A MYB transcription factor GhTT2 of Gossypium hirsutum regulates proanthocyanidin accumulation and improves osmotic tolerance in Arabidopsis

Several MYB transcription factors have been identified as the regulators of proanthocyanidin biosynthesis in plants. However, limited research has been conducted on the functional characterization of MYBs involved in proanthocyanidin biosynthesis in cotton. In the present study, the MYB transcription factor gene GhTT2, which was differentially expressed in our previous study, was identified from a Gossypium hirsutum cultivar Zongxu 1. GhTT2 has a close genetic relationship with proanthocyanidin-related MYBs. Suppression of GhTT2 expression in cotton resulted in a significant reduction in proanthocyanidin content. Conversely, the overexpression of GhTT2 in Arabidopsis led to a substantial increase in proanthocyanidin abundance. Additionally, GhTT2-overexpresing Arabidopsis lines exhibited improved tolerance to osmotic stress compared to wild-type plants. Furthermore, the transcription levels of osmotic stress response genes AtRD22 and AtMYB41, along with the proanthocyanidin biosynthesis structural gene AtBAN, exhibited significant upregulation in the seedlings of transgenic Arabidopsis compared with those in wild-type plants under the osmotic stress condition. These findings establish a theoretical foundation for comprehensively understanding the mechanisms by which MYB transcription factors regulate the proanthocyanidin biosynthesis and their responses to stress in plants. A MYB transcription factor GhTT2 of Gossypium hirsutum functions as a positive regulator in the accumulation of proanthocyanidins and has the potential to improve plant resistance to osmotic stress.