April 3, 2006, Irvine, Calif. -- UC Irvine’s Donald Bren School of Information and Computer Sciences professor Eric Mjolsness and his colleague Elliot Meyerowitz at the California Institute of Technology (Caltech) have released a study titled An auxin-driven polarized transport model for phyllotaxis through the Proceedings of the National Academy of Sciences (PNAS).
The team, also consisting of Henrik Jönsson of Lund University in Sweden, Marcus G. Heisler and Bruce E. Shapiro of Caltech, demonstrates how plant cells, with purely local information about their nearest neighbors' internal concentration of a plant hormone, can generate a global pattern. Biologists have tackled this question since they started wondering about the development of multicellular organisms and all experimental information shows that this mirrors real plant development.
The phyllotactic pattern comes from two basic mechanisms which the team simulated. The first is the polarized transport of a plant hormone (auxin), in a positive feedback loop which is a novel mechanism not previously understood or expected. The second mechanism is the dynamic geometry due to cell growth and cell division, which makes room for the new primordia
Researchers have traditionally used microscopy, mutants and other methods to understand molecular and cellular bases for development. More recently, genomics has become another tool added to the developmental biologists' arsenal.
Advances in biological knowledge, imaging instrumentation, applied biomathematics, and computing, has made it possible to create and apply computational modeling to integrate multidisciplinary approaches and different types of biological data in studying development.
With a $5 million National Science Foundation (NSF) Frontiers in Integrative Biological Research (FIBR) grant, Mjolsness and Meyerowitz have been working on developing a mathematical and computational infrastructure to characterize the pathways and interactions between complex molecules and the cellular environment.
To capture the development, Meyerowitz and his team at Caltech used green fluorescent proteins to mark specific cell types in the meristem (the inner plant tissue where regulated cell division, pattern formation and differentiation give rise to plant parts like leaves and flowers) of the plant Arabidopsis thaliana, an excellent living laboratory due to its quick maturation period.
The marked proteins allowed the group to image the cell’s lineages through meristem development and differentiation leading to specific arrangement of leaves and reproductive growth. Automation of image acquisition and analysis will help them generate and visualize a vast amount of data, which have been used by Mjolsness and his team at the University of California, Irvine to model cells and their patterns in the developing meristem and simulate developmental processes under different conditions. These simulations will result in predictions that will be tested experimentally using mutants, altered hormone gradients, and other manipulations of plant cells.
The paper is available at: http://www.pnas.org/cgi/reprint/0509839103v1
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