BRR2a Affects Flowering Time via FLC Splicing

PLoS Genet. 2016 Apr 21;12(4):e1005924. doi: 10.1371/journal.pgen.1005924. eCollection 2016 Apr.


Several pathways control time to flowering in Arabidopsis thaliana through transcriptional and posttranscriptional gene regulation. In recent years, mRNA processing has gained interest as a critical regulator of flowering time control in plants. However, the molecular mechanisms linking RNA splicing to flowering time are not well understood. In a screen for Arabidopsis early flowering mutants we identified an allele of BRR2a. BRR2 proteins are components of the spliceosome and highly conserved in eukaryotes. Arabidopsis BRR2a is ubiquitously expressed in all analyzed tissues and involved in the processing of flowering time gene transcripts, most notably FLC. A missense mutation of threonine 895 in BRR2a caused defects in FLC splicing and greatly reduced FLC transcript levels. Reduced FLC expression increased transcription of FT and SOC1 leading to early flowering in both short and long days. Genome-wide experiments established that only a small set of introns was not correctly spliced in the brr2a mutant. Compared to control introns, retained introns were often shorter and GC-poor, had low H3K4me1 and CG methylation levels, and were often derived from genes with a high-H3K27me3-low-H3K36me3 signature. We propose that BRR2a is specifically needed for efficient splicing of a subset of introns characterized by a combination of factors including intron size, sequence and chromatin, and that FLC is most sensitive to splicing defects.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arabidopsis / genetics
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / physiology*
  • Flowers / physiology*
  • Genes, Plant
  • Humans
  • Introns
  • MADS Domain Proteins / genetics*
  • Molecular Sequence Data
  • Mutation
  • RNA Splicing*
  • RNA, Messenger / genetics
  • Sequence Homology, Amino Acid


  • Arabidopsis Proteins
  • FLF protein, Arabidopsis
  • MADS Domain Proteins
  • RNA, Messenger

Grant support

This work was supported by grants from the Swiss National Science Foundation (PDFMP3_127358), the Swedish Research Council VR (2011-5010), the Carl-Tryggers-Foundation (CTS 11:189), the Knut-and-Alice-Wallenberg Foundation (KAW 2012.0087) and the Swedish Research Council FORMAS (230-2012-1519) to LH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.