| Summary: | 碩士 === 國立臺灣大學 === 植物科學研究所 === 105 === Sweet potato IbNAC1 is known that activates the defense programs against herbivory. Previous study reported that two bHLH transcription factors, IbbHLH3 and IbbHLH4, dynamically coordinate the expression of IbNAC1 during wounding. In this study, we evidenced that IbbHLH4 interacts with IbbHLH3 by binding the end of HLH-domain of IbbHLH3 which is higher diversity compared to other bHLH homologous. Several proteins, including IbJAZs and IbEIL1, were found that interact with IbbHLH3 to regulate wounding response. When sweet potato leaves are exposed to wounding, the transcriptions of IbJAZ2 and IbEIL1 are immediately repressed, while the expression of IbbHLH3 is induced. The IbbHLH3-IbbHLH3 protein complex activates IbNAC1 against herbivory. Until late wounding, the expression of IbJAZ1 is elevated that repressed the activation function of IbbHLH3 by forming IbbHLH3-IbJAZ1 protein complex as IbbHLH3-IbbHLH4 complex. To characterize the biological functions of these IbbHLH3-intereacting proteins, the genes were overexpressed into Arabidopsis by 35S promoter. Among these transformants, the phenotype of IbJAZ2-overexpressing plants had no significant difference under JA treatment compared with WT. On the other hand, IbJAZ1-overexpressing plants showed insensitity to JA-inhibited anthocyanin accumulation, JA-inhibited root formation, and decrease of JA-regulated defence gene VSP2, LOX2, and COI1. Moreover, overexprssion of IbEIL1 also exhibited JA-insensitive response as IbJAZ1. These results suggested that the IbbHLH3-interacting proteins are multifunctional in response to wound-induced JA responses in sweet potato.
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