Project description:Divergent functions of two clades of flavodoxin in diatoms mitigate oxidative stress and iron limitation Thalassiosira pseudonana and 4 open-ocean diatoms were subjected to iron limitation or short-term oxidative stress (hydrogen peroxide). mRNA profiles of T. pseudonana (CCMP1335), Thalassiosira oceanica (CCMP1005), Amphora coffeaeformis (CCMP1405), Chaetoceros sp. (CCMP199), and Cylindrotheca closterium (CCMP340).
Project description:Diatoms are single celled photosynthetic bloom-forming algae that are responsible for at least 20% of global primary production. Nevertheless, more than 30% of the oceans are considered “ocean deserts” due to iron limitation. We used the diatom Phaeodactylum tricornutum as a model system to explore diatom’s response to iron limitation and its interplay with susceptibility to oxidative stress. By analyzing physiological parameters and proteome profiling, we defined two distinct phases: short-term (< 3 days, phase I) and chronic (> 5 days, phase II) iron limitation. While at phase I no changes in physiological parameters were observed, molecular markers for iron starvation, such as ISIP and flavodoxin, were highly upregulated. At phase II, down regulation of numerous iron-containing proteins was detected in parallel to reduction in growth rate, chlorophyll content, photosynthetic activity, respiration rate and antioxidant capacity. Intriguingly, while application of oxidative stress to phase I and II iron limited cells similarly oxidized the GSH pool, phase II iron limitation exhibited transient resistance to oxidative stress, despite the down regulation of many antioxidant proteins. By comparing proteomic profiles of P. tricornutum under iron limitation and metatranscriptomic data of an iron enrichment experiment conducted in the Pacific Ocean, we propose that iron limited cells in the natural environment resemble the phase II metabolic state. These results provide insights into the trade-off between maximal growth rate and susceptibility to oxidative stress as a possible key determinant in the response of diatoms to iron quota in the marine environment.
Project description:High intracellular levels of unbound iron can contribute to the production of reactive oxygen species (ROS) in the Fenton reaction, while depletion of iron limits the availability of iron containing proteins, some of which have important functions in the oxidative stress defense. Vice versa increased ROS levels lead to damage of proteins with iron sulfur centers. Thus organisms have to coordinate and balance their responses to oxidative stress and iron availability. Our knowledge on the molecular mechanisms underlying the coregulation of these responses is still limited. To discriminate between a direct cellular response to iron limitation and indirect responses, which are the consequence of increased levels of ROS, we compared the response of the alpha proteobacterium Rhodobacter sphaeroides to iron limitation in presence or absence of oxygen. While some genes respond to iron limitation exclusively or much stronger in presence of oxygen, other genes show much stronger response in anaerobic conditions. Remarkably few genes show even opposite response to iron depletion in presence or absence of iron.
Project description:High intracellular levels of unbound iron can contribute to the production of reactive oxygen species (ROS) in the Fenton reaction, while depletion of iron limits the availability of iron containing proteins, some of which have important functions in the oxidative stress defense. Vice versa increased ROS levels lead to damage of proteins with iron sulfur centers. Thus organisms have to coordinate and balance their responses to oxidative stress and iron availability. Our knowledge on the molecular mechanisms underlying the coregulation of these responses is still limited. To discriminate between a direct cellular response to iron limitation and indirect responses, which are the consequence of increased levels of ROS, we compared the response of the alpha proteobacterium Rhodobacter sphaeroides to iron limitation in presence or absence of oxygen. While some genes respond to iron limitation exclusively or much stronger in presence of oxygen, other genes show much stronger response in anaerobic conditions. Remarkably few genes show even opposite response to iron depletion in presence or absence of iron. RNA samples collected from anaerobically grown cultures in presence or absence of iron were analyzed by two-color microarrays
Project description:Pathogens have to cope with oxidative, iron- and carbon-limitation stresses in the human body. To understand how combined iron-carbon limitation alters oxidative stress response, Aspergillus fumigatus was cultured in glucose-peptone or peptone containing media supplemented or not with deferiprone as iron chelator. Changes in the transcriptome in these cultures were recorded after H2O2 treatment. Responses to oxidative stress were highly dependent on the availability of glucose and iron. Out of the 16 stress responsive antioxidative enzyme genes only the cat2 catalase-peroxidase gene was upregulated in more than two culturing conditions. The transcriptional responses observed in iron metabolism also varied substantially in these cultures. Only extracellular siderophore production appeared important regardless to culturing conditions in oxidative stress protection, while enhanced synthesis of Fe-S cluster proteins seemed to be crucial for oxidative stress treated iron-limited and fast growing (glucose rich) cultures. Although pathogens and host cells live together in the same place, their culturing conditions (e.g. iron availability, or occurrence of oxidative stress) can be different. Therefore, inhibition of a universally important biochemical process, like Fe-S cluster assembly, may selectively inhibit the pathogen growth in vivo and represent a potential target for antifungal therapy.
Project description:We investigated the gene expression responses of Candidatus Pelagibacter ubique cultures to iron limitation. Differential expression was observed for genes in iron acquisition and incorporation operons. SfuC in particular was 16 times higher in iron-limited cultures and encodes a periplasmic iron-binding protein.
Project description:High intracellular levels of unbound iron can contribute to the production of reactive oxygen species (ROS) in the Fenton reaction, while depletion of iron limits the availability of iron containing proteins, some of which have important functions in the oxidative stress defense. Vice versa increased ROS levels lead to damage of proteins with iron sulfur centers. Thus organisms have to coordinate and balance their responses to oxidative stress and iron availability. Our knowledge on the molecular mechanisms underlying the coregulation of these responses is still limited. To discriminate between a direct cellular response to iron limitation and indirect responses, which are the consequence of increased levels of ROS, we compared the response of the alpha proteobacterium Rhodobacter sphaeroides to iron limitation in presence or absence of oxygen. While some genes respond to iron limitation exclusively or much stronger in presence of oxygen, other genes show much stronger response in anaerobic conditions. Remarkably few genes show even opposite response to iron depletion in presence or absence of iron.
Project description:Three pairs of total RNA preparations from F. t. LVS grown under iron-replete and iron-restricted conditions were used in the DNA microarray. Seven arrays were used to examine the genes affected by iron limitation. Keywords: Dual Channel (Cy5/Cy3) arrays
Project description:Using RNAseq approach, we performed global a transcriptomic analysis of cells incubated in absence and in presence of iron chelator in Staphylocuccus lugdunensis. 175 genes were identified as members of the iron-limitation stimulon (127 up- and 48 down-regulated).