Physiological responses, bioactivity and differential analysis of protein abundance of the brown seaweed Sargassum (Phaeophyceae, Fucales) submitted to UV radiation

Abstract

The incidence of light in terms of quality and quantity into the aquatic ecosystem is an important factor determining the distribution and abundance of macroalgae. Ultraviolet radiation which is one of the most debated factors that can affect these responses can cause significant cellular damage through photooxidation and oxidative stress, resulting in several vital metabolic changes such as DNA replication, transcription and translation, growth rate and development, photosynthesis and respiration, and promotion of apoptosis. Based on the aforementioned information, the present study aimed to contribute to the knowledge of the effect of UV radiation on macroalgae by using Sargassum spp. as biological model by integrating diverse physiological, cellular defenses, biological activities, and proteomic approaches for understanding the impact and sensitivity of this stressor under laboratory conditions. The different responses of the seaweed were evaluated under PAR, PAR+UVA and PAR+UVB treatments. Physiological parameters showed little variation between the treatments suggesting that moderate UV radiation doses could regulate resistance responses through the activation of antioxidant defense system by production of UV-absorbing compounds with photoprotective function, such as phlorotannins, flavonoids, and carotenoids that could provide adaptive advantages for organisms exposed to UV radiation. Moreover, extracts from the treated algal material presented high antiviral potential, which may be related to the presence of phenolic compounds and sulfated polysaccharides in the tested extracts. Then, the species can be considered as a potential biotechnology source of natural bioactive compounds. In relation to the proteomic profile of S. filipendula, were identified 40 proteins differentially abundant with respect to the UV treatments, which were mainly related to photosynthesis (32%), energy metabolism (12%), carbohydrate metabolism (7%), ROS scavenging defense and stress related metabolism (7%). Proteomic results showed target proteins that could improve the ability of the species to adapt to UV exposure, contribuiting significantly in our understanding of the molecular mechanisms underlying stress tolerance. Additionally, composition and abundance of fatty acids, chlorophylls, and carotenoids of S. vulgare after exposure to different light qualities: SOX (low pressure sodium lamps as control), SOX+Blue, SOX+Green, SOX+Red, and SOX+UV, showed that SOX supplemented with UV radiation provoked the decrease of certain carotenoids. On the other hand, the content of certain fatty acids under these SOX treatments showed slighty variation under the different light qualities, presenting a high percentage of PUFAs; however, there is need to perform future researches that allow the establishment of light condition for the stimulation of these compounds from S. vulgare. RESUMO GERALA incidência de luz em termos de qualidade e quantidade no ecossistema aquático é um fator importante que determina a distribuição e a abundância de ma...