title: Interhaplotypic heterogeneity and heterochromatic features may contribute to recombination suppression at the S locus in apple (Malusxdomestica).
abstract: Gametophytic self-incompatibility (GSI) is controlled by a complex S locus containing the pistil determinant S-RNase and pollen determinant SFB/SLF. Tight linkage of the pistil and pollen determinants is necessary to guarantee the self-incompatibility (SI) function. However, multiple probable pollen determinants of apple and Japanese pear, SFBBs (S locus F-box brothers), exist in each S haplotype, and how these multiple genes maintain the SI function remains unclear. It is shown here by high-resolution fluorescence in situ hybridization (FISH) that SFBB genes of the apple S9 haplotype are physically linked to the S9-RNase gene, and the S locus is located in the subtelomeric region. FISH analyses also determined the relative order of SFBB genes and S-RNase in the S9 haplotype, and showed that gene order differs between the S9 and S3 haplotypes. Furthermore, it is shown that the apple S locus is located in a knob-like large heterochromatin block where DNA is highly methylated. It is proposed that interhaplotypic heterogeneity and the heterochromatic nature of the S locus help to suppress recombination at the S locus in apple.
authors: Graduate School of Horticulture, Chiba University, Matsudo, Chiba 271-8510, Japan.
authors: Sanhong
authors: S
authors: Wang
authors: Hiroyuki
authors: H
authors: Kakui
authors: Shinji
authors: S
authors: Kikuchi
authors: Takato
authors: T
authors: Koba
authors: Hidenori
authors: H
authors: Sassa
mesh_terms: D022202:Chromosomes, Artificial, Bacterial; D032461:Chromosomes, Plant / Q000235:genetics; D019175:DNA Methylation; D022041:Euchromatin / Q000235:genetics; D044783:F-Box Proteins / Q000235:genetics*; D035264:Flowers / Q000235:genetics / Q000502:physiology; D018740:Genetic Heterogeneity; D008040:Genetic Linkage; D006239:Haplotypes; D006570:Heterochromatin / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D027845:Malus / Q000235:genetics* / Q000502:physiology; D049471:Pachytene Stage; D010940:Plant Proteins / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics*; D012260:Ribonucleases / Q000235:genetics*; D060436:Self-Incompatibility in Flowering Plants / Q000235:genetics*
chemical_list: D022041:Euchromatin; D044783:F-Box Proteins; D006570:Heterochromatin; D010940:Plant Proteins; D012260:Ribonucleases; C022542:ribonuclease S