Gene regulatory response to hyposalinity in the brown seaweed Fucus vesiculosus

Abstract

Background: Rockweeds are among the most important foundation species of temperate rocky littoral shores. In the Baltic Sea, the rockweed Fucus vesiculosus is distributed along a decreasing salinity gradient from the North Atlantic entrance to the low-salinity regions in the north-eastern margins, thus, demonstrating a remarkable tolerance to hyposalinity. The underlying mechanisms for this tolerance are still poorly understood. Here, we exposed F. vesiculosus from two range-margin populations to the hyposaline (2.5 PSU -practical salinity unit) conditions that are projected to occur in the region by the end of this century as a result of climate change. We used transcriptome analysis (RNA-seq) to determine the gene expression patterns associated with hyposalinity acclimation, and examined the variation in these patterns between the sampled populations.Results: Hyposalinity induced different responses in the two populations: in one, only 26 genes were differentially expressed between salinity treatments, while the other population demonstrated up-or downregulation in 3072 genes. In the latter population, the projected future hyposalinity induced an acute response in terms of antioxidant production. Genes associated with membrane composition and structure were also heavily involved, with the upregulation of fatty acid and actin production, and the downregulation of ion channels and alginate pathways. Changes in gene expression patterns clearly indicated an inhibition of the photosynthetic machinery, with a consequent downregulation of carbohydrate production. Simultaneously, energy consumption increased, as revealed by the upregulation of genes associated with respiration and ATP synthesis. Overall, the genes that demonstrated the largest increase in expression were ribosomal proteins involved in translation pathways. The fixation rate of SNP:s was higher within genes responding to hyposalinity than elsewhere in the transcriptome. Conclusions: The high fixation rate in the genes coding for salinity acclimation mechanisms implies strong selection for them. The among-population differentiation that we observed in the transcriptomic response to hyposalinity stress suggests that populations of F. vesiculosus may differ in their tolerance to future desalination, possibly as a result of local adaptation to salinity conditions within the Baltic Sea. These results emphasise the importance of considering interspecific genetic variation when evaluating the consequences of environmental change.

Gene expression response of the alga Fucus virsoides (Fucales, Ochrophyta) to glyphosate solution exposure

“…In particular, the expression of GDP-mannose dehydrogenase, which is involved in the synthesis of alginates (Zhang et al, 2016), the main polysaccharides of the brown algal cell wall, was severely altered in all treatments. Metabolomic analyses carried out on thalli exposed to different concentrations of glyphosate revealed an accumulation of glyphosate in F. virsoides (Felline et al, 2019), which may be consistent with structural alterations of this important barrier offered by this polysaccharide against the surrounding milieu, particularly in the osmotic environment (Rugiu et al, 2020).…”

“…In Ectocarpus and Fucus vesciculosus, photoinhibition and reduction of photosynthetic rates are employed as energy-saving mechanisms, to lower the cost of acclimation in response to abiotic stress, as this can redirect more energy to stress-response processes (Dittami et al, 2009;Rugiu et al, 2020). On the other hand, the inhibition of the shikimate cycle, recently demonstrated in the thalli of F. virsoides exposed to glyphosate (Felline et al, 2019), and the consequent prevention of plastoquinone synthesis, have been implicated in the reduction of carotenoid content in glyphosate-sensitive plants (Sandmann et al, 2006).…”

Seaweed Phenolics as Natural Antioxidants, Aquafeed Additives, Veterinary Treatments and Cross-Linkers for Microencapsulation

“…Phlorotannins are synthesised due to polymerisation of phloroglucinol (1,3,5-trihydroxybenzene) monomers [ 59 ]. The biosynthesis of phloroglucinol happens via the acetate-malonate (polyketide) pathway utilising the type III polyketide synthase enzyme followed by oxidative polymerisation process to form phlorotannins [ 77 ].…”

Editorial: Environmental Stress-Promoting Responses in Algae

“…Changes in gene expression also have essential functions in adaptive responses to stress. Moreover, each environmental stress promotes the expression of cognate sets of genes; therefore, stress responses can be recognized based on global changes in the stress-inducible accumulation of newly synthesized proteins and metabolites (Collén et al, 2007;Dittami et al, 2009;Cao et al, 2017;Sun et al, 2019;Rugiu et al, 2020). However, in contrast to the well-studied stress responses of land plants, little is known about the mechanisms regulating these physiological responses and the functions of the accumulated proteins and metabolites in algae.…”