J Integr Plant Biol ›› 2020, Vol. 62 ›› Issue (5): 581-600.DOI: 10.1111/jipb.12820

• Cell and Developmental Biology • Previous Articles     Next Articles

Tillering and small grain 1 dominates the tryptophan aminotransferase family required for local auxin biosynthesis in rice

Tao Guo1†, Ke Chen1,2†, Nai-Qian Dong1, Wang-Wei Ye1, Jun-Xiang Shan1 and Hong-Xuan Lin1,2,3*   

  1. 1National 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
    2University of the Chinese Academy of Sciences, Beijing 100049, China
    3School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China

    These authors contributed equally to this work.
    *Correspondence:
    Email: Hong-Xuan Lin (hxlin@sibs.ac.cn)
  • Received:2019-03-06 Accepted:2019-04-26 Online:2019-05-13 Published:2020-05-01

Abstract:

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.

Auxin is a key phytohormone which has important roles on plant growth and development. In this study, we identified a tryptophan aminotransferase TSG1 which is required for rice plant and panicle development. TSG1 dominates the tryptophan aminotransferase family and plays a prominent role in local auxinproduction in rice.
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