Banana MaABI5 is involved in ABA-induced cold tolerance through interaction with a RING E3 ubiquitin ligase, MaC3HC4-1

Abscisic acid (ABA) is a phytohormone essential for the adaptation of plants to environmental stresses, and transcription factor abscisic acid-insensitive 5 (ABI5) is a key regulator of ABA signaling and response. Although exogenous application of ABA is effective in retarding chilling injury (CI) symptoms of banana fruit, the possible roles of ABI5 in ABA-induced chilling tolerance in banana fruit remain largely unknown. In this study, ABA treatment significantly induced chilling tolerance in banana fruit, as indicated by the changes in the Cl index, peel color, and relative electrolyte leakage. Moreover, MaABI5, a gene encoding banana ABI5, was induced by ABA treatment during low-temperature storage. Importantly, through yeast two-hybrid (Y2H) screening, MaABI5 was found to interact with MaC3HC4-l, a C3HC4-type RING finger E3 ubiquitin ligase. Expression of MaC3HC4-l was downregulated by ABA application. Furthermore, MaC3HC4-l possessed intrinsic ubiquitin ligase activity in vitro. The predicted MaABI5-MaC3HC4-l network will help decipher the possible role of ABA in the cold stress signaling pathway of banana fruit.