RNA PROCESSING FACTOR3 Is Crucial for the Accumulation of MatureccmCTranscripts in Mitochondria of Arabidopsis Accession Columbia    

Abstract

RNA PROCESSING FACTOR1 (RPF1) and RPF2 are pentatricopeptide repeat (PPR) proteins involved in 5# processing of different mitochondrial mRNAs in Arabidopsis (Arabidopsis thaliana). Both factors are highly similar to RESTORERS OF FERTILITY (RF), which are part of cytoplasmic male sterility/restoration systems in various plant species. These findings suggest a predominant role of RF-like PPR proteins in posttranscriptional 5# processing. To further explore the functions of this group of proteins, we examined a number of T-DNA lines carrying insertions in the corresponding PPR genes. This screening identified a nearly complete absence of mature ccmC transcripts in an At1g62930 T-DNA insertion line, a phenotype that could be restored by the introduction of the intact At1g62930 gene into the mutant. The insertion in this nuclear gene, which we now call RPF3, also leads to a severe reduction of the CcmC protein in mitochondria. The analysis of C24/rpf3-1 F2 hybrids lacking functional RPF3 genes revealed that this gene has less influence on the generation of the mature ccmC 5# transcript end derived from a distinct ccmC 5# upstream configuration found in mitochondrial DNAs from C24 and other accessions. These data show that a particular function of an RF-like protein is required only in connection with a distinct mtDNA configuration. Our new results further substantiate the fundamental role of RF-like PPR proteins in the posttranscriptional generation of plant mitochondrial 5# transcript termini.

The Rf and Rf-like PPR in higher plants, a fast-evolving subclass of PPR genes

“…55 Unlike the extended transcripts that accumulate in other rfl mutants, the stability of unprocessed ccmC transcripts was strongly impaired in rpf3 plants indicating a possible role of RPF3 in ccmC mRNA stabilization. Nevertheless, and despite a severe decrease in CCMC protein accumulation, rpf3 mutant plants exhibited a wild-type phenotype.…”

RNA Processing Factor 7 and Polynucleotide Phosphorylase Are Necessary for Processing and Stability of nad2 mRNA in Arabidopsis Mitochondria

“…These factors, exclusively P-class PPR proteins comprising 14 PPR motifs or more, are required for efficient 5′ processing of the major transcript species transcribed from one, two or three different mitochondrial genes, [25][26][27]33 but as found recently by the analysis of the restorer of fertility-like PPR protein 9 (RFL9), are also involved in 5′ processing of rare RNA molecules in particular ecotypes. 38 The relatively high number of PPR motifs present in these proteins allowed to predict the putative binding sites on the RNA targets, which is exclusively found upstream of the 5′ end of the mature transcript.…”

“…24 These include proteins that are similar to restorer of fertility (RF) from other plant species. [25][26][27] RF proteins can rescue cytoplasmic male sterility (CMS), a maternal inherited deficiency to produce or release fertile pollen. [28][29][30][31] Recently CMS in Arabidopsis has been reported, but a nuclear gene restoring male fertility in this system has not been identified.…”

“…26,27 CR-RT-PCR experiments were done according to established protocols. 34 Northern blot analyses were performed with Biodyne A nylon membranes according to protocols given by the manufacturer (Pall Corporation, http://www.pall.com).…”

Function of PPR proteins in plastid gene expression

“…RNA PROCESSING FACTOR3 and 5 are RF-like PPR proteins that are also required for the RNA cleavages that generate the 5' ends of RNAs in mitochondria. 80,81 CRR2 is unique because even a purified recombinant PPR protein might be involved in RNA cleavage. 52,79 Notably, CRR2 truncated in the DYW domain does not complement the crr2 mutant, in contrast with the fact that the DYW domain is not required for RNA editing, as shown in some DYW members.…”