Composition and physiological function of the chloroplast NADH dehydrogenase-like complex in Marchantia polymorpha
Composition and physiological function of the chloroplast NADH dehydrogenase-like complex in Marchantia polymorpha
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DOI：
10.1111/j.1365-313x.2012.05115.x
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发表时间：
2012-11-01
期刊：
影响因子：
7.2
通讯作者：
Shikanai, Toshiharu
中科院分区：
文献类型：
--
作者：
Ueda, Minoru;Kuniyoshi, Tetsuki;Shikanai, Toshiharu
叶绿体类NADH脱氢酶(NDH)复合体由5个亚复合体组成，在被子植物中进一步与光系统I(PSI)结合形成超复合体。在多态地钱中，11个叶绿体编码亚基以及A、B、膜和铁还蛋白结合亚复合体的所有核编码亚基都是保守的。然而，这种地钱的基因组不太可能编码Lhca5和Lhca6，这两个基因都介导了NDHPSI超复合体的形成。管腔亚复合体的亚基PnsL1L4也不太可能由基因组编码。与此相一致的是，蓝色天然凝胶电泳的结果表明，在Marchantia中检测到的NDH亚单位比在拟南芥中检测到的NDHPSI超复合体的分子质量更低。利用叶绿体转化技术，我们敲除了Marchantia的ndhB基因。虽然野生型基因组拷贝被完全分离，但Delta ndhB系的光自养生长与野生型相似。反映被子植物体内NDH活性的叶绿素荧光在光照后的瞬时增强在Delta ndhB品系的叶状体中没有出现。在破裂的叶绿体中，抗霉素A不敏感和铁还蛋白依赖的质醌还原受到损害，这表明叶绿体NDH介导了类似的电子传递，尽管它在结构上可能有所不同。与被子植物一样，Delta ndhb系对线性电子传递的影响不大。然而，在弱光条件下，叶绿体对苯二酚库的减少程度略有增加，这表明叶绿体NDH在系统间的氧化还原平衡中发挥作用，尤其是在弱光条件下。
The chloroplast NADH dehydrogenase-like (NDH) complex mediates cyclic electron transport and chloro-respiration and consists of five sub-omplexes, which in angiosperms further associate with photosystem I (PSI) to form a super-complex. In Marchantia polymorpha, 11 plastid-encoded subunits and all the nuclear-encoded subunits of the A, B, membrane and ferredoxin-binding sub-complexes are conserved. However, it is unlikely that the genome of this liverwort encodes Lhca5 and Lhca6, both of which mediate NDHPSI super-complex formation. It is also unlikely that the subunits of the lumen sub-complex, PnsL1L4, are encoded by the genome. Consistent with this in silico prediction, the results of blue-native gel electrophoresis showed that NDH subunits were detected in a protein complex with lower molecular mass in Marchantia than the NDHPSI super-complex in Arabidopsis. Using the plastid transformation technique, we knocked out the ndhB gene in Marchantia. Although the wild-type genome copies were completely segregated out, the Delta ndhB lines grew like the wild-type photoautotrophically. A post-illumination transient increase in chlorophyll fluorescence, which reflects NDH activity in vivo in angiosperms, was absent in the thalli of the Delta ndhB lines. In ruptured chloroplasts, antimycin A-insensitive, and ferredoxin-dependent plastoquinone reduction was impaired, suggesting that chloroplast NDH mediates similar electron transport in Marchantia and Arabidopsis, despite its possible difference in structure. As in angiosperms, linear electron transport was not strongly affected in the Delta ndhB lines. However, the plastoquinone pool was slightly more reduced at low light intensity, suggesting that chloroplast NDH functions in redox balancing of the inter system, especially under low light conditions.