tae-miR9668 negatively regulates TaRPM1-1A to enhance salt tolerance in wheat

Soil salinity severely affects wheat (Triticum aestivum) yield and quality. Identifying salt-tolerance genes and elucidating their mechanisms are essential for improving salt tolerance in this crop. Previously, the wheat microRNA tae-miR9668 was found to be significantly downregulated by salt stress. Tae-miR9668 was predicted to target TaRPM1-1A, but how these two genes are involved in wheat salt tolerance is unclear. Here, we demonstrated that tae-miR9668 negatively regulates TaRPM1-1A expression, as overexpressing tae-miR9668 in transgenic lines suppressed TaRPM1-1A expression, leading to enhanced sensitivity to salt stress. Conversely, transgenic lines overexpressing TaRPM1-1A exhibited significantly enhanced salt tolerance. Under salt stress, TaRPM1-1A-overexpressing plants exhibited reduced oxidative damage, as shown by reduced MDA content and reactive oxygen species levels. Accordingly, the activities of antioxidant enzymes such as SOD, POD, CAT, and APX increased, together with increased accumulation of osmoprotectants such as proline, soluble sugars, and soluble proteins relative to the control. By contrast, tae-miR9668 overexpression had opposite effects in transgenic plants. Additional molecular studies showed that tae-miR9668 can cleave TaRPM1-1A mRNA, whereas TaRPM1-1A can interact with TaSnRK1.3-D, supporting its role in salt tolerance. Therefore, the tae-miR9668–TaRPM1-1A module might play important roles in salt tolerance in wheat, providing valuable targets for breeding salt-resilient wheat varieties.