Lee Kuo-Wei, Chen Jeremy J W, Wu Chung-Shen, Chang Ho-Chun, Chen Hong-Yue, Kuo Hsin-Hao, Lee Ya-Shan, Chang Yan-Lun, Chang Hung-Chia, Shiue Shiau-Yu, Wu Yi-Chen, Ho Yi-Cheng, Chen Peng-Wen
Department of Bioagricultural Sciences, National Chiayi University, Chiayi, Taiwan.
Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan.
Plant Cell Environ. 2023 Apr;46(4):1157-1175. doi: 10.1111/pce.14434. Epub 2022 Sep 19.
Auxin is well known to stimulate coleoptile elongation and rapid seedling growth in the air. However, its role in regulating rice germination and seedling establishment under submergence is largely unknown. Previous studies revealed that excessive levels of indole-3-acetic acid(IAA) frequently cause the inhibition of plant growth and development. In this study, the high-level accumulation of endogenous IAA is observed under dark submergence, stimulating rice coleoptile elongation but limiting the root and primary leaf growth during anaerobic germination (AG). We found that oxygen and light can reduce IAA levels, promote the seedling establishment and enhance rice AG tolerance. miRNA microarray profiling and RNA gel blot analysis results show that the expression of miR167 is negatively regulated by submergence; it subsequently modulates the accumulation of free IAA through the miR167-ARF-GH3 pathway. The OsGH3-8 encodes an IAA-amido synthetase that functions to prevent free IAA accumulation. Reduced miR167 levels or overexpressing OsGH3-8 increase auxin metabolism, reduce endogenous levels of free IAA and enhance rice AG tolerance. Our studies reveal that poor seed germination and seedling growth inhibition resulting from excessive IAA accumulation would cause intolerance to submergence in rice, suggesting that a certain threshold level of auxin is essential for rice AG tolerance.
众所周知，生长素能刺激胚芽鞘伸长并促进空气中幼苗的快速生长。然而，其在淹水条件下调节水稻种子萌发和幼苗生长的作用却 largely unknown。先前的研究表明，过量的吲哚 - 3 - 乙酸（IAA）常常会抑制植物的生长和发育。在本研究中，观察到在黑暗淹水条件下内源性IAA会高水平积累，这刺激了水稻胚芽鞘伸长，但在无氧萌发（AG）过程中限制了根和初生叶的生长。我们发现氧气和光照可以降低IAA水平，促进幼苗生长并增强水稻对AG的耐受性。miRNA微阵列分析和RNA凝胶印迹分析结果表明，miR167的表达受淹水负调控；随后它通过miR167 - ARF - GH3途径调节游离IAA的积累。OsGH3 - 8编码一种IAA - 酰胺合成酶，其功能是防止游离IAA积累。降低miR167水平或过表达OsGH3 - 8可增加生长素代谢，降低游离IAA的内源性水平并增强水稻对AG的耐受性。我们的研究表明，IAA积累过多导致的种子萌发不良和幼苗生长抑制会使水稻对淹水不耐受，这表明一定阈值水平的生长素对水稻AG耐受性至关重要。
