S locus-linked F-box genes expressed in anthers of Hordeum bulbosum.
Diploid Hordeum bulbosum (a wild relative of cultivated barley) exhibits a two-locus self-incompatibility (SI) system gametophytically controlled by the unlinked multiallelic loci S and Z. This unique SI system is observed in the grasses (Poaceae) including the tribe Triticeae. This paper describes the identification and characterization of two F-box genes cosegregating with the S locus in H. bulbosum, named Hordeum S locus-linked F-box 1 (HSLF1) and HSLF2, which were derived from an S (3) haplotype-specific clone (HAS175) obtained by previous AMF (AFLP-based mRNA fingerprinting) analysis. Sequence analysis showed that both genes encode similar F-box proteins with a C-terminal leucine-rich repeat (LRR) domain, which are distinct from S locus (or S haplotype-specific) F-box protein (SLF/SFB), a class of F-box proteins identified as the pollen S determinant in S-RNase-based gametophytic SI systems. A number of homologous F-box genes with an LRR domain were found in the rice genome, although the functions of the gene family are unknown. One allele of the HSLF1 gene (HSLF1-S (3)) was expressed specifically in mature anthers, whereas no expression was detected from the other two alleles examined. Although the degree of sequence polymorphism among the three HSLF1 alleles was low, a frameshift mutation was found in one of the unexpressed alleles. The HSLF2 gene showed a low level of expression with no tissue specificity as well as little sequence polymorphism among the three alleles. The multiplicity of S locus-linked F-box genes is discussed in comparison with those found in the S-RNase-based SI system.
Kakeda
Katsuyuki
K
Graduate School of Bioresources, Mie University, Tsu, 514-8507, Japan. kakeda@bio.mie-u.ac.jp
D000483:Alleles; D000595:Amino Acid Sequence; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D044783:F-Box Proteins / Q000235:genetics* / Q000378:metabolism; D035264:Flowers / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D001467:Hordeum / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D018076:DNA, Complementary; D018744:DNA, Plant; D044783:F-Box Proteins