CtGSTF3 is associated with anthocyanin accumulation and responses to drought and salt stress in safflower (Carthamus tinctorius L.)

Safflower ( Carthamus tinctorius L.) is an economically valuable medicinal and oil-producing crop. Although plant Phi-class glutathione S-transferases (GSTs) mediate vacuolar anthocyanin transport, genome-wide characterization and functional evidence for dual-function GSTF members coordinating anthocyanin accumulation and abiotic stress adaptation in safflower remain scarce. In this study, we performed a genome-wide identification and functional characterization of the Phi-subfamily member CtGSTF3 . Sixty CtGST genes were identified and classified into nine subfamilies, with tandem duplication serving as the major driving force for family expansion. Most CtGST promoters contained abundant hormone- and stress-responsive cis-acting elements. CtGST genes exhibited distinct tissue- and flower-color-specific expression patterns, and multiple members were significantly induced by drought and salt treatments. Heterologous expression of CtGSTF3 rescued leaf anthocyanin deficiency in the tt19 mutant but failed to restore seed-coat phenotype. In yeast, CtGSTF3 enhanced tolerance to salt and mannitol-simulated osmotic stress. In CtGSTF3- complemented lines, CtGSTF3 was associated with elevated expression of anthocyanin biosynthetic and stress-responsive genes, increased superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities, and reduced reactive oxygen species (ROS) accumulation, thereby improving plant drought and salt tolerance. These results suggest that CtGSTF3 may coordinate anthocyanin deposition and ROS-scavenging capacity to reinforce abiotic-stress resistance. This study advances our understanding of the safflower GST family and identifies CtGSTF3 as a promising candidate for safflower molecular breeding. However, all functional analyses were performed in heterologous systems, and no endogenous genetic evidence from safflower is currently available; thus, further validation in safflower is required.