TaMYB39 positively regulates salt tolerance in wheat seedlings.

Abstract

Salt stress severely restricts wheat growth and productivity, yet the regulatory mechanisms governing the abundance and activity of stress-responsive transcription factors remain incompletely understood. In this study, we characterized the wheat MYB transcription factor TaMYB39 and investigated its role in salt tolerance and protein stability. TaMYB39 expression was rapidly induced by NaCl treatment, and the protein was predominantly localized in the nucleus. Transgenic wheat lines overexpressing TaMYB39 exhibited improved growth and greater dry weight under salt stress, whereas RNAi lines showed increased sensitivity. TaMYB39 overexpression was associated with reduced Na⁺ accumulation, enhanced K⁺ retention, a lower Na⁺/K⁺ ratio, increased proline accumulation, and reduced membrane damage. The overexpression lines also accumulated less H2O2 and O2- and exhibited higher SOD, POD, and CAT activities, consistent with enhanced antioxidant capacity. Yeast two-hybrid screening identified the bZIP transcription factor TabZIP27 as a TaMYB39-interacting protein, and this interaction was confirmed by pairwise Y2H, BiFC, GST pull-down, and Co-IP assays. Salt treatment enhanced the TaMYB39-TabZIP27 interaction. Cell-free degradation and CHX chase assays further showed that TabZIP27 delayed TaMYB39 degradation, whereas MG132 treatment attenuated the decline in TaMYB39 abundance, supporting the involvement of the 26S proteasome pathway in TaMYB39 turnover. Collectively, these findings identify TaMYB39 as a positive regulator of salt tolerance in wheat and suggest that its protein stability is modulated through interaction with TabZIP27 under salt stress.