Biology subjects

Kruse, O.

Publications and source records attributed to Kruse, O..

4 recordsLinked to original sources

bioRxiv2023

Multiple transcription factors mediate acclimation of Chlamydomonas to light stress

Light as a substrate for photosynthesis may be a boon or a bane. To thrive, photosynthetic organisms must constantly respond to changing light and CO2 conditions by balancing energy harvest and consumption in a highly dynamic way. Two major safeguard measures of photoacclimation, that is photoprotection and carbon concentrating mechanism, underlie tight transcriptional control, leading to expression changes under high light and limited CO2 with different dynamics for both systems. Here, by using a consensus gene regulatory network inferred by employing a compendium of 1,869 RNA-seq datasets, we identified and validated in vivo eight candidate transcription factors (TFs) that contribute to photoacclimation in Chlamydomonas reinhardtii. Target gene analyses indicate that the TFs act individually in associated pathways but also influence each other in expression, and function as network parts with partial redundancy with respect to photoprotection. The analyses unveil that stress responses in Chlamydomonas are mediated by a complex, interconnected network of TFs rather than a hierarchical system where multiple regulators can influence each other and target gene expression and thereby mitigate the effects of loss.

plant biology↗

bioRxiv2020

Ubiquitin ligase component LRS1 and transcription factor CrHy5 act as a light switch for photoprotection in Chlamydomonas

Survival under excess light conditions requires the light-induced accumulation of protein LHCSR3 and other photoprotection factors, to enable efficient energy-dependent quenching in the green microalga Chlamydomonas reinhardtii. Here, we demonstrate that the high light-tolerant phenotype of mutant hit1 is caused by a de-repression of promoters belonging to photoprotection genes, which in turn results from an inactivation of the E3 ubiquitin ligase substrate adaptor LRS1. Transcriptome analyses of hit1 revealed massive alterations of gene expression modulation as a consequence of perturbed LRS1 function, indicating its role as a crown regulator. In conjunction with random forest-based network modeling, these transcriptome analyses predicted that LRS1 controls photoprotection gene expression via an algal HY5 homolog as its prime transcription factor target. CrHY5 binds to T-box elements present in the promoters of these genes and its inactivation in the hit1 mutant via CRISPR-Cas9 genome editing, confirmed the regulatory connection between LRS1 and CrHY5, predicted by the network analysis.

plant biology↗

bioRxiv2018

The ‘zoo’ accompanying Botryococcus braunii: Unraveling the fundamentals of algae-bacteria biocoenosis

Bacteria occupy all major ecosystems and maintain an intensive relationship to the eukaryotes, developing together into complex biomes (i.e., phycosphere and rhizosphere). Interactions between eukaryotes and bacteria range from cooperative to competitive, with the associated microorganisms affecting their hosts development, growth, health and disease. Since the advent of non-culture dependent analytical techniques such as metagenome sequencing, consortia have been described but owing to the complex interactions rarely functionally dissected. Multifaceted analysis of the microbial consortium of the ancient phytoplankton Botryococcus as an attractive model food web revealed that its all abundant bacterial members belong to a distinct niche of biotin auxotrophs, essentially depending on the microalga. In addition, hydrocarbonoclastic bacteria without vitamin auxotrophies, which adversely affect the algal cell morphology, appear evidently decimated. Synthetic rearrangement of a minimal community consisting of alga, mutualistic and parasitic bacteria underpins the model of a eukaryote that domesticates its own mutualistic bacterial "zoo" to manipulate and control its surrounding biosphere. This model of domestication of mutualistic bacteria for the defense against destruents by a eukaryotic host could represent ecologically relevant interactions that cross species boundaries. Metabolic and system reconstruction disentangles the relationships and provide a blueprint for the construction of mutually beneficial synthetic ecosystems.

microbiology↗

bioRxiv2018

Synthetic metabolic pathways for photobiological conversion of CO2 into hydrocarbon fuel

Liquid fuels sourced from fossil sources are the dominant energy form for mobile transport today. The consumption of fossil fuels is still increasing, resulting in a continued search for more sustainable methods to renew our supply of liquid fuel. Photosynthetic microorganisms naturally accumulate hydrocarbons that could serve as a replacement for fossil fuel, however productivities remain low. We report successful introduction of five synthetic metabolic pathways in two green cell factories, prokaryotic cyanobacteria and eukaryotic algae. Heterologous thioesterase expression enabled high-yield conversion of native acyl-ACP into free fatty acids (FFA) in Synechocystis sp. PCC 6803 but not in Chlamydomonas reinhardtii where the polar lipid fraction instead was enhanced. Despite no increase in measurable FFA in Chlamydomonas, genetic recoding and over-production of the native fatty acid photodecarboxylase (FAP) resulted in increased accumulation of 7-heptadecene. Implementation of a carboxylic acid reductase (CAR) and aldehyde deformylating oxygenase (ADO) dependent synthetic pathway in Synechocystis resulted in the accumulation of fatty alcohols and a decrease in the native saturated alkanes. In contrast, the replacement of CAR and ADO with Pseudomonas mendocina UndB (so named as it is responsible for 1-undecene biosynthesis in Pseudomonas) or Chlorella variabilis FAP resulted in high-yield conversion of thioesterase-liberated FFAs into corresponding alkenes and alkanes, respectively. At best, the engineering resulted in an increase in hydrocarbon accumulation of 8- (from 1 to 8.5 mg/g dell dry weight) and 19-fold (from 4 to 77 mg/g cell dry weight) for Chlamydomonas and Synechocystis, respectively. In conclusion, reconstitution of the eukaryotic algae pathway in the prokaryotic cyanobacteria host generated the most effective system, highlighting opportunities for mix-and-match synthetic metabolism. These studies describe functioning synthetic metabolic pathways for hydrocarbon fuel synthesis in photosynthetic microorganisms for the first time, moving us closer to the commercial implementation of photobiocatalytic systems that directly convert CO2 into infrastructure-compatible fuels.\n\nHighlightsO_LISynthetic metabolic pathways for hydrocarbon fuels were engineered in algae\nC_LIO_LIFree fatty acids were effectively converted into alkenes and alkanes\nC_LIO_LITransfer of algal pathway into cyanobacteria was the most effective\nC_LIO_LIAlkane yield was enhanced 19-fold in Synechocystis spp. PCC 6803\nC_LIO_LIAlkene yield was enhanced 8-fold in Chlamydomonas reinhardtii\nC_LI

synthetic biology↗