Abstract Detail

Advances in Modelling Plant Development

Hong, Lilan [1], Routier-Kierzkowska, Anne-Lise [2], Dumond, Mathilde [3], Boudaoud, Arezki [3], Smith, Richard S. [2], Roeder, Adrienne [4].

ROS (reactive oxygen species) controls sepal growth.

A fundamental process in organisms is the establishment and maintenance of proper organ shape and size. Overall morphological structure is crucial for proper organ function and is thus tightly regulated. How cell growth and division, which are both highly dynamic, are coordinated to generate robust organ morphology remains largely unknown. We take a computational morphodynamics approach to explore this question, using the Arabidopsis sepal as a novel system because it is accessible to live imaging and manipulation. We initiated a forward screen for mutants with disrupted sepal size uniformity and isolated mutations in the Arabidopsis FtsH4 gene. FtsH4 encodes a mitochondrial protease, which is highly conserved from bacteria to humans. ftsh4 mutants have incresed variability in sepal size, espacially in sepal length. To determine how organ size variability arises in the mutant, we have compared the cellular and organ growth of wild type and ftsh4 mutant sepals through live imaging and image analysis using MorphoGraphX software. We find that while wild type cells grow anisotropically with greater growth in the longitudinal direction, ftsh4 mutant cells grow more isotropically with more randomly oriented growth. In addition, ftsh4 sepals stop growth prematurely. The defect in the mitochondria caused by the ftsh4 mutation increases production of reactive oxygen species (ROS) including hydrogen peroxide and superoxide. Reactive oxygen species are known to directly regulate the stiffness of the cell wall and modulate many signal transduction pathways. NBT staining shows that superoxide has a gradient distribution in wildtype sepals. The gradient starts from the tip and as the sepals grow it advances to the bottom of the sepals. Finally NBT is distributed across the whole sepal when the sepal reach the mature stage. The mutant sepals have an enriched and more variable superoxide accumulation. DAB staining shows that mutant sepals also have much higher levels of hydrogen peroxide. Furthermore, increasing ROS levels in sepal by hydrogen peroxide treatment is sufficient to inhibit growth. While decreasing ROS levels through enzymatic or non-enzymatic scavenger treatment promotes sepal growth, particularly longitudinally. Our findings suggests the possibility that ROS could be a signal to terminate organ growth, and we are building computational models to explain how modulation of this signal affects organ size uniformity.

1 - Cornell University, Weill Institute for Cell and Molecular Biology and Section of Plant Biology, 241 Weill Hall, Cornell University, Ithaca, NY, 14850, USA
2 - Max Planck Institute for Plant Breeding Research, Department of Comparative Development and Genetics, Cologne, Germany
3 - Ecole Normale Supérieure de Lyon, Reproduction et Développement des Plantes, Lyon, France
4 - Cornell University, Weill Institute for Cell and Molecular Biology and Section of Plant Biology, 239, Weill Hall, Cornell University, Ithaca, NY, 14850, USA

Keywords:
organ size
reactive oxygen species
morphodynamics
FtsH4 gene
variability.

Presentation Type: Symposium Presentation
Session: SY10
Location: Salon 13/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 3:45 PM
Number: SY10006
Abstract ID:898
Candidate for Awards:None