Genome-Wide Identification of Maize G Protein Genes and Regulatory Roles of the ZmGG1 Subfamily in Saline-Alkali Stress Response

Saline-alkaline stress is a major constraint in maize (Zea mays L.) production. Heterotrimeric G proteins play pivotal roles in plant stress responses. However, their functional mechanisms in maize under saline-alkaline stress remain poorly understood. This study aimed to characterise the maize G protein gene family and elucidate its regulatory mechanisms in response to saline-alkaline stress. Ten G protein genes (belonging to the Gα, Gβ, and Gγ subunit families) were identified from the maize genome using bioinformatics approaches. Their phylogenetic relationships, gene structures, promoter cis-acting elements, and protein-protein interaction (PPI) networks were systematically analysed. Gene expression patterns in the saline-alkaline tolerant inbred line Zheng58 and the sensitive line Chang7-2 were investigated using qRT-PCR, alongside the determination of reactive oxygen species (ROS)-scavenging enzyme activities. The Gγ subfamily members (ZmGG1, ZmGG3, and ZmGG5) exhibited differential expression patterns. PPI network analysis revealed extensive interactions between G proteins and signalling components such as phospholipase C and MAP kinases. Under stress conditions, Chang7-2 displayed significant fluctuations in ROS-scavenging enzyme activity and accumulation of malondialdehyde (MDA). Therefore, this study elucidated the mechanism by which maize G proteins coordinate saline-alkaline stress responses through subfamily-specific expression regulation and intricate signalling networks, thereby providing potential candidate target genes for breeding stress-tolerant maize.