Tolerance to oxidative stress induced by desiccation in Porphyra columbina (Bangiales, Rhodophyta)

Abstract

Unravelling the mechanisms underlying desiccation tolerance is crucial in order to understand the position of algal species in the intertidal zone. The alga Porphyra columbina lives in the uppermost part of the rocky intertidal zones around the world and was selected as a model for this study. Naturally desiccated plants were collected during low tide and studied for morphological changes, oxidative burst induction, biomolecule oxidation, antioxidant responses, and photosynthetic status. Naturally hydrated plants collected during high tides were used for comparative purposes. In addition, changes induced by desiccation were assessed in vitro and the capacity to recover from desiccation was determined by rehydrating the fronds in seawater. The global results show that desiccation induces morphological and cellular alterations accompanied by a loss of ∼96% of the water content. Overproduction of reactive oxygen species (ROS) was induced by desiccation and two peaks of H2O2 were detected at 1 and 3 h of desiccation. However, during in vitro rehydration post-desiccation, the ROS quickly returned to the basal levels. At the biomolecular level, only a low production of oxidized proteins was recorded during desiccation, whereas the activity of diverse antioxidant enzymes increased. However, this activity diminished to near basal levels during rehydration. The photosynthetic efficiency (Fv/Fm) during desiccation declined by 94–96% of the values recorded in hydrated plants. This reduction was generated by the low levels of trapped energy flux per cross-section (TRo/CS), electron transport flux per CS (ETo/CS), and density of reaction centres (RC/SCo) as well as the chlorophyll content. The inverse pattern was observed for the levels of phycocyanin and phycoerythrin content. Fv/Fm and the photosynthetic indicators were restored to normal levels after only 5 min of rehydration. The results indicate that desiccation in P. columbina causes overproduction of ROS that is efficiently attenuated. The morphological and photosynthetic changes could be operating as tolerance mechanisms due to the fact that these responses principally prevent biomolecular alteration and cellular collapse. Thus, the activation of different physiological mechanisms helps to explain the high tolerance to desiccation of P. columbina and, at least in part, the position of this species at the highest level in the intertidal zone.

Interactive effects of grazing and environmental stress on macroalgal biomass in subtropical rocky shores: Modulation of bottom-up inputs by wave action

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Biochemical and physiological analysis in carrot seeds from different orders of umbels

“…Defence mechanisms are extremely important for the conservation of seed quality. Known as enzymatic systems, they are involved in the antioxidant response for neutralisation of singlet oxygen and other free radicals which are formed under conditions of stress (CONTRERAS-PORCIA et al, 2010;DUSSERT et al, 2006) such as occur during the drying process, for example.…”

Variación estacional en la composición de ensambles sublitorales de macroalgas asociadas al alga roja Gigartina skottsbergii Setchell & Gardner, en el Estrecho de Magallanes, Chile

“…Asimismo, las comunidades algales costeras están sujetas a procesos físicos (e.g. acción del oleaje, inestabilidad del substrato, desecación (Contreras-Porcia et al 2011), temperatura, fotoperiodo, ph entre otros (Dawes, 1998) y biológicos (e.g. herbivoría), los cuales determinan la composición y abundancia, de las especies que allí habitan (Yodzis, 1993).…”