S locus F-box brothers: multiple and pollen-specific F-box genes with S haplotype-specific polymorphisms in apple and Japanese pear.
Although recent findings suggest that the F-box genes SFB/SLF control pollen-part S specificity in the S-RNase-based gametophytic self-incompatibility (GSI) system, how these genes operate in the system is unknown, and functional variation of pollen S genes in different species has been reported. Here, we analyzed the S locus of two species of Maloideae: apple (Malus domestica) and Japanese pear (Pyrus pyrifolia). The sequencing of a 317-kb region of the apple S9 haplotype revealed two similar F-box genes. Homologous sequences were isolated from different haplotypes of apple and Japanese pear, and they were found to be polymorphic genes derived from the S locus. Since each S haplotype contains two or three related genes, the genes were named SFBB for S locus F-box brothers. The SFBB genes are specifically expressed in pollen, and variable regions of the SFBB genes are under positive selection. In a style-specific mutant S haplotype of Japanese pear, the SFBB genes are retained. Apart from their multiplicity, SFBB genes meet the expected characteristics of pollen S. The unique multiplicity of SFBB genes as the pollen S candidate is discussed in the context of mechanistic variation in the S-RNase-based GSI system.
Sassa
Hidenori
H
Faculty of Horticulture, Chiba University, Matsudo, Chiba 271-8510, Japan. sassa@faculty.chiba-u.jp
Kakui
Hiroyuki
H
Miyamoto
Mayu
M
Suzuki
Yusuke
Y
Hanada
Toshio
T
Ushijima
Koichiro
K
Kusaba
Makoto
M
Hirano
Hisashi
H
Koba
Takato
T
D000595:Amino Acid Sequence; D001483:Base Sequence; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D044783:F-Box Proteins / Q000235:genetics; D017343:Genes, Plant; D006239:Haplotypes; D007564:Japan; D027845:Malus / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics; D011058:Pollen / Q000235:genetics; D011110:Polymorphism, Genetic; D031989:Pyrus / Q000235:genetics*; D012260:Ribonucleases / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D018744:DNA, Plant; D044783:F-Box Proteins; D010940:Plant Proteins; D012260:Ribonucleases