Modeling the Aux/IAA Pathway Presentation by Labeed Ben-Ghaly

Modeling the Aux/IAA Pathway Modeling the Aux/IAA Pathway

Presentation by Labeed Ben-Ghaly

Overview:

• Motivation

• Background

• The Project

• Future Work

Motivation

• To provide provide a quantitative and cellular description of plant development

Confocal microscope, Zeiss LSM-510

Phyllotaxis, pattern formation in plants

• New plant organs appear at the SAM in a remarkably symmetric fashion

• The spiral pattern and the connection to the Fibonacci series and Golden angle have attracted theoreticians

• Lots of models exist and new experimental data have illuminated molecular connections to the patterns

Introduction to AuxinsIntroduction to Auxins

• Concentrations of the plant hormone Auxin play a major role in plant development.

How is Auxin activity How is Auxin activity regulated?regulated?

• Lateral inhibition between primordia.

• Reaction-diffusion inhibitor model.

• Depletion of primordium promoting factor.

Jönsson H, et al 2006

• Indole-3-acetic acid (IAA)

• Capable of creating new primordium when added to developing tissues.

Reinhardt et al 2003

Aux/IAAAux/IAA

Modeling the PathwayModeling the Pathway

• Signal from older/incipient primordia • Auxin flux• Auxin concentration

Simple model

Active vs. Passive transport

A- + H+ AH

ii

N

jj

N

jiji

N

jjijidp

ii aNaDPaPaTaKK

dt

daf

iii

ai – auxin concentration

Pij –PIN1

production

degradation activetransport

passivetransport

Modeling the PathwayModeling the Pathway

Mathematica and Mathematica and xCelleratorxCellerator



T - active transportD - inactive transportKd - degradation

Analysis of Auxin Model

)2(2)(2 DKKKDT ddd

• Analysis predicts when the model will spontaneously create auxin peaks

• Also predicts distance between peaks

Animation, Simulation of Animation, Simulation of ModelModel

Concluding remarks

• Models can be used to indicate what players and interactions might be sufficient for driving phyllotaxis

• Experiments to test the auxin model

Thank-you

• SoCalBSI

• Bruce Shapiro

• Elliot Meyerowitz

• BNMC

• WaterTree

• NIH

ReferencesReferences• (2006) Mjolsness E. Modeling transcriptional regulation with

equilibrium molecular complex composition, 5th International Conference on the Bioinformatics of Genome Regulation and Function (BGRS-2006), Volume 1, pp. 118-121.

• (2006) Jönsson H, Heisler M, Shapiro BE, Meyerowitz EM, Mjolsness ED. An Auxin-driven polarized transport model for phyllotaxis. Proc. Natl. Acad. Sci., U.S.A., 103(5):1633-1638.

• (2006) Alon, Uri An Introduction to Systems Biology: Design Principles of Biological Circuits. CRC

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Modeling the Aux/IAA Pathway Presentation by Labeed Ben-Ghaly