An expressed sequence tag analysis of thallus and regenerating protoplasts of Chondrus crispus (Gigartinales, Rhodophyceae)
Résumé
In order to identify genes involved in cell wall regeneration and stress responses in red algae, expressed sequence tags (ESTs) from protoplasts (2002 ESTs) and thalli (2052 ESTs) from the seaweed Chondrus crispus (Stackh.) were studied. Clustering gave 2291 non-redundant sequences; 50% of the ESTs showed similarity (e < 10(-4)) to known sequences. The fraction of stress-related ESTs was five-times higher in the protoplast library than in the thallus library. The ESTs that were statistically over-represented in protoplasts included: glutathione S-transferases, heat shock proteins, vanadium bromoperoxidase, and several genes of unknown function; in all 32 transcripts. Over-represented genes in thallus included: NADH dehydrogenase, a peroxidase, and several genes of unknown function; in all 12 transcripts. In general, the ESTs from the two libraries were very different; for example, only 38% of contigs had members of both catalogues. The approach allowed the identification of numerous stress genes; including 23 different heat shock proteins and molecular chaperones, antioxidative enzymes, and several genes potentially involved in detoxification. Genes potentially involved in the construction of the cell wall or the extracellular matrix included alpha-galactosidase, pullulanase, sulfohydrolase, and several sequences with von Willebrand factor type A domains with similarities to cochlin, integrin, and vitrin.