The Nucleotide Sequences Variability in ITS and 5.8S Regions of the Nuclear rDNA among Cosmarium Species

Algae > Volume 16(2); 2001 > Article

Algae 2001;16(2): 129-136.

Ok-Min Lee

Department of Biology, Kyonggi University

ABSTRACT

The sequences of ITS and 5.8S regions were compared to elucidate the stability of morphological characters based on semicell forms in Cosmarium. The sequence size ranged from 362 bp to 476 bp in ITS 1 and from 272 bp to 402 bp in ITS 2. The 5.8S region was more conservative than ITS region, and its sizes ranged from 152 bp to 161 bp. The high divergence of ITS regions in Cosmarium were similar to that in Volvocalean algae, which demonstrated that the variation of ITS region in unicellular algae was much greater than that in land plants and macroalgae. In addition, the molecular analysis was not congruent with sectional system of Cosmarium based on semicell forms which has been considered as one of the most important characters. Sequence analysis of more conserved genes is needed to elucidate the characteristic stability of semicell form. The intergeneric divergence between Cosmarium and Staurastrum sp. ranged from 39.9% to 57.5%. The intergeneric divergence was lower than the interspecific divergence of Cosmarium (21.3-73.3%). This also suggest that the generic delimition of Cosmarium should be reconsidered.

Key words: Cosmarium, ITS and 5.78S regions, maximum parsimony