Role of FRIGIDA and FLOWERING LOCUS C in Determining Variation in Flowering Time of Arabidopsis

Abstract

(M.J.A., M.N.) Arabidopsis (Arabidopsis thaliana) accessions provide an excellent resource to dissect the molecular basis of adaptation. We have selected 192 Arabidopsis accessions collected to represent worldwide and local variation and analyzed two adaptively important traits, flowering time and vernalization response. There was huge variation in the flowering habit of the different accessions, with no simple relationship to latitude of collection site and considerable diversity occurring within local regions. We explored the contribution to this variation from the two genes FRIGIDA (FRI) and FLOWERING LOCUS C (FLC), previously shown to be important determinants in natural variation of flowering time. A correlation of FLC expression with flowering time and vernalization was observed, but it was not as strong as anticipated due to many late-flowering/vernalizationrequiring accessions being associated with low FLC expression and early-flowering accessions with high FLC expression. Sequence analysis of FRI revealed which accessions were likely to carry functional alleles, and, from comparison of flowering time with allelic type, we estimate that approximately 70% of flowering time variation can be accounted for by allelic variation of FRI. The maintenance and propagation of 20 independent nonfunctional FRI haplotypes suggest that the loss-of-function mutations can confer a strong selective advantage. Accessions with a common FRI haplotype were, in some cases, associated with very different FLC levels and wide variation in flowering time, suggesting additional variation at FLC itself or other genes regulating FLC. These data reveal how useful these Arabidopsis accessions will be in dissecting the complex molecular variation that has led to the adaptive phenotypic variation in flowering time.

The effect of induced mutations on quantitative traits in Arabidopsis thaliana: Natural versus artificial conditions

“…While the traits flowering time and the presence or absence of trichomes have been shown to be under major gene control (Johanson et al., 2000; Karkkainen & Agren, 2002 and Marks, 1997; Shindo et al., 2005; respectively), our results corroborate that these traits also have a polygenic component (Samis et al., 2012; Symonds et al., 2005; Wilczek et al., 2009). For example, flowering time has evolved across an east–west gradient in North American invasive A. thaliana independent of the alleles at the major flowering time loci (Samis et al., 2012).…”

Genome-Wide Association Mapping of Fertility Reduction upon Heat Stress Reveals Developmental Stage-Specific QTLs in Arabidopsis thaliana

“…Haplotype RV1 was, like RV2, identified because of its strong response to vernalization (P. , but no significant difference was found for silique length upon heat between accessions of this haplotype and the SV haplotypes with slow response to vernalization, indicating that RV2 represents the FLC allele associated with heat resistance. However, large variation in flowering time and heat response was observed between accessions belonging to the same haplotype, which might be a consequence of sequence variation at other flowering time loci (Shindo et al, 2005) or heat response genes. Differences between the alleles were not significant anymore when corrected for population structure (Supplemental Data Set 4), which corresponds (A) GWA mapping of silique length in control plants.…”

Key questions in the genetics and genomics of eco-evolutionary dynamics

“…Divergence in Pitx1 is thus parallel at the level of the gene but not at the level of the allele. Additional examples of independent mutations at the same gene having similar phenotypic effects include FRI and flowering time in Arabidopsis (Shindo et al, 2005) and VNR1 and seasonal growth in cereal plants (Cockram et al, 2007). Importantly, parallelism even at the level of the gene is not universal even in the above cases: for instance, some freshwater stickleback populations show lateral plate reduction without variation in EDA (Leinonen et al, 2012;Lucek et al, 2012).…”