National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences and Collaborative Innovation Center of Genetics & Development, Shanghai Institute of Plant Physiology & Ecology, Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
University of the Chinese Academy of Sciences, Beijing, 100049, China.
J Integr Plant Biol. 2020 May;62(5):581-600. doi: 10.1111/jipb.12820. Epub 2019 Sep 9.
Auxin is a crucial phytohormone, controlling multiple aspects of plant growth and responses to the changing environment. However, the role of local auxin biosynthesis in specific developmental programs remains unknown in crops. This study characterized the rice tillering and small grain 1 (tsg1) mutant, which has more tillers but a smaller panicle and grain size resulting from a reduction in endogenous auxin. TSG1 encodes a tryptophan aminotransferase that is allelic to the FISH BONE (FIB) gene. The tsg1 mutant showed hypersensitivity to indole-3-acetic acid and the competitive inhibitor of aminotransferase, L-kynurenine. TSG1 knockout resulted in an increased tiller number but reduction in grain number and size, and decrease in height. Meanwhile, deletion of the TSG1 homologs OsTAR1, OsTARL1, and OsTARL2 caused no obvious changes, although the phenotype of the TSG1/OsTAR1 double mutant was intensified and infertile, suggesting gene redundancy in the rice tryptophan aminotransferase family. Interestingly, TSG1 and OsTAR1, but not OsTARL1 and OsTARL2, displayed marked aminotransferase activity. Meanwhile, subcellular localization was identified as the endoplasmic reticulum, while phylogenetic analysis revealed functional divergence of TSG1 and OsTAR1 from OsTARL1 and OsTARL2. These findings suggest that TSG1 dominates the tryptophan aminotransferase family, playing a prominent role in local auxin biosynthesis in rice.
生长素是一种关键的植物激素，控制着植物生长和对环境变化的多种反应。然而，局部生长素生物合成在作物特定发育程序中的作用仍不清楚。本研究对水稻分蘖和小粒 1（tsg1）突变体进行了特征描述，该突变体分蘖较多，但由于内源生长素减少，穗和籽粒大小减小。TSG1 编码色氨酸氨基转移酶，与 FISH BONE（FIB）基因等位。tsg1 突变体对吲哚-3-乙酸和氨基转移酶竞争性抑制剂 L-犬尿氨酸表现出超敏反应。TSG1 敲除导致分蘖数增加，但粒数和大小减少，高度降低。同时，虽然 TSG1/OsTAR1 双突变体的表型加剧且不育，但 OsTAR1、OsTARL1 和 OsTARL2 的同源物缺失没有明显变化，表明水稻色氨酸氨基转移酶家族存在基因冗余。有趣的是，TSG1 和 OsTAR1，但不是 OsTARL1 和 OsTARL2，表现出明显的氨基转移酶活性。同时，亚细胞定位被鉴定为内质网，而系统发育分析表明 TSG1 和 OsTAR1 与 OsTARL1 和 OsTARL2 功能分化。这些发现表明 TSG1 主导色氨酸氨基转移酶家族，在水稻中局部生长素生物合成中起重要作用。
