Stepwise evolution of supercomplex formation with photosystem I is required for stabilization of chloroplast NADH dehydrogenase-like complex: Lhca5-dependent supercomplex formation in Physcomitrella patens
Stepwise evolution of supercomplex formation with photosystem I is required for stabilization of chloroplast NADH dehydrogenase-like complex: Lhca5-dependent supercomplex formation in Physcomitrella patens
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DOI：
10.1111/tpj.14080
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发表时间：
2018-12-01
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：
Kato, Yoshinobu;Odahara, Masaki;Shikanai, Toshiharu
在被子植物中，如拟南芥和大麦，叶绿体 NADH 脱氢酶样 (NDH) 复合物与两个副本的光系统 I (PSI) 超复合物结合，形成 NDH-PSI 超复合物，以稳定 NDH 复合物。两种连接蛋白 Lhca5 和 Lhca6 是光捕获复合物 I (LHCI) 家族的成员，并介导这种超级复合物的形成。地钱地钱是从基础陆地植物谱系分支出来的，既没有Lhca5，也没有Lhca6。因此，NDH 复合物不会与该植物中的 PSI 形成超级复合物。 Lhca6 基因似乎也不存在于苔藓小立碗藓 (Physcomitrella) 中。相反，Lhca5 基因已在立碗藓中发现，尽管仍缺乏实验证据证明其作为连接子对 NDH-PSI 超复合物形成的贡献。在这里，我们对立碗藓中的 Lhca5 敲除突变体 (lhca5) 进行了生化表征。在野生型立碗藓中观察到的 NDH-PSI 超复合物在 lhca5 突变体中不存在。在该 NDH-PSI 超复合物中检测到 Lhca5 蛋白。一些 PSI 和 NDH 亚基与 Lhca5-HA 进行免疫共沉淀。这些结果表明，Physcomitrella 基因是拟南芥中报道的 Lhca5 的功能直系同源物。在立碗藓和拟南芥中，基质环区域在 Lhca5 蛋白中高度保守，但在其他 LHCI 成员中则不然。我们发现Lhca5有助于NDH复合物的稳定积累，但部分NDH复合物仍然对高光强度敏感，即使在野生型中也是如此。我们认为被子植物获得了另一种连接蛋白 Lhca6，以进一步稳定 NDH 复合物。
In angiosperms, such as Arabidopsis and barley, the chloroplast NADH dehydrogenase-like (NDH) complex associates with two copies of photosystem I (PSI) supercomplex to form an NDH-PSI supercomplex for the stabilization of the NDH complex. Two linker proteins, Lhca5 and Lhca6, are members of the light-harvesting complex I (LHCI) family and mediate this supercomplex formation. The liverwort Marchantia polymorpha has branched from the basal land plant lineage and has neither Lhca5 nor Lhca6. Consequently, the NDH complex does not form a supercomplex with PSI in this plant. The Lhca6 gene does not seem to exist also in the moss Physcomitrella patens (Physcomitrella). Conversely, the Lhca5 gene has been found in Physcomitrella, although experimental evidence is still lacking for its contribution to NDH-PSI supercomplex formation as a linker. Here, we biochemically characterized the Lhca5 knock-out mutant (lhca5) in Physcomitrella. The NDH-PSI supercomplex observed in wild-type Physcomitrella was absent in the lhca5 mutant. Lhca5 protein was detected in this NDH-PSI supercomplex. Some PSI and NDH subunits were co-immunoprecipitated with Lhca5-HA. These results indicate that the Physcomitrella gene is the functional ortholog of Lhca5 reported in Arabidopsis. Between Physcomitrella and Arabidopsis, the stromal loop region is highly conserved in Lhca5 proteins but not in other LHCI members. We found that Lhca5 contributed to the stable accumulation of the NDH complex, but part of the NDH complex was still sensitive to high light intensity, even in the wild-type. We considered that angiosperms acquired another linker protein, Lhca6, to further stabilize the NDH complex.