Abstract9-cis-epoxycarotenoid dioxygenase (NCED) is the rate-limiting enzyme for abscisic acid (ABA) biosynthesis in higher plants. In rice, OsNCED3 was shown to promote ABA synthesis, and improve abiotic stress tolerance, but the function of OsNCED3 in regulating rice defense against the brown planthopper (Nilaparvata lugens; BPH) has been unclear. In this study, several parameters were used to assess rice resistance to BPH, including the average injury level, the functional plant loss index, and electrical penetration graph analysis. Rice lines overexpressing OsNCED3 (OE) were more resistant to BPH than the wild-type cv. Zhonghua11 (WT). Transcriptome analysis was performed on WT, OE, and a RNAi transgenic line silenced for OsNCED3; these three lines were either infested or non-infested with BPH. Seventeen RNA libraries were compared, and most of the differentially expressed genes (DEGs) were upregulated. The number of DEGs in the RNAi line infested with BPH was significantly higher than the OE, and WT lines, and many DEGs were related to the stress response, and biosynthesis of jasmonic acid. This study shows that overexpression of OsNCED3 in rice improves resistance to BPH, and has potential merit in rice breeding programs.

Background: Exogenous abscisic acid (ABA) could improve rice resistance to brown planthopper (BPH) Nilaparvata lugens. The 9-cis-epoxycarotenoid dioxygenase (NCED) is the rate-limiting enzyme for ABA biosynthesis in higher plants. In rice, OsNCED3 gene promoted ABA synthesis and improved abiotic stress tolerance, but the function of OsNCED3 in regulating rice defense against BPH remains unclear. Results: In this study, the average injury level, functional plant loss index and EPG results of rice conferred that insect-resistance of OE rice lines was significantly higher than that of WT. Then transcriptome analysis of overexpression (OE), RNA interference (RNAi) and wild type (WT) of OsNCED3 in Zhonghua11 rice lines after BPH infestation were performed. Seventeen RNA libraries were obtained from OE, RNAi and WT rice lines at 12 h post BPH infestation. The number of all differential expression genes (DEGs) between OE and WT or RNAi and WT were mostly up-regulated. These accounted for more than 75% of the total number of DEGs for each other. The number of DEGs between RNAi and WT rice lines fed by BPH increased significantly, higher than that between OE and WT, and most of these DEGs were related to the adversity stress and the biosynthesis of JA (jasmonic acid).Conclusions: overexpression of OsNCED3 gene could improve rice resistance to BPH.