Metatranscriptomes reveal functional variation in diatom communities from the Antarctic Peninsula

• Published in: The ISME Journal
• Main Authors: Pearson, Gareth A, Lago-Leston, Asuncion, Cánovas, Fernando, Cox, Cymon J, Verret, Frederic, Lasternas, Sebastian, Duarte, Carlos M, Agusti, Susana, Serrão, Ester A
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2015
• Subjects: Ecology, Evolution, Behavior and Systematics; Microbiology; Antarctic; The Antarctic; Antarctic Peninsula; Weddell Sea; Bellingshausen Sea; Bransfield Strait; Weddell; Wilkins; Wilkins Ice Shelf; Antarc*; Ice Shelf; Sea ice
• Online Access: http://dx.doi.org/10.1038/ismej.2015.40; http://www.nature.com/articles/ismej201540.pdf; http://www.nature.com/articles/ismej201540; https://academic.oup.com/ismej/article-pdf/9/10/2275/56371522/41396_2015_article_bfismej201540.pdf

Abstract Functional genomics of diatom-dominated communities from the Antarctic Peninsula was studied using comparative metatranscriptomics. Samples obtained from diatom-rich communities in the Bransfield Strait, the western Weddell Sea and sea ice in the Bellingshausen Sea/Wilkins Ice Shelf yielded more than 500K pyrosequencing reads that were combined to produce a global metatranscriptome assembly. Multi-gene phylogenies recovered three distinct communities, and diatom-assigned contigs further indicated little read-sharing between communities, validating an assembly-based annotation and analysis approach. Although functional analysis recovered a core of abundant shared annotations that were expressed across the three diatom communities, over 40% of annotations (but accounting for <10% of sequences) were community-specific. The two pelagic communities differed in their expression of N-metabolism and acquisition genes, which was almost absent in post-bloom conditions in the Weddell Sea community, while enrichment of transporters for ammonia and urea in Bransfield Strait diatoms suggests a physiological stance towards acquisition of reduced N-sources. The depletion of carbohydrate and energy metabolism pathways in sea ice relative to pelagic communities, together with increased light energy dissipation (via LHCSR proteins), photorespiration, and NO3− uptake and utilization all pointed to irradiance stress and/or inorganic carbon limitation within sea ice. Ice-binding proteins and cold-shock transcription factors were also enriched in sea ice diatoms. Surprisingly, the abundance of gene transcripts for the translational machinery tracked decreasing environmental temperature across only a 4 °C range, possibly reflecting constraints on translational efficiency and protein production in cold environments.