PASADENA, Calif.The sepals of the plant Arabidopsis thalianacommonly known as the mouse-eared cressare characterized by an outer layer of cells that vary widely in their sizes, and are distributed in equally varied patterns and proportions.
Scientists have long wondered how the plant regulates cell division to create these patternsin other words, how it decides which and how many cells will be large, which slightly smaller, and which very small.
Melding time-lapse imaging and computer modeling, a team of scientists led by biologists from the California Institute of Technology (Caltech) has provided a somewhat unexpected answer to this question.
"We conclude that probabilistic decisions of individual cellsrather than organ-wide mechanismscan produce a characteristic and robust cell-size pattern in development," says Elliot Meyerowitz, the George W. Beadle Professor of Biology and chair of the Division of Biology at Caltech.
These findings were published on May 11 in the online journal PLoS Biology.
A plant's sepals are the small green leaf-like organs that cup the petals of a flower, enclosing and protecting the flower before it blooms. The outer layer, or epidermis, of the Arabidopsis sepal consists of cells of widely varying sizes. These cells range in size from very small to very large; the largest cells are a type found only in the sepals and are dubbed, appropriately, "giant cells."
Each of the four sepals that cup an Arabidopsis flower has a unique pattern of cell sizes. What the Caltech-led team wanted to find out was what determines this pattern.
To gain insight into the process, Meyerowitz and Caltech postdoctoral scholar Adrienne Roeder imaged sepals during their early development. They tracked each round of cell divisions to determine how the different cell sizes were created, and what influences their distribution pattern. They then worked with senior
|Contact: Lori Oliwenstein|
California Institute of Technology