PRP8A and PRP8B spliceosome subunits act coordinately to  control pollen tube attraction in Arabidopsis thaliana
Purpose: Alternative splicing is fundamental for post-transcriptional regulation and proteome diversity. The goals of this study are to compare transcriptome and splicing profiling (RNA-seq) between wild type and prp8a prp8b mutant ovules of the spliceosome subunit and define the molecular signature of prp8a prp8b pollen tube attraction phenotype. Methods: mRNA profiles from mature ovules of 6-weeks-old wild-type (WT) and pre-mRNA processing factor 8 (PRP8Aa prp8bb) Arabidopsis plants were generated by deep sequencing, in triplicates, using Illumina HiSeq4000 100bp paired-end reads. The sequence reads that passed quality filters were were mapped to TAIR10 whole genome and analyzed for differential expression, differential exone usage and intron retention as indicated in DATA PROCESSING PIPELINE section. Results: Using an optimized data analysis workflow, about 15 million sequence read pairs per sample were mapped to the Arabidopsis genome (TAIR10). Approximately 2.9% of the transcripts showed differential expression between the WT and PRP8Aa prp8bb ovules, with a fold change =1.5 and p value <0.05. Analysis for differential gene expression, exon usage and intron retention with DESeq2 v1.22.1 and DEXseq v1.28.0 or IRFinder v1.2.3 respectively, uncovered several as yet uncharacterized genes that may contribute to pollen tube attraction and female gametophyte cell fate specification. Conclusions: Our work has uncovered a molecular signature through which PRP8A/PRP8B subunits act redundantly to define male-female signaling competence for successful pollen tube attraction in Arabidopsis. Application of DESeq2 algorithms to our ovule RNA-seq data identified downregulation of over 50 different CRP genes with yet unknown function from the synergid and the central cells including all LURE pollen tube attractants. Whereas use of DEXseq workflow, revealed mis-splicing of key genes involved embryo sac specificiation and genes of the secretory pathway. We concluded that 100bp paired-end RNAseq was a sufficient compromise for detection of differential gene expression and splice isoforms, however, our experiment would have benefited with more number of replicates. Overall design: Mature ovules mRNA profiles of 6-weeks-old wild-type (WT) and pre-mRNA processing factor 8 (PRP8Aa prp8bb) Arabidopsis plants