Genome‑wide analysis of the maize LACS gene family and functional characterization of the ZmLACS9 responses to heat stress

Long-chain acyl-coenzyme A (CoA) synthetases (LACSs) are capable of catalyzing fatty acids to form fatty acyl-CoA thioesters involved in lipid catabolism, serving a crucial role in plant development and adaptation to environmental stresses. However, comprehensive knowledge on LACS family members in maize is lacking to date. In this study, we identified 11 ZmLACS members in maize, divided into four subfamilies based on their phylogenetic relationships and conserved protein motifs. Analysis of their cis-regulatory elements and expression profiles revealed that certain of these ZmLACS genes exhibited high tissue specificity and were regulated by various environmental stimuli - ZmLACS9 in particular was markedly induced by heat and salt stress. The ZmLACS9 protein was found to localize to the chloroplasts, and a ZmLACS9 loss-of-expression mutation resulted in decreased chlorophyll content and fewer thylakoid grana layers compared to the wild type. When exposed to heat stress, the zmlacs9 mutant exhibited a more sensitive phenotype, more damage to chloroplasts, lower photosynthetic rate, and higher reactive oxygen species accumulation. Furthermore, the activation of genes involved in glycolipid synthesis under stress was notably dampened in the zmlacs9 mutant. Together, these findings offer valuable information towards the functional study of the ZmLACS gene family and highlight ZmLACS9 as an excellent candidate gene for heat resistance in maize.