ABA-Insensitive 5 (ABI5) Is Involved in ABA-Induced Dormancy via Activating PavCIG1/2 Expression in Sweet Cherries

Background/Objectives: In perennial plants, developing floral buds survive winter through entering a dormant state, which is induced by low temperature and abscisic acid (ABA). ABA performs vital functions in the dormancy process. ABA-insensitive 5 (ABI5) transcription factor is a key regulator in the ABA signaling pathway. However, little is known about the regulation of ABI5 in the winter dormancy of sweet cherries. Methods: We identified the sweet cherry ABI5 gene and its expression changes using gene cloning and qRT-PCR. Additionally, we validated the interaction between PavABI5 and PavCIG1/2 using Yeast One-Hybrid and Dual-Luciferase Assays. Results: In this study, we identified a basic leucine zipper (bZIP) family gene ABI5 from the sweet cherry, which was closely related to PduABI5 from Prunus dulcis, PpABI5 from Prunus persica, PmABI5 from Prunus mume, and ParABI5 from Prunus armeniaca, through phylogenetic tree analysis. The seasonal expression pattern showed that the PavABI5 level was increased during the winter dormancy stage and induced by exogenous ABA. Specifically, we found that the expression of cherry cold-induced genes (PavCIG1/2) was positively correlated with PavABI5 expression. Furthermore, PavABI5 directly bound to the ABRE elements in the PavCIG1/2 promoters to activate their expression. We further confirmed that the dormancy-associated MADS-box (DAM) genes DAM4 and DAM5 function downstream of the ABA signaling pathway to regulate bud dormancy in sweet cherries. Conclusions: Our findings suggest a putative regulatory model of ABA-mediated bud-dormancy with PavABI5.