Kernel development plays an important role in determining kernel size in maize. Here we present the cloning and characterization of a maize gene, nitrate transporter1.5 (NRT1.5), which controls small kernel phenotype by playing an important role in kernel development. A novel recessive small kernel mutant miniature2-m1 (mn2-m1) was isolated from self-pollinated progenies of breeding materials. The mutant spontaneously showed small kernel character arresting both embryo and endosperm development at an early stage after pollination. Utilizing 21 polymorphic SSR markers, the mn2-m1 locus was limited to a 209.9-kb interval using 9 176 recessive individuals of a BC₁ segregating population from mn2-m1/B73. Only one annotated gene was located in this 209.9 kb region, Zm00001d019294, which was predicted to encode nitrate transporter1.5 (NRT1.5). Allelism tests confirmed that mn2-m1 was allelic to miniature2-m2 (mn2-m2) and miniature2-710B (mn2-710B). The mn2-m1 and mn2-m2 alleles both had nucleotide deletions in the coding region resulting in premature termination, and the mn2-710B allele had some missence mutations. Subcellular localization showed that Miniature 2 (MN2) is localized in the plasma membrane. Quantitative real-time PCR (qRT-PCR) analysis revealed that the expression of MN2 and some genes involved in the basal endosperm transfer layer (BETL) and embryo surrounding region (ESR) development were affected in mn2-m1 seeds. These results suggested that MN2 plays an important role in maize seed development.

内核发育在确定玉米的内核大小中起着重要作用。在这里，我们介绍了玉米基因硝酸盐转运蛋白1.5（NRT1.5）的克隆和鉴定，该基因通过在玉米粒发育中发挥重要作用来控制小的玉米粒表型。从繁殖材料的自花授粉后代中分离出一种新型隐性小核突变体微型2 - m1（mn2-m1）。该突变体在授粉后的早期就自发地表现出小的内核特征，从而阻止了胚胎和胚乳的发育。利用21个多态性SSR标记，使用9 176个BC ₁隐性个体将mn2-m1基因座的间隔限制为209.9-kb将人口与mn2-m1 / B73隔离。仅一个注释的基因位于这个209.9 kb区域Zm00001d019294中，预计该基因编码硝酸盐转运蛋白1.5（NRT1.5）。等位性测试证实，mn2-m1与微型2 - m2（mn2-m2）和微型2-710B（mn2-710B）等位。的MN2-M1和MN2-M2等位基因均具有核苷酸缺失，导致过早终止的编码区，并且mn2-710B等位基因有一些缺失突变。亚细胞定位显示微型2（MN2）定位在质膜中。定量实时PCR（QRT-PCR）分析显示，表达MN2和参与基础胚乳转移层（BETL）和胚胎周围区域（ESR）发展的一些基因受到影响MN2-M1种子。这些结果表明，MN2在玉米种子发育中起重要作用。