A Novel Protective Function for Cytokinin in the Light Stress Response Is Mediated by the ARABIDOPSIS HISTIDINE KINASE2 and ARABIDOPSIS HISTIDINE KINASE3 Receptors
A Novel Protective Function for Cytokinin in the Light Stress Response Is Mediated by the ARABIDOPSIS HISTIDINE KINASE2 and ARABIDOPSIS HISTIDINE KINASE3 Receptors
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DOI：
10.1104/pp.113.224667
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发表时间：
2014-03-01
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;Nitschke, Silvia;Schmuelling, Thomas
细胞分裂素是一种植物激素，调节植物发育的不同过程以及对生物和非生物胁迫的反应。在本研究中，我们发现与野生型植物相比，细胞分裂素状态降低的拟南芥(Arabitopsis Thaliana)植物(即细胞分裂素受体突变体和转基因细胞分裂素缺失植株)对光胁迫更敏感。这反映在强光(约1000mmolm(-2)S(-1))作用24 h后的光抑制增强，表现为光系统II光化学最大量子效率的下降。光系统II，特别是D1蛋白，对光的有害影响高度敏感。因此，当光损伤速率超过D1修复速率时，总是可以观察到光抑制。我们证明，在细胞分裂素状态降低的植物中，D1蛋白水平在轻度胁迫下显著降低。用林可霉素处理抑制了D1修复周期，表明这些植物经历了更强的光损伤。在细胞分裂素状态降低的植物中，非酶和酶清除系统等光保护机制的效率降低，这可能是导致光损伤增加和随后的D1降解的原因之一。此外，这些植物在光胁迫后恢复缓慢且不完全，表明D1修复不足。突变分析表明，细胞分裂素在光胁迫下的保护作用依赖于拟南芥组氨酸激动子2(AHK2)和AHK3受体以及B型拟南芥应答基因ARR1和ARR12。我们的结论是，适当的细胞分裂素信号转导和特定靶基因的调控对于有效保护叶片免受光胁迫是必要的。
Cytokinins are plant hormones that regulate diverse processes in plant development and responses to biotic and abiotic stresses. In this study, we show that Arabidopsis (Arabidopsis thaliana) plants with a reduced cytokinin status (i.e. cytokinin receptor mutants and transgenic cytokinin-deficient plants) are more susceptible to light stress compared with wild-type plants. This was reflected by a stronger photoinhibition after 24 h of high light (approximately 1,000 mu mol m(-2) s(-1)), as shown by the decline in maximum quantum efficiency of photosystem II photochemistry. Photosystem II, especially the D1 protein, is highly sensitive to the detrimental impact of light. Therefore, photoinhibition is always observed when the rate of photodamage exceeds the rate of D1 repair. We demonstrate that in plants with a reduced cytokinin status, the D1 protein level was strongly decreased upon light stress. Inhibition of the D1 repair cycle by lincomycin treatment indicated that these plants experience stronger photodamage. The efficiency of photoprotective mechanisms, such as nonenzymatic and enzymatic scavenging systems, was decreased in plants with a reduced cytokinin status, which could be a cause for the increased photodamage and subsequent D1 degradation. Additionally, slow and incomplete recovery in these plants after light stress indicated insufficient D1 repair. Mutant analysis revealed that the protective function of cytokinin during light stress depends on the ARABIDOPSIS HISTIDINE KINASE2 (AHK2) and AHK3 receptors and the type B ARABIDOPSIS RESPONSE REGULATOR1 (ARR1) and ARR12. We conclude that proper cytokinin signaling and regulation of specific target genes are necessary to protect leaves efficiently from light stress.