The long-term responses of the photosynthetic proton circuit to drought
The long-term responses of the photosynthetic proton circuit to drought
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DOI：
10.1111/j.1365-3040.2008.01912.x
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发表时间：
2009-03-01
影响因子：
7.3
通讯作者：
Kramer, David M.
中科院分区：
文献类型：
--
作者：
Kohzuma, Kaori;Cruz, Jeffrey A.;Kramer, David M.
穿过类囊体膜的质子动能不仅可以利用太阳能进行光合作用固定，还可以触发光系统II天线的反馈调节。在长期的环境胁迫下，如长期干旱，平衡质子回路的这两个作用的机制一直知之甚少。在这项研究中，我们报道了野生西瓜类囊体‘质子回路’对干旱胁迫的响应，利用体内光谱和具有代表性的光合组分的分子分析。虽然干旱胁迫通过光系统I(PS I)周围的循环电子流量(PS I)增加34%而导致质子通量增加，但通过类囊体膜的质子电导率g(H)(+)类似于5倍的下降表明，ATP合成酶活性的降低是维持Q(E)升高的主要因素。Western blotting分析显示，ATP合成酶含量显著降低，表明该复合体的定量调控在g(H)(+)下调中起关键作用。光合作用的另一个关键控制点细胞色素b(6)f复合体的表达水平也下降，可能是为了防止PS I电子受体的过度还原。我们的结论是，植物对长期环境胁迫的适应涉及到光合质子回路的全球变化，其中ATP合成酶是调节电子传递与PMF关系的关键控制点。
Proton motive force (pmf) across thylakoid membranes is not only for harnessing solar energy for photosynthetic CO2 fixation, but also for triggering feedback regulation of photosystem II antenna. The mechanisms for balancing these two roles of the proton circuit under the long-term environmental stress, such as prolonged drought, have been poorly understood. In this study, we report on the response of wild watermelon thylakoid 'proton circuit' to drought stress using both in vivo spectroscopy and molecular analyses of the representative photosynthetic components. Although drought stress led to enhanced proton flux via a similar to 34% increase in cyclic electron flow around photosystem I (PS I), an observed similar to fivefold decrease in proton conductivity, g(H)(+), across thylakoid membranes suggested that decreased ATP synthase activity was the major factor for sustaining elevated q(E). Western blotting analyses revealed that ATP synthase content decreased significantly, suggesting that quantitative control of the complex plays a pivotal role in down-regulation of g(H)(+). The expression level of cytochrome b(6)f complex - another key control point in photosynthesis - also declined, probably to prevent excess-reduction of PS I electron acceptors. We conclude that plant acclimation to long-term environmental stress involves global changes in the photosynthetic proton circuit, in which ATP synthase represents the key control point for regulating the relationship between electron transfer and pmf.