RhbHLH92 positively regulates the dehydration tolerance by interacting with RhMYB123 in rose petals (Rosa hybrida)

Drought increasingly constitutes a significant constraint that detrimentally affects plant growth and the productivity of agricultural crops. The bHLHs is pivotal in enabling plants to withstand various abiotic stresses. However, the specific roles of bHLHs in stress remain limited. Here, we explore the role of RhbHLH92 from the Rosa hybrida according to the previous RNA-seq data. The expression of RhbHLH92 was enhanced under several abiotic stress conditions, especially dehydration. RhbHLH92 is located in the nucleus. Enhanced dehydration and drought tolerance were observed in tobacco and rose petals overexpressing RhbHLH92. These genetically modified plants maintained better water balance, showed decreased levels of reactive oxygen species, and exhibited elevated activity of antioxidant enzymes along with increased expression of drought resistance genes compared to WT. Conversely, suppression of RhbHLH92 in rose petals using virus-induced gene silencing (VIGS) heightened their vulnerability to dehydration and reduced the expression of genes associated with stress tolerance. Yeast two-hybrid and BiFC confirmed that RhbHLH92 physically interacts with RhMYB123, a R2R3-type TF. RhMYB123 overexpression in rose petals similarly boosted dehydration tolerance. RhbHLH92 and RhMYB123 could directly bind to the Δ-1-pyrroline-5-carboxylate synthetase (RhP5CS) promoter, the RhbHLH92-RhMYB123 complex led to higher transcript levels of RhP5CS. These findings elucidate a new pathway through which RhbHLH92 enhances drought tolerance in roses, offering potential strategies for the development of drought-resistant crop varieties.