The Interaction Between MaWRKY26 And MaVQ5 Involving In The Regulation Of MeJA-Induced Chilling Tolerance Of Banana Fruit

Banana fruit are highly susceptible to chilling injury when the storage temperature is below 13 ?. Therefore, it is important to understand the regulatory mechanism of chilling injury or induced chilling tolerance of banana fruit in order to maintain its commercial quality. The plant-specific WRKYs are key transcription factors(TF) that play important roles in plant growth, development and stress responses, as well as jasmonic acid(JA). However, the transcriptional regulatory mechanism of JA biosynthesis by WRKY in relation to Me JA-induced chilling tolerance of banana fruit is rarely investigated.In this study, a cold-responsive Ma WRKY26 was characterized. Moreover, the interaction of Ma WRKY26 with VQ motif-containing protein Ma VQ5 involving in chilling response or chilling tolerance of banana fruit was investigated. The main results are as follows:1. Quantitive real-time PCR analysis reavealed that the expression of Ma WRKY26 was up-regulated by cold stress(7?), and its transcript levels increased rapidly following Me JA treatment during cold storage, suggesting its possible involvement in Me JA-induced chilling tolerance of banana fruit.2. The full-length of Ma WRKY26 was obtained. Amino acid sequence alignment indicated that Ma WRKY26 contained two conserved WRKY domains and belonged to Group I family. Subcellular localization analysis revealed that Ma WRKY26 protein was localized exclusively in the nucleus. Transcriptional activation ability analysis demonstrated that it possessed transcriptional activation activity3. Electrophoretic mobility shift(EMSA) and dual-luciferase reporter(DLR) assays demonstrated that Ma WRKY26 transactivated JA biosynthetic genes such as Ma LOX2, Ma AOS3 and Ma OPR3 via directly binding to their promoters.4. Yeast two-hybrid(Y2H), bimolecular fluorescence complementation(Bi FC) and co-immunoprecipitation(Co-IP) assays revealed that Ma WRKY26 physically interacted with a VQ-motif protein Ma VQ5, and their interaction attenuated the transactivation of WRKY26 to JA biosynthetic genes.These results strongly suggest that Ma WRKY26 is involved in cold reponse or Me JA induced-chilling tolerance of banana fruit via the transcriptional regulation of JA biosynthetic genes, while this process is antagonized by Ma VQ5.