Ethylene increases the NaHCO₃ stress tolerance of grapevines partially via the VvERF1B-VvMYC2-VvPMA10 pathway

Here, we evaluated the role of ethylene in regulating the NaHCO₃ stress tolerance of grapevines and clarified the mechanism by which VvERF1B regulates the response to NaHCO₃ stress. The exogenous application of ACC and VvACS3 overexpression in grapevines and grape calli revealed that ethylene increased NaHCO₃ stress tolerance, and this was accompanied by increased plasma membrane H⁺-ATPase (PMA) activity. The expression of VvERF1B was strongly induced by ACC, and overexpression of this gene in grapevines conferred increased NaHCO₃ stress tolerance and enhanced PMA activity and H⁺ and oxalate secretion. Additionally, the function of VvERF1B was also verified using mutant transgenic grape calli and overexpression in Arabidopsis plants. The expression of VvPMA10 was strongly induced following the overexpression of VvERF1B in grapevine roots, and VvPMA10 was shown to regulate PMA activity, oxalate and H⁺ secretion, and NaHCO₃ stress tolerance via its overexpression and mutation in grapevine roots, calli, and/or Arabidopsis. However, VvPMA10 was not a direct target gene of VvERF1B but was directly transactivated by VvMYC2. The function of VvMYC2 was shown to be similar to that of VvPMA10 via its overexpression and mutation in grape calli. Additional experiments revealed that the interaction of VvERF1B with VvMYC2 increased its ability to activate VvPMA10 expression and that VvMYC2 played a role in the VvERF1B-mediated pathway. Overall, the VvERF1B-VvMYC2-VvPMA pathway played a role in regulating ethylene-induced NaHCO₃ stress tolerance in grapevines, and this process contributed to increases in PMA activity and H⁺ and oxalate secretion.