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Abstract

Plants integrate seasonal cues such as temperature and day length
to optimally adjust their flowering to the environment. We identified
the Arabidopsis 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.