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Mildmay, Canada

Callier V.,Ronin Institute | Frederik Nijhout H.,Duke University
Current Opinion in Insect Science | Year: 2014

The hypoxia-induced reduction of body size in Drosophila and Manduca is ideal for understanding the mechanisms of body size plasticity. The mechanisms of size regulation are well-studied in these species, and the molecular mechanisms of oxygen sensing are also well-characterized. What is missing is the connection between oxygen sensing and the mechanisms that regulate body size in standard conditions. Oxygen functions both as a substrate for metabolism to produce energy and as a signaling molecule that activates specific cellular signaling networks. Hypoxia affects metabolism in a passive, generalized manner. Hypoxia also induces the activation of targeted signaling pathways, which may mediate the reduction in body size, or alternatively, compensate for the metabolic perturbations and attenuate the reduction in size. These alternative hypotheses await testing. Both perspectives - metabolism and information - are necessary to understand how oxygen affects body size. © 2014 Elsevier Inc. Source

Wounding induces systemic potentials in Arabidopsis thaliana that can be abolished by concomitant suppression of the GLUTAMATE RECEPTOR-LIKE GLR3.3 and GLR3.6 genes. However, the roles of specific GLR channels to these potentials remain unclear. Here I applied the Electrical Penetration Graph (EPG) to study the contribution of three GLR channels to wound-induced, systemically propagated electrical potentials in Arabidopsis thaliana. In contrast to recordings made with conventional rigs for whole-plant electrophysiology, the EPG allows for the unambiguous distinction of the phloem-propagated action potential (AP) from the electrical activity outside of the phloem. The data reported here suggest that: (a) the transmission of wound-induced, phloem-propagated AP to neighbor leaves, requires expression of GLR3.3 or GLR3.6, whereas GLR3.5 prevents its transmission to non-neighbor leaves; (b) the generation of wound-induced electrical signals outside the phloem network depends on GLR3.6 expression; and (c) wound-induced systemic potentials initiated in the shoot are transmitted to the root in the adult plant, which suggests a role for these electrical signals in coordinating the plant defenses in the shoot and in the root. Here, I propose a model for wound-induced systemic electrical signals at the molecular, cellular and anatomical level. In this model, GLR3.3 and GLR3.6 function as on switches for the propagation of woundinduced potentials beyond the wounded leaf, while GLR3.5 functions as an off switch that prevents the propagation of wound-induced electrical potentials to distal, non-neighbor leaves. © 2016 Taylor & Francis Group, LLC. Source

Salvador-Recatala V.,Ronin Institute
Plant Signaling and Behavior | Year: 2016

Soil salinization is a major cause of plant stress, partly due to the physicochemical similarities between Na+ and K+. Na+ ions compete with KC ions for their transport into root cells. However, the point of Na+ entry remains unidentified. Here, I have applied the Electrical Penetration Graph as a method for whole plant electrophysiology in order to test if (a) root exposure to NaCl induces depolarization waves that propagate from root to shoot via the phloem, and if (b) the electrophysiological effects of root exposure to NaCl require expression of the potassium channels AKT1 and/or AKT2. The data suggest that AKT2 subunit containing K+ channels mediate NaCl-induced depolarization of root cells, and that this depolarization does not propagate to leaves via the phloem. © 2016 Taylor & Francis Group, LLC. Source

Muirhead C.A.,University of Rochester | Muirhead C.A.,Ronin Institute | Presgraves D.C.,University of Rochester
American Naturalist | Year: 2016

Under allopatric speciation, geographic barriers eliminate gene flow between eventual species at all loci in the genome simultaneously. There is increasing evidence, however, that speciation can be complex, with some loci experiencing gene flow during speciation or during bouts of secondary contact. In taxa with heteromorphic sex chromosomes—birds, butterflies, mammals, and Drosophila—the X (or Z) chromosome generally shows reduced levels of gene flow compared to autosomes. To investigate why, we develop population genetic models of secondary contact and gene flow at a neutral locus that is genetically linked to selected loci involved in hybrid incompatibilities and/or local adaptation. Using models that assume weak migration and strong selection, we compare gene flow at X-linked versus autosomal neutral loci as a function of linkage, dominance, sex-specific selection, and sex-specific recombination. For most cases, gene flow at neutral loci on the X is reduced relative to autosomes, as the greater efficacy of hemizygous selection in XY hybrids reduces the opportunity for neutral migrant alleles to escape their genetically linked, locally disfavored alleles via recombination. There are some circumstances, however, involving sex-limited selection and sex-limited recombination that allow neutral loci on the X to introgress more readily than those on autosomes. © 2015 by The University of Chicago. All rights reserved. Source

Altenberg L.,Ronin Institute
Genetic Programming and Evolvable Machines | Year: 2014

Banzhaf provides a portal to the subject of emergence, noting contentious concepts while not getting sucked into fruitless debate. Banzhaf refutes arguments against downward causation much as Samuel Johnson kicks a stone to ref ute Berkeley - by pointing to concrete examples in genetic programming, such as the growth of repetitive patterns within programs. Repetitive patterns are theoretically predicted to emerge from the evolution of evolvability and robustness under subtree exchange. Selection and genetic operators are co-equal creators of these emergent phenomena. GP systems entirely formal, and thus their emergent phenomena are essentially mathematical. The emergence of Lagrangian distributions for tree shapes under subtree exchange, for example, gives a glimpse of the possibilities for mathematical understanding of emergence in GP. The mathematics underlying emergence in genetic programming should be pursued with vigor. © 2013 Springer Science+Business Media New York. Source

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