Department of Biotechnology and Kumho Life Science Laboratory, Chonnam National University, Gwangju, Korea.
Plant Signal Behav. 2010 Jul;5(7):868-71. doi: 10.4161/psb.5.7.11898. Epub 2010 Jul 1.
Plant red/far-red photoreceptor phytochromes are known as autophosphorylating serine/threonine kinases. However, the functional roles of autophosphorylation and kinase activity of phytochromes are largely unknown. We recently reported that the autophosphorylation of phytochrome A (phyA) plays an important role in regulating plant phytochrome signaling by controlling phyA protein stability. Two serine residues in the N-terminal extension (NTE) region were identified as autophosphorylation sites, and phyA mutant proteins with serine-to-alanine mutations were degraded in plants at a significantly slower rate than the wild-type under light conditions, resulting in transgenic plants with hypersensitive light responses. In addition, the autophosphorylation site phyA mutants had normal protein kinase activities. Collectively, our results suggest that phytochrome autophosphorylation provides a mechanism for signal desensitization in phytochrome-mediated light signaling by accelerating the degradation of phytochrome A.
植物红光/远红光光受体光敏色素被称为自磷酸化丝氨酸/苏氨酸激酶。然而，光敏色素的自磷酸化和激酶活性的功能作用在很大程度上是未知的。我们最近报道，光敏色素 A（phyA）的自磷酸化通过控制 phyA 蛋白稳定性在调节植物光敏色素信号中起着重要作用。在 N 端延伸（NTE）区域的两个丝氨酸残基被鉴定为自磷酸化位点，并且在光条件下，具有丝氨酸到丙氨酸突变的 phyA 突变蛋白在植物中的降解速度明显慢于野生型，导致具有超敏光反应的转基因植物。此外，自磷酸化位点 phyA 突变体具有正常的蛋白激酶活性。总之，我们的结果表明，光敏色素的自磷酸化通过加速光敏色素 A 的降解为光敏色素介导的光信号提供了一种信号脱敏机制。
