OsCRP1, a Ribonucleoprotein Gene, Regulates Chloroplast mRNA Stability That Confers Drought and Cold Tolerance.

Seung Woon Bang,Jun Sung Seo,Soo-Chul Park,Dong-Keun Lee,Su-Hyun Park,Ju-Kon Kim,Ho Suk Lee,Youn Shic Kim

doi:10.3390/ijms22041673

Abstract

Chloroplast ribonucleoproteins (cpRNPs) are nuclear-encoded and highly abundant proteins that are proposed to function in chloroplast RNA metabolism. However, the molecular mechanisms underlying the regulation of chloroplast RNAs involved in stress tolerance are poorly understood. Here, we demonstrate that CHLOROPLAST RNA-BINDING PROTEIN 1 (OsCRP1), a rice (Oryza sativa) cpRNP gene, is essential for stabilization of RNAs from the NAD(P)H dehydrogenase (NDH) complex, which in turn enhances drought and cold stress tolerance. An RNA-immunoprecipitation assay revealed that OsCRP1 is associated with a set of chloroplast RNAs. Transcript profiling indicated that the mRNA levels of genes from the NDH complex significantly increased in the OsCRP1 overexpressing compared to non-transgenic plants, whereas the pattern in OsCRP1 RNAi plants were opposite. Importantly, the OsCRP1 overexpressing plants showed a higher cyclic electron transport (CET) activity, which is essential for elevated levels of ATP for photosynthesis. Additionally, overexpression of OsCRP1 resulted in significantly enhanced drought and cold stress tolerance with higher ATP levels compared to wild type. Thus, our findings suggest that overexpression of OsCRP1 stabilizes a set of mRNAs from genes of the NDH complex involved in increasing CET activity and production of ATP, which consequently confers enhanced drought and cold tolerance.

Highlights

Members of the green plant lineage have chloroplasts with their own organellar genomes that have their evolutionary origins in endosymbiotic cyanobacteria
Nuclear-encoded chloroplast ribonucleoproteins consist of a transit peptide (TP) and two RNA recognition motifs (RRM) that are involved in the interaction with
The A. thaliana genome is predicted to encode 10 Chloroplast ribonucleoproteins (cpRNPs) (Figure 1a), and we identified 8 cpRNP proteins encoded by the rice genome based on the conserved RRM protein sequence of AtCP31A, using SmartBLAST

Summary

Introduction

Members of the green plant lineage have chloroplasts with their own organellar genomes that have their evolutionary origins in endosymbiotic cyanobacteria. Expression of chloroplast mRNAs is regulated at both the transcriptional and posttranscriptional levels [1,2,3], and during post-transcriptional regulation, numerous nucleus-encoded RNA-binding proteins (RBPs) act as a regulator of cleavage, splicing, editing, or stabilization of chloroplast RNAs [3,4]. The consensus RNP structure of five tobacco (Nicotiana sylvestris) cpRNPs (cp, cp29A, cp29B, cp, and cp33) has been solved and their binding affinities to RNA homopolymers, such as poly (G) and poly (U), have been determined. These studies suggest that cpRNPs have a key function in chloroplast RNA metabolism [10,11]. While a number experimental systems have been used to elucidate the molecular mechanisms and functions of cpRNPs, there are still several important crop species for which such information is absent, notably rice (Oryza sativa)

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