Gibberellin signaling regulates pectin biosynthesis in Arabidopsis.

Pectin is an abundant polysaccharide with essential roles in various biological processes. Despite considerable advances in understanding the regulatory mechanisms of pectin biosynthesis, the influence of phytohormones on this process remains unclear. Here we report that gibberellins (GA) promotes pectin biosynthesis in Arabidopsis. The DELLA proteins, as GA signaling repressors, interact with TRANSPARENT TESTA GLABRA2 (TTG2) and components of the MYB-bHLH-WD40 (MBW) complex, the key regulators of pectin biosynthesis, to repress their transcriptional regulatory activities. Furthermore, the MBW proteins and TTG2 physically interact and synergistically activate the downstream target GLABRA2, whereas this interaction and collaboration are competitively attenuated by DELLAs. Genetic analyses validate that GA-mediated pectin biosynthesis relies on functional TTG2 and MBW proteins. Moreover, the pectin biosynthesis mediated by the GA-DELLA-MBW-TTG2 module contributes to GA-regulated seedling growth. Our findings reveal the significance of the GA-DELLA-MBW-TTG2 signaling cascade in the regulation of pectin biosynthesis and plant development.