MOLECULAR MECHANISMS OF DESICCATION TOLERANCE IN FUCUS

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Publications

Molecular mechanisms of disiccation tolerance in Fucus

Publication . Mota, Catarina Figueiredo da; Pearson, Gareth; Serrão, Ester

Intertidal algae (brown, red and green) are three understudied and independent multicellular lineages possessing related intolerant and desiccation tolerant species, making them good models for desiccation tolerance research. Recent focus on distribution of Fucus vesiculosus under climate change led us to determine the upper thermal limits of this brown algae, using physiological indicators and gene expression responses to describe the induction and thermal characteristics of the heat-shock response in diverse populations. Ambient temperatures were poor predictors of the heat-stress experienced by intertidal algae, instead the microhabitats created by the algal canopy modulated the local thermal environment and influenced the stress response. Surprisingly, in the hottest microhabitat algae appeared to be protected from thermal stress by fast and intense desiccation. Proteomic research in brown algae has recently been facilitated by genomic resources, complete genome sequencing of model species and large-scale transcriptomic resources from Fucus species, and by technical advances in work on organisms with similar interfering compounds. We tested and optimized a protein extraction protocol suitable for intertidal Fucus algae and used it to investigate differential expression of proteins in response to desiccation, both by conventional 2DE and by DIGE. No significant changes of the protein profiles were detected after desiccation or rehydration, suggesting the importance of constitutive tolerance mechanisms, minimizing the metabolic cost of gene expression, while the desiccated state provides protection against heat stress. Studies of distinct field environments (desiccation-prone or –protected), of sequential emersion stress exposure and of laboratory desiccation under controlled conditions, all failed to identify robust protein expression changes attributable to desiccation tolerance. We characterized the first extractable proteome of F. vesiculosus by LC-MS/MS identification and annotation against brown algal protein databases, with considerable success despite limited functional annotation in brown algae proteins, and the presence of multiple proteins in some spots.

2017-05-05Doctoral thesis

Open Access

Some don't like it hot: microhabitat-dependent thermal and water stresses in a trailing edge population

Publication . Mota, Catarina F.; Engelen, Aschwin H.; Serrao, Ester A.; Pearson, Gareth A.

The distributional limits of species in response to environmental change are usually studied at large temporal and/or geographical scales. However, organismal scale habitat variation can be overlooked when investigating large-scale averages of key factors such as temperature. We examine how microhabitat thermal conditions relate to physiological limits, which may contribute to recent range shifts in an intertidal alga. We defined the onset and maximum temperatures of the heat-shock response (HSR) for a southern edge population of Fucus vesiculosus, which has subsequently become extinct. The physiological threshold for resilience (assayed using chlorophyll fluorescence) coincided with declining HSR, determined from the temperature-dependent induction of seven heat-shock protein transcripts. In intertidal habitats, temperature affects physiology directly by controlling body temperature and indirectly through evaporative water loss. We investigated the relationship between the thermal environment and in situ molecular HSR at microhabitat scales. Over cm to m scales, four distinct microhabitats were defined in algal patches (canopy surface, patch edge, subcanopy, submerged channels), revealing distinct thermal and water stress environments during low-tide emersion. The in situ HSR agreed with estimated tissue temperatures in all but one microhabitat. Remarkably, in the most thermally extreme microhabitat (canopy surface), the HSR was essentially absent in desiccated tissue, providing a potential escape from the cellular metabolic costs of thermal stress. Meteorological records, microenvironmental thermal profiles and HSR data indicate that the maximum HSR is approached or exceeded in hydrated tissue during daytime low tides for much of the year. Furthermore, present-day summer seawater temperatures are sufficient to induce HSR during high-tide immersion, preventing recovery and resulting in continuous HSR during daytime low-tide cycles over the entire summer. HSR in the field matched microhabitat temperatures more closely than local seawater or atmospheric data, suggesting that the impacts of climatic change are best understood at the microhabitat scale, particularly in intertidal areas.

2015-05Journal article

Open Access

Differentiation in fitness-related traits in response to elevated temperatures between leading and trailing edge populations of marine macrophytes

Publication . Mota, Catarina; Engelen, Aschwin; Serrao, Ester; Coelho, Márcio; Marba, Nuria; Krause-Jensen, Dorte; Pearson, Gareth

The nature of species distribution boundaries is a key subject in ecology and evolution. Edge populations are potentially more exposed to climate-related environmental pressures. Despite research efforts, little is known about variability in fitness-related traits in leading (i.e., colder, high latitude) versus trailing (i.e., warmer, low latitude) edge populations. We tested whether the resilience, i.e. the resistance and recovery, of key traits differs between a distributional cold (Greenland) and warm (Portugal) range edge population of two foundation marine macrophytes, the intertidal macroalga Fucus vesiculosus and the subtidal seagrass Zostera marina. The resistance and recovery of edge populations to elevated seawater temperatures was compared under common experimental conditions using photosynthetic efficiency and expression of heat shock proteins (HSP). Cold and warm edge populations differed in their response, but this was species specific. The warm edge population of F. vesiculosus showed higher thermal resistance and recovery whereas the cold leading edge was less tolerant. The opposite was observed in Z. marina, with reduced recovery at the warm edge, while the cold edge was not markedly affected by warming. Our results confirm that differentiation of thermal stress responses can occur between leading and trailing edges, but such responses depend on local population traits and are thus not predictable just based on thermal pressures.

2018-09Journal article

Open Access