Project description:Coilin is a scaffold protein essential for the structural integrity of Cajal Bodies, which are non-membranous nuclear organelles that are thought to facilitate assembly and maturation of nuclear RNPs, including spliceosomal snRNPs. To investigate further coilin’s functions in plant cells, and to identify proteins that may functionally interact with coilin, we performed a genetic suppressor screen in Arabidopsis thaliana using a coilin (coi) mutant displaying altered splicing of a GFP pre-mRNA. The modified splicing pattern results in a ‘hyper-GFP’ phenotype in young coi seedlings relative to the intermediate level of GFP in wild-type seedlings. Additionally, in newly emerging leaves of older coi seedlings, the GFP gene frequently undergoes abrupt siRNA-associated posttranscriptional gene silencing that persists during growth. In the suppressor screen, we searched for mutations that subdue one or both of these GFP phenotypes and identified several understudied factors in plants: WRAP53, a putative Cajal body protein; SMU2, a predicted splicing-related factor; and ZC3HC1, an uncharacterized zinc finger protein. All three mutations return the hyper-GFP phenotype of the coi mutant to approximately the intermediate wild-type level. The zc3hc1 mutations in particular induce premature and more extensive posttranscriptional gene silencing similar to mutations in SOP1 and DCL4, which are known modifiers of posttranscriptional gene silencing. Candidate coilin-interacting proteins identified by immunoprecipitation-mass spectrometry include many splicing-related factors, nucleolar proteins, and mRNA export factors. Our results demonstrate the usefulness of the coi mutant to identify new modifiers of alternative splicing and posttranscriptional gene silencing, and suggest diverse roles for coilin in plant cells.
Project description:Two Arabidopsis thaliana splicing factor [AtU2AF65 isoforms (AtU2AF65a and AtU2AF65b)] mutants displayed the opposite flowering phenotypes. To assay the RNA processing including alternative splicing and pre-mRNA splicing of target genes of this protein in Arabidopsis, the 7-day seedlings (shoot apices) of wild type atu2af65a and atu2af65b mutants were used for RNA-Seq.
Project description:We used RNA-seq platform to determine role of a splicing factor RBM25 in regulation of gene expression and pre-mRNA splicing. We found that a loss-of-function allele of RBM25, rbm25-1, causes up- and down-regulation of a large number of genes. We further found that the rbm25-1 mutation results in defects in altenative splicing of transcripts of many genes including signal transduction components in stress responses. Examination of mRNA levels in bulked individual wild type and rbm25-1 mutant seedlings before and after ABA treatment.
Project description:Alternative splicing is prevalent in plants, but little is known about its regulation in the context of developmental and signaling pathways. We describe here a new factor that influences pre-mRNA splicing and is essential for embryonic development in Arabidopsis thaliana. This factor was retrieved in a genetic screen that identified mutants impaired in expression of an alternatively spliced GFP reporter gene. In addition to the known spliceosomal component PRP8, the screen retrieved a previously uncharacterized protein containing a Replication termination factor2 (Rtf2) domain defined by a C2HC2 zinc finger. The Rtf2 protein was discovered in fission yeast, where it stabilizes paused DNA replication forks by an unknown mechanism. When homozygous, a null mutation in Arabidopsis RTF2 (AtRTF2) is embryo-lethal, indicating that it encodes an essential protein. As revealed by quantitative RT-PCR, impaired expression of GFP in atrtf2 and prp8 mutants is attributable to inefficient splicing of the GFP pre-mRNA. A genome-wide analysis using RNA-seq demonstrated that 12% of total introns display a significant degree of retention in atrtf2 mutants. Intron-retaining transcripts are enriched from genes encoding proteins involved in signaling pathways and membrane transport. Affinity purification of AtRTF2 followed by mass spectrometry identified several known and predicted splicing proteins. In a yeast two-hybrid screen, AtRTF2 interacted with Exo70B1, a peripheral subunit of the exocyst, which is involved in vesicle trafficking. Considering these results and previous suggestions that Rtf2 constitutes an ubiquitin-related domain, we discuss possible roles of AtRTF2 in ubiquitin-based regulation of pre-mRNA splicing and membrane signaling to the spliceosome. Rtf2 is SDR1 (= AtRTF2) and was discovered in a genetic suppressor screen using the dms4 mutant. DMS4 was described in Kanno et al (2010) EMBO Rep. 11:65-71. Examination of whole-genome DNA methylation status in transgenic Arabidopsis plants