Poster: Genome evolution

Abs # 842: Karyotype analysis of B. campestris using rDNA and centromeric repeats by FISH

Presenter:	Jin, Yong-Moon , ymjin@rda.go.kr
Authors	Jin, Yong-Moon  (A)   Lim, Ki-Byung  (A)   Kim, Jung Sun  (A)   Lee, Soo-In Lee  (A)   Yang, Tae-Jin Yang  (A)   Kwon, Soo-Jin  (A)   Lim, Myung-Ho  (A)   Kim, Jin-A  (A)   Jin, Mina  (A)   Park, Jee-Yonung  (A)   Kim, Ho-Il  (A)   Park, Beom-Seok  (A)
Affiliations:	(A): National Institute of Agricultural Biotechnology
Web Site:	http://www.niab.go.kr

The karyotype of four subspecies belonging to Brassica campestris (A-genome) was analyzed and compared to understand the genome evolution. Each chromosomes of all four subspecies were characterized in terms of the composition of heterochromatin and euchromatin through DAPI banding and FISH using rDNA and centromeric repeats. A detailed karyotype analysis was discussed with respect to the phenotypic characteristics that show big difference between subspecies. We have isolated two classes of 176bp centromeric repeat (named as CentBr) from two BAC clones. The CentBr1 and CentBr2 showing 86% sequence identity occupied the centromeric regions of eight chromosomes (Nos. 1, 3, 4, 6, 7, 8, 9, and 10) and two chromosomes (Nos. 2 and 5), respectively. The repeat units in same class showed 90 to 100% sequence homology. The striking huge block of rDNA is detected on the short arm of chromosome 2 of all four subspecies. On the other hand, small blocks of 45s and 5s rDNA repeats on the other chromosomes show difference among four subspecies. The constitutive heterochromatin blocks were seen in all the interphase cells with bright staining of DAPI representing that they never degenerated fully but they became differ in a certain ratio among cell to cell. The CentBr repeats are localized all over the constitutive heterochromatin block in interphase cell without any exceptions demonstrating the CentBr is the core centromere