BcSTP6, a sugar transporter of STP family, modulates flowering time and plant growth by regulating sugar signaling in flowering Chinese cabbage.
TL;DR
A comprehensive analysis of the BcSTP gene family confirms the composition and core features of the BcSTP gene family, reveals the regulatory role of BcSTP6 in bolting and flowering, and provides a foundation for understanding the STP-mediated sugar transport mechanisms underlying plant growth and development.
Abstract
Flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee.), an cultivated variant of Brassica rapa var. chinensis in the Brassicaceae family, is distinguished from Chinese cabbage (Brassica rapa var. chinensis) by its basal leaves, which have non-stippled petioles and slender, grooved leaf stalks. Sugar transport proteins (STPs), a key subfamily within the plant monosaccharide transporter (MST) superfamily, serves as primary hexose transporters that facilitate the transmembrane movement of glucose, fructose, and other hexoses. These proteins play a crucial role in plant growth, development, and responses to environmental stress. We conducted a comprehensive analysis of the BcSTP gene family through genome-wide identification, phylogenetic analysis, tissue expression profiling, yeast functional complementation, and heterologous overexpression assays. Twenty-seven BcSTP genes were identified, grouped into four major clades, and found to share conserved domains, motifs, and genomic structures. Tissue-specific expression profiling showed that most BcSTPs were highly expressed in flowers and flower buds during the flowering stage. Functional complementation in hexose transport-deficient yeast confirmed that BcSTP6 and its homologs (BcSTP6-like1, BcSTP6-like2) possess hexose transport activity, with BcSTP6 capable of transporting glucose, fructose, and galactose, and responding to exogenous glucose treatment. Heterologous overexpression assays demonstrated that BcSTP6 promotes flowering in flowering Chinese cabbage by upregulating flowering-related genes, including FT and LFY. Together, these findings clarify the composition and core features of the BcSTP gene family, reveal the regulatory role of BcSTP6 in bolting and flowering, and provide a foundation for understanding the STP-mediated sugar transport mechanisms underlying plant growth and development.