Tu Yayi, Jin Yongsheng, Ma Dongyuan, Li Heng, Zhang Zhenqian, Dong Jiangli, Wang Tao
State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Sci Rep. 2015 Oct 26;5:15605. doi: 10.1038/srep15605.
The photosynthetic rate of virus-infected plants is always reduced. However, the molecular mechanism underlying this phenomenon remains unclear. The helper component-proteinase (HC-Pro) of Potato virus Y (PVY) was found in the chloroplasts of PVY-infected tobacco, indicating some new function of HC-Pro in the chloroplasts. We generated HC-Pro transgenic plants with a transit peptide to target the protein to chloroplast. The HC-Pro transgenic tobacco showed a decreased photosynthetic rate by 25% at the light intensity of 600 μmol m(-2) s(-1). Using a yeast two-hybrid screening assay to search for chloroplast proteins interacting with HC-Pro, we identified that PVY HC-Pro can interact with the chloroplast ATP synthase NtCF1β-subunit. This interaction was confirmed by GST pull-down and co-immunoprecipitation assays. HC-Pro didn't interfere with the activity of assembled ATP synthase in vitro. The HC-Pro/NtCF1β-subunit interaction might affect the assembly of ATP synthase complex. Quantitative western blot and immunogold labeling of the ATP synthase indicated that the amount of ATP synthase complex was decreased in both the HC-Pro transgenic and the PVY-infected tobacco. These results demonstrate that HC-Pro plays an important role in reducing the photosynthetic rate of PVY-infected plants, which is a completely new role of HC-Pro besides its multiple known functions.
病毒感染的植物光合速率总是降低。然而，这一现象背后的分子机制仍不清楚。在感染马铃薯Y病毒（PVY）的烟草叶绿体中发现了PVY的辅助成分蛋白酶（HC-Pro），这表明HC-Pro在叶绿体中具有一些新功能。我们构建了带有转运肽的HC-Pro转基因植物，使该蛋白靶向叶绿体。在600 μmol m(-2) s(-1)的光照强度下，HC-Pro转基因烟草的光合速率降低了25%。利用酵母双杂交筛选试验寻找与HC-Pro相互作用的叶绿体蛋白，我们鉴定出PVY HC-Pro可与叶绿体ATP合酶NtCF1β亚基相互作用。通过谷胱甘肽-S-转移酶（GST）下拉试验和免疫共沉淀试验证实了这种相互作用。HC-Pro在体外不干扰组装好的ATP合酶的活性。HC-Pro/NtCF1β亚基相互作用可能影响ATP合酶复合体的组装。ATP合酶的定量蛋白质免疫印迹和免疫金标记表明，在HC-Pro转基因烟草和感染PVY的烟草中，ATP合酶复合体的数量均减少。这些结果表明，HC-Pro在降低PVY感染植物的光合速率中起重要作用，这是HC-Pro除其多个已知功能外的一个全新作用。
