Structural and Transcriptional Analysis of the Self-Incompatibility Locus of Almond: Identification of a Pollen-Expressed F-Box Gene with Haplotype-Specific Polymorphism

AUTOR(ES)

Ushijima, Koichiro

FONTE

American Society of Plant Biologists

RESUMO

Gametophytic self-incompatibility in Rosaceae, Solanaceae, and Scrophulariaceae is controlled by the S locus, which consists of an S-RNase gene and an unidentified “pollen S” gene. An ∼70-kb segment of the S locus of the rosaceous species almond, the S haplotype–specific region containing the S-RNase gene, was sequenced completely. This region was found to contain two pollen-expressed F-box genes that are likely candidates for pollen S genes. One of them, named SFB (S haplotype–specific F-box protein), was expressed specifically in pollen and showed a high level of S haplotype–specific sequence polymorphism, comparable to that of the S-RNases. The other is unlikely to determine the S specificity of pollen because it showed little allelic sequence polymorphism and was expressed also in pistil. Three other S haplotypes were cloned, and the pollen-expressed genes were physically mapped. In all four cases, SFBs were linked physically to the S-RNase genes and were located at the S haplotype–specific region, where recombination is believed to be suppressed, suggesting that the two genes are inherited as a unit. These features are consistent with the hypothesis that SFB is the pollen S gene. This hypothesis predicts the involvement of the ubiquitin/26S proteasome proteolytic pathway in the RNase-based gametophytic self-incompatibility system.

Documentos Relacionados

• The F-Box Protein AhSLF-S2 Controls the Pollen Function of S-RNase–Based Self-Incompatibility
• Loss of Pollen-S Function in Two Self-Compatible Selections of Prunus avium Is Associated with Deletion/Mutation of an S Haplotype–Specific F-Box Gene
• Polymorphism at the self-incompatibility locus in Solanaceae predates speciation.
• Hypervariable Domains of Self-Incompatibility RNases Mediate Allele-Specific Pollen Recognition.
• The pollen determinant of self-incompatibility in Brassica campestris