Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Purdue researchers solve decades-old corn, sorghum problem

06.10.2003


A team of Purdue University researchers has recently uncovered the genetic mechanism that prevents certain crop plants from growing tall – a finding that has future crop production applications since some grains produce greater yields if plants are kept short.


Guri Johal, assistant professor of botany and plant pathology at Purdue University, kneels before a dwarf form of corn. Johal and his colleagues have recently identified the genetic mechanism responsible for this dwarfed appearance. (Purdue Agriculture Communication Service photo/Tom Campbell)



Guri Johal, assistant professor of botany and plant pathology, and his colleagues have identified the process that generates dwarfed corn and sorghum plants, which grow to roughly half the height of their normal counterparts. This discovery may help in the development of dwarf forms in other crops, which hold the potential to improve food production in certain regions of the world.

In the study, they also have revealed the genetic process behind an unstable variety of sorghum frequently used in commercial production. Their findings are reported in Friday’s (10/3) issue of Science.


Dwarf forms of crops, including wheat, rice and sorghum, are of significant agronomic importance, Johal said.

"Dwarf plants put more of their energy into producing grains, instead of growing tall," he said. That means farmers can apply fertilizers to crops with the intent of increasing yield without the worry that plants will grow so tall they topple over from wind, rain or even their own weight. Increased yields of dwarf varieties of wheat, introduced throughout India, Pakistan, and Southeast Asia during the 1960s, prevented massive food shortages in those regions, he said.

A dwarf form of corn called brachytic2 (br2) was recognized in 1951, but until now, scientists have not understood the genetic mechanism underlying the plant’s mutation. These dwarf mutants are somewhat unusual, as their lower stalks are highly compressed but the upper portions of the plant, including the ears and tassels, are normal. A related mutant in sorghum called dwarf 3 (dw3) has been put into widespread cultivation because it displays ideal crop characteristics, such as increased grain yield and improved stalk strength and quality, Johal said.

Johal and his colleagues found that loss of a gene product called a p-glycoprotein generates these dwarf corn and sorghum plants by interfering with the movement of auxin, an essential hormone in plant growth and development. They also have identified the genetic mechanism that causes dwarf sorghum plants to spontaneously revert to a taller form.

In corn, the normal gene Br2 produces a p-glycoprotein, and the researchers found that a mutation in this gene is responsible for the altered growth of the dwarf plant. They also found that the dwarf mutants, while shorter than their taller counterparts, have more cells per unit area in the stalk, which makes the stalks stronger and perhaps more effective at retaining water.

Although p-glycoproteins are involved in transporting molecules across cell membranes, their exact function still has not been conclusively shown.

"This finding in br2 dwarf mutants demonstrates the ’real-world’ impact of research involving model plants," said Angus Murphy, assistant professor of horticulture and a collaborator on the study. Murphy recently demonstrated that in Arabidopsis, a plant commonly used as a model system in plant genetics and molecular biology, mutations in a p-glycoprotein gene similar to Br2 disrupt auxin flow, leading to alteration of the plant’s form.

"After discovering that p-glycoproteins control hormonal movement in Arabidopsis, we were able to apply that information to demonstrate that the same mechanism underlies a well-described phenomenon in corn," Murphy said. "The kind of collaboration that produced this discovery is one of the unique characteristics of the Purdue research environment."

Johal and Murphy work in different academic departments located in different buildings – but they both agree that the combination of their diverse areas of expertise was key to their success.

"This study has been a perfect match between genetics and physiology," Johal said. "Geneticists have known about this mutation for years, but without this collaboration, we would not have been able to reveal the physiological changes that cause it. Our combined areas of research complement one another very well."

Johal and his colleagues also report in the current study that a genetic phenomenon involving a direct duplication of a part of a normal gene causes instability in the sorghum dwarf mutant dw3. A direct duplication occurs in a gene when a portion of its DNA sequence is repeated elsewhere in the gene. In the case of the dw3 mutant, Johal and his colleagues show that a direct duplication in the normal gene not only generates the dwarf mutation, but also is responsible for the mutant occasionally reverting to its tall form.

"Direct duplications, like the one we see in dw3, are unstable because they can self-correct," Johal said.

In another phenomenon of genetics, called recombination, a duplicated portion of a gene can be removed by a process called unequal crossing over, during which pairs of chromosomes slightly misalign to exchange corresponding segments of DNA. The end result of this unequal crossing over is that the dw3 dwarf reverts back to its normal form.

Curiously, one of the sorghum plants in the study had the dwarfed appearance typical of dw3, but Johal found that it lacked the duplication responsible for dwarfing in other dw3 plants they studied. According to Johal, the dw3 gene in this plant experienced unequal crossing over, which, by removing the direct duplication, should have restored normal height. However, this crossing over event introduced a few minor changes in the gene that were significant enough to disrupt its function and still cause the plant’s dwarfed growth.

Because this gene lacks the duplication, Johal said it is a stable mutant that will not revert back to a tall form.

"This single discovery of a stable mutant will have an immediate impact on sorghum breeding," Johal said. "Now that we have identified this stable mutant, the dw3 mutant can be corrected for commercial breeding."

Unlike dwarf sorghum, dwarf corn has not been put into commercial use partly because corn hybrids grown in the United States are not excessively tall. In addition, br2 tends to produce barren plants when grown at high densities. Furthermore, the equipment in use in the United States today would not be able to effectively harvest significantly shorter plants, he said.

However, he said the discovery of the dwarfing mechanism may renew interest in developing a dwarf corn with improved yield, which could be of particular interest in developing countries.

Dwarf varieties of rice and wheat, introduced during the 1960s throughout the Indian subcontinent and Southeast Asia, were largely responsible for thwarting famine, Johal said.

"The population explosion in those regions placed many people at risk of starvation," he said. "The introduction of dwarfing lines tripled or even quadrupled the yield of wheat and helped prevent massive food shortages."

This increase in crop yield, brought on by the introduction of dwarf crops and other technologies, is often referred to as the "green revolution" in agriculture.

According to Johal, sorghum may be crucial to the future impact of the green revolution.

"The next round of the green revolution must impact Africa," he said. "Sorghum, which is a staple in many parts of Africa, especially sub-Saharan Africa, could play a key role there."

Other cereal crops, including teff, a grain grown primarily in Ethiopia, and basmati rice, grown in India, which both grow unusually tall, also may benefit from the discovery reported in this study, Johal said.

This research was supported by start-up funds made available to Johal by Purdue University and a National Science Foundation grant awarded to Murphy. Other collaborators on the study included Dilbag S. Multani and Mark Chamberlin of Pioneer Hi-Bred International Inc., Steven P. Briggs of Diversa Corp., and Joshua J. Blakeslee of Purdue University.

Writer: Jennifer Cutraro, (765) 496-2050, jcutraro@purdue.edu

Sources: Guri Johal, (765) 494-4448, gjohal@purdue.edu

Angus Murphy, (765) 496--7956, murphy@purdue.edu

Ag Communications: (765) 494-2722; Beth Forbes, bforbes@aes.purdue.edu; http://www.agriculture.purdue.edu/AgComm/public/agnews/



PHOTO CAPTION:
Guri Johal, assistant professor of botany and plant pathology at Purdue University, kneels before a dwarf form of corn. Johal and his colleagues have recently identified the genetic mechanism responsible for this dwarfed appearance. (Purdue Agriculture Communication Service photo/Tom Campbell)

A publication-quality photograph is available at http://ftp.purdue.edu/pub/uns/johal.corn.jpeg


--------------------------------------------------------------------------------


ABSTRACT


Loss of an MDR transporter in compact stalks of maize br2 and sorghum dw3 mutants.


Dilbag S. Multani, Steven P. Briggs, Mark A. Chamberlin, Joshua A. Blakeslee, Angus S. Murphy, Gurmukh S. Johal

Agriculturally advantageous reduction in plant height is usually achieved by blocking the action or production of gibberellins. Here we describe a different dwarfing mechanism found in maize brachytic2 (br2) mutants characterized by compact lower stalk internodes. The height reduction in these plants results from the loss of a P-glycoprotein that modulates polar auxin transport in the maize stalk. The sorghum ortholog of br2 is dwarf3 (dw3), an unstable mutant of longstanding commercial interest and concern. A direct duplication within the dw3 gene is responsible for its mutant nature and also for its instability, because it facilitates unequal crossing-over at the locus.

Jennifer Cutraro | Purdue News
Further information:
http://news.uns.purdue.edu/html4ever/031002.Johal.corn.html
http://www.agriculture.purdue.edu/AgComm/public/agnews

More articles from Agricultural and Forestry Science:

nachricht Kakao in Monokultur verträgt Trockenheit besser als Kakao in Mischsystemen
18.09.2017 | Georg-August-Universität Göttingen

nachricht Ultrasound sensors make forage harvesters more reliable
28.08.2017 | Fraunhofer-Institut für Zerstörungsfreie Prüfverfahren IZFP

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: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>