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Journal articleKral N, Hanna Ougolnikova A, Sena G, 2016,
Externally imposed electric field enhances plant root tip regeneration
, Regeneration, Vol: 3, Pages: 156-167, ISSN: 2052-4412In plants, shoot and root regeneration can be induced in the distinctive conditions oftissue culture (in vitro), but is also observed in intact individuals (in planta) recoveringfrom tissue damage. Roots, for example, can regenerate their fully excised meristems inplanta, even in mutants with impaired apical stem cell niches. Unfortunately, to date acomprehensive understanding of regeneration in plants is still missing.Here, we provide evidence that an imposed electric field can perturb apical rootregeneration in Arabidopsis. Crucially, we explored both spatial and temporalcompetences of the stump to respond to electrical stimulation, respectively by varyingthe position of the cut and the time interval between excision and stimulation.Our data indicate that a brief pulse of an electric field parallel to the root is sufficient toincrease by up to two-fold the probability of its regeneration, and to perturb the localdistribution of the hormone auxin, as well as cell division regulation. Remarkably, theorientation of the root towards the anode or the cathode is shown to play a role.
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Journal articleJean L, Lee CF, Hodder P, et al., 2016,
Dynamics of the formation of a hydrogel by a pathogenic amyloid peptide: islet amyloid polypeptide
, Scientific Reports, Vol: 6, ISSN: 2045-2322Many chronic degenerative diseases result from aggregation of misfolded polypeptides to form amyloids. Many amyloidogenic polypeptides are surfactants and their assembly can be catalysed by hydrophobic-hydrophilic interfaces (an air-water interface in-vitro or membranes in-vivo). We recently demonstrated the specificity of surface-induced amyloidogenesis but the mechanisms of amyloidogenesis and more specifically of adsorption at hydrophobic-hydrophilic interfaces remain poorly understood. Thus, it is critical to determine how amyloidogenic polypeptides behave at interfaces. Here we used surface tensiometry, rheology and electron microscopy to demonstrate the complex dynamics of gelation by full-length human islet amyloid polypeptide (involved in type II diabetes) both in the bulk solution and at hydrophobic-hydrophilic interfaces (air-water interface and phospholipids). We show that the hydrogel consists of a 3D supramolecular network of fibrils. We also assessed the role of solvation and dissected the evolution over time of the assembly processes. Amyloid gelation could have important pathological consequences for membrane integrity and cellular functions.
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Journal articleRichards D, Endres RG, 2016,
Target-shape dependence in a simple model of receptor-mediated endocytosis and phagocytosis
, Proceedings of the National Academy of Sciences of the United States of America, Vol: 113, Pages: 6113-6118, ISSN: 1091-6490Along with other forms of internalisation, phagocytosis and receptormediatedendocytosis are vitally important for many cell types, rangingfrom single-cell organisms to immune cells. It is known experimentallythat engulfment in both cases depends critically on particleshape and orientation. However, most previous theoretical workhas focused only on spherical particles and hence disregards the widerangingparticle shapes occurring in nature, such as those of bacteria.Here, by implementing a simple model in one- and two-dimensions, wecompare and contrast receptor-mediated endocytosis and phagocytosisfor a range of biologically-relevant shapes, including spheres, ellipsoids,capped-cylinders and hourglasses. We find a whole range of different engulfmentbehaviours with some ellipsoids engulfing quicker than spheres,and that phagocytosis is able to engulf a greater range of target shapesthan other types of endocytosis. Further, the two-dimensional modelcan explain why some non-spherical particles engulf quickest (not at all)when presented to the membrane tip-first (lying flat). Our work revealshow some bacteria may avoid being internalised simply by their shape,and suggests shapes for optimal drug delivery.
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Journal articleLee CF, Pruessner G, 2016,
Percolation mechanism drives actin gels to the critically connected state
, Physical Review E, Vol: 93, ISSN: 1539-3755Cell motility and tissue morphogenesis depend crucially on the dynamic remodelling of actomyosinnetworks. An actomyosin network consists of an actin polymer network connected by crosslinkerproteins and motor protein myosins that generate internal stresses on the network. A recent discoveryshows that for a range of experimental parameters, actomyosin networks contract to clusterswith a power-law size distribution [Alvarado J. et al. (2013) Nature Physics 9 591]. Here, weargue that actomyosin networks can exhibit robust critical signature without fine-tuning becausethe dynamics of the system can be mapped onto a modified version of percolation with trapping(PT), which is known to show critical behaviour belonging to the static percolation universalityclass without the need of fine-tuning of a control parameter. We further employ our PT model togenerate experimentally testable predictions.
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