Table_5_Functional analysis of ZmG6PE reveals its role in responses to low-phosphorus stress and regulation of grain yield in maize.xls

A previous metabolomic and genome-wide association analysis of maize screened a glucose-6-phosphate 1-epimerase (ZmG6PE) gene, which responds to low-phosphorus (LP) stress and regulates yield in maize’s recombinant inbred lines (RILs). However, the relationship of ZmG6PE with phosphorus and yield remained elusive. This study aimed to elucidate the underlying response mechanism of the ZmG6PE 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 zmg6pe 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. ZmG6PE regulates LP stress by mediating the expression of ZmSPX6 and ZmPHT1.13. Overall, this study revealed that ZmG6PE affected the number of grains per ear, ear thickness, and ear weight under LP stress, indicating that ZmG6PE participates in the phosphate signaling pathway and affects maize yield-related traits through balancing carbohydrates homeostasis.

此前一项针对玉米的代谢组学分析与全基因组关联分析研究，筛选获得了葡萄糖-6-磷酸1-表异构酶（glucose-6-phosphate 1-epimerase，ZmG6PE）基因。该基因可响应低磷胁迫（low-phosphorus stress，LP），并能调控玉米重组自交系（recombinant inbred lines，RILs）的籽粒产量。然而，ZmG6PE与磷素代谢及籽粒产量之间的关联机制此前仍未明确。本研究旨在阐明ZmG6PE基因响应低磷胁迫的内在分子机制，及其对玉米籽粒产量的调控效应。分析结果显示，ZmG6PE需依赖醛糖表异构酶保守结构域（Aldose_epim conserved domain）以维持其酶活性，且该蛋白定位于细胞核与细胞膜中。在低磷胁迫条件下，zmg6pe基因突变体的生物量与可溶性糖含量均显著下降，但其叶片中的淀粉含量却有所升高。联合转录组（transcriptome）与代谢组（metabolome）分析结果表明，低磷胁迫可通过碳代谢、氨基酸代谢与脂肪酸代谢通路，激活植物响应低磷胁迫的调控网络。值得注意的是，低磷胁迫会显著抑制葡萄糖-1-磷酸（glucose-1-phosphate）、甘露糖-6-磷酸（mannose-6-phosphate）及β-丙氨酸（β-alanine）相关代谢物的合成，并改变相关基因的表达水平。ZmG6PE可通过调控ZmSPX6与ZmPHT1.13的基因表达，参与低磷胁迫响应过程。综上，本研究发现，在低磷胁迫条件下，ZmG6PE可影响玉米的穗粒数、穗粗与穗重，表明ZmG6PE通过调控碳水化合物稳态（carbohydrates homeostasis）平衡，参与磷信号通路（phosphate signaling pathway）并影响玉米产量相关性状。