School of Biological Sciences, Seoul National University, Seoul 151-747, Korea.
Dev Cell. 2012 Apr 17;22(4):736-48. doi: 10.1016/j.devcel.2012.01.024. Epub 2012 Apr 5.
For optimal survival, various environmental and endogenous factors should be monitored to determine the appropriate timing for seed germination. Light is a major environmental factor affecting seed germination, which is perceived by phytochromes. The light-dependent activation of phytochrome B (PHYB) modulates abscisic acid and gibberellic acid signaling and metabolism. Thus far, several negative regulators of seed germination that act when PHYB is inactive have been reported. However, neither positive regulators of seed germination downstream of PHYB nor a direct mechanism for regulation of the hormone levels has been elucidated. Here, we show that the histone arginine demethylases, JMJ20 and JMJ22, act redundantly as positive regulators of seed germination. When PHYB is inactive, JMJ20/JMJ22 are directly repressed by the zinc-finger protein SOMNUS. However, upon PHYB activation, JMJ20/JMJ22 are derepressed, resulting in increased gibberellic acid levels through the removal of repressive histone arginine methylations at GA3ox1/GA3ox2, which in turn promotes seed germination.
为了实现最佳的生存，应该监测各种环境和内源性因素，以确定种子发芽的适当时机。光是影响种子发芽的主要环境因素，它被光敏色素感知。光依赖性的 PHYB（phytochrome B）激活调节脱落酸和赤霉素信号和代谢。到目前为止，已经报道了几种在 PHYB 不活跃时作用的种子发芽的负调控因子。然而，尚未阐明 PHYB 下游的种子发芽的正调控因子，也没有阐明激素水平的直接调节机制。在这里，我们表明组蛋白精氨酸去甲基酶 JMJ20 和 JMJ22 作为种子发芽的正调控因子是冗余的。当 PHYB 不活跃时，锌指蛋白 SOMNUS 直接抑制 JMJ20/JMJ22。然而，当 PHYB 被激活时，JMJ20/JMJ22 被去抑制，导致通过去除 GA3ox1/GA3ox2 上的抑制性组蛋白精氨酸甲基化来增加赤霉素水平，从而促进种子发芽。
