State Key Laboratory of Plant Physiology and Biochemistry (SKLPPB) and National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing 100193, China.
State Key Laboratory of Plant Physiology and Biochemistry (SKLPPB), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Plant Cell. 2022 Oct 27;34(11):4232-4254. doi: 10.1093/plcell/koac256.
Maternal-to-filial nutrition transfer is central to grain development and yield. nitrate transporter 1/peptide transporter (NRT1-PTR)-type transporters typically transport nitrate, peptides, and ions. Here, we report the identification of a maize (Zea mays) NRT1-PTR-type transporter that transports sucrose and glucose. The activity of this sugar transporter, named Sucrose and Glucose Carrier 1 (SUGCAR1), was systematically verified by tracer-labeled sugar uptake and serial electrophysiological studies including two-electrode voltage-clamp, non-invasive microelectrode ion flux estimation assays in Xenopus laevis oocytes and patch clamping in HEK293T cells. ZmSUGCAR1 is specifically expressed in the basal endosperm transfer layer and loss-of-function mutation of ZmSUGCAR1 caused significantly decreased sucrose and glucose contents and subsequent shrinkage of maize kernels. Notably, the ZmSUGCAR1 orthologs SbSUGCAR1 (from Sorghum bicolor) and TaSUGCAR1 (from Triticum aestivum) displayed similar sugar transport activities in oocytes, supporting the functional conservation of SUGCAR1 in closely related cereal species. Thus, the discovery of ZmSUGCAR1 uncovers a type of sugar transporter essential for grain development and opens potential avenues for genetic improvement of seed-filling and yield in maize and other grain crops.
母体到子代的营养传递对谷物的发育和产量至关重要。硝酸盐转运体 1/肽转运体（NRT1-PTR）- 型转运体通常运输硝酸盐、肽和离子。在这里，我们报告了一种玉米（Zea mays）NRT1-PTR 型转运体的鉴定，该转运体能够运输蔗糖和葡萄糖。这种糖转运体的活性，被命名为蔗糖和葡萄糖载体 1（SUGCAR1），通过示踪标记的糖摄取和一系列电生理研究，包括双电极电压钳、非侵入性微电极离子通量估计测定在非洲爪蟾卵母细胞中的研究，以及在 HEK293T 细胞中的膜片钳研究得到了系统的验证。ZmSUGCAR1 在基部胚乳传递层中特异性表达，ZmSUGCAR1 的功能丧失突变导致蔗糖和葡萄糖含量显著降低，随后玉米籽粒收缩。值得注意的是，SbSUGCAR1（来自高粱）和 TaSUGCAR1（来自小麦）的 ZmSUGCAR1 同源物在卵母细胞中显示出相似的糖转运活性，支持 SUGCAR1 在密切相关的谷类物种中的功能保守性。因此，ZmSUGCAR1 的发现揭示了一种对谷物发育至关重要的糖转运体，为玉米和其他谷物作物的种子灌浆和产量的遗传改良开辟了潜在途径。
