The Functional Significance of Leaf Shape Variation - Towards a Consensus from Gene to Community
Langlade, Nicolas B. , Feng, Xianzhong , Costa, Maria Manuela , Hudson, Andrew , Coen, Enrico .
Natural variation and genetic control of leaf and flower allometry.
Flower appeared through recruitment of developmental programs from pre-existing organs such as leaves. Reproductive and vegetative organ dimensions may then have been subjected to synergistic or antagonistic selective pressures. To understand the genetic control of leaf size and shape, it is therefore important to integrate leaf and petal development. Our approach has been to combine a genetic and a modeling approaches to reveal the shared and independent developmental pathways between these organs.
Genetic natural variation was dissected by generating an F2 population between Antirrhinum majus and A. charidemi. We have chosen A. charidemi for comparison to the model plant A. majus because (1) it has relatively small leaves and flowers, (2) it is grows on an isolated single volcanic outcrop and (3) it defines a distinct clade from other Antirrhinum species. The small organ size of A. charidemi is thought to reflect an adaptation to low moisture since it lives in the driest place in Europe. A molecular map has been constructed for this population.
We adapted statistical shape modeling methods to describe independently and jointly leaf and flower morphologies. Each independent shape variation in our population is described by a Principal Component (PC). Thus, each organ is characterized by its deviations to the mean that can be used to identify QTLs. We created 3 models: leaves alone, petals alone and leaf and petal combined. Most of the QTLs affect the size of leaves or petals independently, only one being common to both organs. Only one of the organ allometry loci maps to a locus that also affects cell size, suggesting that most allometric differences result from cell proliferation and not cell expansion.
These findings raise questions about how these allometric genes act during development and how they vary between species.
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Related article on Antirrhinum evolution and statistical models applied to genetics
Website for the modeling toolbox used in our studies
1 - Ecole Normale Superieure, Reproduction and Plant Development, 46 Allee d'Italie, Lyon Cedex 07, 69364, France
2 - John Innes Centre, Cell and Developmental Biology, Colney Lane, Norwich, NR4 7UH, United Kingdom
3 - University of Edinburgh, Institute of Molecular Plant Sciences, King’s Buildings, Mayfield Road, Edinburgh, EH9 3JH, United Kingdom
Presentation Type: Symposium or Colloquium Presentation
Location: Williford B/Hilton
Date: Monday, July 9th, 2007
Time: 8:45 AM