State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, 271018, China.
College of Life Sciences, Capital Normal University, Beijing, 100048, China.
Plant Sci. 2021 Jul;308:110901. doi: 10.1016/j.plantsci.2021.110901. Epub 2021 Mar 30.
Nitrogen is an essential macronutrient for plants and regulates many aspects of plant growth and development. Nitrate is one of the major forms of nitrogen in plants. However, the role of nitrate uptake and allocation in seed development is not fully understood. Here, we identified the maize (Zea mays) small-kernel mutant zmnpf7.9 and characterized the candidate gene, ZmNPF7.9, which was the same gene as nitrate transport 1.5 (NRT1.5) in maize. This gene is specifically expressed in the basal endosperm transfer layer cells of maize endosperm. Dysfunction of ZmNPF7.9 resulted in delayed endosperm development, abnormal starch deposition and decreased hundred-grain weight. Functional analysis of cRNA-injected Xenopus oocytes showed that ZmNPF7.9 is a low-affinity, pH-dependent bidirectional nitrate transporter. Moreover, the amount of nitrate in mature seeds of the zmnpf7.9 mutant was reduced. These suggest that ZmNPF7.9 is involved in delivering nitrate from maternal tissues to the developing endosperm. Moreover, most of the key genes associated with glycolysis/gluconeogenesis, carbon fixation, carbon metabolism and biosynthesis of amino acids pathways in the zmnpf7.9 mutant were significantly down-regulated. Thus, our results demonstrate that ZmNPF7.9 plays a specific role in seed development and grain weight by regulating nutrition transport and metabolism, which might provide useful information for maize genetic improvement.
氮是植物必需的大量营养素，调节植物生长和发育的许多方面。硝酸盐是植物中氮的主要形式之一。然而，硝酸盐吸收和分配在种子发育中的作用还不完全清楚。在这里，我们鉴定了玉米（Zea mays）小粒突变体 zmnpf7.9，并对候选基因 ZmNPF7.9 进行了特征描述，该基因与玉米中的硝酸盐转运蛋白 1.5（NRT1.5）相同。该基因在玉米胚乳的基底端胚乳转移层细胞中特异性表达。ZmNPF7.9 功能失调导致胚乳发育延迟、淀粉沉积异常和百粒重降低。对 cRNA 注射非洲爪蟾卵母细胞的功能分析表明，ZmNPF7.9 是一种低亲和力、pH 依赖性双向硝酸盐转运蛋白。此外，zmnpf7.9 突变体成熟种子中的硝酸盐含量减少。这表明 ZmNPF7.9 参与将硝酸盐从母体组织输送到发育中的胚乳。此外，zmnpf7.9 突变体中与糖酵解/糖异生、碳固定、碳代谢和氨基酸生物合成途径相关的大多数关键基因显著下调。因此，我们的研究结果表明，ZmNPF7.9 通过调节营养物质的运输和代谢，在种子发育和粒重中发挥特定作用，这可能为玉米遗传改良提供有用信息。
