Natural haplotypes of <i>FLM</i> non-coding sequences fine-tune flowering time in ambient spring temperatures in Arabidopsis.

Abstract

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 <i>Arabidopsis thaliana</i>, <i>FLOWERING LOCUS M</i> (<i>FLM</i>) regulates flowering in the ambient temperature range and <i>FLM</i> is transcribed and alternatively spliced in a temperature-dependent manner. We identify polymorphic promoter and intronic sequences required for <i>FLM</i> 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 <i>FLM-ß</i> splice form strictly correlate (R² = 0.94) with flowering time over an extended vegetative period. The <i>FLM</i> polymorphisms lead to changes in <i>FLM</i> expression (PRO2+) but may also affect <i>FLM</i> 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.