Cyanobacterial regulated cell death and its impacts on plant interactions

REGALINI, SOFIA; CUNIOLO, ANTONELLA; BERÓN, CORINA M; SALERNO, GRACIELA; MARTIN, MARÍA VICTORIA

Mar del Plata

Congreso; XVIII Congreso de la Sociedad Argentina de Microbiología General; 2023

SAMIGE

Cyanobacteria, ancient oxygenic photosynthetic prokaryotes, are globally widespread. Under optimal growth conditions, they demonstrate the remarkable ability to synthesize an extensive array of bioactive compounds, including potent toxins produced by some species. Intriguingly, a subset of these compounds exhibits variations when compared to those synthesized by cyanobacteria exposed to different forms of stress, whether biotic or abiotic. In the last decades, the phenomenon of Regulated Cell Death (RCD) triggered by environmental stresses, has emerged as a significant mechanism to account for the decline of cyanobacterial blooms. However, our understanding of RCD programs is poorly understood. Recently, we elucidated a novel cell death program triggered by heat stress in cyanobacteria. This program exhibits biochemical and morphological traits resembling eukaryotic ferroptosis. This is the first report of ferroptosis in a prokaryotic organism, demonstrating that ferroptosis serves as an ancient cell death program conserved not only in eukaryotic but also in certain prokaryotic organisms. Interactions between plants and cyanobacteria exhibit a range of manifestations at diverse levels, encompassing both beneficial and detrimental impacts. This study is centered around the assessment of the consequences arising from the compounds released during the regulated cell death of cyanobacteria due to elevated temperatures. The focus is on their effects on other organisms within the environment, including specific plant species such as the terrestrial model plant Arabidopsis thaliana, as well as Lemna sp., an aquatic plant. To address this, interaction assays were performed. The results showed a decrease in the plant growth rate, leaf area, root inhibition, and chlorosis in both plant species. Moreover, the viability of plant tissues was investigated through the utilization of SYTOX GREEN staining in conjunction with fluorescence microscopy. Additionally, oxidative damage was evaluated by means of colorimetric staining techniques, including DAB (3,3´- diaminobenzidine) and the Schiff method, to detect peroxide and lipid ROS production. We have observed that the roots of the treated plants remain viable in comparison to the control group, despite their production of reactive oxygen species and oxidized lipids. In conclusion, the results indicate that ferroptotic cyanobacteria can negatively impact plant growth, but they do not lead to the death of the roots in Lemna and Arabidopsis. Thus this study contributes to our understanding of the intricate connections between cyanobacteria, plant life, and the environment. It highlights the importance of investigating the mechanisms that govern cell death when a bloom declines its ecological responses and the potential impacts of stress-induced compound releases. As our comprehension becomes more profound, this knowledge can guide efforts toward ecosystem management.