An F-box gene linked to the self-incompatibility (S) locus of Antirrhinum is expressed specifically in pollen and tapetum |
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Authors: | Lai Zhao Ma Wenshi Han Bin Liang Lizhi Zhang Yansheng Hong Guofan Xue Yongbiao |
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Institution: | (1) Chinese Academy of Sciences, Institute of Genetics and Developmental Biology, Beijing, 100080, China;(2) National Center for Gene Research, Chinese Academy of Sciences, Shanghai, 200233, China |
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Abstract: | In many flowering plants, self-fertilization is prevented by an intraspecific reproductive barrier known as self-incompatibility (SI), that, in most cases, is controlled by a single multiallelic S locus. So far, the only known S locus product in self-incompatible species from the Solanaceae, Scrophulariaceae and Rosaceae is a class of ribonucleases called S RNases. Molecular and transgenic analyses have shown that S RNases are responsible for pollen rejection by the pistil but have no role in pollen expression of SI, which appears to be mediated by a gene called the pollen self-incompatibility or Sp gene. To identify possible candidates for this gene, we investigated the genomic structure of the S locus in Antirrhinum, a member of the Scrophulariaceae. A novel F-box gene, AhSLF-S
2, encoded by the S
2 allele, with the expected features of the Sp gene was identified. AhSLF-S
2 is located 9 kb downstream of S
2 RNase gene and encodes a polypeptide of 376 amino acids with a conserved F-box domain in its amino-terminal part. Hypothetical genes homologous to AhSLF-S
2 are apparent in the sequenced genomic DNA of Arabidopsis and rice. Together, they define a large gene family, named SLF (S locus F-box) family. AhSLF-S
2 is highly polymorphic and is specifically expressed in tapetum, microspores and pollen grains in an allele-specific manner. The possibility that Sp encodes an F-box protein and the implications of this for the operation of self-incompatibility are discussed. |
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Keywords: | Antirrhinum F-box gametophyte self-incompatibility S locus structure |
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