The S haplotype-specific F-box protein gene, SFB, is defective in self-compatible haplotypes of Prunus avium and P. mume.
Many Prunus species, including sweet cherry and Japanese apricot, of the Rosaceae, display an S-RNase-based gametophytic self-incompatibility (GSI). The specificity of this outcrossing mechanism is determined by a minimum of two genes that are located in a multigene complex, termed the S locus, which controls the pistil and pollen specificities. SFB, a gene located in the S locus region, encodes an F-box protein that has appropriate S haplotype-specific variation to be the pollen determinant in the self-incompatibility reaction. This study characterizes SFBs of two self-compatible (SC) haplotypes, S(4') and S(f), of Prunus. S(4') of sweet cherry is a pollen-part mutant (PPM) that was produced by X-ray irradiation, while S(f) of Japanese apricot is a naturally occurring SC haplotype that is considered to be a PPM. DNA sequence analysis revealed defects in both SFB(4') and SFB(f). A 4 bp deletion upstream from the HVa coding region of SFB(4') causes a frame-shift that produces transcripts of a defective SFB lacking the two hypervariable regions, HVa and HVb. Similarly, the presence of a 6.8 kbp insertion in the middle of the SFB(f) coding region leads to transcripts for a defective SFB lacking the C-terminal half that contains HVa and HVb. As all reported SFBs of functional S haplotypes encode intact SFB, the fact that the partial loss-of-function mutations in SFB are present in SC mutant haplotypes of Prunus provides additional evidence that SFB is the pollen S gene in GSI in Prunus.
Ushijima
Koichiro
K
Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Yamane
Hisayo
H
Watari
Akiko
A
Kakehi
Eiko
E
Ikeda
Kazuo
K
Hauck
Nathanael R
NR
Iezzoni
Amy F
AF
Tao
Ryutaro
R
D000595:Amino Acid Sequence; D001483:Base Sequence; D044783:F-Box Proteins / Q000235:genetics*; D006239:Haplotypes; D008954:Models, Biological; D008969:Molecular Sequence Data; D010802:Phylogeny; D020161:Physical Chromosome Mapping; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics*; D011058:Pollen; D027861:Prunus / Q000145:classification / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
D044783:F-Box Proteins; D010940:Plant Proteins