Identification of soybean trans-factors associated with plastid RNA editing sites

RNA editing is a posttranscriptional process that changes nucleotide sequences, among which cytosine-to-uracil by a deamination reaction can revert non-neutral codon mutations. Pentatricopeptide repeat (PPR) proteins comprise a family of RNA-binding proteins, with members acting as editing trans-factors that recognize specific RNA cis-elements and perform the deamination reaction. PPR proteins are classified into P and PLS subfamilies. In this work, we have designed RNA biotinylated probes based in soybean plastid RNA editing sites to perform trans-factor specific protein isolation. Soybean cis-elements from these three different RNA probes show differences in respect to other species. Pulldown samples were submitted to mass spectrometry for protein identification. Among detected proteins, five corresponded to PPR proteins. More than one PPR protein, with distinct functional domains, was pulled down with each one of the RNA probes. Comparison of the soybean PPR proteins to Arabidopsis allowed identification of the closest homologous. Differential gene expression analysis demonstrated that the PPR locus Glyma.02G174500 doubled its expression under salt stress, which correlates with the increase of its potential rps14 editing. The present study represents the first identification of RNA editing trans-factors in soybean. Data also indicated that potential multiple trans-factors should interact with RNA cis-elements to perform the RNA editing.