Role of the CONSTANS protein in regulating flowering time in Thlaspi arvense L

The floral transition, which denotes the shift from vegetative to reproductive growth, is a fundamental process in plant development that critically influences both plant reproductive success and crop yield. Photoperiod, defined as the perception of day length, acts as a crucial environmental cue regulating floral transition in numerous plant species. Thlaspi arvense L., a promising oilseed crop within the Brassicaceae family, demonstrates photoperiod-insensitive flowering in its Kunming ecotype. To elucidate the underlying mechanisms, homologs of the Arabidopsis thaliana CONSTANS (CO) and FLOWERING LOCUS T (FT) genes were identified in Thlaspi arvense L., and designated TaCO-like1 (TaCO1) and TaFT-like1 (TaFT1). Both genes exhibit core conserved characteristics akin to their Arabidopsis counterparts. The TaCO1 protein localizes to the nucleus with predominant leaf expression, whereas TaFT1 distributes in both the nucleus and cytoplasm. Moreover, both genes show rhythmic expression. Functionally, the heterologous overexpression of either TaCO1 or TaFT1 accelerates flowering in Arabidopsis, and TaCO1 activates TaFT1 transcription. Importantly, TaCO1 significantly diminished the disparity in flowering time between long-day and short-day conditions in Arabidopsis co-9 mutants, suggesting that it may have a more important flowering-promoting function under short-day conditions. This functional diversification of TaCO1 provides a molecular basis for the unique flowering mechanism observed in the Kunming ecotype and presents a potential target for the genetic manipulation of flowering time in this oilseed crop.