Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, Gothenburg, 40530, Sweden.
Copenhagen Plant Science Centre, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark.
Sci Rep. 2019 Jun 14;9(1):8639. doi: 10.1038/s41598-019-44972-z.
In variable light environments, plants adjust light use in photosynthetic electron transport and photoprotective dissipation in the thylakoid membrane. In this respect, roles of the K/H antiporter KEA3, the Cl channel/transporter CLCe and the voltage-dependent Cl channel VCCN1 have been unraveled in Arabidopsis thaliana. Here we report that they independently adjust photosynthesis on the basis of analyses using single and higher order loss-of-function mutants. In short experiments of photosynthetic response on transition from dark to low light, we reveal a sequential functioning of VCCN1 and CLCe in the activation of photoprotection and of KEA3 in its downregulation to a low steady state while adjusting the electron transport. On transition from low to high light, VCCN1 accelerates the activation of photoprotection, whereas KEA3 slows it down on transition from high to low light. Based on parallel electrochromic band shift measurements, the mechanism behind is that VCCN1 builds up a pH gradient across the thylakoid membrane, whereas KEA3 dissipates this gradient, which affects photoprotection. CLCe regulates photosynthesis by a pH-independent mechanism likely involving Cl homeostasis. Nevertheless, all genotypes grow well in alternating high and low light. Taken together, the three studied ion channels/transporters function independently in adjusting photosynthesis to the light environment.
在可变光照环境中，植物会调整光合电子传递和类囊体膜中光保护耗散的光利用。在这方面，已在拟南芥中揭示了 K/H 反向转运蛋白 KEA3、Cl 通道/转运蛋白 CLCe 和电压依赖性 Cl 通道 VCCN1 的作用。在这里，我们报道了它们通过使用单突变体和更高阶的功能丧失突变体的分析，独立地调节光合作用。在从黑暗到低光的光合作用响应的简短实验中，我们揭示了 VCCN1 和 CLCe 在光保护的激活中的顺序作用，以及 KEA3 在电子传递下调至低稳态时的下调作用。在从低光到高光的转变中，VCCN1 加速了光保护的激活，而 KEA3 在从高光到低光的转变中减缓了光保护的激活。基于平行的电致变色带位移测量，其背后的机制是 VCCN1 在类囊体膜两侧建立 pH 梯度，而 KEA3 耗散该梯度，从而影响光保护。CLCe 通过一种可能涉及 Cl 稳态的 pH 独立机制来调节光合作用。然而，所有基因型在交替的高光和低光下都能良好生长。综上所述，这三种研究的离子通道/转运蛋白独立地调节光合作用以适应光照环境。
