拟南芥DG1参与叶绿体早期光合蛋白合成功能

DG1 Participates in the Photosynthetic Protein Synthesis at the Early Stage of Chloroplast Development of Arabidopsis

拟南芥中已有466个PPR蛋白,已有研究证实许多PPR蛋白参与细胞器基因表达的转录后调节,但大部分PPR蛋白分子作用机制尚不清楚。Delayed greening1(DG1)是定位于叶绿体中的的PPR蛋白,研究结果证实该蛋白是通过与SIG6因子相互作用降低PEP转录活性从而影响叶绿体早期发育。本研究利用拟南芥Dg1基因功能缺陷型突变体研究了DG1蛋白对光系统蛋白复合体组成及其光转化效率的影响。77K荧光发射光谱分析发现dg1突变体幼叶PSⅡ中电子传递速度明显低于野生型,而成熟叶片与野生型基本一致;蓝绿温和胶分析结果表明:相对于野生型在dg1突变体新生叶中PSⅡ、PSⅠ及其超聚复合物含量均有不同程度降低;进一步温和胶二向电泳及蛋白免疫印迹分析显示,在dg1突变体新生叶中,由叶绿体编码的光系统蛋白复合物组成亚基含量显著降低,而核编码复合物组成亚基含量与野生型相比没有明显区别。上述实验结果进一步确定了DG1蛋白是通过调控叶绿体编码基因的表达进而调节光系统复合物的生物合成与组装,最终影响拟南芥叶绿体早期发育。因此,我们认为DG1蛋白对于叶绿体发育早期光合蛋白的合成是必需的。

There are at least 466 PPR proteins identified in Arabidopsis, and a number of which are involved in the regulation of posttranscriptional modification of organelle genes. However, the mechanism of most PPR proteins remain unclear. Delayed greening 1 （DG1） is one of PPR proteins located in the chloroplast, whose interaction with SIG6 had been proven to down-regulates the PEP-dependent chloroplast gene transcription and subsequently affects the early development of the chloroplast. To further investigate the impact of the DG1 on chloroplast photosystem protein complexes and the light conversion efficiency, we detected the 77K fluorescence emission spectra in the dgl mutant and wild-type plant, and discovered that the fluorescence emission spectral peak which represented PS II electronic transmission speed was obviously decreased in the young leaves of the dgl mutant; while there was no significant difference within the mature leaves of the dgl mutant and wild-type plant. The blue native page analysis indicated that the amount of PS I1, PSI and supercomplex in thylakoid of young leaves in the dgl mutant should decrease to varying degrees compared to the wild-type plant; further two dimensional electrophoresis and western blot analysis showed that the amount of subunits of photosystem complexes encoded by chloroplast decreased severely in young leaves of the dgl mutant while the amount of nucleus-encoded subunits was similar to the wild-type plants. In conclusion, the above results confirmed that DG1 affected photosystem complex synthesis by regulating the expression of the chloroplast encoded genes, which eventually influenced the early development of the chloroplasts. Our results suggested that DG1 should be essen- tial for the synthesis of photosynthetic protein in the early development of chloroplasts in.