RIKEN Plant Science Center, Tsurumi, Yokohama, Kanagawa, Japan.
Plant Signal Behav. 2011 Jan;6(1):26-8. doi: 10.4161/psb.6.1.14114. Epub 2011 Jan 1.
Gibberellins (GAs) are phytohormones that regulate growth and development throughout the life cycle of plants. Negative feedback contributes to homeostasis of GA levels. DELLA proteins are involved in this process. Since DELLA proteins do not have apparent DNA binding motifs, other DNA binding proteins might act as a mediator downstream of DELLA proteins in the GA feedback regulation. In this review, we highlight the mechanisms of GA feedback regulation, specifically the differential regulation of GA 20-oxidase (GA20ox) and GA 3-oxidase (GA3ox) by transcription factors. RSG (REPRESSION OF SHOOT GROWTH) is a tobacco (Nicotiana tabacum) transcriptional activator with a basic leucine zipper domain that controls the levels of endogenous GAs through the regulation of GA biosynthesis genes. Recently we reported that RSG not only regulates the expression of ent-kaurene oxidase gene but is also involved in the negative feedback of NtGA20ox1 by GAs. RSG plays a role in the homeostasis of GAs through direct binding to the NtGA20ox1 promoter triggered by a decrease in GA levels in the cell. Furthermore, decreases in GA levels promote modifications of active histone marks on the NtGA20ox1 promoter. We have developed a hypothetical model to explain how RSG regulates dual target genes via epigenetic regulation.
赤霉素（GAs）是一种植物激素，调节植物生命周期中的生长和发育。负反馈有助于 GA 水平的内稳态。DELLA 蛋白参与了这个过程。由于 DELLA 蛋白没有明显的 DNA 结合基序，其他 DNA 结合蛋白可能在 GA 反馈调节中作为 DELLA 蛋白下游的介质发挥作用。在这篇综述中，我们强调了 GA 反馈调节的机制，特别是转录因子对 GA20-氧化酶（GA20ox）和 GA3-氧化酶（GA3ox）的差异调节。RSG（抑制茎生长）是一种烟草（Nicotiana tabacum）转录激活因子，具有碱性亮氨酸拉链结构域，通过调节 GA 生物合成基因来控制内源性 GAs 的水平。最近我们报道，RSG 不仅调节 ent-贝壳杉烯氧化酶基因的表达，还参与 GA 对 NtGA20ox1 的负反馈。RSG 通过细胞内 GA 水平下降触发的直接结合到 NtGA20ox1 启动子上，在 GAs 的内稳态中发挥作用。此外，GA 水平的降低促进了 NtGA20ox1 启动子上活性组蛋白标记的修饰。我们已经提出了一个假设模型来解释 RSG 如何通过表观遗传调控来调节双重靶基因。
