Genome-scale analysis of maize ALA genes identifies ZmALA9 as a regulator of saline-alkali tolerance during germination

: P4-type ATPases (ALA) mediate the translocation of phospholipids across biological membranes, thereby establishing and maintaining membrane lipid asymmetry, a property fundamental to plant growth and development. Although ALA gene families have been characterized in several plant species, their composition and biological roles in maize remain poorly defined. In this work, eleven ZmALA genes were uncovered through a genome-wide search of the maize genome. These genes were subsequently characterized with respect to protein properties, structural organization, conserved motifs, evolutionary relationships, and promoter regulatory features. Expression profiling during germination under saline-alkali stress revealed that ZmALA9 is strongly associated with stress responsiveness. An EMS mutant line disrupted in ZmALA9 displayed markedly reduced tolerance to saline-alkali conditions compared with the wild type during germination. Functional evidence suggests that ZmALA9 may operate downstream of the abscisic acid (ABA) signaling pathway, contributing to stress adaptation by maintaining membrane integrity, producing lipid-derived signaling molecules, and regulating membrane-associated processes. Together, our results expand current understanding of the biological roles of the ZmALA gene family and highlight ZmALA9 as a potential genetic resource for enhancing saline-alkali tolerance in maize during germination.