Gibberellic Acids and ethylene antagonistically regulate stem growth via SlGAI-SlERF1B-SlXTH19 module in tomato.
TL;DR
Results reveal a signaling module in which GA signaling modulates the degradation of SlGAI, attenuates ethylene (ETH) signaling to inhibit SlXTH19 expression, and regulates stem growth in tomato plants.
Abstract
Stem growth and development greatly influence on plant architecture and yield, which are intimately associated with cell wall remodeling. However, the regulatory mechanisms governing cell-wall remodeling in crops remain poorly understood. Xyloglucan endotransglucosylase/hydrolase (XTH) plays a pivotal role in xyloglucan metabolism. Here, we demonstrated that SlXTH19 controls cell wall remodeling and stem growth. Knockout or knockdown of SlXTH19 decreased cell wall thickness and cellulose and hemicellulose content in tomato stems. We demonstrated that ETHYLENE RESPONSE FACTOR (ERF) transcription factor SlERF1B binds directly to the SlXTH19 promoter, repressing its expression. Knockdown of SlERF1B showed greater stem growth and cell wall composition, whereas SlERF1B-overexpressing plants had a shorter plant heights and thinner stems than the wild type. Further investigation revealed that SlERF1B directly binds to the SlGA3ox1 promoter and represses production of GA. In addition, SlGAI, the core negative regulator of GA signaling, interacts with SlERF1B, and these interactions enhanced the inhibitory effect of SlERF1B on its downstream targets SlXTH19 and SlGA3ox1. Collectively, these results reveal a signaling module in which GA signaling modulates the degradation of SlGAI, attenuates ethylene (ETH) signaling to inhibit SlXTH19 expression, and regulates stem growth in tomato plants.