Biology subjects

Staal, J.

Publications and source records attributed to Staal, J..

6 recordsLinked to original sources

bioRxiv2024

Multi-Step Pathway Engineering in Probiotic Saccharomyces boulardii for Abscisic Acid Production in the Gut

The plant hormone abscisic acid (ABA) has gained attention for its role in animals and humans, particularly due to its protective effects in various immune and inflammatory disorders. Given its high concentrations in fruits like figs, bilberries and apricots, ABA shows promise as a nutraceutical. However scalability, short half-life and cost limit the use of ABA-enriched fruit extracts and synthetic supplements. In this study, we propose an alternative ABA administration method to overcome these challenges. We genetically engineered a strain of the probiotic Saccharomyces boulardii to produce and deliver ABA directly to the gut of mice. Using the biosynthesis pathway from Botrytis cinerea, four genes (bcaba1-4) were integrated into S. boulardii, enabling ABA production at 30{degrees}C, as previously described in Saccharomyces cerevisiae. Introducing an additional cytochrome P450 reductase gene resulted in a 7-fold increase in ABA titers, surpassing previous ABA-producing S. cerevisiae strains. Supplementation of the ABA-producing S. boulardii in the diet of mice (at a concentration of 5 x 108 CFU/g) led to effective gut colonization but resulted in low serum ABA levels (approximately 1.8 ng/mL). The absence of detectable serum ABA after administration of the ABA-producing probiotic through oral gavage, prompted further investigation to determine the underlying cause. The physiological body temperature (37{degrees}C) was identified as a major bottleneck for ABA production. Modifications to enhance the mevalonate pathway flux improved ABA levels at 37{degrees}C. However, additional modifications are needed to optimize ABA production before testing this probiotic in disease contexts in mice.

synthetic biology↗

bioRxiv2024

Shedding light on plant proteolysis: genetically encoded fluorescent sensors as tools for profiling protease activities

Proteolysis, a ubiquitous process in living organisms, is driven by proteases that regulate numerous signaling pathways through the hydrolysis of peptide bonds in protein substrates. Understanding the temporal and spatial dynamics of proteolysis and the activation of proteases is crucial for elucidating their roles in biological pathways. Here, we introduce a suite of genetically encoded FRET reporters designed to detect various proteolytic activities in plants. These sensors effectively reported in planta the specific activity of both Tobacco Etch Virus protease and caspase-3. Furthermore, we developed sensors for detecting plant metacaspase activity, validated through both in vitro and in planta experiments. These experiments revealed the spatial dynamics of proteolysis triggered by metacaspase activation following wounding and programmed cell death in roots. The implementation of these tools in plant biology research opens new avenues for investigating proteolytic mechanisms, significantly enhancing the potential for in-depth studies. Our work demonstrates the feasibility of using these sensors to detect diverse protease activities in vivo with high spatiotemporal resolution. These plant proteolytic biosensors hence represent a valuable toolbox for understanding protease functions within their natural context, paving the way for future advancements in plant biology research.

plant biology↗

bioRxiv2023

Extreme miniaturization in plasmid design: generation of the 903 bp cloning vector pICOt2

Inspired by the size optimizations in the recently published pUdO series of plasmids, we set out to break our previous world record (pICOz, 1185 bp) in designing the smallest possible self-replicating high copy cloning vector. By replacing the zeocin resistance marker with trimethoprim resistance, deleting the parts upstream of -35 in the ampicilin resistance promoter and replacing the extended multiple cloning site with a single SpeI site, we managed to reduce the plasmid size to 903 bp, almost a 24% reduction in size compared to our previous accomplishments.

synthetic biology↗

bioRxiv2023

"Franken-CARD9": chimeric proteins for high-resolution studies of activating mutations in CARD10, CARD11 and CARD14

CARD9, -10, -11 and -14 all belong to the CARD-coiled coil (CC) protein family and originated from a single common ancestral protein early in vertebrate evolution. All four proteins form CARD-CC/BCL10/MALT1 (CBM) complexes leading to NF-{kappa}B activation after upstream phosphorylation by various protein kinase C (PKC) isoforms. CBM complex signaling is critical for innate and adaptive immunity, but aberrant activation can cause autoimmune or autoinflammatory diseases, or be oncogenic. CARD9 shows a superior auto-inhibition with very low spontaneous activity when overexpressed in HEK293T cells. In contrast, the poor auto-inhibition of other CARD-CC family proteins, especially CARD10 (CARMA3) and CARD14 (CARMA2), is hampering characterization of upstream activators or activating mutations in overexpression studies. We grafted different domains from CARD10, -11 and 14 on CARD9 to generate chimeric CARD9 backbones for functional characterization of activating mutants using NF-{kappa}B reporter gene activation in HEK293T cells as readout. CARD11 (CARMA1) activity was not further reduced by grafting on CARD9 backbones. The chimeric CARD9 approach was subsequently validated by using several known disease-associated mutations in CARD10 and CARD14, and additional screening allowed us to identify several novel activating natural variants in human CARD9 and CARD10. Using Genebass as a resource of exome-based disease association statistics, we found that activated alleles of CARD9 correlate with irritable bowel syndrome (IBS), constipation, osteoarthritis, fibromyalgia, insomnia, anxiety and depression, which can occur as comorbidities.

genetics↗

bioRxiv2021

Different resource allocation in a Bacillus subtilis population displaying bimodal motility

To cope with sudden changes in their environment, bacteria can use a bet-hedging strategy by dividing the population into cells with different properties. This so-called bimodal or bistable cellular differentiation is generally controlled by positive feedback regulation of transcriptional activators. Due to the continuous increase in cell volume, it is difficult for these activators to reach an activation threshold concentration when cells are growing exponentially. This is one reason why bimodal differentiation is primarily observed from the onset of the stationary phase when exponential growth ceases. An exception is the bimodal induction of motility in Bacillus subtilis, which occurs early during exponential growth. Several mechanisms have been put forward to explain this, including double negative-feedback regulation and the stability of the mRNA molecules involved. In this study, we used fluorescence-assisted cell sorting to compare the transcriptome of motile and non-motile cells and noted that expression of ribosomal genes is lower in motile cells. This was confirmed using an unstable GFP reporter fused to the strong ribosomal rpsD promoter. We propose that the reduction in ribosomal gene expression in motile cells is the result of a diversion of cellular resources to the synthesis of the chemotaxis and motility systems. In agreement, single-cell microscopic analysis showed that motile cells are slightly shorter than non-motile cells, an indication of slower growth. We speculate that this growth rate reduction can contribute to the bimodal induction of motility during exponential growth. IMPORTANCETo cope with sudden environmental changes, bacteria can use a bet-hedging strategy and generate different types of cells within a population, so called bimodal differentiation. For example, a Bacillus subtilis culture can contain both motile and non-motile cells. In this study we compared the gene expression between motile and non-motile cells. It appeared that motile cells express less ribosomes. To confirm this, we constructed a ribosomal promoter fusion that enabled us to measure expression of this promoter in individual cells. This reporter fusion confirmed our initial finding. The re-allocation of cellular resources from ribosome synthesis towards synthesis of the motility apparatus results in a reduction in growth. Interestingly, this growth reduction has been shown to stimulate bimodal differentiation.

microbiology↗

bioRxiv2017

Defining the relevant combinatorial space of the PKC/CARD-CC signal transduction nodes

Biological signal transduction typically display a so-called bow-tie or hour glass topology: Multiple receptors lead to multiple cellular responses but the signals all pass through a narrow waist of central signaling nodes. One such critical signaling node for several inflammatory and oncogenic signaling pathways in humans are the CARD-CC / Bcl10 / MALT1 (CBM) complexes, which get activated by upstream protein kinase C (PKC). In humans, there are four phylogenetically distinct CARD-CC family (CARD9, -10, -11 and -14) proteins and 9 true PKC isozymes ( to {iota}). At this moment, less than a handful of PKC/CARD-CC relationships are known from experimental evidence. In order to explore the biologically relevant combinatorial space out of all 36 potential permutations in this two-component signaling event, we made use of CRISPR/Cas9 genome-edited HEK293T cells to mutate CARD10 for subsequent pairwise cotransfections of all CARD-CC family members and activated mutants of all true PKCs. By quantitative reporter gene expression readout, we could define specific strong and weak PKC/CARD-CC relationships. Surprisingly as many as 21 PKC/CARD-CC combinations were found to have synergistic effects. We also discovered heterodimerization between different CARD-CC proteins, and that this can influence their PKC response profile. This information will be valuable for future studies of novel signaling pathways dependent on the CBM complex signaling nodes.

systems biology↗