Abstract
Repetitive DNA represents the major component of the genome in both plant and animal species. It includes transposable elements (TEs), which are dispersed throughout the genome, and satellite DNAs (satDNAs), which are tandemly organized in long arrays. The study of the structure and organization of repetitive DNA contributes to our understanding of genome architecture and the mechanisms leading to its evolution. Molluscs represent one of the largest groups of invertebrates and include organisms with a wide variety of morphologies and lifestyles. To increase our knowledge of bivalves at the genome level, we analysed the Antarctic scallop Adamussium colbecki. The screening of the genomic library evidenced the presence of two novel satDNA elements and the CvA transposon. The interspecific investigation performed in this study demonstrated that one of the two satDNAs isolated in A. colbecki is widespread in polar molluscan species, indicating a possible link between repetitive DNA and abiotic factors. Moreover, the transcriptional activity of CvA and its presence in long-diverged bivalves suggests a possible role for this ancient element in shaping the genome architecture of this clade.
Highlights
Repetitive DNA has been identified in all major taxonomic groups of both plant and animal species, in many cases representing the majority of the DNA content in the genome [1,2,3]
The interspecific investigation performed in this study demonstrated that one of the two satellite DNAs (satDNAs) isolated in A. colbecki is widespread in Antarctic species, indicating a link between repetitive DNA and abiotic factors
Genomic DNA from A. colbecki was digested with the restriction enzyme EcoRI and cloned, and the resultant colonies were hybridized with labelled genomic DNA from the Antarctic scallop
Summary
Repetitive DNA has been identified in all major taxonomic groups of both plant and animal species, in many cases representing the majority of the DNA content in the genome [1,2,3]. Repetitive elements include transposable elements (TEs), which are dispersed throughout the genome, and satellite DNAs (satDNAs), which are tandemly organized in long arrays. TEs are characterized by their ability to proliferate and move throughout the genome. They are classified as retrotransposons or DNA transposons depending on whether there is an RNA intermediate step in the transposition mechanism. TE abundance is correlated with genome size, explaining the C-value paradox, that is, the lack of correlation between DNA content and organism complexity in different species [3].
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