SlRBP1 promotes translational efficiency via SleIF4A2 to maintain chloroplast function in tomato 

第一作者：Liqun Ma

第一单位：中国农业大学

通讯作者：Hongliang Zhu

 Abstarct 

背景回顾：Many glycine-rich RNA binding proteins (GR-RBPs) have critical functions in RNA processing and metabolism. 

很多富含甘氨酸RNA结合蛋白GR-RBPs在RNA加工和代谢过程中发挥关键作用。

主要发现：Here, we describe a role for the tomato (Solanum lycopersicum) GR-RBP SlRBP1 in regulating mRNA translation. 

本文中，作者鉴定了番茄GR-RBP蛋白SlRBP1在调控mRNA翻译方面的功能。

结果1-SlRBP1敲低表型：We found that SlRBP1 knock-down mutants (slrbp1) displayed reduced accumulation of total chlorophyll and impaired chloroplast ultrastructure. These phenotypes were accompanied by deregulation of the levels of numerous key transcripts associated with chloroplast functions in slrbp1. 

作者发现，SlRBP1敲低突变体slrbp1会表现出总叶绿素积累减少，并且叶绿体超微结构缺陷的表型。这些缺陷表型还伴随着与叶绿体功能相关的很多关键转录本水平异常。

结果2-SlRBP1靶向RNAs：Furthermore, native RNA immunoprecipitation-sequencing (nRIP-seq) recovered 61 SlRBP1-associated RNAs, most of which are involved in photosynthesis. SlRBP1 binding to selected target RNAs was validated by nRIP-qPCR. 

此外，nRIP-seq分析鉴定了61个与SlRBP1相关的RNAs，大多数都参与光合作用。作者进一步通过nRIP-qPCR验证了SlRBP1能够结合到这些靶标RNAs上。

结果3-SlRBP1通过SleIF4A2影响靶向RNAs的翻译：Intriguingly, the accumulation of proteins encoded by SlRBP1-bound transcripts, but not the mRNAs themselves, was reduced in slrbp1 mutants. Polysome profiling followed by RT-qPCR assays indicated that the polysome occupancy of target RNAs was lower in slrbp1 plants than in wild type. Furthermore, SlRBP1 interacted with the eukaryotic translation initiation factor SleIF4A2. Silencing of SlRBP1 significantly reduced SleIF4A2 binding to SlRBP1-target RNAs. 

有趣的是，由SlRBP1结合的转录本所翻译的蛋白在slrbp1突变体中降低，但是这些转录本mRNA水平却无明显变化。多聚核糖体图谱结合RT-qPCR实验显示，相比于野生型，由SlRBP1靶向RNAs的多聚核糖体占据水平在slrbp1突变体中要更低。此外，SlRBP1能够与真核翻译起始因子SleIF4A2进行互作。沉默SlRBP1基因会显著减少SleIF4A2结合到由SlRBP1靶向RNAs。

结论：Taking these observations together, we propose that SlRBP1 binds to and channels RNAs onto the SleIF4A2 translation initiation complex and promotes the translation of its target RNAs to regulate chloroplast functions.

综上，本文的研究显示SlRBP1能够结合靶向RNAs，并将其引导到SleIF4A2翻译起始复合物，从而促进这些靶向RNAs的翻译，最终调控叶绿体的功能。

** 朱鸿亮 **

doi: https://doi.org/10.1093/plcell/koac104

​Journal: The Plant Cell

First Published: April 06, 2022