MaMAPK3-MaICE1-MaPOD P7 pathway, a positive regulator of cold tolerance in banana.

BACKGROUND: Banana is a tropical fruit with a high economic impact worldwide. Cold stress greatly affects the development and production of banana. RESULTS: In the present study, we investigated the functions of MaMAPK3 and MaICE1 involved in cold tolerance of banana. The effect of RNAi of MaMAPK3 on Dajiao (Musa spp. 'Dajiao'; ABB Group) cold tolerance was evaluated. The leaves of the MaMAPK3 RNAi transgenic plants showed wilting and severe necrotic symptoms, while the wide-type (WT) plants remained normal after cold exposure. RNAi of MaMAPK3 significantly changed the expressions of the cold-responsive genes, and the oxidoreductase activity was significantly changed in WT plants, while no changes in transgenic plants were observed. MaICE1 interacted with MaMAPK3, and the expression level of MaICE1 was significantly decreased in MaMAPK3 RNAi transgenic plants. Over-expression of MaICE1 in Cavendish banana (Musa spp. AAA group) indicated that the cold resistance of transgenic plants was superior to that of the WT plants. The POD P7 gene was significantly up-regulated in MaICE1-overexpressing transgenic plants compared with WT plants, and the POD P7 was proved to interact with MaICE1. CONCLUSIONS: Taken together, our work provided new and solid evidence that MaMAPK3-MaICE1-MaPOD P7 pathway positively improved the cold tolerance in monocotyledon banana, shedding light on molecular breeding for the cold-tolerant banana or other agricultural species.

Cold-inducible MaC2H2s are associated with cold stress response of banana fruit via regulating MaICE1.

KEY MESSAGE: MaC2H2s are involved in cold stress response of banana fruit via repressing the transcription of MaICE1. Although C2H2 zinc finger proteins have been found to be involved in banana fruit ripening through transcriptional controlling of ethylene biosynthetic genes, their involvement in cold stress of banana remains elusive. In this study, another C2H2-ZFP gene from banana fruit was identified, which was named as MaC2H2-3. Gene expression analysis revealed that MaC2H2-1, MaC2H2-2 and MaC2H2-3 were cold inducible in the peel of banana during low temperature storage. MaC2H2-3 functions as a transcriptional repressor and localizes predominantly in nucleus. Particularly, promoters of MaC2H2-2 and MaC2H2-3 were noticeably activated by cold as well, further indicating the potential roles of C2H2 in cold stress of banana. Moreover, MaC2H2-2 and MaC2H2-3 significantly repressed the transcription of MaICE1, a key component in cold signaling pathway. Overall, these findings suggest that MaC2H2s may take part in controlling cold stress of banana through suppressing the transcription of MaICE1, providing new insight of the regulatory basis of C2H2 in cold stress.