GASA/snakin proteins in plants: structural conservation, phylogenomic expansion, and functional diversity.

Plant GASA/Snakin proteins (GASA: Gibberellic Acid-Stimulated Arabidopsis) constitute a family of secreted cysteine-rich peptides. The family is defined by 12 highly conserved cysteine residues forming up to six disulfide bonds within a thermostable helical scaffold. Phylogenetically restricted to vascular plants, the family ranges from 10 members in rice to approximately 40 in polyploid species such as peanut (Arachis hypogaea), with paralogous expansion driven by whole-genome, segmental, and tandem duplication events, while the 12-cysteine spacing pattern is maintained under purifying selection across surveyed lineages. Phylogenetic analyses predominantly resolve three conserved subfamilies across monocots and eudicots, generally associated with GA-responsive growth regulation (Subfamily I), antimicrobial defense (Subfamily II), and abiotic stress adaptation (Subfamily III). GASA/Snakin proteins integrate inputs from at least six phytohormone pathways-gibberellin (GA), abscisic acid (ABA), brassinosteroid (BR), salicylic acid (SA), jasmonic acid (JA), and auxin-through combinatorial cis-regulatory elements and direct protein-protein interactions; GA, ABA, and BR integration is most robustly validated experimentally, whereas JA and auxin connections remain primarily inferential. Their redox output (antioxidant protection versus oxidative sensitization) is subfamily-specific and modulated by metal-binding capacity and cellular context. Given the rapid accumulation of genome-wide characterizations across more than 35 species between 2020 and 2026, this review synthesizes evolutionary, structural, regulatory, and functional dimensions of the GASA/Snakin family into a unified redox-hormone hub model, identifies critical knowledge gaps including the absence of any identified receptor and the limited availability of experimental three-dimensional structures, and outlines a research roadmap toward translational deployment in sustainable agriculture.