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- Transcriptomic insights into metabolic reprogramming and exopolysaccharide synthesis in porphyridium purpureum under gradual nitrogen deprivationPublication . GUERREIRO, Maurean; Emmanuel, Coline; Dupuits, Céline; Gardarin, Christine; Mouzeyar, Said; Varela, João; Roche, Jane; laroche, célinePorphyridium species are known red microalgae for producing valuable bioactive compounds such as sulfated exopolysaccharides (EPS) with diverse industrial biomedical applications due to their functional and rheological properties. Recent studies have investigated how abiotic stresses, particularly nitrogen deprivation, affect Porphyridium’s metabolic regulation and EPS production through transcriptomic analysis. Still, the mechanisms governing EPS biosynthesis and the involvement of carbohydrate-activated enzymes (CAZymes) remain poorly understood. This study investigated the progressive effects of nitrate consumption on the unicellular red alga, P. purpureum, by integrating physiological, biochemical, and transcriptomic analyses through RNA-Seq, further validated by RT-qPCR. P. purpureum displayed a gradual, phase-dependent metabolic response to progressive nitrogen stress. EPS release coincided with the decline in nitrate uptake, linking nitrogen availability to carbon redirection towards polysaccharide secretion. Transcriptomic data revealed global metabolic downregulation with targeted upregulation of stress-responsive, carbohydrate catabolic, and nucleotide–sugar synthesis pathways, including the upregulation of CAZyme families GT4, GT8, and GT77. Our results give insights into the coordinated nitrogen and carbon metabolic regulation underlying polysaccharide biosynthesis, while opening future perspectives on enzyme compartmentalization and regulatory flux distribution under nitrogen stress in P. purpureum.
- Land-use evolution and trends in portugal: an approach based on the standard outputPublication . Xavier, António; Rosário, Maria do Socorro; Fragoso, Rui; Carvalho. Maria Leonor da Silva; Ferreira da Silva da Costa Freitas, Maria de BelémSince Portugal acceded to the European Union, the measures introduced under the Common Agricultural Policy (CAP) have significantly influenced farmers’ behavior and their choices of agricultural activities, with different consequences on agricultural sustainability. This paper analyses changes in crop-based income following the CAP evolution in Portuguese agriculture from 1989 until 2023 and their consequences on agricultural sustainability. The analysis is based on the Standard Output (SO) for temporary and permanent crops. These data were sourced from the Agricultural Census, conducted every ten years, and the Farm Structure Surveys were held every three years. To examine the evolution of land use and establish relationships between variables, the study employed HJ-Biplot methodology and cluster analysis. Then, a comparative analysis with agricultural sustainability trends, using several social and environmental indicators, was carried out. Regarding temporary crops, the results reveal a decline in the total SO weight of cereals for grain, alongside an increase in vegetables and floriculture. For permanent crops, a decrease was observed in fresh fruits and citrus fruits, while nuts and subtropical fruits showed notable growth. Also, the positive evolution of several SOs was accompanied by improvements in agricultural sustainability on environmental and social indicators.