Originally published as Genetics Published Articles Ahead of Print on August 24, 2007.

Genetics, Vol. 177, 949-958, October 2007, Copyright © 2007
doi:10.1534/genetics.107.073825

Effects of Recombination on Hitchhiking Diversity in the Brassica Self-incompatibility Locus Complex

Shohei Takuno¹, Ryo Fujimoto^1,2, Tetsu Sugimura, Keiichi Sato³, Shunsuke Okamoto, Shao-Ling Zhang⁴ and Takeshi Nishio⁵

Laboratory of Plant Breeding and Genetics, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 981-8555, Japan

⁵ Corresponding author: Laboratory of Plant Breeding and Genetics, Graduate School of Agricultural Science, Tohoku University, 1-1, Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi 981-8555, Japan.
E-mail: nishio{at}bios.tohoku.ac.jp

In self-incompatibility, a number of S haplotypes are maintained by frequency-dependent selection, which results in trans-specific S haplotypes. The region of several kilobases (40–60 kb) from SP6 to SP2, including self-incompatibility-related genes and some adjacent genes in Brassica rapa, has high nucleotide diversity due to the hitchhiking effect, and therefore we call this region the "S-locus complex." Recombination in the S-locus complex is considered to be suppressed. We sequenced regions of >50 kb of the S-locus complex of three S haplotypes in B. rapa and found higher nucleotide diversity in intergenic regions than in coding regions. Two highly similar regions of >10 kb were found between BrS-8 and BrS-46. Phylogenetic analysis using trans-specific S haplotypes (called interspecific pairs) of B. rapa and B. oleracea suggested that recombination reduced the nucleotide diversity in these two regions and that the genes not involved in self-incompatibility in the S-locus complex and the kinase domain, but not the S domain, of SRK have also experienced recombination. Recombination may reduce hitchhiking diversity in the S-locus complex, whereas the region from the S domain to SP11 would disfavor recombination.

This article has been cited by other articles:

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