Insights into PPR Gene Family in Cajanus Cajan and Other Legume Species

PPR proteins comprises of several hundred members among land plants and govern a fascinating array of functions in organeller genomes that ranges from participation in stabilization of organeller transcripts, RNA editing to fertility restoration of CMS lines. Despite the availability of genome sequences of several legume species, comprehensive cataloguing of members of PPR gene family has not been carried out. In the current study, we identified 523, 830, 534, 816, 441 and 677 PPR proteins in Cajanus, Glycine, Phaseolus, Medicago, Vigna and Cicer genomes, respectively and their complete in silico categorization was undertaken to classify them into various sub-classes and their localization prediction. Chromosomal coordinates of 271 Cajanus PPR genes were predicted and their homologues were identified in 5 other legumes revealing extensive genome conservation. PPR genes of all 6 legume species were further probed to identify restorer of fertility-like PPRs (RFLs) on the basis of protein clustering and followed by homology searches to already known Rf-PPR genes. Seventy RFL PPR genes (P sub-class) were identified and were scrutinized by phylogenetic analysis which revealed extended similarity and common features shared by these RFLs across the species. Some of these RFL PPRs were present as small clusters in Glycine, Phaseolus, Vigna and Cicer genomes. This study has generated a knowledge base about PPR gene family in legumes and opens several avenues for future investigations into their molecular functions, evolutionary relationships and their potential in identifying markers to enable cloning of Rf genes.