Publicação
The photoprotective role of karyostrophy in benthic marine diatoms
| Resumo: | Diatoms play a crucial role in marine primary productivity and are exposed to significant fluctuations in abiotic factors, such as light, in their natural habitats. In this context, the action of photoprotective mechanisms is crucial for their survival under conditions of light stress. This study investigated the dynamics, conditioning factors, and importance of karyostrophy, the contraction of the plastids towards the center of the cell, in the photoprotection in the benthic diatom Pleurosigma strigosum exposed to different light intensities and wavelengths, and under different states of photoacclimation. Cultures from subtidal and intertidal environments acclimated to low and high light were used in this study, evaluating parameters such as the effective quantum yield (ΔF/Fm’) and the rate of photosystem II photoinactivation, and karyostrophy was quantified through automated analysis of microscopy images using dedicated software (OpenCV). The results demonstrate that cultures acclimated to low light conditions exhibited a faster and more pronounced karyostrophy response when exposed to intensities of 800 μmol photons m⁻² s⁻¹ (10 times higher than the growth light intensity) and 300 μmol photons m⁻² s⁻¹, whereas high lightacclimated cells showed a delayed karyostrophy response or, in some cases, no occurrence at all. Cells that underwent karyostrophy exhibited a similar decrease in ΔF/Fm' during light stress compared to those that did not. However, during the post-stress phase, these cells reached higher Fv/Fm values, indicating that they underwent less photoinactivation, thereby confirming the photoprotective role of karyostrophy. In addition, it was demonstrated that karyostrophy can be selectively induced by blue (460 nm), but not red (626 nm), light stimuli without resorting to chemical inhibitors. This study advanced the knowledge on the role of karyostrophy in benthic diatoms and contributes new quantitative methodologies to the study of intracellular motility and physiological resilience under environmental variations. |
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| Autores principais: | Póvoa, Mariana Duarte dos Santos |
| Assunto: | Diatoms Karyostrophy Photoacclimation Photoinhibition Photoprotection Microphytobenthos |
| Ano: | 2025 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | Diatoms play a crucial role in marine primary productivity and are exposed to significant fluctuations in abiotic factors, such as light, in their natural habitats. In this context, the action of photoprotective mechanisms is crucial for their survival under conditions of light stress. This study investigated the dynamics, conditioning factors, and importance of karyostrophy, the contraction of the plastids towards the center of the cell, in the photoprotection in the benthic diatom Pleurosigma strigosum exposed to different light intensities and wavelengths, and under different states of photoacclimation. Cultures from subtidal and intertidal environments acclimated to low and high light were used in this study, evaluating parameters such as the effective quantum yield (ΔF/Fm’) and the rate of photosystem II photoinactivation, and karyostrophy was quantified through automated analysis of microscopy images using dedicated software (OpenCV). The results demonstrate that cultures acclimated to low light conditions exhibited a faster and more pronounced karyostrophy response when exposed to intensities of 800 μmol photons m⁻² s⁻¹ (10 times higher than the growth light intensity) and 300 μmol photons m⁻² s⁻¹, whereas high lightacclimated cells showed a delayed karyostrophy response or, in some cases, no occurrence at all. Cells that underwent karyostrophy exhibited a similar decrease in ΔF/Fm' during light stress compared to those that did not. However, during the post-stress phase, these cells reached higher Fv/Fm values, indicating that they underwent less photoinactivation, thereby confirming the photoprotective role of karyostrophy. In addition, it was demonstrated that karyostrophy can be selectively induced by blue (460 nm), but not red (626 nm), light stimuli without resorting to chemical inhibitors. This study advanced the knowledge on the role of karyostrophy in benthic diatoms and contributes new quantitative methodologies to the study of intracellular motility and physiological resilience under environmental variations. |
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