Functional analysis of ZmG6PE reveals its role in responses to low-phosphorus stress and regulation of grain yield in maize

Abstract

A previous metabolomic and genome-wide association analysis of maize screened a glucose-6-phosphate 1-epimerase (<i>ZmG6PE</i>) gene, which responds to low-phosphorus (LP) stress and regulates yield in maize's recombinant inbred lines (RILs). However, the relationship of <i>ZmG6PE</i> with phosphorus and yield remained elusive. This study aimed to elucidate the underlying response mechanism of the <i>ZmG6PE</i> gene to LP stress and its consequential impact on maize yield. The analysis indicated that ZmG6PE required the Aldose_epim conserved domain to maintain enzyme activity and localized in the nucleus and cell membrane. The <i>zmg6pe</i> mutants showed decreased biomass and sugar contents but had increased starch content in leaves under LP stress conditions. Combined transcriptome and metabolome analysis showed that LP stress activated plant immune regulation in response to the LP stress through carbon metabolism, amino acid metabolism, and fatty acid metabolism. Notably, LP stress significantly reduced the synthesis of glucose-1-phosphate, mannose-6-phosphate, and β-alanine-related metabolites and changed the expression of related genes. <i>ZmG6PE</i> regulates LP stress by mediating the expression of <i>ZmSPX6</i> and <i>ZmPHT1.13</i>. Overall, this study revealed that <i>ZmG6PE</i> affected the number of grains per ear, ear thickness, and ear weight under LP stress, indicating that <i>ZmG6PE</i> participates in the phosphate signaling pathway and affects maize yield-related traits through balancing carbohydrates homeostasis.