VvbHLH10 promotes axillary bud growth and salt-alkali tolerance in grapevine

Abstract Salt‑alkali stress severely constrains grape ( Vitis vinifera ) growth and productivity, yet the underlying molecular mechanisms remain largely elusive. Here, we identify VvbHLH10, a group 9 bHLH transcription factor, as a positive regulator of salt‑alkali tolerance in grapevine. VvbHLH10 transcription is rapidly and strongly induced by salt and alkali treatments, and the gene is predominantly expressed in actively growing tissues, including latent buds, young stems, and young tendrils. The VvbHLH10‑GFP fusion protein localizes to the nucleus. Using a combination of homologous overexpression in grape calli and heterologous expression in tomato, we demonstrate that VvbHLH10 confers enhanced salt‑alkali tolerance. Overexpression of VvbHLH10 significantly improved the survival and growth of grape calli under salt and alkali stress, accompanied by reduced accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA). Similarly, transgenic tomato lines overexpressing VvbHLH10 exhibited markedly improved tolerance to salt‑alkali treatment compared with the controls, as evidenced by reduced oxidative damage and better overall growth. Remarkably, beyond its stress‑protective function, ectopic expression of VvbHLH10 in tomato promoted axillary bud outgrowth and altered vegetative architecture, implicating this transcription factor in both stress defense and developmental regulation. Collectively, our findings position VvbHLH10 as a promising candidate for genetic improvement of salt‑alkali tolerance and plant architecture in grapevine, and broaden our understanding of the functional diversification of bHLH transcription factors in horticultural crops.