Penfield Steven, Josse Eve-Marie, Kannangara Rubini, Gilday Alison D, Halliday Karen J, Graham Ian A
Center for Novel Agricultural Products, Department of Biology, University of York, P.O. box 373, York, YO10 5YW, United Kingdom.
Curr Biol. 2005 Nov 22;15(22):1998-2006. doi: 10.1016/j.cub.2005.11.010.
Plants integrate signals from the environment and use these to modify the timing of development according to seasonal cues. Seed germination is a key example of this phenomenon and in Arabidopsis is promoted by the synergistic interaction of light and low temperatures in dormant seeds. This signaling pathway is known to converge on the regulation of the gibberellin (GA) biosynthetic genes GA3 oxidase (GA3ox), whose expression is transcriptionally induced by light and cold in imbibed seeds. However, the molecular basis of this response has until now been unknown.
Here we show that the bHLH transcription factor SPATULA is a light-stable repressor of seed germination and mediates the germination response to temperature. Furthermore, SPT is required in dormant seeds for maintaining the repression of GA3ox transcription. We also show that the related protein PIL5 represses seed germination and GA3ox expression in the dark.
We conclude that SPT and PIL5 form part of a regulatory network coupling seed germination and GA3ox expression to light and temperature signaling in the seed.
植物整合来自环境的信号，并利用这些信号根据季节线索调整发育时间。种子萌发是这一现象的关键实例，在拟南芥中，休眠种子的萌发受到光和低温的协同作用促进。已知该信号通路汇聚于赤霉素（GA）生物合成基因GA3氧化酶（GA3ox）的调控，其表达在吸胀种子中受到光和冷的转录诱导。然而，这种反应的分子基础至今仍不清楚。
在此我们表明，bHLH转录因子SPATULA是种子萌发的光稳定抑制因子，并介导对温度的萌发反应。此外，休眠种子中需要SPT来维持对GA3ox转录的抑制。我们还表明，相关蛋白PIL5在黑暗中抑制种子萌发和GA3ox表达。
我们得出结论，SPT和PIL5构成了一个调控网络的一部分，该网络将种子萌发和GA3ox表达与种子中的光和温度信号联系起来。
