MaJAZ1 Attenuates the MaLBD5-Mediated Transcriptional Activation of Jasmonate Biosynthesis Gene MaAOC2 in Regulating Cold Tolerance of Banana Fruit

摘要

Previous studies indicated that methyl jasmonate (MeJA) treatment could effectively reduce the chilling injury of many fruits, including banana, but the underlying mechanism is poorly understood. In this study, one lateral organ boundaries (LOB) domain (LBD) gene, designated as MaLBDS, was isolated and characterized from banana fruit. Expression analysis revealed that accumulation of MaLBDS was induced by cold temperature and MeJA treatment. Subcellular localization and transactivation assays showed that MaLBDS was localized to the nucleus and possessed transcriptional activation activity. Protein protein interaction analysis demonstrated that MaLBDS physically interacted with MaJAZ1, a potential repressor of jasmonate signaling. Furthermore, transient expression assays indicated that MaLBDS transactivated a jasmonate biosynthesis gene, termed MaAOC2, which was also induced by cold and MeJA. More interestingly, MaJAZ1 attenuated the MaLBDS-mediated transactivation of MaAOC2. These results suggest that MaLBDS and MaJAZ1 might act antagonistically in relation to MeJA-induced cold tolerance of banana fruit, at least partially via affecting jasmonate biosynthesis. Collectively, our findings expand the knowledge of the transcriptional regulatory network of MeJA-mediated cold tolerance of banana fruit.