Architecture of the PPR gene family in the moss Physcomitrella patens

Abstract

Pentatricopeptide repeat (PPR) proteins are widespread in eukaryotes and in particular, include several hundred members in land plants. The majority of PPR proteins are localized in mitochondria and plastids, where they play a crucial role in various aspects of RNA metabolism at the post-transcriptional level in gene expression. However, many of their functions remain to be characterized. In contrast to vascular plants, the moss Physcomitrella patens has only 105 PPR genes. This number may represent a minimum set of PPR proteins required for post-transcriptional regulation in plant organelles. Here, we review the overall structure of the P. patens PPR gene family and the current status of the functional characterization of moss PPR proteins.

Keywords: DYW domain; PPR protein; Physcomitrella patens; RNA cleavage; RNA editing; RNA splicing; homologous recombination; moss; targeted gene disruption.

Figure 1. Examples of intron conservation in the homologous PPR genes. In each figure, the first panel shows the gene structure and the second panel shows the motif structure of the predicted PPR proteins.

Figure 2. Detection of RNase activity of the recombinant moss DYW proteins. (α-³²P-UTP)-labeled mitochondrial ccmFc RNA (402 nt) or nad3 RNA (433 nt) was incubated at 28°C for 15, 30 or 60 min (indicated as wedge-shape) with the indicated r-DYW proteins (r-56, r-65, r-71, r-77, r-78 or r-79, 50 ng each) or without protein (No r-DYW) in the presence of 6 mM MgCl₂ and 25 mM EDTA as previously described. (³²P)-labeled RNA was analyzed on 6% polyacrylamide gels containing 6 M urea, and detected by autoradiography.