Cytokinin Regulates the Etioplast-Chloroplast Transition through the Two-Component Signaling System and Activation of Chloroplast-Related Genes
Cytokinin Regulates the Etioplast-Chloroplast Transition through the Two-Component Signaling System and Activation of Chloroplast-Related Genes
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DOI：
10.1104/pp.16.00640
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发表时间：
2016-09-01
期刊：
影响因子：
7.4
通讯作者：
Schmuelling, Thomas
中科院分区：
文献类型：
--
作者：
Cortleven, Anne;Marg, Ingke;Schmuelling, Thomas
植物激素细胞分裂素的经典功能之一是调节质体发育，但其潜在的分子机制仍不清楚。在这项研究中，我们采用了遗传学的方法来评估细胞分裂素及其信号通路在光诱导的叶绿体发育拟南芥（Arabidopsis thaliana）的作用。细胞分裂素增加绿化率，并刺激超微结构的变化特征的黄化体到叶绿体的转变。导致叶绿素产生的四吡咯生物合成途径的代谢物的稳态水平被细胞分裂素增强。细胞分裂素对代谢物水平的这种影响是由于叶绿素生物合成基因如HEMA 1、GUN 4、GUN 5和CHLM的表达的调节而产生的。HEMA 1的表达增加反映在编码的谷氨酰-tRNA还原酶的水平提高，其催化叶绿素生物合成的限速步骤之一。突变体分析表明，细胞分裂素受体拟南芥组氨酸激酶2（AHK 2）和AHK 3在这一过程中发挥核心作用。此外，B型拟南芥应答调节因子1（ARR 1）、ARR 10和ARR 12在介导叶绿体-叶绿体转换过程中的转录输出中起重要作用。B型ARRs与HEMA 1和LHCB 6基因的启动子结合，表明细胞分裂素依赖性转录因子直接调节叶绿素生物合成和捕光复合物的基因。总之，这些结果表明，细胞分裂素信号通路在叶绿体发育中的重要作用，叶绿素生物合成基因的直接转录调控作为这种激素控制的一个关键方面。
One of the classical functions of the plant hormone cytokinin is the regulation of plastid development, but the underlying molecular mechanisms remain elusive. In this study, we employed a genetic approach to evaluate the role of cytokinin and its signaling pathway in the light-induced development of chloroplasts from etioplasts in Arabidopsis (Arabidopsis thaliana). Cytokinin increases the rate of greening and stimulates ultrastructural changes characteristic for the etioplast-to-chloroplast transition. The steady-state levels of metabolites of the tetrapyrrole biosynthesis pathway leading to the production of chlorophyll are enhanced by cytokinin. This effect of cytokinin on metabolite levels arises due to the modulation of expression for chlorophyll biosynthesis genes such as HEMA1, GUN4, GUN5, and CHLM. Increased expression of HEMA1 is reflected in an enhanced level of the encoded glutamyl-tRNA reductase, which catalyzes one of the rate-limiting steps of chlorophyll biosynthesis. Mutant analysis indicates that the cytokinin receptors ARABIDOPSIS HIS KINASE2 (AHK2) and AHK3 play a central role in this process. Furthermore, the B-type ARABIDOPSIS RESPONSE REGULATOR1 (ARR1), ARR10, and ARR12 play an important role in mediating the transcriptional output during etioplast-chloroplast transition. B-type ARRs bind to the promotors of HEMA1 and LHCB6 genes, indicating that cytokinin-dependent transcription factors directly regulate genes of chlorophyll biosynthesis and the light harvesting complex. Together, these results demonstrate an important role for the cytokinin signaling pathway in chloroplast development, with the direct transcriptional regulation of chlorophyll biosynthesis genes as a key aspect for this hormonal control.