Abstract
In rocky shores, desiccation is triggered by daily tide changes, and experimental evidence suggests that local distribution of algal species across the intertidal rocky zone is related to their capacity to tolerate desiccation. In this context, the permanence of Pyropia columbina in the high intertidal rocky zone is explained by its exceptional physiological tolerance to desiccation. This study explored the metabolic pathways involved in tolerance to desiccation in the Chilean P. columbina, by characterizing its transcriptome under contrasting conditions of hydration. We obtained 1,410 ESTs from two subtracted cDNA libraries in naturally hydrated and desiccated fronds. Results indicate that transcriptome from both libraries contain transcripts from diverse metabolic pathways related to tolerance. Among the transcripts differentially expressed, 15% appears involved in protein synthesis, processing and degradation, 14.4% are related to photosynthesis and chloroplast, 13.1% to respiration and mitochondrial function (NADH dehydrogenase and cytochrome c oxidase proteins), 10.6% to cell wall metabolism, and 7.5% are involved in antioxidant activity, chaperone and defense factors (catalase, thioredoxin, heat shock proteins, cytochrome P450). Both libraries highlight the presence of genes/proteins never described before in algae. This information provides the first molecular work regarding desiccation tolerance in P. columbina, and helps, to some extent, explaining the classical patterns of ecological distribution described for algae across the intertidal zone.
Highlights
Red algae (Rhodophyta), the most ancient lineage of photosynthetic eukaryotes (Baldauf et al, 2000; Yoon et al, 2004), are distributed worldwide and include several commercially important species
Desiccation is triggered by daily tide changes, and experimental evidence suggests that local distribution of algal species across the intertidal rocky zone is related to their capacity to tolerate desiccation
Given the ecological and economic relevance of Pyropia and that some basic biochemical and physiological information on the mechanisms involved in tolerance to desiccation is known, we focused this work in determining the genes/proteins that are differentially expressed in P. columbina during the hydration-desiccation cycle, using Suppression Subtractive Hybridization (SSH) and expressed sequences tags (ESTs) determined by pyrosequencing (454 Life Sciences, Roche)
Summary
Red algae (Rhodophyta), the most ancient lineage of photosynthetic eukaryotes (Baldauf et al, 2000; Yoon et al, 2004), are distributed worldwide and include several commercially important species. In Chile, Pyropia columbina (Montagne) W.A. Nelson (formerly Porphyra columbina (Sutherland et al, 2011) is one of the economically important species, together with members of the rhodophycean genera Mazzaella, Gracilaria and Gelidium (Santelices, 1989; Hoffmann & Santelices, 1997; Buschmann et al, 2008), and it is found along the Chilean coast from 20° to 54°S (Hoffmann & Santelices, 1997; Guiry & Guiry, 2013).
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