Unraveling GhMYB102: dual roles of Gh_A01G069800 in inhibiting anthocyanin biosynthesis and inducing drought tolerance in cotton

BACKGROUND: Cotton exhibits considerable genetic variation in petal coloration, a trait that plays an important role in plant adaptation by enhancing resistance to pests and diseases, protecting tissues from ultraviolet radiation mitigation, and attracting pollinators. The MYB gene family is known to regulate anthocyanin biosynthesis and thereby influence floral pigmentation. However, the specific regulatory roles of members of the fourth subfamily in cotton flower color formation remain largely unexplored. METHODS: This study investigated the function of the MYB gene Gh_A01G069800 in regulating floral pigmentation using virus-induced gene silencing (VIGS) in cotton. RESULTS: VIGS plants displayed markedly increased pigment intensity across four cotton varieties, with the highest anthocyanin observed in Zhongyihong (5.5 nmol/g) and Y52 (5.7 nmol/g), exceeding the levels detected in their respective wild types. Conversely, overexpression (OE) of Gh_A01G069800 led to reduced pigmentation (3.0 nmol/g) compared with both wild types and mutants, which recorded anthocyanin contents of 4.0 and 7.5 nmol/g, respectively. Gene expression analyses revealed strong upregulation of chalcone synthase (CHS) and flavonoid glycosyltransferase (UFGT) in wild-type plants. In contrast, chalcone isomerase (CHI), flavonoid-3-hydroxylase (F3H), dihydroflavonol-4-reductase (DFR), and anthocyanin synthase (ANS) were significantly upregulated in VIGS plants, indicating that Gh_A01G069800 functions as a negative regulator of anthocyanin biosynthesis. Further analysis demonstrated that GhMYB102 directly suppresses the expression of CHI, ANS, and F3'5'H, thereby modulating anthocyanin production. Overall, these findings suggest that Gh_A01G069800 plays a key regulatory role in floral color formation and may also contribute to enhanced drought tolerance in cotton plants.