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Coupling between reaction-diffusion prepattern and expressed morphogenesis, applied to desmids and dasyclads

1988; Elsevier BV; Volume: 130; Issue: 4 Linguagem: Inglês

10.1016/s0022-5193(88)80213-3

1095-8541

Lionel G. Harrison, Miroslav Kolář,

Algal biology and biofuel production

A complete self-organizing mechanism for extension of a cell surface by tip growth, including cases in which the growing tip branches, e.g. in desmids such as Micrasterias and dasyclads such as Acetabularia, requires (if it is to be within the general class of kinetic theory) the following feedback loops:o1.Molecular-kinetic feedback involving at least two morphogens, if the prepattern generation is to be expressed in terms of reaction-diffusion theory.2.Catalysis of extension of the cell surface by one of the morphogens, leading to a change in shape of the region on which the chemical prepattern continues to readjust. This chemistry-geometry feedback can be programmed for computation without analytical expression in equations.3.Control by the morphogenetic mechanism of its own boundaries. The boundary of the growing tip must move up in pace with its growth, for tip growth to be established at all. When growing tips branch, by the same token the growth habit of each branch is not defined as tip growth until the self-organizing mechanism has, without external help, drawn a new boundary around the morphogenetic region of each branch. Here we use feedback between the average local age of the cell surface and the input of a reactant into the reaction-diffusion system to form this loop. Molecular-kinetic feedback involving at least two morphogens, if the prepattern generation is to be expressed in terms of reaction-diffusion theory. Catalysis of extension of the cell surface by one of the morphogens, leading to a change in shape of the region on which the chemical prepattern continues to readjust. This chemistry-geometry feedback can be programmed for computation without analytical expression in equations. Control by the morphogenetic mechanism of its own boundaries. The boundary of the growing tip must move up in pace with its growth, for tip growth to be established at all. When growing tips branch, by the same token the growth habit of each branch is not defined as tip growth until the self-organizing mechanism has, without external help, drawn a new boundary around the morphogenetic region of each branch. Here we use feedback between the average local age of the cell surface and the input of a reactant into the reaction-diffusion system to form this loop. A mechanism including these three kinds of feedback, and using the Brusselator as the reaction-diffusion mechanism, is used first to show how a spherical cell may terminate its own growth. Reduced in dimensionality to a closed loop initially of circular shape, the model is used to produce: (a) development to non-circular shapes which are neither tip-growing nor branched; (b) development to an elongated shape with non-branching growing tip; (c) development to branching tip growth giving shapes suggesting those of semicells of the desmids Euastrum and Micrasterias.