Two organelle RNA recognition motif proteins affect distinct sets of RNA editing sites in the Arabidopsis thaliana plastid.

Audrey M Searing,Yan Lu,Manasa B Satyanarayan,James P O Donnell

doi:10.1002/pld3.213

Audrey M Searing, Yan Lu + Show 2 more

Open Access

https://doi.org/10.1002/pld3.213

Copy DOI

Journal: Plant Direct	Publication Date: Apr 1, 2020
Citations: 5	License type: CC BY 4.0

Affiliation: Western Michigan University

Abstract

Plastid and mitochondrial RNAs in vascular plants are subjected to cytidine‐to‐uridine editing. The model plant species Arabidopsis thaliana (Arabidopsis) has two nuclear‐encoded plastid‐targeted organelle RNA recognition motif (ORRM) proteins: ORRM1 and ORRM6. In the orrm1 mutant, 21 plastid RNA editing sites were affected but none are essential to photosynthesis. In the orrm6 mutants, two plastid RNA editing sites were affected: psbF‐C77 and accD‐C794. Because psbF encodes the β subunit of cytochrome b 559 in photosystem II, which is essential to photosynthesis, the orrm6 mutants were much smaller than the wild type. In addition, the orrm6 mutants had pale green leaves and reduced photosynthetic efficiency. To investigate the functional relationship between ORRM1 and ORRM6, we generated orrm1 orrm6 double homozygous mutants. Morphological and physiological analyses showed that the orrm1 orrm6 double mutants had a smaller plant size, reduced chlorophyll contents, and decreased photosynthetic efficiency, similar to the orrm6 single mutants. Although the orrm1 orrm6 double mutants adopted the phenotype of the orrm6 single mutants, the total number of plastid RNA editing sites affected in the orrm1 orrm6 double mutants was the sum of the sites affected in the orrm1 and orrm6 single mutants. These data suggest that ORRM1 and ORRM6 are in charge of distinct sets of plastid RNA editing sites and that simultaneous mutations in ORRM1 and ORRM6 genes do not cause additional reduction in editing extent at other plastid RNA editing sites.

Highlights

RNA editing is a post-transcriptional process through which discrete changes are introduced to RNA sequences
Recombinant ORRM6 protein showed some binding activity toward the synthetic RNA flanking psbE-C214, a plastid RNA editing site not affected by the loss-of-function mutations in the ORRM6 gene (Hackett et al, 2017)
The results showed that ORRM1 and ORRM6 are in charge of distinct sets of plastid RNA editing sites

Summary

| INTRODUCTION

RNA editing is a post-transcriptional process through which discrete changes are introduced to RNA sequences. In plant plastids and mitochondria, C-to-U RNA editing is carried out by the RNA editing complex, which contains at least four types of editing factors: pentatricopeptide repeat (PPR) and PPR-related proteins, RNA editing interacting proteins/multiple organellar RNA editing factors (RIPs/MORFs), organelle zinc finger (OZ) proteins, and organelle RNA recognition motif (ORRM) proteins (Lu, 2018; Shi, Hanson, et al, 2017; Sun et al, 2016; Takenaka et al, 2013). RIPs/MORFs were found to interact with other types of RNA editing factors, including PPRs (Bentolila et al, 2012; Takenaka et al, 2012; Zhang et al, 2014), OZ1 (Sun et al, 2015), and ORRMs (Hackett et al, 2017; Shi, Germain, Hanson, & Bentolila, 2016b; Shi, Hanson, & Bentolila, 2015). Recombinant ORRM6 protein showed some binding activity toward the synthetic RNA flanking psbE-C214, a plastid RNA editing site not affected by the loss-of-function mutations in the ORRM6 gene (Hackett et al, 2017). The results showed that ORRM1 and ORRM6 are in charge of distinct sets of plastid RNA editing sites

| MATERIALS AND METHODS

| DISCUSSION

Findings

C RARE1 or LPA66