Quantification and characterization of nuclear genomes in commercial red seaweeds (Gracilariales) from the Philippines

Abstract

Eight species of Gracilariaceae from the Philippines, representing the genera <i>Gracilaria, Gracilariopsis</i> and <i>Hydropuntia</i>, were investigated to quantify and characterize their nuclear genomes. DNA reassociation kinetics were used to determine nuclear genome organization and complexity in six of these species. Results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repetitive sequences varied from 13–74% and unique DNA ranged from 26–84%. Microspectrophotometry with the DNA-localizing fluorochrome DAPI was used to quantify nuclear DNA contents. Comparisons of mean nuclear DNA (I f ) values to chicken erythrocytes (RBC) resulted in an estimate of 0.38–0.43 pg/2 C genomes for seven of the species investigated. Preliminary analyses of agar content and quality confirm the economic potential of <i>Gracilaria firma, Gracilaria</i> sp. 2 from Sorsogon and <i>Gracilariopsis bailinae</i>. Nuclear genome profiles developed from data for genome size, organization and complexity are compared with data for agar quantity and quality. Gel quality and quantity do not appear to be correlated with either large repetitive fraction DNA or a high degree of genome complexity.