부산대학교 도서관

We investigated the molecular basis of an extremely late bolting, non-heading 'Leafy Green Parental Line No. 2 (Tsukena No. 2)', to obtain suitable DNA markers for breeding the late bolting trait in Chinese cabbage ( Brassica rapa L. ssp. pekinensis). We found that Tsukena No. 2 contains a ~5 kbp large insertion near the 5′ end of the first intron of BrFLC2, BrFLC3 and BrFLC3′, which are homologs of an Arabidopsis repressor gene for floral transition, FLOWERING LOCUS C ( FLC). The transcript abundance of BrFLC1 in Tsukena No. 2 was repressed during cold exposure to the same level as found in a mid-season bolting commercial F variety 'Muso' (heading Chinese cabbage) and an early-bolting parent of commercial F varieties, 'Early' (Sakata Co.), whereas repression of BrFLC2 and BrFLC3 containing the large insertion was weak. Furthermore, QTL analysis of a F population derived from the Tsukena No. 2 × 'Early' revealed that polymorphisms at the BrFLC2 and BrFLC3 loci explained 46.0 and 9.9 % of the phenotypic variation in the bolting time of vernalized plants, respectively. In Arabidopsis, cold-induced repression of FLC and maintenance of that repression are associated with the first intron of FLC. Our study suggests that a naturally occurring large insertion in the first intron resulted in weak repression of BrFLC2 and BrFLC3 during cold exposure and therefore explains the extremely late bolting of the Tsukena No. 2 cultivar. [ABSTRACT FROM AUTHOR]