Abstract
BackgroundBrown algae of the genus Ectocarpus exhibit high levels of genetic diversity and variability in morphological and physiological characteristics. With the establishment of E. siliculosus as a model and the availability of a complete genome sequence, it is now of interest to analyze variability among different species, ecotypes, and strains of the genus Ectocarpus both at the genome and the transcriptome level.ResultsWe used an E. siliculosus gene expression microarray based on EST sequences from the genome-sequenced strain (reference strain) to carry out comparative genome hybridizations for five Ectocarpus strains: four E. siliculosus isolates (the male genome strain, a female strain used for outcrosses with the genome strain, a strain isolated from freshwater, and a highly copper-tolerant strain), as well as one strain of the sister species E. fasciculatus. Our results revealed significant genomic differences between ecotypes of the same species, and enable the selection of conserved probes for future microarray experiments with these strains. In the two closely related strains (a male and a female strain used for crosses), genomic differences were also detected, but concentrated in two smaller genomic regions, one of which corresponds to a viral insertion site.ConclusionThe high variability between strains supports the concept of E. siliculosus as a complex of cryptic species. Moreover, our data suggest that several parts of the Ectocarpus genome may have evolved at different rates: high variability was detected particularly in transposable elements and fucoxanthin chlorophyll a/c binding proteins.
Highlights
Brown algae of the genus Ectocarpus exhibit high levels of genetic diversity and variability in morphological and physiological characteristics
We used an E. siliculosus gene expression microarray based on expressed sequence tag (EST) sequences from the genomesequenced strain to carry out comparative genome hybridizations for five Ectocarpus strains: four E. siliculosus isolates, as well as one strain of the sister species E. fasciculatus
In the two closely related strains, genomic differences were detected, but concentrated in two smaller genomic regions, one of which corresponds to a viral insertion site
Summary
Brown algae of the genus Ectocarpus exhibit high levels of genetic diversity and variability in morphological and physiological characteristics. With the establishment of E. siliculosus as a model and the availability of a complete genome sequence, it is of interest to analyze variability among different species, ecotypes, and strains of the genus Ectocarpus both at the genome and the transcriptome level. Brown algae are multicellular and almost exclusively marine organisms, which live along the coastlines of all continents. They are economically important [1] as a food product mainly in Asian countries, as animal food or fertilizer due to their high mineral and trace element contents, and as a source of polysaccharides such as alginates. It was generally accepted that the genus Ectocarpus included only two species, E. siliculosus and
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