Cheap antifungal drug may fight cancer: study

A common antifungal drug can slow tumors growing in mice and should be investigated as a potentially cheap and easy way to fight cancer in people, researchers reported on Monday.

Although it did not completely wipe out the tumors, the drug called itraconazole may boost the effects of other drugs, the researchers reported in the journal Cancer Cell.

Itraconazole is marketed under the brand name Sporanox by Johnson & Johnson subsidiary Janssen Pharmaceutica, mostly for treating a fungal infection called aspergillus.

The drug affects a so-called cascade of effects through a molecular pathway called Hedgehog, the researchers reported.

The researchers at Stanford University in California were looking for potential cancer drugs. They know that the Hedgehog pathway is involved in the development of cancer, so they looked for drugs that interfere with it.

"There is a fairly broad range of tumors in which this molecular cascade, called the Hedgehog pathway, plays an important role," Stanford's Philip Beachy, who worked on the study, said in a statement.

"The virtue of screening existing drugs is that you already have all the information about dosage and toxicity, and you can move into clinical trials fairly readily."

The researchers looked at 2,400 different drugs in a so-called library of drugs that had either been tested in people or already approved by the Food and Drug Administration, looking at the mechanism of action. The least toxic one they found was itraconazole.

"Itraconazole has been studied for nearly 25 years, and we therefore have a good understanding of its safety and potential side effects," the researchers wrote.

They tested mice and found an oral solution of itraconazole significantly slowed the growth of tumors injected under the skin. Untreated mice grew giant tumors during the same time and were euthanized.

Testing mice this way is far different from the natural development of cancer in people, but the drug should be tested in cancer patients, the researchers said.

"It might be possible with two compounds to achieve a more potent block at even lower drug concentrations," said Beachy. "If so, it's possible that there is a population of patients that can be treated relatively soon."

Courtesy: ScienceDaily

Study Says Overuse Threatens Gains From Modified Crops

Genetically engineered crops have provided “substantial” environmental and economic benefits to American farmers, but overuse of the technology is threatening to erode the gains, a national science advisory organization said Tuesday in a report.

The report is described as the first comprehensive assessment of the impact of genetically modified crops on American farmers, who have rapidly adopted them since their introduction in 1996. The study was issued by the National Research Council, which is affiliated with the National Academy of Sciences and provides advice to the nation under a Congressional charter.

The report found that the crops allowed farmers to either reduce chemical spraying or to use less harmful chemicals. The crops also had lower production costs, higher output or extra convenience, benefits that generally outweighed the higher costs of the engineered seeds.

“That’s a long and impressive list of benefits these crops can provide, and have provided to adopting farmers,” David E. Ervin, the chairman of the committee that wrote the report, said on Tuesday during a webcast news conference from Washington.

But Dr. Ervin, a professor of environmental management and economics at Portland State University in Oregon, warned that farmers were jeopardizing the benefits by planting too many so-called Roundup Ready crops. These crops are genetically engineered to be impervious to the herbicide Roundup, allowing farmers to spray the chemical to kill weeds while leaving the crops unscathed.

Overuse of this seductively simple approach to weed control is starting to backfire. Use of Roundup, or its generic equivalent, glyphosate, has skyrocketed to the point that weeds are rapidly becoming resistant to the chemical. That is rendering the technology less useful, requiring farmers to start using additional herbicides, some of them more toxic than glyphosate.

“Farmer practices may be reducing the utility of some G.E. traits as pest-management tools and increasing the likelihood of a return to more environmentally damaging practices,” the report concluded. It said the problem required national attention.

More than 80 percent of the corn, soybean and cotton grown in the United States is genetically engineered. The crops tolerate Roundup, are resistant to insects, or both.

American farmers were the first to widely adopt the technology and still account for about half of all the engineered crops grown. The crops are also being widely grown in Latin America and parts of Asia but are still largely shunned in Europe.

The rapid adoption of the crops is evidence that American farmers see the technology as beneficial.

Critics of biotechnology, who say the crops may be risky to health and the environment, have issued studies saying that use of the crops has resulted in increased reliance on pesticides and has had only a minimal effect on crop yields.

The National Research Council report, more than 200 pages, was prepared by a committee of mainly academic scientists, and it relied primarily on peer-reviewed papers.

Still, the report is not likely to win over critics of the crops.

One critic, Charles Benbrook, said the conclusion that the crops help farmers might not be true in the future. That is because the report relies mostly on data from the first few years, before prices of the biotech seeds rose sharply and the glyphosate-resistant weeds proliferated.

“This is a very different future,” said Dr. Benbrook, an agricultural economist who is chief scientist at the Organic Center, which promotes organic food and farming. “The cost is going to be way higher. The environmental impacts are going to go up fairly dramatically.”

As prices of the biotech seeds have risen sharply, even some farmers are now starting to question whether they are worth it. Just last week, Monsanto, the leading agricultural biotechnology company, said it would lower the prices of its newest genetically engineered soybeans and corn seeds because farmers were not buying as many as it had expected.

The Justice Department is investigating whether Monsanto, which has patents on the Roundup Ready system, is violating antitrust laws, unduly increasing prices or hindering innovation.

The National Research Council report addresses this issue briefly without mentioning Monsanto. It says that patent licensing terms have “not adversely affected the economic welfare of farmers who adopt G.E. crops.” But it said there was some evidence that the availability of nonengineered crops “may be restricted for some farmers.”

Monsanto, in a statement, said the report “affirms what farmers know — that agricultural biotechnology has delivered substantial environmental and economic benefits.” It said it was working with farmers to help manage and monitor herbicide-resistant weeds.

Shares of Monsanto, which have been falling since January, slipped nearly 2 percent Tuesday to $67.75.

The report said that the use of Roundup Ready crops had led to a huge increase in the spraying of glyphosate but a nearly equal decrease in the use of other herbicides. That is a net environmental benefit, the report said, because glyphosate is less toxic to animals than many other herbicides and does not last long in the environment.

The report compared genetically modified crops with the conventionally grown crops they replaced, not to organic crops.

The use of herbicide-tolerant crops has also made it easier for farmers to forgo tilling as a way to control weeds. So-called no-till farming helps prevent soil erosion and the runoff of rainwater containing sediments and chemicals. The improvement in water quality could prove to be the largest benefit of the crops, the report said, though it added that efforts should be made to measure any such effects.

The other major class of genetically engineered crops consists of the so-called BT corn and BT cotton, which contain bacterial genes allowing the plants to produce an insecticide.

The report said that use of chemical insecticides had declined as BT crops had spread. In areas with heavy insect pressure, it said, the use of the crops has increased farmer income because of higher yields and reduced spending on insecticide.

The report said that when genetically engineered crops were introduced, some had lower yields than conventional varieties, a finding often cited by critics. But the report said newer studies showed either a modest increase in yield or no effect.

Chuck Myers, a corn and soybean farmer from Nebraska who was not involved in the report, said that even if biotechnology had not increased the intrinsic yield potential of the crops, “If you’re controlling a pest, you’re preserving your yield.”

Courtesy: Newyorktimes

New Pathway Involved in Rheumatoid Arthritis Identified

Investigators from Hospital for Special Surgery have identified a pathway involved in turning off inflammation that does not work properly in people with inflammatory arthritis. The finding, reported in the April 23 issue of the journal Immunity, could lead to the development of new therapeutic approaches to treating arthritis in the future.

"This is the first study to link this pathway to rheumatoid arthritis. In the twenty years or so that I have been studying regulation of inflammation, this seems to be the most potent inhibitory mechanism that we have seen," said Lionel Ivashkiv, M.D., associate chief scientific officer at Hospital for Special Surgery in New York City and lead author of the study that has appeared online ahead of print.

For several years, Dr. Ivashkiv's lab has been studying what regulates the production of cytokines in inflammatory diseases. Cytokines are small proteins that regulate inflammation; some cytokines spark inflammation and some cytokines are anti-inflammatory. By identifying pathways involved in cytokine production, the researchers hope to open up new therapeutic avenues for diseases such as arthritis in which cytokine production does not work properly.

Prior to this study, researchers knew that so-called immunoreceptor tyrosine-based activation motif (ITAM)-coupled receptors were involved in regulating inflammation, but they did not know how the ITAM pathways actually turned off inflammatory signaling. Previous studies had shown that the ITAM pathway signaling components directly suppressed so-called Toll-like receptor signaling molecules involved in inflammation, but there was a hint that an alternative pathway may also be involved. The researchers thought that maybe the ITAM pathway might be involved in triggering another pathway that then inhibits inflammation.

In studies using white blood cells similar to those that cause disease, the researchers set out to investigate what signaling pathways might be induced by the activation of ITAM-associated receptors. They used fibrin(ogen) and immune complexes, proteins that are highly expressed at inflammatory sites, to activate the ITAM-associated receptors and then watched what happened. The researchers found that activation of the ITAM receptor set off a pathway known as DAP12-Syk-Pyk2-p38-MSK that was dependent on calcium signaling and discouraged pro-inflammatory cytokine production.

They also found that ITAM receptors induce IL-10, an anti-inflammatory cytokine, and proteins SOCS3, ABIN-3, A20, and Hes1 that have been implicated in the suppression of cytokines. In other studies, they showed that this ITAM inhibitory pathway does not work properly in people with inflammatory arthritis.

"When we looked at macrophages from patients with arthritis, we found that the whole inhibitory pathway would not work," Dr. Ivashkiv said. "What this study suggests is that one of the things that contributes to inflammation in arthritis is crippling of beneficial pathways that usually serve to turn inflammation off." He said clinicians in the future may be able to focus on therapies that will augment or reinstitute these beneficial or homeostatic pathways as a way of turning off inflammation in chronic arthritis.

"Before this study we knew that ITAM-coupled receptors had the potential to inhibit inflammatory cytokine production, but there was very limited knowledge about how that worked," Dr. Ivashkiv said. "What we accomplished with the study is that we have increased our understanding of an indirect inhibitory mechanism that we think can serve as the basis for designing new approaches to therapy. This work implicates for the first time a negative role for calcium signaling downstream of these ITAM-coupled receptors and explains how that works,"

He added that investigators believe that there is extensive crosstalk among the various pathways and they think that the ITAM receptors play a very important role in deciding how all the signaling gets integrated. "In terms of the homeostatic pathways that control inflammation, we think that this pathway that we have described is one of the strongest ones. It completely turns things off," Dr. Ivashkiv said. "What you usually see are these partial inhibitions or attenuations in terms of inflammatory cytokine production. What we saw was a complete inhibition of the response."

Dr. Ivashkiv said future work would focus on further elucidating molecular details of the pathway and further testing of its importance in arthritis and animal models of disease.

The work was funded by grants from the National Institutes of Health. Other authors of the study include Lu Wang, Ph.D., Rachael Gordon, Linda Huynh, Xiaodi Su, Kyung-Hyun Park Min, M.D., and George D. Kalliolias, M.D., from Hospital for Special Surgery; Jiahuai Han, Ph.D., from the Scripps Research Institute in La Jolla, Calif.; and J. Simon Arthur, M.D., from the MRC Protein Phosphorylation Unit, University of Dundee in Dundee, Scotland.

Journal Reference:

1. Lu Wang, Rachael A. Gordon, Linda Huynh, Xiaodi Su, Kyung-Hyun Park Min, Jiahuai Han, J. Simon Arthur, George D. Kalliolias, Lionel B. Ivashkiv. Indirect Inhibition of Toll-like Receptor and Type I Interferon Responses by ITAM-Coupled Receptors and Integrins. Immunity, 2010; DOI: 10.1016/j.immuni.2010.03.014

Courtesy: ScienceDaily

Why the Japanese Can Easily Digest Sushi

Porphyran, a polysaccharide present in the cell walls of a red algae that is used notably in the preparation of sushi, is broken down specifically by an enzyme called porphyranase. This new enzymatic activity has been identified in marine bacteria and, surprisingly, in the bacteria that populate the gut of the Japanese. Scientists from CNRS and UPMC have explained this discovery by a transfer of genes between the bacteria, that allows the gut microbiota of the Japanese to acquire all the "machinery" it needs to consume the algae that surround sushi. Their results are published in Nature on April 8, 2010.

Without intestinal flora, humans cannot break down the polysaccharides in their diet, which are one of the principal sources of energy for the brain. Indeed, intestinal bacteria contain enzymes that are known to "break down" polysaccharides (1), which are polymers made up of carbohydrates. They are essential because the human genome is not endowed with such enzymes.

Two research teams working at the Station Biologique in Roscoff (CNRS / UPMC) have been working on porphyranase, an enzyme that breaks down polysaccharides but whose true activity was previously unsuspected. These teams have thus discovered that porphyranase breaks down a highly specific molecule: porphyran, and not another substrate, as had previously been thought (2). Porphyran is a polysaccharide, one of the components in the walls of a red-colored marine algae called Porphyra. These algae are used to prepare Japanese sushi. According to historical documents, this alga has been consumed for many generations by the Japanese (3). Of considerable cultural importance in Japan, it has sometimes served as a gift or to pay certain taxes.

The researchers then demonstrated the process of recognition between the enzyme (porphyranase) and its substrate (porphyran). They were thus able to identify the "signature" of the sequence involved in this recognition (the specific site on the enzyme to which the reagent binds). As expected, this novel enzymatic activity was detected in marine bacteria. Further investigations led the scientists to compare genomic data regarding the gut microbiota of 13 Japanese individuals and 18 North Americans. They thus discovered that porphyranase was also present in the gut microbiota of the Japanese (but not in that of the North Americans).

The scientists suppose that the presence of this enzyme in the gut microbiota of the Japanese is directly linked to their dietary habits. As major consumers of Porphyra for several centuries, the Japanese have thus been in contact with the marine bacteria that contain porphyranases via their diet. Mirjam Czjzek and her team presume that a transfer of genes from marine bacteria to intestinal bacteria must have allowed the microbiota of the Japanese to accept the "machinery" required to break down the polysaccharides in Porphyra algae. These findings suggest that food associated with marine bacteria may constitute a means for the human gut microbiota to acquire new enzymes, which may, among other factors, explain their diversity.

Notes

(1) For example, cellulose and starch.

(2) It was previously thought that agarose, a carbohydrate polymer that is also extracted from red algae, was the substrate for this enzyme.

(3) Writings testify that the algae served as a form of payment in the 8th century.

Journal Reference:

1. Jan-Hendrik Hehemann, Gaëlle Correc, Tristan Barbeyron, William Helbert, Mirjam Czjzek, Gurvan Michel. Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota. Nature, 2010; 464 (7290): 908 DOI: 10.1038/nature08937

Courtesy: ScienceDaily

Judge Invalidates Human Gene Patent

A federal judge on Monday struck down patents on two genes linked to breast and ovarian cancer. The decision, if upheld, could throw into doubt the patents covering thousands of human genes and reshape the law of intellectual property

United States District Court Judge Robert W. Sweet issued the 152-page decision, which invalidated seven patents related to the genes BRCA1 and BRCA2, whose mutations have been associated with cancer.

The American Civil Liberties Union and the Public Patent Foundation at the Benjamin N. Cardozo School of Law in New York joined with individual patients and medical organizations to challenge the patents last May: they argued that genes, products of nature, fall outside of the realm of things that can be patented. The patents, they argued, stifle research and innovation and limit testing options.

Myriad Genetics, the company that holds the patents with the University of Utah Research Foundation, asked the court to dismiss the case, claiming that the work of isolating the DNA from the body transforms it and makes it patentable. Such patents, it said, have been granted for decades; the Supreme Court upheld patents on living organisms in 1980. In fact, many in the patent field had predicted the courts would throw out the suit.

Judge Sweet, however, ruled that the patents were “improperly granted” because they involved a “law of nature.” He said that many critics of gene patents considered the idea that isolating a gene made it patentable “a ‘lawyer’s trick’ that circumvents the prohibition on the direct patenting of the DNA in our bodies but which, in practice, reaches the same result.”

The case could have far-reaching implications. About 20 percent of human genes have been patented, and multibillion-dollar industries have been built atop the intellectual property rights that the patents grant.

“If a decision like this were upheld, it would have a pretty significant impact on the future of medicine,” said Kenneth Chahine, a visiting law professor at the University of Utah who filed an amicus brief on the side of Myriad. He said that medicine was becoming more personalized, with genetic tests used not only to diagnose diseases but to determine which medicine was best for which patient.

Mr. Chahine, who once ran a biotechnology company, said the decision could also make it harder for young companies to raise money from investors. “The industry is going to have to get more creative about how to retain exclusivity and attract capital in the face of potentially weaker patent protection,” he said.

Edward Reines, a patent lawyer who represents biotechnology firms but was not involved in the case, said loss of patent protection could diminish the incentives for genetic research.

“The genetic tools to solve the major health problems of our time have not been found yet,” said Mr. Reines, who is with the Silicon Valley office of the firm Weil, Gotshal & Manges. “These are the discoveries we want to motivate by providing incentives to all the researchers out there.”

The lawsuit also challenged the patents on First Amendment grounds, but Judge Sweet ruled that because the issues in the case could be decided within patent law, the constitutional question need not be decided.

The decision is likely to be appealed. Representatives of Myriad did not return calls seeking comment. But this month, the company’s chief executive, Peter Meldrum, told investors that “regardless of the outcome of this particular lawsuit, it will not have a material adverse effect on the company,” or its future revenues, according to the Pharmacogenomics Reporter, “or on the future revenues of our products.”

Myriad sells a test costing more than $3,000 that looks for mutations in the two genes to determine if a woman is at a high risk of getting breast cancer and ovarian cancer. Plaintiffs in the case had said Myriad’s monopoly on the test, conferred by the gene patents, kept prices high and prevented women from getting a confirmatory test from another laboratory.

Janice Oh, a spokeswoman for the United States attorney’s office in Manhattan, which represented the Patent and Trademark Office in the case, had no comment.

One of the individual plaintiffs in the suit, Genae Girard, who has breast cancer and has been tested for ovarian cancer, applauded the decision as “a big turning point for all women in the country that may have breast cancer that runs in their family.” Chris Hansen, an A.C.L.U. staff lawyer, said: “The human genome, like the structure of blood, air or water, was discovered, not created. There is an endless amount of information on genes that begs for further discovery, and gene patents put up unacceptable barriers to the free exchange of ideas.”

Bryan Roberts, a prominent Silicon Valley venture capitalist, said the decision could push more work aimed at discovering genes and diagnostic tests to universities. “The government is going to become the funder for content discovery because it’s going to be very hard to justify it outside of academia.”

John Ball, executive vice president of the American Society for Clinical Pathology, one of the plaintiffs in the case, called the decision “a big deal.”

“It’s good for patients and patient care, it’s good for science and scientists,” he said. “It really opens up things.”

Courtesy: NewyorkTimes

Individual Light Atoms, Such as Carbon and Oxygen, Identified With New Microscope

Individual boron and nitrogen atoms are clearly distinguished by their intensity in this Z-contrast scanning electron transmission microscope image from Oak Ridge National Laboratory. Each single hexagonal ring of the boron-nitrogen structure, for instance the one marked by the green circle in the figure a, consists of three brighter nitrogen atoms and three darker boron atoms. The lower (b) image is corrected for distortion. (Credit: Department of Energy, Oak Ridge National Laboratory)

Using the latest in aberration-corrected electron microscopy, researchers at the Department of Energy's Oak Ridge National Laboratory and their colleagues have obtained the first images that distinguish individual light atoms such as boron, carbon, nitrogen and oxygen.

The ORNL images were obtained with a Z-contrast scanning transmission electron microscope (STEM). Individual atoms of carbon, boron, nitrogen and oxygen--all of which have low atomic numbers--were resolved on a single-layer boron nitride sample.

"This research marks the first instance in which every atom in a significant part of a non-periodic material has been imaged and chemically identified," said Materials Science and Technology Division researcher Stephen Pennycook. "It represents another accomplishment of the combined technologies of Z-contract STEM and aberration correction."

Pennycook and ORNL colleague Matthew Chisholm were joined by a team that includes Sokrates Pantelides, Mark Oxley and Timothy Pennycook of Vanderbilt University and ORNL; Valeria Nicolosi at United Kingdom's Oxford University; and Ondrej Krivanek, George Corbin, Niklas Dellby, Matt Murfitt, Chris Own and Zotlan Szilagyi of Nion Company, which designed and built the microscope. The team's Z-contrast STEM analysis is described in an article published March 25 in the journal Nature.

The new high-resolution imaging technique enables materials researchers to analyze, atom by atom, the molecular structure of experimental materials and discern structural defects in those materials. Defects introduced into a material--for example, the placement of an impurity atom or molecule in the material's structure--are often responsible for the material's properties.

The group analyzed a monolayer hexagonal boron nitride sample prepared at Oxford University and was able to find and identify three types of atomic substitutions--carbon atoms substituting for boron, carbon substituting for nitrogen and oxygen substituting for nitrogen. Boron, carbon, nitrogen and oxygen have atomic numbers--or Z values-- of five, six, seven and eight, respectively.

The annular dark field analysis experiments were performed on a 100-kilovolt Nion UltraSTEM microscope optimized for low-voltage operation at 60 kilovolts.

Aberration correction, in which distortions and artifacts caused by lens imperfections and environmental effects are computationally filtered and corrected, was conceived decades ago but only relatively recently made possible by advances in computing. Aided by the technology, ORNL's Electron Microscopy group set a resolution record in 2004 with the laboratory's 300-kilovolt STEM.

The recent advance comes at a much lower voltage, for a reason.

"Operating at 60 kilovolts allows us to avoid atom-displacement damage to the sample, which is encountered with low Z-value atoms above about 80 kilovolts," Pennycook said. "You could not perform this experiment with a 300-kilovolt STEM."

Armed with the high-resolution images, materials, chemical and nanoscience researchers and theorists can design more accurate computational simulations to predict the behavior of advanced materials, which are key to meeting research challenges that include energy storage and energy efficient technologies.

The research was funded by the DOE Office of Science.

Journal Reference:

1. Ondrej L. Krivanek, Matthew F. Chisholm, Valeria Nicolosi, Timothy J. Pennycook, George J. Corbin, Niklas Dellby, Matthew F. Murfitt, Christopher S. Own, Zoltan S. Szilagyi, Mark P. Oxley, Sokrates T. Pantelides, Stephen J. Pennycook. Atom-by-atom structural and chemical analysis by annular dark-field electron microscopy. Nature, 2010; 464 (7288): 571 DOI: 10.1038/nature08879

Courtesy: ScienceDaily

Single Gene Dramatically Boosts Yield, Sweetness in Tomato Hybrids

Giving tomato breeders and ketchup fans something to cheer about, a Cold Spring Harbor Laboratory (CSHL) scientist and his colleagues at the Hebrew University in Israel have identified a gene that pushes hybrid tomato plants to spectacularly increase yield. The yield-boosting power of this gene, which controls when plants make flowers, works in different varieties of tomato, and crucially, across a range of environmental conditions.

"This discovery has potential to have a significant impact on both the billion-dollar tomato industry, as well as agricultural practices designed to get the most yield from other flowering crops," says CSHL's Zach Lippman, Ph.D., one of the three authors on the study, which appears in the journal Nature Genetics online on March 28th. The study is co-authored by Israeli scientists Uri Krieger and Professor Dani Zamir.

The team made the discovery while hunting for genes that boost hybrid vigor, a revolutionary breeding principle that spurred the production of blockbuster hybrid crops like corn and rice a century ago. Hybrid vigor, also known as heterosis, is the miraculous phenomenon by which intercrossing two varieties of plants produces more vigorous hybrid offspring with higher yields. First observed by Charles Darwin in 1876, heterosis was rediscovered by CSHL corn geneticist George Shull 30 years later, but how heterosis works has remained a mystery.

Shull's studies suggested that harmful, vigor-killing gene mutations that accumulate naturally in every generation are exposed by inbreeding, but hidden by crossbreeding. "But there is still no consensus as to what causes heterosis," says Lippman. "Another theory for heterosis, supported by our discovery, postulates that improved vigor stems from only a single gene -- an effect called "superdominance" or "overdominance."

To find overdominant genes, the team developed a novel approach by turning to a vast tomato "mutant library" -- a collection of 5,000 plants, each of which has a single mutation in a single gene that causes defects in various aspects of tomato growth, such as fruit size, leaf shape, etc. Selecting a diverse set of mutant plants, most of which produced low yield, the team crossed each mutant with its normal counterpart and searched for hybrids with improved yield.

Among several cases, the most dramatic example increased yield by 60%. This hybrid, the team found, produced greater yields because there was one normal copy and one mutated copy of a single gene that produces a protein called florigen. This protein, touted as the breakthrough discovery of the year in 2005 in Science magazine, instructs plants when to stop making leaves and start making flowers, which in turn produce fruit.

In plants such as tomatoes, flowering (and therefore yield) is controlled by a delicate balance between the florigen protein, which promotes flowering, and another related protein, that delays flowering. A mutation in only one copy of the florigen gene causes the hybrid to produce more flowers in less time -- the key to improved yield.

"It's the Goldilocks concept," explains Lippman. "What we find is that to maximize yield, you can't have too much or too little florigen. A mutation in one copy of the gene results in the exact dose of florigen required to cause heterosis."

The scientists have observed the gene's heterosis effect in different varieties of tomatoes and in plants grown in different climate and soil conditions, both in Israel and locally in New York at CSHL and the Cornell Horticultural Experiment Station at Riverhead, NY.

In addition to superior yield, the hybrids also display another, perhaps equally important quality -- taste. Tomato plants only produce a finite amount of sugar, which they distribute equally among their fruits. So higher yields usually result in each fruit having less sugar. But, remarkably, the florigen gene also boosted the sugar and sweetness of individual fruits.

The researchers are already planning to explore if genes related to florigen in other crops can cause heterosis and improve yield. The concept that a mutation in only one copy of a single gene can improve yield has broad implications for plant breeding. "Mutant plants are usually thrown away because of the notion that mutations would have negative effects on growth," says Lippman. "Our results indicate that breeding with hybrid mutations could prove to be a powerful new way to increase yields, not only in tomato, but all crops."

The research was funded by grants from the National Science Foundation, the Israel Science Foundation and EU-SOL.

Journal Reference:

1. Uri Krieger, Zachary B. Lippman and Dani Zamir. The flowering gene SINGLE FLOWER TRUSS drives heterosis for yield in tomato. Nature Genetics, 2010; DOI: 10.1038/ng.550

Courtesy: ScienceDaily