Comprehensive genomic analysis of the maize ACP gene family reveals ZmACP1-mediated salt stress tolerance in Arabidopsis.

key messageThis study identifies 11 ZmACP genes in maize, revealing their role in salt stress adaptation, with ZmACP1 overexpression enhancing salt tolerance in Arabidopsis. Soil salinity is an escalating global threat that compromises crop yields. Acyl carrier proteins (ACPs) are essential cofactors of type II fatty acid synthase that determine acyl-chain length and unsaturation, yet their evolutionary diversification and functional relevance to salt stress remain poorly understood in maize (Zea mays L.). In this study, we identified 11 nonredundant ZmACP genes encoding proteins of 105-141 amino acids that are distributed across eight chromosomes. Phylogenomic analysis of 73 ACPs from seven species revealed two clades that reflected monocot-dicot divergence. Duplication analyses revealed one segmental duplication (ZmACP1/ZmACP5), indicating that the family expanded through small-scale events. We detected 33 collinear gene pairs between maize and four monocots, but none between maize and two dicots, further supporting monocot-dicot divergence. All ZmACPs retained the canonical DSL motif and adopted a four-helix bundle fold. Analysis of the cis-acting elements in the ZmACP promoters revealed their potential involvement in hormone and stress responses. Expression profiling of selected ZmACPs under salt stress revealed rapid induction of ZmACP1, peaking at 6-12 h and then declining. Ectopic overexpression of ZmACP1 in Arabidopsis enhanced salt tolerance, increasing shoot dry weight and chlorophyll retention (SPAD) 2.3 and 4.2-fold, respectively, under 300 mM NaCl, indicating a positive role in the salt response, potentially through mechanisms related to lipid metabolism. Taken together, our integrated genomic, evolutionary, and functional data confirm that ZmACP genes participate in salt stress regulation and provide candidate genes and molecular targets for breeding salt-tolerant maize.