Limitation of nocturnal import of ATP into Arabidopsis chloroplasts leads to photooxidative damage
Limitation of nocturnal import of ATP into Arabidopsis chloroplasts leads to photooxidative damage
复制标题
DOI：
10.1111/j.1365-313x.2007.03049.x
复制
发表时间：
2007-04-01
期刊：
影响因子：
7.2
通讯作者：
Neuhaus, H. Ekkehard
中科院分区：
文献类型：
--
作者：
Reinhold, Thomas;Alawady, Ali;Neuhaus, H. Ekkehard
当生长在短日照条件和弱光下时，编码两个质体ATP/ADP转运蛋白的基因突变的拟南芥植物（所谓的无效突变体）的叶子自发地发生坏死性病变。在这些条件下，突变体还显示光诱导的H2 O2积累和铜/锌超氧化物歧化酶2和抗坏血酸过氧化物酶1基因的组成型表达。在光相，无效突变体积累高水平的光毒性原卟啉IX，但只有轻微降低水平的镁原卟啉IX。生理变化与镁螯合酶活性降低有关。由于编码镁螯合酶的三个亚基中的任何一个的基因的表达在野生型和无效突变体中是相似的，酶活性降低可能是由于翻译后修饰，这可能是由于在夜间质体中ATP的可用性有限。令人惊讶的是，当无效突变体在长日照和低光照强度或短日照和高光照强度下生长时，不存在坏死病变的形成。我们将缺乏病变表型归因于淀粉糖酵解降解导致的夜间ATP供应增加，这可能导致基质中额外的底物水平磷酸化。因此，夜间输入的ATP进入叶绿体代表了一个重要的，以前未知的过程，需要控制叶绿素的生物合成和防止光氧化损伤。
When grown in short day conditions and at low light, leaves of Arabidopsis plants with mutations in the genes encoding two plastidial ATP/ADP transporters (so-called null mutants) spontaneously develop necrotic lesions. Under these conditions, the mutants also display light-induced accumulation of H2O2 and constitutive expression of genes for copper/zinc superoxide dismutase 2 and ascorbate peroxidase 1. In the light phase, null mutants accumulate high levels of phototoxic protoporphyrin IX but have only slightly reduced levels of Mg protoporphyrin IX. The physiological changes are associated with reduced magnesium-chelatase activity. Since the expression of genes encoding any of the three subunits of magnesium-chelatase is similar in wild type and null mutants, decreased enzyme activity is probably due to post-translational modification which might be due to limited availability of ATP in plastids during the night. Surprisingly, the formation of necrotic lesions was absent when null mutants were grown either in long days and low light intensity or in short days and high light intensity. We ascribe the lack of lesion phenotype to increased nocturnal ATP supply due to glycolytic degradation of starch which may lead to additional substrate-level phosphorylation in the stroma. Thus, nocturnal import of ATP into chloroplasts represents a crucial, previously unknown process that is required for controlled chlorophyll biosynthesis and for preventing photooxidative damage.