Unfolding how to make a leaf

June 06, 2002

Whether plants make complex, divided leaves like those of ferns or tomatoes instead of simple, single leaves such as blades of grass is controlled by whether a set of genes, called KNOX1, is switched on in the leaves, according to researchers led by Neelima Sinha, an associate professor of plant biology at the University of California, Davis.

The group of genes, called KNOX1, is found in all plants. KNOX1 genes were switched on in the leaves of all plants with complex leaves, such as tomato, carrot, fennel, cycads and ferns. KNOX1 was not active in the leaves of simple-leaved plants, such as maize, rice, tobacco and Arabidopsis.

The findings are published in the June 7 issue of Science.

At first sight, the researchers found KNOX1 gene expression in the leaves of some plants with "simple" leaves. But when they studied those leaves under a microscope, they found that they actually started as complex leaves but grew into simple-looking leaves.

In one plant, the researchers found both patterns. Neobeckia aquatica (lake cress) is a water plant with simple leaves above the water and complex leaves below. KNOX1 is expressed in the submerged leaves, but not in the aerial ones.

KNOX1 is a group of homeobox genes. Homeobox genes control the development of plants and animals from fertilized eggs to mature adults by telling other genes what to do. They have been found in all kinds of living things, including yeasts, fruit flies, mammals and plants. For scientists studying development and evolution, homeobox genes are intriguing because small changes in their behavior can cause big changes in the appearance of an animal or plant.

Leaves in the earliest types of vascular land plants, such as ferns and cycads, are complex, Sinha said. The first flowering plants, or angiosperms, are thought to have had simple leaves. The complex leaf trait then reappeared several times as different groups of flowering plants evolved, she said. The researchers surveyed more than 400 different types of plants from collections at UC Davis, State University of New York-Stony Brook, UC Santa Cruz and elsewhere. They found that, except in one small group of plants related to peas, KNOX1 was used whenever compound leaves reappeared.

"It's interesting that evolution goes back to the same tool kit again and again," Sinha said.

Sinha teamed up with Geeta Bharathan, now an assistant professor at the State University of New York, Stony Brook, to look at how genes regulate the evolution of leaf shape. The other contributors to the paper are researcher Thomas Goliber; graduate student Sharon Kessler; undergraduate students Christopher Moore and Thinh Pham, all at UC Davis.
-end-
Media contacts:

-- Neelima Sinha, UC Davis Plant Biology, 530-754-8441, nrsinha@ucdavis.edu

-- Geeta Bharathan, SUNY Stony Brook Ecology and Evolution, 631-632-9508, geeta@life.bio.sunysb.edu

-- Andy Fell, UC Davis News Service, 530-752-4533, ahfell@ucdavis.edu

-- Iva Kocijan, 631-632-6310, SUNY Stony Brook Public Relations, ikocijan@notes.cc.sunysb.edu

University of California - Davis

Related Evolution Articles from Brightsurf:

Seeing evolution happening before your eyes
Researchers from the European Molecular Biology Laboratory in Heidelberg established an automated pipeline to create mutations in genomic enhancers that let them watch evolution unfold before their eyes.

A timeline on the evolution of reptiles
A statistical analysis of that vast database is helping scientists better understand the evolution of these cold-blooded vertebrates by contradicting a widely held theory that major transitions in evolution always happened in big, quick (geologically speaking) bursts, triggered by major environmental shifts.

Looking at evolution's genealogy from home
Evolution leaves its traces in particular in genomes. A team headed by Dr.

How boundaries become bridges in evolution
The mechanisms that make organisms locally fit and those responsible for change are distinct and occur sequentially in evolution.

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.

Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.

A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.

Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?

Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.

Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.

Read More: Evolution News and Evolution Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.