Function Characterization Of Herbivore Resistance-related Genes OsWRKY24,OsWRKY70and OsNPR1in Rice

In natural, rice plants are always suffered by different herbivores, for example, rice striped stem borer (SSB) Chilo suppressalis, rice brown planthopper (BPH) Niaparvata lugens, rice leaf folder (LF) Cnaphalocrocis medinalis, and so on. Rice large-scale transcriptional changes include activating herbivore induced defense signal pathways and some defense-related genes after infesting by herbivores. Among this, the transcription regulators play a central role. Here, we selected two herbivore induced transcription factors and OsNPRl gene and study the function in herbivore induced resisitance.1) OsWRKY70is strongly induced by mechnical wounding and SSB infested, but weakly induced by BPH infested. OsWRKY70localized in the nucleus, binding W-box motif and is a transcription activator. In vitro pull-down assay demonstrated that OsWRKY70interacted with OsMPK3and OsMPK6, and act downstream of MAPKs. OsWRKY70positively regulated JA, TrypPIs levels and plant resistance to SSB, whereas negatively regulated GA, SA and H2O2levels and rice resistance to BPH. It’s the first time we demastrated that GA signal pathway involved in herbivore induced defense. OsWRKY70is a key node in different herbivore induced signal network.2) OsWRKY24is strongly induced by mechnical wounding and SSB infested, but weakly induced by BPH infested. OsWRKY24also act downstream of MAPKs, slight positively affect JA and TrypPIs levels and rice resistance to SSB, however it has no affection to BPH. We found OsWRKY24contribute little to rice SSB resistance by detected OsWRKY24and OsWRKY70doubt mutant ir-wrky24/70.3) OsNPR1expression levels were up-regulated in response to infestation by the rice striped stem borer (SSB) Chilo suppressalis and rice leaf folder (LF) Cnaphalocrocis medinalis, and to mechanical wounding and treatment with jasmonic acid (JA) and salicylic acid (SA). Moreover, mechanical wounding induced the expression of OsNPR1more quickly than did herbivore infestation. The antisense expression of OsNPR1(as-nprl), which reduced the expression of the gene by50%, increased elicited levels of JA and ethylene (ET) as well as of expression of a lipoxygenase gene OsHI-LOX and an ACC synthase gene OsACS2. The enhanced JA and ethylene signaling in as-nprl plants increased the levels of herbivore-induced trypsin protease inhibitors (TrypPIs) and volatiles, and reduced the performance of SSB. Our results suggest that OsNPR1is an early responding gene in herbivore-induced defense and that plants can use it to activate an effective and specific defense against invaders by modulating signaling pathways. Our result indicated that all three genes involved in rice herbivore induced denfense by regulate plant hormone signal pathways.