Post-translational regulation of SHORT VEGETATIVE PHASE as a major mechanism for thermoregulation of flowering

In contrast to our extensive knowledge of vernalization, we know relatively little about the regulation of ambient temperature-responsive flowering. Recent reports revealed that FLOWERING LOCUS M (FLM) and SHORT VEGETATIVE PHASE (SVP) regulate high ambient temperature-responsive flowering through two different mechanisms: degradation of SVP protein and formation of a non-functional SVP-FLM-δ complex. To investigate further the mechanism of thermoregulation of flowering, we performed real-time quantitative polymerase chain reaction (RT -qPCR) and in vitro pull-down assays. We found that FLM-β and FLM-δ transcripts show similar absolute levels at different temperatures. Also, His-SVP protein bound to the GST-FLM-β or -δ proteins with similar binding intensities. These results suggest that functional SVP-FLM-β and non-functional SVP-FLM-δ complexes form similarly at warmer temperatures, thus indicating that posttranslational regulation of SVP functions as a major mechanism for thermoregulation in flowering.