Molecular And Biochemical Mechanisms Of OsRCI-1 Induced Resistance To BPH And WBPH In Rice

Lipoxygenase（LOX）is a key enzyme involved in plant jasmonate metabolic pathway.The chemicals deviated from LOX not only play important roles in the plant growth,development,but also play essential roles in plants response to biological and abiotic stresses.Rice（Oryza sativa）is an important staple crop in the world,its output and quality would have an important impact on living of population in Asia.Rice Brown planthopper（BPH）or whitebacked planthopper（WBPH）is one of the most important pests in rice cultivate.In this paper,we investigated the roles of a rice lipoxygenase gene OsRCI-1 by means of reverse genetics,rice defense against BPH and WBPH.The results are as follows:（1）qRT-PCR results indicats that OsRCI-1 gene expression levels were up-regulated by mechanical wounding,jasmonic acid（JA）,salicylic acid（SA）treatment and response to BPH female adults.（2）OsRCI-1 positively modulated BPH and WBPH-induced direct resistance of rice.Rice overexpression of OsRCI-1 enhanced the resistance to two rice planthopper;significantly affected the WBPH performance on feeding and oviposition;prolonged developmental duration of WBPH nymphs;significantly decrease the eclosion rate,mass of newly emerged adults;hatching rate of eggs,and first generation female fecundity.The parasite rate of Anagrus nilaparvatae in the mutant strain was significantly increased.（3）Overexpression of OsRCI-1 significantly increased the activity of LOX enzymes.In addition,not only the content of jasmonic acid（JA）and jasmonoy-isoleucine（JA-Ile）but transcript levels of OsHI-LOX、OsAOS2、OsJAR1 and OsJAR2 in mutant rice was significantly higher than that of wild type rice after being attacked by BPH.In mutant plants,activity of rice LOX and content of trypsin inhibitor（TrypPIs）which induced by planthoppers were significantly higher than that in Xiushui 11.（4）The Effect to hydrogen peroxide and ethylene content:After damaged by BPH and WBPH,the content of hydrogen peroxide and ethylene in mutant plants,were significantly higher than those in the control group.Pharmacological methods confirmed that,elevated part of the H₂O₂ produced by the NADPH-oxidase pathway.In addition,the release of partial volatiles in the mutants significantly increased after damaged by two planthopper.Our results indicated that OsRCI-1 gene plays a crucial role in hebivore-induced rice defense by integrated regulating JA、ethylene、hydrogen peroxide,then affects the direct and indirect defense of rice.