Xiao Yuguo, Chen Yi, Charnikhova Tatsiana, Mulder Patrick P J, Heijmans Jeroen, Hoogenboom Angela, Agalou Adamantia, Michel Corinne, Morel Jean-Benoit, Dreni Ludovico, Kater Martin M, Bouwmeester Harro, Wang Mei, Zhu Zhen, Ouwerkerk Pieter B F
Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE, Leiden, The Netherlands.
Plant Mol Biol. 2014 Sep;86(1-2):19-33. doi: 10.1007/s11103-014-0212-y. Epub 2014 Jun 20.
Jasmonates are important phytohormones regulating reproductive development. We used two recessive rice Tos17 alleles of OsJAR1, osjar1-2 and osjar1-3, to study the biological function of jasmonates in rice anthesis. The florets of both osjar1 alleles stayed open during anthesis because the lodicules, which control flower opening in rice, were not withering on time. Furthermore, dehiscence of the anthers filled with viable pollen, was impaired, resulting in lower fertility. In situ hybridization and promoter GUS transgenic analysis confirmed OsJAR1 expression in these floral tissues. Flower opening induced by exogenous applied methyl jasmonate was impaired in osjar1 plants and was restored in a complementation experiment with transgenics expressing a wild type copy of OsJAR1 controlled by a rice actin promoter. Biochemical analysis showed that OsJAR1 encoded an enzyme conjugating jasmonic acid (JA) to at least Ile, Leu, Met, Phe, Trp and Val and both osjar1 alleles had substantial reduction in content of JA-Ile, JA-Leu and JA-Val in florets. We conclude that OsJAR1 is a JA-amino acid synthetase that is required for optimal flower opening and closing and anther dehiscence in rice.
茉莉酸酯是调节生殖发育的重要植物激素。我们利用水稻OsJAR1的两个隐性Tos17等位基因osjar1 - 2和osjar1 - 3，研究茉莉酸酯在水稻开花过程中的生物学功能。在开花期，这两个osjar1等位基因的小花保持开放状态，因为控制水稻花朵开放的浆片没有按时枯萎。此外，充满有活力花粉的花药开裂受损，导致育性降低。原位杂交和启动子GUS转基因分析证实了OsJAR1在这些花器官组织中的表达。在osjar1植株中，由外源施加茉莉酸甲酯诱导的花朵开放受到损害，而在表达由水稻肌动蛋白启动子控制的野生型OsJAR1拷贝的转基因互补实验中得以恢复。生化分析表明，OsJAR1编码一种将茉莉酸（JA）与至少异亮氨酸、亮氨酸、蛋氨酸、苯丙氨酸、色氨酸和缬氨酸结合的酶，并且两个osjar1等位基因的小花中JA - 异亮氨酸、JA - 亮氨酸和JA - 缬氨酸的含量大幅降低。我们得出结论，OsJAR1是一种JA - 氨基酸合成酶，是水稻最佳的花朵开合和花药开裂所必需的。
