Chromosomal location of major ribosomal RNA genes in three species ofostreidae (Bivalvia, mollusca)

摘要

The chromosomal location of the major ribosomal RNA genes (rDNA) was studied using fluorescence in situ hybridization (FISH) in three species of Ostreidae: the Asian-Pacific species Crassostrea sikamea, the Eastern-Pacific species Ostreola conchaphila (Ostrea lurida) and the Atlantic species Ostrea edulis. FISH probes were made by PCR amplification of the intergenic transcribed spacer between the 18S and 5.8S rRNA genes, and labeled with digoxigenin-11-dUTP. FISH with metaphase chromosomes detected a single telomeric locus in C. sikamea and Ostreola conchaphila, and two telomeric loci in Ostrea edulis without any variation. FISH signals were located on the long arm of Chromosome 10 (10q) - the smallest chromosome in C. sikamea and on the short arm of Chromosome 4 (4p) in Ostreola conchaphila. In Ostrea edulis, the major rRNA genes are terminally located on long arms of Chromosome 8 and 10 (8q and 10q). All three species had a haploid number of ten chromosomes. The size and shape of rDNA-bearing chromosomes provide clear distinction among the three oyster species. Results of this and other studies support the conclusion that significant chromosomal divergence occurred during the evolution of Ostreidae, despite conservation in haploid number (n = 10).