Final Activity Report Summary - PHYTODEATH (Effect of ultraviolet radiation on programmed cell death in phytoplankton: impact on biomass cycling and biodiversity)
In this project we:
1. established the ultraviolet-B radiation (UVB) doses which promoted programmed cell death and determined the species sensitivity to UVB by comparison of the different algal responses at the cellular level.
2. examined the effect of UV radiation in deoxyribonucleic acid (DNA) damage in promoting cell death.
3. studied other effects of UV in the oxidative burst and activation of caspases.
In short, we demonstrated the ability of UVB on promoting programmed cell death.
Global increases in UVB have the potential to alter marine primary production and affect carbon cycles and marine trophic dynamics. Previous estimates of UVB-induced photoinhibition and effects varied greatly, indicating that a common dose-response by marine phytoplankton might not occur from place to place. When UVB radiation was included in the treatments, such as in PAB treatment, induced a decline of the culture associated with a drastic reduction in cell numbers, a rapid loss of photosynthetic efficiency and an increase in the number of dead cells. The same was observed in the diatom thalassiosira pseudonana. A fluorescence-based measure of photosynthetic efficiency, namely Fv/Fm, decreased from 0.69 to 0.58 in the presence of UVB, whereas ultraviolet-A (UVA) caused a minor decrease of Fv/Fm, as observed by Heraud and Beardall, 2000, and Rijstenbil, 2002.
This effect was corroborated by the fact of membrane integrity loss revealed by Sytox staining and esterase activity loss revealed by fluorescein diacetate (FDA) staining. Similar results were also described by Buma et al in 1997, when they studied the effect of UVB radiation on growth of marine phytoplankton in relation to DNA damage. These results paralleled the results obtained with TUNEL staining, in which DNA fragmentation under UVB was shown. Cells produced reactive oxygen species (ROS) after one hour under PAB, as it was shown by the green fluorescence of algae in contrast to the red autofluorescence observed under P or PA. Quantitative analysis of confocal images showed a minor increase of active oxygen production associated with supplemental UVA alone and a 100% increase with additional UVB in thalassiosira pseudonana, as mentioned by Rijstenbil, 2002.
1. established the ultraviolet-B radiation (UVB) doses which promoted programmed cell death and determined the species sensitivity to UVB by comparison of the different algal responses at the cellular level.
2. examined the effect of UV radiation in deoxyribonucleic acid (DNA) damage in promoting cell death.
3. studied other effects of UV in the oxidative burst and activation of caspases.
In short, we demonstrated the ability of UVB on promoting programmed cell death.
Global increases in UVB have the potential to alter marine primary production and affect carbon cycles and marine trophic dynamics. Previous estimates of UVB-induced photoinhibition and effects varied greatly, indicating that a common dose-response by marine phytoplankton might not occur from place to place. When UVB radiation was included in the treatments, such as in PAB treatment, induced a decline of the culture associated with a drastic reduction in cell numbers, a rapid loss of photosynthetic efficiency and an increase in the number of dead cells. The same was observed in the diatom thalassiosira pseudonana. A fluorescence-based measure of photosynthetic efficiency, namely Fv/Fm, decreased from 0.69 to 0.58 in the presence of UVB, whereas ultraviolet-A (UVA) caused a minor decrease of Fv/Fm, as observed by Heraud and Beardall, 2000, and Rijstenbil, 2002.
This effect was corroborated by the fact of membrane integrity loss revealed by Sytox staining and esterase activity loss revealed by fluorescein diacetate (FDA) staining. Similar results were also described by Buma et al in 1997, when they studied the effect of UVB radiation on growth of marine phytoplankton in relation to DNA damage. These results paralleled the results obtained with TUNEL staining, in which DNA fragmentation under UVB was shown. Cells produced reactive oxygen species (ROS) after one hour under PAB, as it was shown by the green fluorescence of algae in contrast to the red autofluorescence observed under P or PA. Quantitative analysis of confocal images showed a minor increase of active oxygen production associated with supplemental UVA alone and a 100% increase with additional UVB in thalassiosira pseudonana, as mentioned by Rijstenbil, 2002.