A Hybrid Systems Approach to Modeling and Analyzing

We present a hybrid systems approach to understanding the signaling system that regulates the polarity of epithelial cells orthogonal to their apical-basal axes, termed planar cell polarity (PCP). Our approach combines expertise from developmental biology, numerical analysis, and engineering control theory. By pursuing an iterative process of modeling and experimentation using Drosophila as a model system, we have developed a working molecular and cell biological understanding of the controls governing PCP, and we have constructed a preliminary mathematical model of this control network. The application of a hybrid model admits the use of tools and analytical methods that will improve our understanding of the systems architecture of this multicellular signaling network

AtPIN4 Mediates Sink-Driven Auxin Gradients and Root Patterning in Arabidopsis

AbstractIn contrast to animals, little is known about pattern formation in plants. Physiological and genetic data suggest the involvement of the phytohormone auxin in this process. Here, we characterize a novel member of the PIN family of putative auxin efflux carriers, Arabidopsis PIN4, that is localized in developing and mature root meristems. Atpin4 mutants are defective in establishment and maintenance of endogenous auxin gradients, fail to canalize externally applied auxin, and display various patterning defects in both embryonic and seedling roots. We propose a role for AtPIN4 in generating a sink for auxin below the quiescent center of the root meristem that is essential for auxin distribution and patterning