State Key Laboratory of Plant Physiology and Biochemistry, Engineering Research Center of Plant Growth Regulator, College of Agronomy and Biotechnology, China Agricultural University, Beijing, China.
Jiangsu Key Laboratory of Crop Genetics and Physiology, Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, Yangzhou University, Yangzhou, China.
Plant Biotechnol J. 2023 Dec;21(12):2560-2573. doi: 10.1111/pbi.14153. Epub 2023 Aug 12.
Stomatal density (SD) is closely related to crop drought resistance. Understanding the genetic basis for natural variation in SD may facilitate efforts to improve water-use efficiency. Here, we report a genome-wide association study for SD in maize seedlings, which identified 18 genetic variants that could be resolved to seven candidate genes. A 3-bp insertion variant (InDel1089) in the last exon of Zea mays (Zm) IRX15A (Irregular xylem 15A) had the most significant association with SD and modulated the translation of ZmIRX15A mRNA by affecting its secondary structure. Dysfunction of ZmIRX15A increased SD, leading to an increase in the transpiration rate and CO assimilation efficiency. ZmIRX15A encodes a xylan deposition enzyme and its disruption significantly decreased xylan abundance in secondary cell wall composition. Transcriptome analysis revealed a substantial alteration of the expression of genes involved in stomatal complex morphogenesis and drought response in the loss-of-function of ZmIRX15A mutant. Overall, our study provides important genetic insights into the natural variation of leaf SD in maize, and the identified loci or genes can serve as direct targets for enhancing drought resistance in molecular-assisted maize breeding.
气孔密度（SD）与作物抗旱性密切相关。了解 SD 自然变异的遗传基础可能有助于提高水分利用效率。在这里，我们对玉米幼苗的 SD 进行了全基因组关联研究，鉴定出 18 个遗传变异，可解析为 7 个候选基因。ZmIRX15A（不规则木质部 15A）最后一个外显子中的 3 个碱基插入变异（InDel1089）与 SD 关联最显著，并通过影响其二级结构来调节 ZmIRX15A mRNA 的翻译。ZmIRX15A 的功能失调会增加 SD，导致蒸腾速率和 CO 同化效率增加。ZmIRX15A 编码木聚糖沉积酶，其功能丧失会显著降低次生细胞壁组成中的木聚糖含量。转录组分析显示，ZmIRX15A 突变体在气孔复合体形态发生和干旱响应相关基因的表达发生了显著改变。总的来说，我们的研究为玉米叶片 SD 的自然变异提供了重要的遗传见解，鉴定出的基因座或基因可作为提高分子辅助玉米育种中抗旱性的直接靶标。
