Search for stress-responsive genes in the red alga Furcellaria lumbricalis (Rhodophyta) by expressed sequence tag analysis

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 (35 psu), subjected to highly stressful low salinity conditions (6 psu). The obtained sequences were compared with EST sequence data originating from algal material growing naturally at 6 psu 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.

Research highlights► The aim was to find genes involved in stresses in red alga Furcellaria lumbricalis. ► EST libraries and cDNA sequences were obtained for ocean and brackish algae. ► In all, 28% of annotated gene regions had a putative role in stress responses. ► Results show moderate functional divergence between ocean and brackish water algae.