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[交流] [优秀文章推荐] 独脚金内酯信号转导分子机制研究取得新进展已有3人参与

IPA1介导的独脚金内酯信号途径

独脚金内酯是一种新型的植物激素，在植物株型建成中发挥重要作用，能作为长距离信号分子抑制植物侧芽的伸长进而抑制分枝的产生，对其信号途径的研究具有重要的科学意义和应用价值。中国科学院遗传与发育生物学研究所李家洋研究组与合作者长期从事水稻株型建成分子机制的研究，对理想株型以及独脚金内酯的合成及信号转导进行了系统深入的解析。此前他们克隆了水稻理想株型的主效基因IPA1（Ideal Plant Architecture 1），证明其编码一个含有SBP-box结构域的转录因子，调控多个生长发育过程，对水稻产量具有重要影响（Jiao et al., Nat Genet, 2010），且在育种中增产效果显著。同时，他们鉴定了独脚金内酯信号通路中关键的负调控因子Dwarf 53 (D53)，解析了独脚金内酯信号转导的“去抑制化激活”机制 (Jiang et al., Nature, 2013)。

最新的研究表明，IPA1功能缺失突变体表现出分蘖数增多的表型，且对外源施加的独脚金内酯人工合成类似物rac-GR24不敏感；D53蛋白可直接与IPA1蛋白相互作用，抑制IPA1的转录激活活性，从而抑制下游基因表达。此外，还发现IPA1能直接结合D53的启动子并激活D53基因的表达，从而形成负反馈调节。该研究结果揭示了IPA1即是长期寻找的D53下游的转录因子，参与独脚金内酯信号途径，并直接受到D53的调控。

Phenotypic characterization of IPA1 loss-of-function mutants

Strigolactones (SLs), a group of carotenoid derived terpenoid lactones, are root-to-shoot phytohormones suppressing shoot branching by inhibiting the outgrowth of axillary buds. DWARF 53 (D53), the key repressor of the SL signaling pathway, is speculated to regulate the downstream transcriptional network of the SL response. However, no downstream transcription factor targeted by D53 has yet been reported. Here we report that Ideal Plant Architecture 1 (IPA1), a key regulator of the plant architecture in rice, functions as a direct downstream component of D53 in regulating tiller number and SL-induced gene expression. We showed that D53 interacts with IPA1 in vivo and in vitro and suppresses the transcriptional activation activity of IPA1. We further showed that IPA1 could directly bind to the D53 promoter and plays a critical role in the feedback regulation of SL-induced D53 expression. These findings reveal that IPA1 is likely one of the long-speculated transcription factors that act with D53 to mediate the SL-regulated tiller development in rice.

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