| In well-characterized laboratory strains of Arabidopsis , a late-flowering phenotype depends upon the possession of strong alleles of both FLOWERING LOCUS C (FLC) and FRIGIDA (FRI). In these strains, flowering is accelerated by the experience of prolonged winter cold, which, during a process called vernalization, acts to stably reduce FLC expression. However, many naturally-occurring variants of Arabidopsis, called accessions, exhibit alternate flowering behaviors, the molecular explanations of which remain unknown. In this study, we begin work with Tul-0, an accession that exhibits two unusual flowering phenotypes: first, it is late-flowering despite possessing a weak FLC allele, and, second, it remains late-flowering following vernalization. Using near-isogenic lines (NILs), created both by the introgression of Tul-0 loci into laboratory accessions and by the introgression of loci from laboratory accessions into Tul-0, we begin to dissect these phenotypes and to define roles for multiple Tul-0 loci. We show that late flowering is conferred by both FLC-independent and FLC-dependent mechanisms and, at the same time, document the existence of new FLC-enhancer loci, that, in addition to FRI, contribute to natural variation. Finally, we show that Tul-0's reduced vernalization sensitivity is genetically separable from late flowering per se and that it is accompanied by changes in vernalization-associated FLC silencing. |
