水稻颖花自然开放过程中茉莉酸(JA)生物合成的变化

外源茉莉酸(JA)及其甲酯(MeJA)对水稻、小麦、黑麦和高粱等禾本科植物颖花开放具有强烈的诱导效应,然而内源JA是否参与颖花开放的调控目前还缺乏充分的证据。本研究应用高效液相色谱-串联质谱(HPLC-MS/MS)系统检测了粳稻武运粳7号和籼稻明恢63颖花自然开放过程中JA水平变化,并以实时定量反转录PCR (real-time RT-PCR)技术分析了武运粳7号颖花开放过程中JA生物合成途径关键基因表达变化。结果发现,水稻颖花JA水平的变化与开颖进程相一致。JA水平在上午颖花开颖前较平稳,开颖时急剧上升至峰值,闭颖后又下降。开颖时JA水平的峰值比开颖前1 h提高4~5倍。与JA水平变化相对应,催化JA生物合成途径关键步骤同工酶的编码基因OsDAD1-3、OsLOX-RCI1、OsAOS1、OsAOC和OsOPR7的表达在开颖时会有不同程度的上调,闭颖后又下调。同一稻穗上正在开放的颖花JA含量及上述JA生物合成途径基因的表达水平也比已开放和未开放的颖花高。颖花开放时JA水平及其生物合成基因表达的上升和闭颖后的下降有力地表明内源JA参与水稻颖花开放的调控。

Dynamic Changes of Jasmonic Acid Biosynthesis in Rice Florets during Natural Anthesis

Exogenously applied jasmonic acid (JA) or its methyl ester (MeJA) could significantly induce floret opening in gramineous plants such as rice, wheat, sorghum and rye. However, whether the endogenous JA is involved in the regulation of rice floret opening has remained unclear. To elucidate the role of endogenous JA in natural floret opening, we measured the JA levels in florets of Wuyunjing 7 (japonica cultivar) and Minghui 63 (indica cultivar) by HPLC-electrospray ionization tandem mass spectrometry system (HPLC-MS/MS) during natural anthesis, and analyzed the expression of key genes involved in JA biosynthesis in florets of Wuyunjing 7 by real-time reverse transcription-PCR (real-time RT-PCR). The results showed that the JA levels in rice florets were related with the process of anthesis. JA levels in rice florets kept relatively constant before anthesis in the morning, and reached a peak rapidly during anthesis, and then decreased after the floret closing. The peak levels of JA in opening florets were 4–5 times higher than those in florets 1 h before anthesis. Consistent with the changes of JA levels in florets during anthesis, the expression of OsDAD1-3, OsLOX-RCI1, OsAOS1, OsAOC, and OsOPR7 that encode isozymes catalyzing the key steps in JA biosynthetic pathway was up-regulated to some extent during floret opening, and was down-regulated after floret closing. Meanwhile, the levels of JA and transcripts of JA biosynthetic genes were higher in opening florets than in opened or closed florets at the same panicle. The increasing of JA levels and transcripts of JA biosynthetic genes in florets at the time of opening and their decreasing in florets after closing strongly indicated that endogenous JA is involved in the regulation of floret opening in rice.