JIPB|中国水稻研究所胡培松、魏祥进发现叶绿体RNA剪接的五肽重复蛋白低温条件下影响水稻叶绿体发育

PPR 蛋白在植物细胞器 rna 的转录后修饰中起着重要作用。然而，大多数 PPR 蛋白的功能仍然是未知的。对水稻叶片发育早期表型为白化突变体的叶绿素缺乏4号(cde4)进行了研究，发现该突变体在低温(20 ° c)条件下叶绿素含量下降，叶绿体异常。图位克隆表明，CDE4编码一个位于叶绿体内的 p 型 PPR 蛋白。在 cde4突变体中，质体编码的聚合酶(PEP)依赖的转录本水平显著降低，但核编码基因的转录本水平比野生型植物在20 ° c 的转录本水平增加。CDE4与叶绿体基因 rpl2、 ndhA 和 ndhB 的转录产物直接结合。Cde4突变体在20 ° c 时这些基因的内含子剪接有缺陷，但在32 ° c 时正常。此外，CDE4与鸟苷酸激酶 viresccent 2(V2)相互作用，V2的过度表达增强了 CDE4蛋白的稳定性，从而在20 ° c 下挽救了 CDE4表型。结果表明，CDE4参与了质体 RNA 剪接，在低温条件下水稻叶绿体的发育过程中起着重要作用。

Pentatricopeptide repeat (PPR) proteins play important roles in the posttranscriptional modification of organellar RNAs in plants. However, the function of most PPR proteins remains unknown. Here, we characterized the rice (Oryza sativa L.) chlorophyll deficient 4 (cde4) mutant which exhibits an albino phenotype during early leaf development, with decreased chlorophyll contents and abnormal chloroplasts at low-temperature (20°C). Positional cloning revealed that CDE4 encodes a P-type PPR protein localized in chloroplasts. In the cde4 mutant, plastid-encoded polymerase (PEP)-dependent transcript levels were significantly reduced, but transcript levels of nuclear-encoded genes were increased compared to wild-type plants at 20°C. CDE4 directly binds to the transcripts of the chloroplast genes rpl2, ndhA and ndhB. Intron splicing of these transcripts was defective in the cde4 mutant at 20°C, but was normal at 32°C. Moreover, CDE4 interacts with the guanylate kinase VIRESCENT 2 (V2); overexpression of V2 enhanced CDE4 protein stability, thereby rescuing the cde4 phenotype at 20°C. Our results suggest that CDE4 participates in plastid RNA splicing and plays an important role in rice chloroplast development under low-temperature conditions.

https://doi.org/10.1111/jipb.13147

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