Probing the actin-auxin oscillator

Abstract

When plants began to settle on terrestrial habitats, they had to develop flexible and simultaneously robust mechanical lattices to overcome the constraints of mechanical load that was not any longer compensated by buoyancy. The invention of load-bearing modules consisting of central vasculature, surrounded by parenchymatic tissue and a water-tight epidermis with controllable stomata, the so called telomes, was a key achievement in the success story of land plants.1 Asymmetric branching of the originally dichotomous telomes, their planation with subsequent fusion, or their spherical fusion and subsequent reduction, generated all organs found in the recent true land plants. These transitions are well documented by fossile records, leading to the conclusion that the Bauplan of land plants can be explained by patterning of vasculature as core element of the telomic building blocks.The central regulator for patterning is the plant hormone auxin.2 Auxin-dependent patterning is linked to a directional flow of

CLASP: a microtubule-based integrator of the hormone-mediated transitions from cell division to elongation

“…Thus, PIN-dependent auxin transport, through its control of microtubule entrainment and consequent mechanochemical wall properties and cell shape, can reinforce its own polarity. Whereas cytoskeletal involvement in auxin responses as well as endocytosis-mediated control of auxin transport has been documented [39][40][41], whether Microtubule-mediated meristem maintenance Ruan and Wasteneys 151 and how the cytoskeleton regulates auxin and auxin polar transport has remained obscure or controversial. Unlike the polar secretion mode described for epithelial cells [42], Arabidopsis PIN proteins are targeted symmetrically to both sides of the cell plate during cytokinesis under the guidance of the microtubule-based phragmoplast and subsequently, PIN polarity is achieved post-mitotically through retrieval from selective cell faces by clathrinmediated endocytosis (CME) [43,44].…”

Arabidopsis Actin Depolymerizing Factor4 Modulates the Stochastic Dynamic Behavior of Actin Filaments in the Cortical Array of Epidermal Cells

“…Primarily based on experiments with monocot coleoptiles and exogenous expression of a bundling factor, it has been proposed that the extent of actin bundling inhibits axial cell expansion adf4 Stochastic Dynamics (Waller et al, 2002;Nick et al, 2009;Nick, 2010). Furthermore, treatments with the auxin efflux inhibitor triiodobenzoic acid (TIBA) display excessively bundled actin arrays (Dhonukshe et al, 2008), and this correlates with reductions in rice (Oryza sativa) coleoptile growth (Nick et al, 2009;Nick, 2010). Although the exact mechanism of TIBA-induced actin bundling is not known, some component of the cytoskeleton is considered to be the target (Dhonukshe et al, 2008).…”

Plant Cells Use Auxin Efflux to Explore Geometry

“…This gradient of PIN activity has been shown to arise from a gradient in PIN cycling between the plasma membrane and intracellular stores22. This cycling, in turn, depends on the concentration of auxin in the environment23, and on dynamic actin filaments that are remodelled in response to auxin (for review see 24). When the cycling of PINs would differ as a function of local auxin concentration, this would explain in principle, why the cell axis aligns with auxin gradients and would circumvent the need to sense fluxes of auxin.…”