Temperature-Dependent Flowering of Arabidopsis thaliana is Modulated By Natural Variation of FLOWERING LOCUS M

Plants integrate seasonal cues such as temperature and day length to optimally adjust their flowering to the environment. We identified the Arabidopsis thaliana accession Killean-0 (Kil-0), which showed accelerated flowering time in a range of environmental conditions. By combining classical marker-based mapping with next generation sequencing-based approaches (Pool-Seq and RNA-Seq), we identified FLOWERING LOCUS M (FLM) as a high-confidence candidate gene. FLM was recently described as an important regulator of ambient temperature-regulated flowering. The FLM transcript was strongly down-regulated in Kil-0 and sequencing of the Kil-0 FLM locus identified a 5.7 kb insertion in the first intron. By screening a large set of accessions, we identified nine further accessions with this polymorphism, which all showed a down-regulation of FLM combined with an early flowering phenotype when compared to the Col-0 reference. By combining information from transgenic lines, T-DNA insertion lines, and additional ecotypes that all exhibited large length polymorphisms in the first intron, we showed that not only the length but also the position of the insertion might control FLM abundance. Furthermore we observed that the intronic regions harbor essential elements for the expression and relative abundance of two dominant FLM splice forms.We thus conclude that modulation of FLM abundance is an important mechanism for the adaptation of plants and flowering to changing ambient temperature.