ASKtheta, a group-III Arabidopsis GSK3, functions in the brassinosteroid signalling pathway.
ASKtheta, a group-III Arabidopsis GSK3, functions in the brassinosteroid signalling pathway.
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DOI：
10.1111/j.1365-313x.2010.04145.x
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发表时间：
2010-04
期刊：
影响因子：
--
通讯作者：
Jonak C
中科院分区：
文献类型：
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作者：
Rozhon W;Mayerhofer J;Petutschnig E;Fujioka S;Jonak C
油菜素类固醇(BRs)是一种植物激素，调节细胞伸长、叶片发育、花粉管生长和木质部分化等多种过程。GSK3/Saggy-like kinase(GSK)是由BR与BRI1受体复合体结合而启动的细胞内信号转导的关键调节因子。已经有三个GSK被证明可以传递BR反应，包括转录调节因子BES1的磷酸化。然而，最近的研究表明，一个或多个尚未确定的蛋白激酶参与了BR信号转导。在这里，我们表明，第三组葛兰素史克的体内蛋白激酶活性，ASKθ，是负调控的BRI1。ASKθ活性增强的拟南芥植株表现出类似BRI1的表型。ASKθ过表达株积累了较高水平的油菜素内酯、蓖麻甾酮和类固醇，对BR不敏感。问θ定位于细胞核并直接磷酸化BES1和BZR1.此外，在酵母双杂交筛选中还分离到BES1/BZR1样转录因子BEH2作为ASKθ相互作用伙伴。无论是在体外还是在体内，Askθ都能使BEH2磷酸化。总体而言，这些数据提供了强有力的证据，表明ASKθ是BR信号级联中的一个新组件，靶向转录因子BES1、BZR1和BEH2。
Brassinosteroids (BRs) are plant hormones that regulate many processes including cell elongation, leaf development, pollen tube growth and xylem differentiation. GSK3/shaggy-like kinases (GSK) are critical regulators of intracellular signalling initiated by the binding of BR to the BRI1 receptor complex. Three GSKs have already been shown to relay BR responses, including phosphorylation of the transcriptional regulator BES1. However, recent studies indicate that one or more yet unidentified protein kinases are involved in BR signalling. Here, we show that the in vivo protein kinase activity of the group-III GSK, ASKθ, was negatively regulated by BRI1. Arabidopsis thaliana plants with enhanced ASKθ activity displayed a bri1-like phenotype. ASKθ overexpressors accumulated high levels of brassinolide, castasterone and typhasterol, and were insensitive to BR. ASKθ localized to the nucleus and directly phosphorylated BES1 and BZR1. Moreover, the BES1/BZR1-like transcription factor BEH2 was isolated as an ASKθ interaction partner in a yeast two-hybrid screen. ASKθ phosphorylated BEH2 both in vitro and in vivo. Overall, these data provide strong evidence that ASKθ is a novel component of the BR signalling cascade, targeting the transcription factors BES1, BZR1 and BEH2.