TaWAK5 perceives OGs to activate drought responses in wheat

INTRODUCTION: Numerous studies have elucidated plants' drought response, yet how plant leaves perceive this stress remains unclear. OBJECTIVES: This study aims to deepen the understanding of how leaves perceive and respond to water loss. METHODS: Detached-leaf water loss rate was detected, which can effectively eliminate the effects of water absorption and water transport. Subsequently, a genome-wide association study (GWAS) was carried out on the detached-leaf water loss rate. RESULTS: There was a significant association between the TaWAK5 (cell wall-associated kinase) gene and the detached-leaf water loss rate. Phenotypic analyses of overexpression and CRISPR/Cas9-based knockout lines revealed the function of TaWAK5 in wheat response to drought stress. Subsequent study exhibited that drought induced the degradation of pectin into oligogalacturonides (OGs), and OGs have a higher affinity for TaWAK5 than pectin does. OGs can activate TaWAK5 kinase, leading to stomatal closure. Additionally, TaWAK5 phosphorylates TaSLAC1 (slow anion channel-associated 1), a key component regulating stomatal movement. A single nucleotide polymorphism site SNP-947 (G/A), at 947 bp of the cis-element in the TaWAK5 promoter region, is significantly associated with TaWAK5 expression, detached-leaf water loss rate and canopy temperature, and leads to the bZIP transcription factor TaPAN (PERIANTHIA) functioning as a transcriptional activator in haplotype Hap3/4, but not in Hap1/2 of TaWAK5. CONCLUSION: This study suggests that TaWAK5 perceives OGs to activate drought responses in wheat, highlighting a potential target for enhancing the drought tolerance of wheat.