TaWAK5 perceives OGs to activate drought responses in wheat

Numerous studies have elucidated plants' drought response, yet how plant leaves perceive this stress remains unclear.

This study aims to deepen the understanding of how leaves perceive and respond to water loss.

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.

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.

This study suggests that TaWAK5 perceives OGs to activate drought responses in wheat, highlighting a potential target for enhancing the drought tolerance of wheat.