title: Crassostrea angulata bindin gene and the divergence of fucose-binding lectin repeats among three species of Crassostrea.
abstract: Bindin is a major protein for species-specific recognition between sperm and congenetic egg in many free-spawning marine invertebrates. We cloned a novel bindin gene from the oyster Crassostrea angulata by 3' and 5' rapid amplification of cDNA ends. The full-length bindin cDNA was 1,049 bp with a 771-bp open reading frame encoding 257 amino acids. The deduced amino acid sequence contained a putative signal peptide of 24 amino acids. The length of the bindin genomic DNA was 8,508 bp containing four exons and three introns. Three haplotypes of F-lectin repeat were detected from seven sequences of F-lectin repeat of six male oysters. Both neighbor-joining and minimum-evolution phylogenetic trees show that haplotype an1 was close to Crassostrea gigas while an2 and an3 were close to Crassostrea sikamea. Intron-4 in the middle of F-lectin repeat is highly variable in both size and sequence. We classified intron-4 into three types according to their size and the F-lectin repeat they were located in. Intron-4 may play an important role in recombination. We compared the number of nonsynonymous substitutions (Dn) and synonymous substitutions (Ds) per nucleotide site among 19 F-lectin haplotypes of the three species. Dn/Ds ratios suggested that positive selection occurred between C. gigas and C. sikamea and between C. gigas and C. angulata. Nine positive selected positions (p > 90%) are identified among 19 haplotypes of three species. They are located on the F-lectin binding face around the three recognition motif residues. We assume that these nine clustered amino acids are related with species-specific recognition.
authors.affiliation: Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Rd., Qingdao, 266071, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Wu
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Guofan
authors.initials: G
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion / Q000235:genetics; D003001:Cloning, Molecular; D049896:Crassostrea / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D005306:Fertilization / Q000235:genetics; D005643:Fucose / Q000235:genetics* / Q000378:metabolism; D037102:Lectins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013084:Sperm-Ovum Interactions / Q000235:genetics; D013094:Spermatozoa / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D037102:Lectins; C027112:fucose-binding lectin; D005643:Fucose