Tissue-specific alternative splicing of pentatricopeptide repeat (PPR) family genes in Arabidopsis thaliana

Alternative splicing is a post- and co-transcriptional regulatory mechanism of gene expression. Pentatricopeptide repeat (PPR) family proteins were recently found to be involved in RNA editing in plants. The aim of this study was to investigate the tissue-specific expression and alternative splicing of PPR family genes and their effects on protein structure and functionality. Of the 27 PPR genes in Arabidopsis thaliana, we selected six PPR genes of the P subfamily that are likely alternatively spliced, which were confirmed by sequencing. Four of these genes show intron retention, and the two remaining genes have 3' alternative-splicing sites. Alternative-splicing events occurred in the coding regions of three genes and in the 3' UTRs of the three remaining genes. We also identified five previously unannotated alternatively spliced isoforms of these PPR genes, which were confirmed by PCR and sequencing. Among these, three contain 3' alternative-splicing sites, one contains a 5' alternative-splicing site, and the remaining gene contains a 3'-5' alternative-splicing site. The new isoforms of two genes affect protein structure, and three other alternativesplicing sites are located in 3' UTRs. These findings suggest that tissue-specific expression of different alternatively spliced transcripts occurs in Arabidopsis, even at different developmental stages.