Increased BnaMFT-transcript level is associated with secondary dormancy in oilseed rape (Brassica napus L.)

Brassica napus cultivars have little or no primary dormancy; however, they are prone to secondary dormancy induction. Secondary dormant seeds can produce volunteer plants, which can result in genetic contamination, reduced quality and biosafety issues. However, information regarding the molecular mechanism underlying secondary dormancy is limited. The MOTHER OF FT AND TFL1 (MFT) gene, which is evolutionarily conserved in the plant kingdom, acts in a complex gene network in the seed dormancy or germination processes. In this study, we identified four B. napus genes that share high homology with AtMFT, named as BnaMFT. Analyses of cis-acting elements showed that BnaMFT promoters contain multiple seed-specific regulatory elements, and various stress- and hormone-responsive elements. Further experiments validated that BnaMFTs were specifically expressed during seed maturation and in the dry seed, with peaks at 35–42 days after pollination. BnaMFTs were not sufficient for primary dormancy; however, they were significantly enhanced by secondary dormancy induction with PEG6000 treatment. Moreover, BnaMFT transcripts were elevated by treatment with abscisic acid (ABA), which is known to be accumulated during secondary dormancy. These results collectively suggest that increased BnaMFT transcription levels are associated with secondary dormancy induction in an ABA-dependent manner in B. napus.