Project description:Many cyanobacteria can form nitrogen-fixing symbioses with a broad range of plant species. Unlike other plant-bacteria symbioses, little is understood about the immunological responses induced by plant cyanobionts (symbiotic cyanobacteria). Here, we used Arabidopsis thaliana suspension cell cultures as a model system to demonstrate that the model plant-symbiotic cyanobacteria, Nostoc punctiforme is capable of protecting against plant programmed cell death (PCD). We also profiled the early transcriptomic changes that were induced in response to conditioned medium (CM) from N. punctiforme cell cultures. Interestingly, the PCD reduction was preceded by the induction of genes associated with defence and immunity, the most striking of which were a number of WRKY-family transcription factors. Down-regulated included genes involved in the regulation of cell growth and differentiation. This work is the first to show that a cyanobacteria can regulate plant PCD and provides a useful transcriptome resource for studying early plant cell responses to symbiotic cyanobacteria.
Project description:Emergence of the symbiotic lifestyle fostered the immense diversity of all ecosystems on Earth, but symbiosis plays a particularly remarkable role in marine ecosystems. Photosynthetic dinoflagellate endosymbionts power reef ecosystems by transferring vital nutrients to their coral hosts. The mechanisms driving this symbiosis, specifically those which allow hosts to discriminate between beneficial symbionts and pathogens, are not well understood. Here, we uncover that host immune suppression is key for dinoflagellate endosymbionts to avoid elimination by the host using a comparative, model systems approach. Unexpectedly, we find that the clearance of non-symbiotic microalgae occurs by non-lytic expulsion (vomocytosis) and not intracellular digestion, the canonical mechanism used by professional immune cells to destroy foreign invaders. We provide evidence that suppression of TLR signalling by targeting the conserved MyD88 adapter protein has been co-opted for this endosymbiotic lifestyle, suggesting that this is an evolutionarily ancient mechanism exploited to facilitate symbiotic associations ranging from coral endosymbiosis to the microbiome of vertebrate guts.
Project description:Emergence of the symbiotic lifestyle fostered the immense diversity of all ecosystems on Earth, but symbiosis plays a particularly remarkable role in marine ecosystems. Photosynthetic dinoflagellate endosymbionts power reef ecosystems by transferring vital nutrients to their coral hosts. The mechanisms driving this symbiosis, specifically those which allow hosts to discriminate between beneficial symbionts and pathogens, are not well understood. Here, we uncover that host immune suppression is key for dinoflagellate endosymbionts to avoid elimination by the host using a comparative, model systems approach. Unexpectedly, we find that the clearance of non-symbiotic microalgae occurs by non-lytic expulsion (vomocytosis) and not intracellular digestion, the canonical mechanism used by professional immune cells to destroy foreign invaders. We provide evidence that suppression of TLR signalling by targeting the conserved MyD88 adapter protein has been co-opted for this endosymbiotic lifestyle, suggesting that this is an evolutionarily ancient mechanism exploited to facilitate symbiotic associations ranging from coral endosymbiosis to the microbiome of vertebrate guts.
Project description:Green hydra (Hydra viridissima) harbors endosymbiotic Chlorella and have established a mutual relation. To identify the host hydra genes involved in the specific symbiotic relationship, transcriptomes of intact H. viridissima colonized with symbiotic Chlorella strain A99, aposymbiotic H.viridissima and H. viridissima artificially infected with other symbiotic Chlorella were compared by microarray analysis. The results indicated that genes involved in nutrition supply to Chlorella were upregulated in the symbiotic hydra. In addition, it was induced by supply of photosynthates from the symbiont to the host, suggesting cooperative metabolic interaction between the host and the symbiotic algae.
Project description:Iron (Fe) and phosphorus (P) are essential nutrients with close geochemical association. They exist at low concentrations in surface waters and may be co-limiting resources for phytoplankton growth. However, the adaptive strategies of photosynthetic organisms to Fe/P co-limitation remain largely unknown. Here, we show that phosphorus deficiency increases the growth of Fe-limited cyanobacteria through a PhoB-mediated regulatory network. In addition to its well-recognized role in controlling phosphate homeostasis, PhoB regulates key metabolic processes crucial for Fe-limited cyanobacteria, including ROS detoxification and Fe uptake. Transcript abundances of PhoB-targeted genes are enriched in samples from the P-deplete ocean, and a conserved PhoB binding site is widely present in the promoters of the targets, suggesting that the strategy we discovered may be highly conserved. Our findings provide important molecular insights into the response of cyanobacteria to simultaneous Fe/P nutrient limitation and help in understanding how nutrient availability affects primary productivity in aquatic environments.
Project description:Cyanobacteria are attractive hosts for producing pharmaceuticals, renewable fuels, and chemicals due to their ability to use sunlight as their energy source. Despite the application of traditional genetic tools such as the identification of strong promoters to enhance the expression of heterologous genes, however, cyanobacteria have lagged behind other microorganisms such as E.coli and yeast as economically efficient bioreactors. The previous approaches have ignored large-scale constraints within cyanobacterial metabolic networks on transcription, predominantly the pervasive control of gene expression by the circadian (daily) clock. Here we adopt a novel strategy and show that reprogramming gene expression within cyanobacteria by inactivation of the circadian oscillator coupled with release of circadian repressor elements in the transcriptional regulatory pathways enables a dramatic enhancement of expression in cyanobacteria of heterologous genes encoding both catalytically active enzymes and polypeptides of biomedical significance.
Project description:Transcriptional comparison between symbiotic and non-symbiotic (bleached) sea anemones Anemonia viridis were analysed in several specimens. We generated an oligonucleotide microarray (2000 selected features), which is to date the only available oligonucleotide array for symbiotic cnidarians. We were able to identify a subset of genes clearly involved in symbiosis.
Project description:Plant-cyanobacteria symbiosis is considered one of the pivotal events in the history of life. In this symbiosis, the cyanobacterium provides to the plant fixed nitrogen compounds and plant hormones and, in return, the plant provides to the cyanobacterium fixed carbon. Despite the large knowledge in the physiology and ecology of plant-cyanobacteria symbioses, little is known about the molecular mechanisms involved in the crosstalk between partners. It has been shown recently that Nostoc punctiforme is able to stablish an endophytic symbiosis with Oryza sativa. This finding opens a door to explore this symbiotic interaction as a sustainable alternative to nitrogen fertilization of paddy fields. However, molecular mechanisms behind Oryza-Nostoc endosymbiosis are still not clarified. To gain further insights, an LC-MS/MS based label-free quantitative technique was used to evaluate the differential proteomics under N. punctiforme treatment vs. control plants at 1 day and 7 days. Differential expression profiling reveals a significant number of proteins to be down-regulated or missing in both partners, while others were more abundant or only expressed when both partners were in contact. In N. punctiforme, the differential protein expression was primarily connected to primary metabolism, signal transduction and perception, transport of substances and photosynthesis. In O. sativa, the differential protein expression was connected to a wide range of biological functions regulating carbon and nitrogen metabolism and response to biotic and abiotic stresses.