Molecular Ecology Group, State Key Laboratory of Grassland Farming System, Lanzhou University, Lanzhou, Gansu 730000, People's Republic of China.
Plant Physiol. 2011 Oct;157(2):608-19. doi: 10.1104/pp.111.183301. Epub 2011 Aug 23.
Numerous auxiliary nuclear factors have been identified to be involved in the dynamics of the photosystem II (PSII) complex. In this study, we characterized the high chlorophyll fluorescence243 (hcf243) mutant of Arabidopsis (Arabidopsis thaliana), which shows higher chlorophyll fluorescence and is severely deficient in the accumulation of PSII supercomplexes compared with the wild type. The amount of core subunits was greatly decreased, while the outer antenna subunits and other subunits were hardly affected in hcf243. In vivo protein-labeling experiments indicated that the synthesis rate of both D1 and D2 proteins decreased severely in hcf243, whereas no change was found in the rate of other plastid-encoded proteins. Furthermore, the degradation rate of the PSII core subunit D1 protein is higher in hcf243 than in the wild type, and the assembly of PSII is retarded significantly in the hcf243 mutant. HCF243, a nuclear gene, encodes a chloroplast protein that interacts with the D1 protein. HCF243 homologs were identified in angiosperms with one or two copies but were not found in lower plants and prokaryotes. These results suggest that HCF243, which arose after the origin of the higher plants, may act as a cofactor to maintain the stability of D1 protein and to promote the subsequent assembly of the PSII complex.
许多辅助核因子已被鉴定参与光系统 II (PSII) 复合物的动态变化。在这项研究中，我们对拟南芥（Arabidopsis thaliana）的高叶绿素荧光 243（hcf243）突变体进行了表征，与野生型相比，该突变体表现出更高的叶绿素荧光，并且 PSII 超级复合物的积累严重不足。核心亚基的含量大大降低，而 hcf243 中外天线亚基和其他亚基几乎没有受到影响。体内蛋白标记实验表明，hcf243 中 D1 和 D2 蛋白的合成速率严重下降，而其他质体编码蛋白的速率没有变化。此外，hcf243 中 PSII 核心亚基 D1 蛋白的降解速率高于野生型，并且 hcf243 突变体中 PSII 的组装明显受阻。HCF243 是一个核基因，编码一种与 D1 蛋白相互作用的叶绿体蛋白。在被子植物中鉴定到了 HCF243 的同源物，有一个或两个拷贝，但在低等植物和原核生物中没有发现。这些结果表明，HCF243 可能在高等植物起源后作为一种辅助因子发挥作用，以维持 D1 蛋白的稳定性，并促进 PSII 复合物的后续组装。
