engleski

Short introns indicate a compact genome in marine sponges

Sponges are among the oldest multicellular animals and therefore very interesting from an evolutionary point of view. Current knowledge on their genome size and organization is contradictory. The aim of this study was an analysis of intron-size distribution in marine sponges. All poriferan protein-coding nuclear genomic sequences longer than 1 kilobase were retrieved from the National Center for Biotechnology Information (NCBI) database. Two sets of sequences were extracted from this initial group. The first set consisted of 18 genes with experimentally verified exon/intron structures. This set contained 15 genomic clones, in total 59 kilobases. The second set consisted of 14 unannotated Reniera sp. genomic stretches, in total 516 kilobases. Genscan software was used to predict the genes in both sets. Three groups of results were obtained, one experimentally verified and two predicted.The size distributions of exons and introns in the three groups of results were very similar. The distributions were highly skewed with median sizes of introns being 181, 184 and 204 nucleotides, and the expected difference in long introns making a much larger fraction in the Reniera sp. genes, with 30% of introns longer than 400 nucleotides compared to about 10% in the other two groups. Our results indicate that marine sponges have short introns.

Prifera; exon; intron; prediction

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