A Frosty Genetic Screen Unmasks a Major Regulatory Role for SHORT VEGETATIVE PHASE of Flowering in Response to a Cold Snap.

Flowering in plants is controlled by internal and environmental signals, with temperature playing a critical role. Accordingly, Arabidopsis thaliana plants show temperature-dependent variation in flowering time. Because unexpected cold periods can occur at any time, plants have evolved mechanisms to detect such cold snaps and delay flowering. Plants are more cold-tolerant in the vegetative stage, whereas flowers are sensitive and often show reduced reproductive success due to damage to floral structures and gametes. At the molecular level, delayed flowering can be caused by repression of the FLOWERING LOCUS T (FT) gene, and several MADS-box transcription factors repress FT expression in response to cold. In this article, we used a forward genetic screen to investigate how a cold snap affects the transition to flowering. We germinated an A. thaliana EMS M2 population at 20°C, gradually lowered the temperature to 10°C, and selected early-flowering mutants. Whole-genome sequencing identified seven mutant alleles of SHORT VEGETATIVE PHASE (SVP), which we named frosty. Yeast two-hybrid assays showed that the corresponding FROSTY protein isoforms differ in their ability to interact with the MADS-box proteins AGL6 and SOC1. These findings establish a central role for SVP in repressing flowering in response to a cold snap and provide novel alleles, several of which affect splice junctions. Our study offers new insights into the molecular mechanisms that govern temperature-responsive flowering in Arabidopsis and highlights the dynamic interplay between SVP and environmental cues.