Tolerance pathways to desiccation stress in seaweeds

Abstract

Seaweeds are sessile organisms that inhabit coastal benthic systems and are key species for the equilibrium of marine communities. Rocky intertidal zone seaweeds are distributed in marked patterns determined by interactions between biotic and abiotic factors influenced by tide levels. It has been proposed that the distribution and abundance of organisms in the upper intertidal zones, with longer emersions, are mostly regulated by abiotic factors. Desiccation is a particularly noteworthy abiotic factor since, during low tide, algae of the upper intertidal zones can lose more than 90% of cellular water content, which can ultimately induce oxidative stress. Considering the necessary activation of several desiccation tolerance mechanisms, these algal species are ideal research models in ecophysiology. In fact, several studies using physiological, transcriptomic, and proteomic approaches have determined that desiccation tolerance mechanisms are expressed within a well-coordinated network that includes morphological and cell wall changes, photosynthetic activity diminishment, increased expression of desiccation-associated proteins, hormone accumulation, ROS scavenging by antioxidant enzymes and compounds, and osmolyte and protein synthesis. These mechanisms explain the permanence of tolerant algae species in the upper intertidal zone in comparison with lower intertidal species. Therefore, this chapter focuses on identifying tolerant algal species, and explaining the mechanisms underlying the high capacity of these species to cope with desiccation- induced oxidative stress.