Molecular Pathways of WRKY Genes in Regulating Plant Salinity Tolerance

Salinity is a natural and anthropogenic process that plants overcome using various responses. Salinity imposes a two-phase effect, simplified into the initial osmotic challenges and subsequent salinity-specific ion toxicities from continual exposure to sodium and chloride ions. Plant responses to salinity encompass a complex gene network involving osmotic balance, ion transport, antioxidant response, and hormone signaling pathways typically mediated by transcription factors. One particular transcription factor mega family, WRKY, is a principal regulator of salinity responses. Here, we categorize a collection of known salinity-responding WRKYs and summarize their molecular pathways. WRKYs collectively play a part in regulating osmotic balance, ion transport response, antioxidant response, and hormone signaling pathways in plants. Particular attention is given to the hormone signaling pathway to illuminate the relationship between WRKYs and abscisic acid signaling. Observed trends among WRKYs are highlighted, including group II WRKYs as major regulators of the salinity response. We recommend renaming existing WRKYs and adopting a naming system to a standardized format based on protein structure.