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ABSTRACT Expressed sequence tag (EST) libraries were generated from two populations of the red alga Furcellaria lumbricalis (Hudson) Lamouroux originating from different environmental conditions (the Atlantic Ocean and the brackish Baltic Sea), compared with each other and used to guide the design of single nucleotide polymorphism (SNP) markers. The species is endemic to the northern Atlantic, while in the low-salinity conditions of the Baltic Sea it occurs at the margin of its distribution and is presently threatened by eutrophication., Primers were developed for 13 transcribed regions, five of which were found to be variable at population level, containing a total of 20 SNP sites, which were then utilized in population genetic analyses on F. lumbricalis originating from different geographical locations and salinity conditions in northern and western Europe, and the results were compared with previous data of putatively neutral and adaptive (EST-derived) microsatellites., Although no conclusive evidence of selection was detected in neutrality tests, the level of genetic differentiation based on SNP variation (FST = 0.522; but 0.398 and 0.095 for EST-derived and putatively neutral microsatellites, respectively) is so great that the role of selection is evident. The Bayesian structure analysis supported the view of great differentiation between marine and brackish populations., Although the new primers were designed for F. lumbricalis, the same gene regions may have utility in population genetic and phylogenetic studies across red algal species., Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Furcellaria lumbricalis is a red algae occurring in low salinity to fully marine conditions. Here, both putatively neutral and EST-derived microsatellite markers were developed and used to examine the genetic structure of northern European populations inhabiting different salinity conditions ranging from 35 to 3.6 psu. The amount of genetic variation did not differ between ocean and brackish populations, but differences were observed between marker types; EST-derived markers possessed less variation and showed greater differentiation than the putatively neutral microsatellites. No multicopy multilocus genotypes were detected despite expected asexuality in brackish populations. The Bayesian STRUCTURE analysis, when conducted for expressed marker data, indicated the presence of two main clusters, the Atlantic Ocean and Baltic Sea, while no clear structuring was observed based on putatively neutral microsatellites. The moderate level of genetic differentiation at neutral loci is probably due to genetic drift, a feasible explanation considering long distances between many populations, while the high level of differentiation in EST-linked markers reflects selection pressures. [ABSTRACT FROM AUTHOR]

Abstract: In order to identify candidate genes with potential involvement in the salinity tolerance and other stress responses in the red alga Furcellaria lumbricalis (Hudson) Lamouroux, and to generate new markers for population genetic and stress tolerance adaptation studies, we constructed EST libraries from algal material originating from the marine environment of the Atlantic Ocean (35psu), subjected to highly stressful low salinity conditions (6psu). The obtained sequences were compared with EST sequence data originating from algal material growing naturally at 6psu salinity in the northern Baltic Sea. The EST libraries composed of the Atlantic Ocean and Baltic Sea algal cDNA sequences consisted of 4971 and 4466 contigs, respectively. Of the contigs present in the Atlantic Ocean and Baltic Sea EST libraries, 60.5% and 56.0%, respectively, were present only within one library, while the rest, a total of 1963 contigs, were shared by the two EST libraries. The mean GC content of the EST sequences was 46.9%. The sequence searches resulted in 1612 hits in the Atlantic Ocean dataset and in 1582 hits in the Baltic Sea dataset. The majority of the gene regions remained unannotated, as gene ontology could be allocated only to altogether 576 sequences (11.6%) representing 393 different sequence regions in the Atlantic Ocean dataset, and 582 sequences (13.0%) representing 404 regions in the Baltic Sea dataset. Putatively, 28% of annotated ESTs (26% and 30% in the Atlantic Ocean and Baltic Sea, respectively) had a role in general or specific abiotic stress responses, while 4.3% of annotated ESTs were similar to genes that are known to play roles in specific salinity stress responses (4.9% and 3.8% in the Atlantic Ocean and Baltic Sea samples, respectively). Some differences between the two datasets were observed in the proportions of ESTs representing different functional categories indicating moderate functional divergence between the ocean and brackish water populations of F. lumbricalis. [Copyright &y& Elsevier]