A circadian rhythm set by dusk determines the expression of FT homologs and the short-day photoperiodic flowering response in Pharbitis
A circadian rhythm set by dusk determines the expression of FT homologs and the short-day photoperiodic flowering response in Pharbitis
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DOI：
10.1105/tpc.107.052480
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发表时间：
2007-10-01
期刊：
影响因子：
11.6
通讯作者：
Coupland, George
中科院分区：
文献类型：
--
作者：
Hayama, Ryosuke;Agashe, Bhavna;Coupland, George
通过对日照长度的响应来控制开花的季节性变化表现出极端的变化。不同物种的花对长日照或短日照（SDs）的反应不同，这种差异进化了好几次。赋予这些反应的分子机制仅在拟南芥和水稻（Oryza sativa）中进行了详细的比较，并表明保守的途径通过CONSTANS（CO）调节FLOWERLOCUS T（FT）转录来赋予昼长反应。我们研究了牵牛属（牵牛属，以前，牵牛属），一个广泛使用的SD模式物种和旋花科的成员，并显示使用转基因植物连同详细的表达分析，两个推定的直系同源的FT（Pn FT 1和Pn FT 2）促进开花，特别是在SD。这些基因仅在SDs下表达，夜间的闪光会降低它们的表达并阻止开花。我们表明，在牵牛花的昼夜节律设置的光到暗的过渡在黄昏调节Pn FT的表达，只有当夜晚超过11小时上升。此外，牵牛属在其临界夜长响应方面不同的种质在黄昏后的不同时间表达Pn FT，表明影响调节Pn FT表达的时钟的自然遗传变异改变了开花响应。在这些试验中，Pn FT mRNA丰度与Pn CO表达无关，表明在牵牛属中Pn FT可能受不同的转录因子调节。我们的结论是，SD响应牵牛花是由一个专用的光敏感的时钟，设置黄昏，激活Pn FT转录在黑暗中，一个不同的机制，测量日照长度比拟南芥和水稻。
Seasonal control of flowering through responsiveness to daylength shows extreme variation. Different species flower in response to long days or short days (SDs), and this difference evolved several times. The molecular mechanisms conferring these responses have been compared in detail only in Arabidopsis thaliana and rice (Oryza sativa) and suggest that a conserved pathway confers daylength responses through regulation of FLOWERING LOCUS T (FT) transcription by CONSTANS (CO). We studied Pharbitis (Ipomoea nil; formerly, Pharbitis nil), a widely used SD model species and a member of the Convolvulaceae, and showed using transgenic plants together with detailed expression analysis that two putative orthologs of FT (Pn FT1 and Pn FT2) promote flowering specifically under SDs. These genes are expressed only under SDs, and light flashes given during the night reduce their expression and prevent flowering. We demonstrate that in Pharbitis a circadian rhythm set by the light-to-dark transition at dusk regulates Pn FT expression, which rises only when the night is longer than 11 h. Furthermore, Pharbitis accessions that differ in their critical night- length responses express Pn FT at different times after dusk, demonstrating that natural genetic variation influencing the clock regulating Pn FT expression alters the flowering response. In these assays, Pn FT mRNA abundance was not related to Pn CO expression, suggesting that Pn FT may be regulated by a different transcription factor in Pharbitis. We conclude that SD response in Pharbitis is controlled by a dedicated light sensitive clock, set by dusk, that activates Pn FT transcription in darkness, a different mechanism for measuring daylength than described for Arabidopsis and rice.