Analysis of the Roles of the Arabidopsis nMAT2 and PMH2 Proteins Provided with New Insights into the Regulation of Group II Intron Splicing in Land-Plant Mitochondria.

Michal Zmudjak,Sofia Shevtsov,Ido Keren,Oren Ostersetzer-Biran,Laure Sultan

doi:10.3390/ijms18112428

Abstract

Plant mitochondria are remarkable with respect to the presence of numerous group II introns which reside in many essential genes. The removal of the organellar introns from the coding genes they interrupt is essential for respiratory functions, and is facilitated by different enzymes that belong to a diverse set of protein families. These include maturases and RNA helicases related proteins that function in group II intron splicing in different organisms. Previous studies indicate a role for the nMAT2 maturase and the RNA helicase PMH2 in the maturation of different pre-RNAs in Arabidopsis mitochondria. However, the specific roles of these proteins in the splicing activity still need to be resolved. Using transcriptome analyses of Arabidopsis mitochondria, we show that nMAT2 and PMH2 function in the splicing of similar subsets of group II introns. Fractionation of native organellar extracts and pulldown experiments indicate that nMAT2 and PMH2 are associated together with their intron-RNA targets in large ribonucleoprotein particle in vivo. Moreover, the splicing efficiencies of the joint intron targets of nMAT2 and PMH2 are more strongly affected in a double nmat2/pmh2 mutant-line. These results are significant as they may imply that these proteins serve as components of a proto-spliceosomal complex in plant mitochondria.

Highlights

Plants are able to regulate and coordinate their energy demands during particular growth and developmental stages
Proteins that interact with group II introns to facilitate their splicing are divided into two main categories, based on their topology and predicted evolutionary origins [14,15,54,55,56]: (i) proteins that are encoded within the introns themselves (i.e., Intron Encoded Proteins, IEPs; or maturases); and (ii) various ‘trans-acting’ factors that function in the splicing of group II introns
Maturases encoded within group II introns contain several functional domains that are required for both the splicing activity and intron mobility [15,28,57]

Summary

Introduction

Plants are able to regulate and coordinate their energy demands during particular growth and developmental stages These activities require complex cellular signaling between the nucleus and the mitochondrial genome (i.e., mitogenome (mtDNA)) (reviewed by e.g., [1,2]). Mitochondria contain their own genetic material, encoding some proteins and structural RNAs, the vast majority of mitochondrial proteins are encoded by nuclear loci, and are imported from the cytosol post-translationally [3,4,5,6]. The processing of the organellar pre-RNAs is essential for respiratory activities and relies on the activities of many different cofactors which belong to a diverse set of RNA-binding protein families

Methods

Results

Conclusion