Biology subjects

Kessel, A.

Publications and source records attributed to Kessel, A..

3 recordsLinked to original sources

bioRxiv2023

Arbitrium communication controls phage life-cycle through modulation of a bacterial anti-phage defense system

Bacterial temperate viruses (phages) have to decide between a quiescent (lysogenic) and virulent (lytic) lifestyle in the face of a variety of phage defense systems. Multiple Bacilli phage families have been shown to use the arbitrium communication system, but the mechanism by which the arbitrium system exerts its function remains largely unknown. Here we study phage {phi}3T, in which arbitrium was originally identified, and find that arbitrium communication controls the phage life-cycle through interactions with a host-encoded defense system. Under lytic conditions, the arbitrium system expresses an anti-toxin, AimX, which blocks the RNA ribonuclease activity of MazF, part of the MazEF toxin-antitoxin system. When arbitrium signal concentration is high, AimX is not expressed and MazF remains active. We find that this activity is necessary for lysogenization. Finally, we show that MazEF acts as a defense system, and protects bacteria against a lytic {phi}3T mutant which lacks AimX and an additional later-expressed MazE-like antitoxin, YosL. Altogether, our results show how a bacterial defense system has been co-opted by phages to control their lysis/lysogeny decision-making.

microbiology↗

bioRxiv2023

Alleviating the barrier of adventitious roots formation in recalcitrant mature tissue by slow release of a synthetic auxin

Clonal propagation of plants by induction of adventitious roots (ARs) from stem cuttings is a requisite step in breeding programs. A major barrier exists for propagating valuable plants that naturally have low capacity to form ARs. Due to the central role of auxin in organogenesis, indole-3-butyric acid (IBA) is often used as part of commercial rooting mixtures, yet many recalcitrant plants do not form ARs in response to this treatment. Here, we describe the synthesis and screening of a focused library of synthetic auxin conjugates in Eucalyptus grandis cuttings and identify 4-chlorophenoxyacetic acid-L-tryptophan-OMe as a competent enhancer of adventitious rooting in a number of recalcitrant woody plants, including apple and argan. Comprehensive metabolic and functional analyses reveal that this activity is engendered by prolonged auxin signaling due to initial fast uptake and slow release and clearance of the free auxin 4-chlorophenoxyacetic acid. This work highlights the utility of a slow-release strategy for bioactive compounds for more effective plant growth regulation.

plant biology↗

bioRxiv2022

Proteins with multiple G protein-coupled receptor domains

Currently known G protein-coupled receptors (GPCRs) have a single transmembrane domain. Many GPCRs form dimers that have two transmembrane domains (one per protein), and there are indications that this dimeric interaction is functionally meaningful. Here, based on sequence analysis and structure predictions, we report the existence of 57 proteins with two, three, or four GPCR domains within the same protein chain. We analyze the structures of these multi-GPCRs and show that almost all have DRY/NPxxY motifs, a strong indication of signaling activity. By homology, most of the multi-GPCRs that we identified are olfactory-related; a few are chemokine-related. Multi-GPCR candidates are found in various Chordata species including fish, camel, marmite, Chinese hamster, and new world monkeys. The discovery of receptors with multiple transmembrane domains suggests the possibility for signal regulation and amplification within an individual receptor, revealing another step in GPCR evolution and a new layer of complexity in signal transduction.

bioinformatics↗