OsAOC Participates in Rice (Oryza sativa) Resistance to Rice Blast and Bacterial Blight by Regulating Basal Immunity
LIN Qiao-Xia1, XU Dan-Jie1, LING Yu1, LI Zheng-Kang1, ZHUANG Xiao-Qian1, YI Zi-Jun1, LI Rui-Xue1, CHEN Xiao-Ting1,*, LU Guo-Dong2
1 College of Life Sciences/Fujian Provincial Key Laboratory for Plant and Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou 350002, China; 2 Key Laboratory of Biopesticide and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou 350002, China
Abstract：Rice (Oryza sativa) allene oxide cyclase (OsAOC) is an important enzyme in the jasmonic acid (JA) biosynthesis pathway and is involved in development and stress responses. However, the research on the molecular mechanism of OsAOC in rice's disease resistance to rice blast and bacterial blight is rather limited. In this study, the expression levels of OsAOC in wild type 'Nipponbare' (NPB) were induced by the inoculation of Magnaporthe oryzae, methyl jasmonate (MeJA) and salicylic acid (SA) treatments. Then, the OsAOC knockout (OsAOC-KO) and OsAOC overexpression (OsAOC-OE) transgenic rice lines were obtained. Further study showed that OsAOC knockout led to growth defects and even death in rice. This phenotype could be alleviated by spraying MeJA to the seedlings. The plants overexpressing OsAOC showed enhanced resistance to the inoculation of M. oryzae and Xanthomonas oryzae pv. oryzae (Xoo). Under the induction of chitin and bacterial flagellin (flg22), reactive oxygen species (ROS) accumulation in OsAOC-OE was significantly higher than that of NPB (P<0.05). The expression of JA pathway genes (OsAOC and OsJAZ8) and SA pathway genes (OsPR1b and OsPAL1) in OsAOC-OE were up-regulated compared with NPB after inoculation with M. oryzae. Subcellular localization analysis showed that OsAOC protein was localized in chloroplasts. The interactions between OsAOC and OsOPR3 as well as OsbZIP81 were confirmed by yeast two-hybrid, glutathione-S-transferase (GST) pull-down and luciferase complementation assays. This study confirmed the localization and protein interaction of OsAOC in rice. OsAOC was involved in the pattern-triggered immunity (PTI) response of rice and mediated disease resistance response through the JA and SA pathways, positively regulating rice resistance to rice blast and bacterial blight. This study provides genetic resources for the breeding of disease-resistant rice varieties.
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