A methyltransferase required for proper timing of the vernalization response in Arabidopsis

Abstract

Prolonged exposure to winter cold enables flowering in many plant species through a process called vernalization. In Arabidopsis, vernalization results from the epigenetic silencing of the floral repressor FLOWERING LOCUS C (FLC) via a Polycomb Repressive Complex 2 (PRC2)-mediated increase in the density of the epigenetic silencing mark H3K27me3 at FLC chromatin. During cold exposure, a gene encoding a unique, cold-specific PRC2 component, VERNALIZATION INSENSITIVE 3 (VIN3), which is necessary for PRC2-mediated silencing of FLC, is induced. Here we show that SET DOMAIN GROUP 7 (SDG7) is required for proper timing of VIN3 induction and of the vernalization process. Loss of SDG7 results in a vernalization-hypersensitive phenotype, as well as more rapid cold-mediated up-regulation of VIN3. In the absence of cold, loss of SDG7 results in elevated levels of long noncoding RNAs, which are thought to participate in epigenetic repression of FLC. Furthermore, loss of SDG7 results in increased H3K27me3 deposition on FLC chromatin in the absence of cold exposure and enhanced H3K27me3 spreading during cold treatment. Thus, SDG7 is a negative regulator of vernalization, and loss of SDG7 creates a partially vernalized state without cold exposure.vernalization | flowering time | SET DOMAIN GROUP 7 S easonal timing of flowering is critical for reproductive success in many plant species. The timing of flowering is often strongly influenced by seasonal variables, such as day length and temperature. Vernalization, the process by which exposure to the prolonged cold of winter enables flowering in the spring, is an example of a temperature effect on flowering (1).Arabidopsis thaliana contains both vernalization-requiring accessions (winter annual) and accessions that do not require vernalization (summer annual). The vernalization requirement is conferred by FRIGIDA (FRI)-mediated up-regulation of the potent flowering repressor FLOWERING LOCUS C (FLC) (2, 3). The presence of active alleles of FRI and FLC ensures that flowering is repressed in the fall season. Summer annual accessions do not require vernalization to flower, because these accessions typically contain a mutant allele of FRI that is not able to up-regulate FLC (4).On perception of a sufficiently long period of cold, vernalization results in the chromatin-level suppression of FLC, which in turn provides competence to flower (3, 5). Thus, in Arabidopsis, vernalization is an environmentally induced epigenetic switch (6).Vernalization-mediated FLC silencing is associated with an increase of two chromatin modifications involving trimethylation of histone 3 at lysine 9 (H3K9me3) and at lysine 27 (H3K27me3) (7,8). The increase in H3K27me3 results from the action of the Polycomb Repressive Complex 2 (PRC2) on FLC chromatin (9). Many of the PRC2 components are conserved among plants, animals, and fungi (10, 11); however, a plant-specific PRC2-associated protein, VERNALIZATION INSENSITIVE 3 (VIN3), is required for vernalization and is uniquely expressed during cold (6). Thus, the...

A possible role for flowering locus T‐encoding genes in interpreting environmental and internal cues affecting olive (Olea europaea L.) flower induction

“…The source of the signal that forms the 'biochemical memory' might be the seed (Stutte and Martin 1986). It might include histone modifications, as shown to be crucial in preserving the 'memory' of vernalization in Arabidopsis (Berry and Dean 2015; Lee et al 2015). The range of inductive cold temperatures in olive is different (higher temperatures) from those that induce a vernalization response in Arabidopsis or Arabis alpina (Bergonzi et al 2013).…”

The Binding Specificity of the PHD-Finger Domain of VIN3 Moderates Vernalization Response

“…However, the ectopic expression of VIN3 alone does not result in any alteration in vernalization response or FLC expression as determined by flowering time, although it is capable of complementing vin3 mutants ( Fig. 2; Lee et al, 2015).…”

Parallel Evolution of Common Allelic Variants Confers Flowering Diversity in Capsella rubella

“…Our results suggested nucleosome occupancy may be altered at the FLC locus. Because epigenetic regulation is a critical component of the regulation of FLC expression in A. thaliana and the chromatin structure state is closely associated with epigenetic modifications (He et al, 2003;Zhao et al, 2005;Jiang et al, 2007Jiang et al, , 2008Liu et al, 2007Liu et al, , 2010Pien et al, 2008;Xu et al, 2008;He, 2009;Zhang et al, 2012;Lee et al, 2015), we tested whether the 5′ UTR deletions are associated with changes in histone modifications using transgenic A. thaliana plants expressing the MTE-FLC, 86IT1-FLC, and 762-FLC alleles. We examined histone modification levels in six regions (A-F; Figure 4D) covering the whole C. rubella FLC locus.…”