.Importantly,phenolamides,conjugates of the phenolic acids with amines,were detected in large number and mostly at higher levels in dsOW62/76 compared with ZH17 plants;however,the free pools of flavonoids were mostly decreased in dsOW62/76.In the transcriptomics,839 differently expressed genes were found,810 of them were up-regulated,and 29 were down-regulated.They are in the different pathways,including phenylaprapanoid pathway,terpenoids biosynthesis pathway,phytohormone signiling pathway,and pathways involved with biotic stress.Metabolome and transcriptome data had good correlations,plants are priorities to synthesis defence-related compounds to overcome pathogen infection.Salicylic acid(SA)and jasmonic acid(JA)/JA-Ile contents were increased in dsOW62/76 and knockout lines of individual OsWRKY62(W62-KO)and OsWRKY76(W76-KO)genes.Transcription of isochorismate synthase(OsICS1)gene in chloroplast was suppressed in dsOW62/76 and in MeJA-treated rice plants,whereas the transcription level of cinnamoyl-CoA hydratase-dehydrogenase(OsCHD)gene for ?-oxidation in peroxisome was increased.The chd mutant showed markedly decreased SA accumulation.These results indicate that OsWRKY62 and OsWRKY76 function as negative regulators of biosynthetic defense-related metabolites and provide evidence for an important role of phenylpropanoid pathway in SA production in rice.