RcbHLH59-RcPRs module enhances salinity stress tolerance by balancing Na/K through callose deposition in rose ().

Basic helix-loop-helix (bHLH) proteins play pivotal roles in plant growth, development, and stress responses. However, the molecular and functional properties of bHLHs have not been fully characterized. In this study, a novel XI subgroup of the bHLH protein gene was isolated and identified in rose ( sp). This gene was induced by salinity stress in both rose leaves and roots, and functioned as a transactivator. Accordingly, silencing affected the antioxidant system, Na /K balance, and photosynthetic system, thereby reducing salt tolerance, while the transient overexpression of improved salinity stress tolerance. Additionally, RcbLHLH59 was found to regulate the expression of sets of pathogenesis-related () genes in -silenced (TRV-) and -overexpressing (OE) rose plants. The and transcript levels showed opposite changes in the TRV- and OE lines, suggesting that these two genes are regulated by . Further analysis revealed that RcbHLH59 binds to the promoters of RcPR4/1 and RcPR5/1, and that the silencing of or led to decreased tolerance to salinity stress. Moreover, callose degradation- and deposition-related genes were impaired in - or -silenced plants, which displayed a salt tolerance phenotype by balancing the Na/K ratio through callose deposition. Collectively, our data highlight a new RcbLHLH59-RcPRs module that positively regulates salinity stress tolerance by balancing Na/K and through callose deposition in rose plants.