Identification of prp4 kinase and sac3a mutations in a genetic screen for mutants altered in pre-mRNA splicing of a GFP reporter gene

In a forward genetic screen for mutants showing modified splicing of an alternatively-spliced GFP reporter gene in the model plant Arabidopsis thaliana, we identified mutations in genes encoding PRP4 kinase-a (PRP4Ka) and SAC3a. Although not yet studied in plants, these proteins have been have been shown in other organisms to be, respectively, a spliceosome-associated protein kinase and a factor involved nucleo-cytoplasmic transport of mRNA. To understand further the roles of PRP4Ka and SAC3a in transcription and alternative splicing in Arabidopsis, we analyzed RNA-seq data from selected prp4ka and sac3a mutants to identify differentially expressed genes and changes in alternative splicing patterns. To investigate protein substrates of PRP4Ka, we carried out iTRAQ phosphoproteomics using proteins extracted from a prp4ka mutant and wild-type plants. Analysis of the collective results will increase knowledge of previously uncharacterized splicing factors in plants.