Maize stress-associated proteins ZmSAP1 and ZmSAP7 positively regulate salt stress tolerance

Global soil salinization increasingly constrains crop growth and productivity. Stress-associated proteins (SAPs) are key regulators of plant stress responses and development. Here, we characterize two maize SAPs, ZmSAP1 and ZmSAP7, that confer enhanced salt tolerance. ZmSAP1 and ZmSAP7 genes harbor a 531 bp and 516 bp coding sequence (CDS), respectively, encoding intron-less A20/AN1-type zinc-finger proteins, and are ubiquitously expressed across maize tissues. Ectopic overexpression of ZmSAP1 or ZmSAP7 in Arabidopsis and rice significantly improved survival rate, root length, biomass, and relative water content (RWC) under salt stress. The transgenic lines also exhibited reduced relative electrical conductivity (REC), lower malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) levels, and elevated superoxide dismutase (SOD) and peroxidase (POD) activities, indicating enhanced reactive oxygen species (ROS) scavenging in rice. Integrated RNA-seq and qRT-PCR analyses further revealed that ZmSAP1 and ZmSAP7 modulate the expression of multiple stress-responsive genes, thereby bolstering plant salt tolerance. These findings provide a basis for further elucidating the molecular mechanisms underlying SAP-mediated salt stress responses.