Mutations in theArabidopsis SWC6gene, encoding a component of the SWR1 chromatin remodelling complex, accelerate flowering time and alter leaf and flower development

Abstract

Mutations affecting the Arabidopsis SWC6 gene encoding a putative orthologue of a component of the SWR1 chromatin remodelling complex in plants have been characterized. swc6 mutations cause early flowering, shortened inflorescence internodes, and altered leaf and flower development. These phenotypic defects resemble those of the photoperiod independent early flowering 1 (pie1) and early in short days 1 (esd1) mutants, also affected in homologues of the SWR1 complex subunits. SWC6 is a ubiquitously expressed nuclear HIT-Zn finger-containing protein, with the highest levels found in pollen. Double mutant analyses suggest that swc6 abolishes the FLC-mediated late-flowering phenotype of plants carrying active alleles of FRI and of mutants of the autonomous pathway. It was found that SWC6 is required for the expression of the FLC repressor to levels that inhibit flowering. However, the effect of swc6 in an flc null background and the down-regulation of other FLC-like/MAF genes in swc6 mutants suggest that flowering inhibition mediated by SWC6 occurs through both FLC- and FLC-like gene-dependent pathways. Both genetic and physical interactions between SWC6 and ESD1 have been demonstrated, suggesting that both proteins act in the same complex. Using chromatin immunoprecipitation, it has been determined that SWC6, as previously shown for ESD1, is required for both histone H3 acetylation and H3K4 trimethylation of the FLC chromatin. Altogether, these results suggest that SWC6 and ESD1 are part of an Arabidopsis SWR1 chromatin remodelling complex involved in the regulation of diverse aspects of plant development, including floral repression through the activation of FLC and FLC-like genes.

The role of the transcript elongation factors FACT and HUB1 in leaf growth and the induction of flowering

“…14,25 Similarly, an effect on FLC expression by alterations in chromatin structure (while the expression of other genes is not changed) is also observed for defects in other Arabidopsis chromatin modifiers that promote chromatin-regulated transcription, including a chromatin-remodeling complex of the SWR1-type and the histone H3 methyltransferase SDG25. 28,29 Consistently, transcript profiling experiments revealed that defects in various chromatin modifiers, including HUB1 and SDG25, cause differential expression of only a subset of genes. 18,28 Experiments with various chromatin factors have demonstrated that proper expression of FLC appears to be complexity and different from those of elo or hub1 mutants (Fig.…”

The Arabidopsis E3 Ubiquitin Ligase HOS1 Negatively Regulates CONSTANS Abundance in the Photoperiodic Control of Flowering

“…For RT-PCR analysis, the HOS1-specific primers 59-TTGTCCTCTATTTGCGTTTGT-39 and 59-TCAAATTGGGGAA-GAAGTTATG-39 were designed to amplify the N-terminal part of the HOS1 coding region. The FLC, CO, FT, and SOC1 primers used were described elsewhere (Piñ eiro et al, 2003;Lá zaro et al, 2008). UBIQUITIN10 (UBQ10) was used as a loading control in these experiments.…”

DNA Damage Repair in the Context of Plant Chromatin

“…In Arabidopsis (Arabidopsis thaliana), the complex has a major role in transcriptional regulation, as SWR1-C mutants exhibit a characteristic early-flowering phenotype due to the dysregulation of several developmental genes (Noh and Amasino, 2003;Choi et al, 2005;Deal et al, 2005;Lázaro et al, 2008;March-Díaz and Reyes, 2009). A role of Arabidopsis SWR1-C in DNA repair has only recently been documented.…”