An F-box gene linked to the self-incompatibility (S) locus of Antirrhinum is expressed specifically in pollen and tapetum.
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-S2, encoded by the S2 allele, with the expected features of the Sp gene was identified. AhSLF-S2 is located 9 kb downstream of S2 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-S2 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-S2 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.
Lai
Zhao
Z
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing.
Ma
Wenshi
W
Han
Bin
B
Liang
Lizhi
L
Zhang
Yansheng
Y
Hong
Guofan
G
Xue
Yongbiao
Y
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D023061:Gene Order; D019684:Magnoliopsida / Q000235:genetics*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics*; D011058:Pollen / Q000235:genetics*; D011110:Polymorphism, Genetic; D018626:Retroelements / Q000235:genetics; D012260:Ribonucleases / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D018744:DNA, Plant; D010940:Plant Proteins; D018626:Retroelements; D012260:Ribonucleases; C022542:ribonuclease S