Duplication of the S-locus F-box gene is associated with breakdown of pollen function in an S-haplotype identified in a natural population of self-incompatible Petunia axillaris

• Published in: Plant molecular biology 2005, Vol.57 (1), p.141-153
• Main Authors: Tsukamoto, T, Ando, T, Watanabe, H, Marchesi, E, Kao, T.H
• Format: Article
• Language: English
• Subjects: alleles; Amino Acid Sequence; amino acid sequences; Blotting, Southern; Cloning, Molecular; DNA - chemistry; DNA - genetics; DNA, Plant - genetics; F-Box Proteins - genetics; Fertility - genetics; Gene Duplication; gene expression; Gene Expression Regulation, Plant; genes; Haplotypes; Haplotypes - genetics; Irradiation; loci; Molecular Sequence Data; Mutation; nucleotide sequences; Petunia - genetics; Petunia axillaris; plant fertility; Plant Proteins - genetics; Pollen; Pollen - genetics; Pollen - physiology; ribonucleases; selfing; Sequence Alignment; Sequence Analysis, DNA; Sequence Homology, Amino Acid
• ISSN: 0167-4412; 1573-5028
• DOI: 10.1007/s11103-004-6852-6

We previously identified both self-incompatible and self-compatible plants in a natural population of self-incompatible Petunia axillaris subsp. axillaris, and found that all the self-compatible plants studied carried either S(C1)- or S(C2)-haplotype. Genetic crosses showed that S(C2) was identical to S17 identified from another natural population of P. axillaris, except that its pollen function was defective, and that the pollen-part mutation in S(C2) was tightly linked to the S-locus. Recent identification of the S-locus F-box gene (SLF) as the gene that controls pollen specificity in S-RNase-based self-incompatibility has prompted us to examine the molecular basis of this pollen-part mutation. We cloned and sequenced the S17-allele of SLF of P. axillaris, named PaSLF17, and found that S(C2)S(C2) plants contained extra restriction fragments that hybridized to PaSLF17 in addition to all of those observed in S17S17 plants. Moreover, these additional fragments co-segregated with S(C2). We used the S(C2)-specific restriction fragments as templates to clone an allele of PaSLF by PCR. To determine the identity of this allele, named PaSLF(x), primers based on its sequence were used to amplify PaSLF alleles from genomic DNA of 40 S-homozygotes of P. axillaris, S1S1 through S40S40. Sequence comparison revealed that PaSLF(x) was completely identical with PaSLF19 obtained from S19S19. We conclude that the S-locus of S(C2) contained both S17-allele and the duplicated S19-allele of PaSLF. S(C2) is the first naturally occurring pollen-part mutation of a solanaceous species that was shown to be associated with duplication of the pollen S. This finding lends support to the proposal, based on studies of irradiation-generated pollen-part mutants of solanaceous species, that duplication, but not deletion, of the pollen S, causes breakdown of pollen function.