Cyanobacteria gene expression in response to environmental stress and seasonal changes.

Cyanobacteria hold a remarkable physiological capacity to adapt to stress, which may arise from rapid environmental changes. These changes induce the expression of specific genes crucial for acclimatization and cell protection under unfavorable conditions. This study was performed in two aquatic systems in the Tropics (Brazil): an oligo-mesotrophic and a hypereutrophic reservoir. We aimed to investigate the effect of environmental changes in the expression of genes associated with cellular responses to stress (ntcA, pstS, fur, and prxM) in cyanobacterial populations living in these systems. Additionally, by assessing the gene expression of some cyanopeptides (microcystin - mcyD, cyanopeptolin - cnp, and aeruginosin - aerA) we intended to verify their potential connection to cell acclimation processes. Samples were collected during the rainy and dry seasons. Biotic and abiotic parameters were measured and correlated with molecular data. Gene expression was quantified by qPCR. Temperature and nutrient concentration were identified as primary factors correlated with gene expression. However, nitrogen played a more significant role in the oligo-mesotrophic reservoir, while phosphorus in the hypereutrophic system. Furthermore, we found that the peptide cyanopeptolin exhibited a similar response and a positive correlation to genes related to environmental stress (prxM, ntcA, and pstS), suggesting its potential role in the cellular acclimation process. The molecular approach employed in this work proved highly sensitive in detecting organismal responses to stress caused by environmental changes. Integrating gene expression analyses into environmental studies can contribute to the understanding of cyanobacterial resilience and develop more effective strategies for bloom management and environmental recovery.