PpBRE1A-PpHY5L-PpGA2ox5 cascade module regulating drought resistance in Poa pratensis L.
Drought is a major abiotic stress that compromises turfgrass quality and escalates maintenance costs in urban and recreational landscapes. Although gibberellin (GA) plays a central role in coordinating plant growth and stress responses, the regulatory network governing GA dynamics in drought-exposed turfgrasses remains elusive. Here, we show that drought stress enhances drought resistance in Kentucky bluegrass (Poa pratensis L.) by inducing PpGA2ox5, a gene encoding a GA-deactivating enzyme, thereby reducing bioactive GA levels. Mechanistically, we identify the bZIP transcription factor PpHY5L as a key upstream repressor that directly binds the PpGA2ox5 promoter to suppress its transcription. Drought alleviates this repression through a dual mechanism: downregulating PpHY5L transcript abundance and upregulating the E3 ubiquitin ligase PpBRE1A. PpBRE1A directly interacts with PpHY5L, promoting its ubiquitination and subsequent degradation via the 26S proteasome pathway. This degradation relieves transcriptional inhibition of PpGA2ox5, enhances GA catabolism, and boosts reactive oxygen species (ROS) scavenging capacity. Collectively, our findings reveal a novel PpBRE1A-PpHY5L-PpGA2ox5 module that fine-tunes GA homeostasis to positively regulate drought adaptation, providing critical molecular targets and a theoretical foundation for breeding stress-resilient turfgrass cultivars.