Effect of vernalization on tuberization and flowering in the Tibetan turnip is associated with changes in the expression of homologues.

The turnip ( var) is a biennial crop that is planted in late summer/early fall and forms fleshy tubers for food in temperate regions. The harvested tubers then overwinter and are planted again the next spring for flowering and seeds. () is a MADS-box transcription factor that acts as a major repressor of floral transition by suppressing the flowering promoters and . Here we show that vernalization effectively represses tuber formation and promotes flowering in Tibetan turnip. We functionally characterized four homologues (, , , and ), and found that and play a major role in repressing flowering in turnip and in transgenic In contrast, tuber formation was correlated with expression in the hypocotyl and was repressed under cold treatment following the quantitative downregulation of . Grafting experiments of non-vernalized and vernalized turnips revealed that vernalization independently suppressed tuberization in the tuber or hypocotyl of the rootstock or scion, which occurred in parallel with the reduction in activity. Together, our results demonstrate that the Tibetan turnip is highly responsive to cold exposure, which is associated with the expression levels of genes.