PARN-like Proteins Regulate Gene Expression in Land Plant Mitochondria by Modulating mRNA Polyadenylation.

Takashi Hirayama

doi:10.3390/ijms221910776

Abstract

Mitochondria have their own double-stranded DNA genomes and systems to regulate transcription, mRNA processing, and translation. These systems differ from those operating in the host cell, and among eukaryotes. In recent decades, studies have revealed several plant-specific features of mitochondrial gene regulation. The polyadenylation status of mRNA is critical for its stability and translation in mitochondria. In this short review, I focus on recent advances in understanding the mechanisms regulating mRNA polyadenylation in plant mitochondria, including the role of poly(A)-specific ribonuclease-like proteins (PARNs). Accumulating evidence suggests that plant mitochondria have unique regulatory systems for mRNA poly(A) status and that PARNs play pivotal roles in these systems.

Highlights

IntroductionMitochondria carry out oxidative phosphorylation (respiration) and various metabolic processes
Overall View of Mitochondrial TranscriptionMitochondria carry out oxidative phosphorylation and various metabolic processes
Transgenic Marchantia strongly expressing MpAGS1 accumulate polyadenylated mitochondrial mRNA even though recombinant MpAGS1 protein show no poly(A) polymerase activity in vitro [36]. These observations strongly suggest that the regulation of mitochondrial mRNA polyadenylation status by poly(A)-specific ribonuclease (PARN) and PAP is conserved in Arabidopsis and Marchantia and that this regulatory system is likely conserved at least among land plants (Figure 1)

Summary

Introduction

Mitochondria carry out oxidative phosphorylation (respiration) and various metabolic processes. Uncovering the systems that regulate gene expression in mitochondria is important for understanding mitochondrial function and the relationships between organellar and cellular activities. Regulation of gene expression, including that of genes in both the nucleus and the mitochondria, primarily involves regulation of transcription initiation, translation, or stability of transcripts or proteins. The resulting transcripts are translated independently and have different translation efficiencies [23] Another unique feature of plant mitochondrial mRNAs is that their nucleotide sequences are edited considerably after transcription. Many excellent articles provide an overall view of mitochondrial RNA metabolism and its diversity [46,47,48] In this short review, I will focus on the regulation of the poly(A) tail in mitochondria and describe recent progress in elucidating the regulation and functions of poly(A) tracts of plant mitochondrial mRNAs

Polyadenylation of Mitochondrial mRNAs

Another PARN-Like Arabidopsis Protein Also Functions in Mitochondria

Physiological Role of the Polyadenylation of Plant Mitochondrial mRNA

10. Concluding Remarks and Future Prospects