Distance Maps and Plant Development #1: Uniform Production and Proportional Destruction

TL;DR

This paper develops a mathematical model linking auxin distribution and venation pattern formation in plants, using distance maps and reaction-diffusion equations to unify macroscopic and molecular data.

Contribution

It introduces a novel model based on distance maps and uniform destruction principles that predicts plant venation patterns from cellular signals.

Findings

Model accurately predicts auxin distribution in leaves and roots.

Distance maps encode global shape information locally.

Simulations match observed venation patterns.

Abstract

Experimental data regarding auxin and venation formation exist at both macroscopic and molecular scales, and we attempt to unify them into a comprehensive model for venation formation. We begin with a set of principles to guide an abstract model of venation formation, from which we show how patterns in plant development are related to the representation of global distance information locally as cellular-level signals. Venation formation, in particular, is a function of distances between cells and their locations. The first principle, that auxin is produced at a constant rate in all cells, leads to a (Poisson) reaction-diffusion equation. Equilibrium solutions uniquely codify information about distances, thereby providing cells with the signal to begin differentiation from ground to vascular. A uniform destruction hypothesis and scaling by cell size leads to a more biologically-relevant (Helmholtz) model, and simulations demonstrate its capability to predict leaf and root auxin distributions and venation patterns. The mathematical development is centered on properties of the distance map, and provides a mechanism by which global information about shape can be presented locally to individual cells. The principles provide the foundation for an elaboration of these models in a companion paper \cite{plos-paper2}, and together they provide a framework for understanding organ- and plant-scale organization.