Wang Xuemei, Yang Zhipan, Zhang Yi, Zhou Wen, Zhang Aihong, Lu Congming
Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
J Integr Plant Biol. 2020 Nov;62(11):1741-1761. doi: 10.1111/jipb.12936. Epub 2020 May 15.
To gain a better understanding of the molecular mechanisms of photosystem I (PSI) biogenesis, we characterized the Arabidopsis thaliana photosystem I biogenesis factor 2 (pbf2) mutant, which lacks PSI complex. PBF2 encodes a P-class pentatricopeptide repeat (PPR) protein. In the pbf2 mutants, we observed a striking decrease in the transcript level of only one gene, the chloroplast gene ycf3, which is essential for PSI assembly. Further analysis of ycf3 transcripts showed that PBF2 is specifically required for the splicing of ycf3 intron 1. Computational prediction of binding sequences and electrophoretic mobility shift assays reveal that PBF2 specifically binds to a sequence in ycf3 intron 1. Moreover, we found that PBF2 interacted with two general factors for group II intron splicing CHLOROPLAST RNA SPLICING2-ASSOCIATED FACTOR1 (CAF1) and CAF2, and facilitated the association of these two factors with ycf3 intron 1. Our results suggest that PBF2 is specifically required for the splicing of ycf3 intron 1 through cooperating with CAF1 and CAF2. Our results also suggest that additional proteins are required to contribute to the specificity of CAF-dependent group II intron splicing.
为了更好地理解光系统I（PSI）生物发生的分子机制，我们对拟南芥光系统I生物发生因子2（pbf2）突变体进行了表征，该突变体缺乏PSI复合物。PBF2编码一种P类五肽重复（PPR）蛋白。在pbf2突变体中，我们观察到只有一个基因（叶绿体基因ycf3）的转录水平显著下降，ycf3对PSI组装至关重要。对ycf3转录本的进一步分析表明，PBF2是ycf3内含子1剪接所特需的。结合序列的计算预测和电泳迁移率变动分析表明，PBF2特异性结合ycf3内含子1中的一个序列。此外，我们发现PBF2与II类内含子剪接的两个通用因子叶绿体RNA剪接2相关因子1（CAF1）和CAF2相互作用，并促进这两个因子与ycf3内含子1的结合。我们的结果表明，PBF2通过与CAF1和CAF2合作，是ycf3内含子1剪接所特需的。我们的结果还表明，需要其他蛋白质来促进CAF依赖性II类内含子剪接的特异性。
