Researchers Determine How Plants Decide Where to Position Their Leaves and Flowers

One of the quests of modern biologists is to understand how cells talk to each other in order to determine where to form major organs. An international team of biologists has solved a part of this puzzle by combining state-of-the-art imaging and mathematical modeling to reveal how plants go about positioning their leaves and flowers.

In the January 31 issue of the Proceedings of the National Academy of Sciences, researchers from the California Institute of Technology, the University of California at Irvine, and Lund University in Sweden reported their success in determining how a plant hormone known as auxin affects plant organ positioning. Experts already knew that auxin played some role in the development of plant organs, but the new study employs imaging techniques and computer modeling to propose a new theory about how the mechanism works.

The research involves the growing tip of the shoot of the plant Arabidopsis thaliana, a relative of the mustard plant that has been studied intensely by modern biologists. With its simple and very well understood genome, Arabidopsis lends itself to a wide variety of experiments.

The achievement of the researchers is their demonstration of how plant cells, with purely local information about their nearest neighbors' internal concentration of auxin, can communicate to determine the position of new flowers or leaves, which form in a regular pattern, with many cells separating the newly formed primordia (the first traces of an organ or structure). The authors theorize that the template the plant uses to make the larger parts comes from two mechanisms: a polarized transport of auxin into a feedback loop and a dynamic geometry arising from the growth and division of cells.

To capture the development, Beadle Professor of Biology Elliot Meyerowitz, division chair of the biology division at Caltech, and his team used green fluorescent proteins to mark specific cell types in the plant's meristem, the plant tissue in which regulated cell division, pattern formation, and differentiation give rise to plant parts like leaves and flowers.

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, and also to follow changes in the concentration and movement of auxin.

Although the study applies specifically to the Arabidopsis plant, Meyerowitz says the mechanism is probably similar for other plants and even other biological systems in which patterning occurs in the course of development.

In addition to Meyerowitz, the paper's authors are Henrik Jönsson of Lund University, Marcus G. Heisler of Caltech's Division of Biology, Bruce E. Shapiro of Caltech's Biological Network Modeling Center, and Eric Mjolsness of UC Irvine's Institute of Genomics and Bioinformatics and department of computer science.

Source: Caltech

Related stories:

The bonsai effect: Wounded plants make jasmonates, inhibiting cell division, stunting growth
It is well known that plants growing under unfavourable conditions are generally smaller than those growing in stress-free conditions: indeed it is estimated that in the US, abiotic stress reduces the yield of agricultural crops by an average of 22%. A spectacular example of the effect of stress – in this case, repeated wounding – on plant growth is given by bonsai trees, in which every aspect of their stature, including height, girth, and size of leaves, is uniformly reduced to as little as 5% of that of their untreated sister trees. However, the mechanism of wound-induced stunting remains obscure.
Global warming's ecosystem double whammy
Plants and soils act like sponges for atmospheric carbon dioxide, but new research finds that one abnormally warm year can suppress the amount of carbon dioxide taken up by some grassland ecosystems for up to two years. The findings, which followed an unprecedented four-year study of sealed, 12-ton containerized grassland plots at DRI is the cover story in this week's issue (September 18) of the journal Nature.
The emerging story of plant roots
An international group of European and US scientists led by the Centre for Plant Integrative Biology at The University of Nottingham have uncovered a fascinating new insight into the unseen side of plant biology — the root.
Crop management strategies key to a healthy Gulf, planet
Improved management of crops and perennials could go a long way toward alleviating the problem of hypoxia, which claims thousands of fish, shrimp and shellfish in the Gulf of Mexico each spring.
Killer freeze of '07 illustrates paradoxes of warming climate
Widespread damage to plants from a sudden freeze that occurred across the Eastern United States from 5 April to 9 April 2007 was made worse because it had been preceded by two weeks of unusual warmth, according to an analysis published in the March 2008 issue of BioScience.
Volunteers Across Nation to Track Climate Clues in Spring Flowers
A nationwide initiative starting this week will enable volunteers to track climate change by observing the timing of flowers and foliage. Project BudBurst, operated by the University Corporation for Atmospheric Research (UCAR) and a team of partners, allows students, gardeners and other citizen scientists in every state to enter their observations into an online database that will give researchers a detailed picture of our warming climate.
Scientists unlock secret of what makes plants flower
A protein acting as a long-distance signal from leaf to shoot-tip tells plants when to flower, says new research published in Science Express on Thursday 19 April 2007.
How plants manage calcium may reduce effects of acid rain
A new understanding of how plants manage their internal calcium levels could lead to modifying plants to avoid damage from acid rain. The pollutant disrupts calcium balance in plants by leaching significant amounts of the mineral from leaves as well as the agricultural and forest soils the plants live in.

News discussion:

General Science news