Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Pod corn develops leaves in the inflorescences

A leaf gene active in the maize cob causes leaves to grow in the male and female inflorescences
In a variant of maize known as pod corn, or tunicate maize, the maize kernels on the cob are not ‘naked’ but covered by long membranous husks known as glumes. According to scientists from the Max Planck Institute for Plant Breeding Research in Cologne and Friedrich Schiller University in Jena, this variant arises from the activity of a leaf gene in the maize cob that is not usually active there. Thus, pod corn is not a wild ancestor of maize, but a mutant that forms leaves in the wrong place.

Pod corn has a spectacular appearance that has fascinated naturalists for two centuries. In this maize variant, the kernels are wrapped in fine glumes which look like thin paper in their dried form and resemble a leaf sheath. The male flowers, which are arranged in a panicle at the end of the stem axis, are also surrounded by long glumes, and sometimes even develop kernels that can otherwise only be found in the cob. The pod corn leaves resemble those of the normal maize plant. Pod corn had a ritual significance for some Native American tribes and can therefore be found throughout the American continent.

The putatitive significance of pod corn for the domestication of maize has long been a matter of controversy. Some scientists believed pod corn to be a wild, precursor of the varieties with naked kernels common today. Others disagreed with this view – and they were right, as we now know. The wild ancestor of today’s common maize varieties is not pod corn but the unimpressive sweet grass teosinte.

Heinz Saedler, Günter Theißen and their colleagues have now discovered how the spectacular appearance of pod corn arises. Their findings reveal that this variant has nothing to do with the domestication of maize, but is a mutant that forms leaves in the wrong place. Genetic experiments from the 1950s provided important inspiration for the research. “We knew from the old crossing experiments that the mutation must consist of at least two genetic components that can be inherited separately. If just one component is inherited, the glumes that surround the kernels in this mutant are significantly smaller and less conspicuous than the glumes in mutants with both components. However, they are not as tiny as the glumes found in common maize plants in which the kernels sit naked on the cob,” explains Heinz Saedler from the Max Planck Institute for Plant Breeding Research.

The researchers succeeded in showing that the components in question are two copies of the same gene which are located in tandem on chromosome 4. Although the gene itself is intact in pod corn, the region that controls the transcription of the gene is damaged. As a result of this defect, spatial control of gene activity in the right plant organs is lost. Therefore, in its mutated form, this gene is also active in the cob and not only in the growing leaves. “The gene contains the information for a transcription factor. Through its ectopic activity in the male and female inflorescence, it controls a set of so called ‘target genes’ and hence a programme in the glumes that is normally reserved for leaf development and should not be active in the inflorescence. As a result of this erroneous activity, the glumes assume a leaf-like growth pattern and grow until the kernels are completely covered,” says Günter Theißen from the University of Jena.

These findings also explain the existence of pod corn with smaller glumes. “The extent of this phenotype depends on whether there are one or two copies of the damaged gene on the chromosome and whether the plant is homozygous or heterozygous for this gene,” says Theißen. “If one gene copy is present, the effect on the leaf development programme is only half as strong as it is in one with two copies. Therefore this genetic effect is additive. The gene dosage decides, on the strength of the mutant phenotype.” Theißen and his colleagues were also able to show that the mutated gene belongs to an entire family of developmental control genes known as the MADS-box gene family. Other representatives of this family control other development processes in the plant.
Professor em. Dr. Heinz Saedler
Max Planck Institute for Plant Breeding Research
Phone: +49 22 150-620
Email: saedler@­
Professor Dr. Günter Theißen
Phone: +49 36 4194-9550
Email: guenter.theissen@­

Original publication
Luzie U. Wingen, Thomas Münster, Wolfram Faigl, Wim Deleu, Hans Sommer, Heinz Saedler, Günter Theißen
Molecular genetic basis of pod corn (Tunicate maize)
PNAS 2012; online publication, April 18, 2012, doi:10.1073/pnas.1111670109

Professor em. Dr. Heinz Saedler | EurekAlert!
Further information:

More articles from Agricultural and Forestry Science:

nachricht Harnessing a peptide holds promise for increasing crop yields without more fertilizer
25.11.2015 | University of Massachusetts at Amherst

nachricht Study shows how crop prices and climate variables affect yield and acreage
18.11.2015 | University of Illinois College of Agricultural, Consumer and Environmental Sciences

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Innovative Photovoltaics – from the Lab to the Façade

Fraunhofer ISE Demonstrates New Cell and Module Technologies on its Outer Building Façade

The Fraunhofer Institute for Solar Energy Systems ISE has installed 70 photovoltaic modules on the outer façade of one of its lab buildings. The modules were...

Im Focus: Lactate for Brain Energy

Nerve cells cover their high energy demand with glucose and lactate. Scientists of the University of Zurich now provide new support for this. They show for the first time in the intact mouse brain evidence for an exchange of lactate between different brain cells. With this study they were able to confirm a 20-year old hypothesis.

In comparison to other organs, the human brain has the highest energy requirements. The supply of energy for nerve cells and the particular role of lactic acid...

Im Focus: Laser process simulation available as app for first time

In laser material processing, the simulation of processes has made great strides over the past few years. Today, the software can predict relatively well what will happen on the workpiece. Unfortunately, it is also highly complex and requires a lot of computing time. Thanks to clever simplification, experts from Fraunhofer ILT are now able to offer the first-ever simulation software that calculates processes in real time and also runs on tablet computers and smartphones. The fast software enables users to do without expensive experiments and to find optimum process parameters even more effectively.

Before now, the reliable simulation of laser processes was a job for experts. Armed with sophisticated software packages and after many hours on computer...

Im Focus: Quantum Simulation: A Better Understanding of Magnetism

Heidelberg physicists use ultracold atoms to imitate the behaviour of electrons in a solid

Researchers at Heidelberg University have devised a new way to study the phenomenon of magnetism. Using ultracold atoms at near absolute zero, they prepared a...

Im Focus: Climate Change: Warm water is mixing up life in the Arctic

AWI researchers’ unique 15-year observation series reveals how sensitive marine ecosystems in polar regions are to change

The warming of arctic waters in the wake of climate change is likely to produce radical changes in the marine habitats of the High North. This is indicated by...

All Focus news of the innovation-report >>>



Event News

Fraunhofer’s Urban Futures Conference: 2 days in the city of the future

25.11.2015 | Event News

Gluten oder nicht Gluten? Überempfindlichkeit auf Weizen kann unterschiedliche Ursachen haben

17.11.2015 | Event News

Art Collection Deutsche Börse zeigt Ausstellung „Traces of Disorder“

21.10.2015 | Event News

Latest News

Harnessing a peptide holds promise for increasing crop yields without more fertilizer

25.11.2015 | Agricultural and Forestry Science

Earth's magnetic field is not about to flip

25.11.2015 | Earth Sciences

Tracking down the 'missing' carbon from the Martian atmosphere

25.11.2015 | Physics and Astronomy

More VideoLinks >>>