Natural haplotypes of non-coding sequences fine-tune flowering time in ambient spring temperatures in Arabidopsis.

Cool ambient temperatures are major cues determining flowering time in spring. The mechanisms promoting or delaying flowering in response to ambient temperature changes are only beginning to be understood. In , () regulates flowering in the ambient temperature range and is transcribed and alternatively spliced in a temperature-dependent manner. We identify polymorphic promoter and intronic sequences required for expression and splicing. In transgenic experiments covering 69% of the available sequence variation in two distinct sites, we show that variation in the abundance of the splice form strictly correlate (R = 0.94) with flowering time over an extended vegetative period. The polymorphisms lead to changes in expression (PRO2+) but may also affect intron 1 splicing (INT6+). This information could serve to buffer the anticipated negative effects on agricultural systems and flowering that may occur during climate change.