Project description:Photoperiodic Time Measurement (PPTM) is the ability of plants and animals to measure differences in day/night-length (photoperiod, PP) and use that information to anticipate seasonal changes in key environmental factors such as annual changes in average temperature. This timekeeping phenomenon, which is well documented for higher organisms, enables processes such as gonadal growth/regression, flowering, hibernation, and diapause to optimally adapt to annual transformations of the environment. We discovered PPTM capability in cyanobacteria, which is unexpected since cyanobacteria are unicellular prokaryotes with generation times as short as 5-6 hours. Therefore PPTM is not confined to eukaryotes with long generation times. Here we show that cyanobacteria can distinguish between short and long daylengths (photoperiods) and respond to short winter-like days by developing an enhanced resistance to cold. This capability develops over several cycles of photoperiod, and therefore they harbor a “photoperiodic counter” that is a common characteristic of PPTM in higher organisms. These photoperiodic responses are dependent on the presence of the kaiABC genes that encode the central circadian clockwork in cyanobacteria. Short days that herald winter stimulated desaturation of membrane lipids, which is a seasonally adaptive response to lower temperatures. Long vs. short days evoke differential programs of gene transcription, including differential expression of stress response genes, suggesting that PPTM originally evolved from stresses that recur seasonally. Therefore, PPTM is a property of much simpler organisms than previously appreciated, with important implications for the evolution of biological timekeeping mechanisms.
2024-06-01 | GSE252562 | GEO
Project description:Diversity of symbiotic cyanobacteria in hornworts
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: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:As an essential primary producer, cyanobacteria play an important role in the global cycle for both carbon and nitrogen in the ecosystems. Though the influence of nanoplastics on the carbon metabolism of cyanobacteria, especial Microcystis aeruginosa, a dominant species causing cyanobacterial blooms, is well studied, little is known about nanoplastics affecting the nitrogen metabolism.