February 11, 2009, 6:20 AM CT

Why those fruits ripen and flowers die

Best known for its effects on fruit ripening and flower fading, the gaseous plant hormone ethylene shortens the shelf life of a number of fruits and plants by putting their physiology on fast-forward. In recent years, researchers learned a lot about the different components that transmit ethylene signals inside cells. But a central regulator of ethylene responses, a protein known as EIN2, resisted all their efforts.

Finally, after more than a decade of constant probing, a team of scientists led by Joseph Ecker, Ph.D., a professor in the Plant Biology laboratory and director of the Salk Institute Genomic Analysis Laboratory, successfully pinned down the elusive protein. Turns out, the presence of ethylene stabilizes the otherwise ephemeral EIN2 allowing it to gather up enough strength to pass on ethylene's message.

Their findings, reported in the Feb. 15, 2009 edition of the journal Genes and Development, are an important step toward defining EIN2's role in growth and development and modifying key processes to improve agriculture, preventing crop losses due to ethylene related processes.

"Ethylene is involved in a wide variety of processes and we knew from genetic experiments that EIN2 is right at the center of ethylene signaling pathway, but for the longest time we were unable to figure out how it is regulated," says Ecker. "Now that we know that EIN2 is negatively regulated by protein degradation, we can begin to understand how it triggers all these different ethylene responses in plants"......... Posted by: Erica      Read more         Source

February 11, 2009, 6:03 AM CT

Stopping the spread of rice virus

Building on plant virus research started more than 20 years ago, a biologist at Washington University in St. Louis and his colleague at the Donald Danforth Plant Science Center in St. Louis have discovered a technology that reduces infection by the virus that causes Rice Tungro Disease, a serious limiting factor for rice production in Asia.

Roger N. Beachy, Ph.D., WUSTL professor of biology in Arts & Sciences and president of the Donald Danforth Plant Science Center, and Danforth Center research scientist Shunhong Dai, Ph.D., demonstrated that transgenic rice plants that overexpress either of two rice proteins are tolerant to infection caused by the rice tungro bacilliform virus (RTVB), which is largely responsible for the symptoms linked to Rice Tungro disease.

The two proteins, RF2a and RF2b, were discovered in Beachy's lab several years ago and are transcription factors known to be important for plant development; the new data suggest that they appears to be involved in regulating defense mechanisms that protect against virus infection. The discovery, reported in the December 22, 2008, issue of the Proceedings of the National Academy of Sciences, may open new avenues in the search for disease resistance genes and pathways in plants and other organisms.

Plant viral diseases cause serious economic losses in agriculture, second only to those caused by fungal diseases. Rice Tungro disease is prevalent primarily in south and southeast Asia and accounts for nearly $1.5 billion annual loss in rice production worldwide. Preventing the occurrence and spread of this virus could result in increased yields ranging from five to 10 percent annually in affected areas......... Posted by: Erica      Read more         Source

February 6, 2009, 6:07 AM CT

Silencing of jumping genes in pollen

Researchers at the Instituto Gulbenkian de Cincia (IGC), in Portugal, are to date the only research group in the world capable of isolating the sperm cells in the pollen grain of the model plant Arabidopsis thaliana This technique was crucial in a study to be reported in the latest issue of the journal Cell, which describes how mobile sequences of DNA (called transposable elements) are silenced in the sperm cells, thus ensuring suppression of the mutagenic effects of these DNA elements.

Jrg Becker, Jos Feij and their team, at the IGC, and Robert Martienssen and his colleagues, at the Cold Spring Harbor Laboratory, CSHL,in the USA, have unveiled a mechanism for controlling transposable elements that may be extensible to other eukaryotes, such as the fruit fly, amoebae and algae.

Transposable elements are very common in all known genomes. In the human genome, for example, they make up 45% of the total genome. They are involved in the evolution of genomes, since when integrated back into the genome they can affect the function and organisation of other genes. However, transposable elements are mutagens, and, therefore, their activation needs to be under tight control, as it appears to be harmful to the cell and the organism. If such harmful mutations occur in sexual cells, they will be transmitted to the progeny and spread in the population......... Posted by: Erica      Read more         Source

February 4, 2009, 6:22 AM CT

Methyl bromide for North Carolina tomato production

Methyl bromide (MeBr) is a highly effective broad-spectrum fumigant used extensively in U.S. agriculture to control a wide variety of pests. Under the Montreal protocol of 1991, however, MeBr was defined as one of the chemicals that contributed to the depletion of the stratospheric ozone layer, resulting in an incremental reduction in the amount of MeBr produced and imported in the U.S. In January 2005, a total phase out of MeBr (except for emergency and critical-use exceptions) was imposed.

The U.S. Department of Agriculture has indicated that the phaseout of MeBr as a preplant soil fumigant may have substantial impact on the production levels of a number of agricultural crops. No known single alternative fumigant, chemical, or other technology exists that can readily substitute for MeBr in efficacy, cost, ease of use, availability, worker safety, and environmental safety.

Fresh-market tomatoes were planted on 124,400 acres in the United States in 2007, with a gross production value of almost $1300 million. Southeastern states, including Georgia, North Carolina, South Carolina, Tennessee, and Virginia, accounted for about 17% of the total tomato production in the U.S. Tomatoes accounted for 25% of the use of MeBr in the U.S., making tomato growers one of the main groups impacted by the MeBr regulations......... Posted by: Erica      Read more         Source

February 4, 2009, 6:20 AM CT

Does hotter mean healthier?

Phytophthora blight, caused by Phytophthora capsici, is a major plant disease that affects a number of crop species worldwide, including chile peppers in New Mexico. Farmers' observations suggested that Phytophthora capsici caused less damage in pepper crops of the hot pepper varieties than low-heat pepper varieties.

A study reported in the October 2008 issue of HortScience by the research team of Mohammed B. Tahboub (postdoctoral researcher), Soumaila Sanogo (plant pathologist and team leader), Paul W. Bosland (chile pepper breeder), and Leigh Murray (statistician) set out to determine whether or not the severity of Phytophthora blight would be greater in low-heat than in hot chile peppers.

The most effective means for controlling Phytophthora blight are chile pepper cultivars that are genetically resistant to the disease. Some resistant lines have been identified, but currently there are no cultivars that are resistant to the blight in all environments.

Chile pepper fruit become infected during prolonged periods of heavy rain and high humidity in flooded and poorly drained fields. Previous to this study, there had been no systematic assessment of the relationship of chile pepper heat level to chile pepper response to Phytophthora capsici If such a connection could be found, information might have been revealed that would assist breeding programs intended for developing disease-resistant cultivars of pepper......... Posted by: Erica      Read more         Source

February 2, 2009, 6:29 AM CT

Preparing for climate change

The global climate is changing, and this change is already impacting food supply and security. People living in regions already affected by aridity need plants that can thrive / grow under dry conditions.

One example is sorghum: Also known as milo, durra, or broomcorn, sorghum is a grass species that can grow up to five meters in height and is extremely resistant to aridity and hot conditions. The grass, which originates from Africa, can thrive under conditions and locations where other cereal plants cannot survive due to lack of water. In arid-warm and moderate regions of the Americas, Asia and Europe it is mainly utilized for food and fodder and is also gaining in significance as a basis for bio-fuel. The plant also provides fibers as well as combustible material for heating and cooking.

As part of an international consortium of scientists, scientists at Helmholtz Zentrum München are analyzing the genes of sorghum, the first plant of African origin whose genome has been sequenced.

Dr. Klaus Mayer of the Institute of Bioinformatics and Systems Biology of the Helmholtz Zentrum München described the scientists' research goal: "We want to elucidate the functional and structural genomics of sorghum." He went on to explain: "That is the prerequisite for making this important grain even more productive through targeted breeding strategies. As German Research Center for Environmental Health, sustaining the food supply is one of our most important research topics. That is why we are trying to learn something about the molecular basis of the plant's pronounced drought tolerance in order to apply this knowledge to other crop plants in our latitude zone as well. "The first results of the study have been reported in the current issue of Nature......... Posted by: Erica      Read more         Source

January 29, 2009, 6:16 AM CT

Genetic blueprint of key biofuels crop

Researchers at the U.S. Department of Energy (DOE) Joint Genome Institute (JGI) and several partner institutions have published the sequence and analysis of the complete genome of sorghum, a major food and fodder plant with high potential as a bioenergy crop. The genome data will aid researchers in optimizing sorghum and other crops not only for food and fodder use, but also for biofuels production. The comparative analysis of the sorghum genome appears in the January 29 edition of the journal Nature

Prized for its drought resistance and high productivity, sorghum is currently the second most prevalent biofuels crop in the United States, behind corn. Grain sorghum produces the same amount of ethanol per bushel as corn while utilizing one-third less water. As the technology for producing "cellulosic" (whole plant fiber-based) biofuels matures, sorghum's rapid growth--rising from eight to 15 feet tall in one season--is likely to make it desirable as a cellulosic biofuels "feedstock."

"This is an important step on the road to the development of cost-effective biofuels made from nonfood plant fiber," said Anna C. Palmisano, DOE Associate Director of Science for Biological and Environmental Research. "Sorghum is an excellent candidate for biofuels production, with its ability to withstand drought and prosper on more marginal land. The fully sequenced genome will be an indispensable tool for scientists seeking to develop plant variants that maximize these benefits."........ Posted by: Erica      Read more         Source

January 15, 2009, 7:32 PM CT

Cooling the planet with crops

By carefully selecting which varieties of food crops to cultivate, much of Europe and North America could be cooled by up to 1C during the summer growing season, say scientists from the University of Bristol, UK. This is equivalent to an annual global cooling of over 0.1C, almost 20% of the total global temperature increase since the Industrial Revolution.

The growing of crops already produces a cooling of the climate because they reflect more sunlight back into space, compared with natural vegetation. Different varieties of the same crop vary significantly in their solar reflectivity (called 'albedo'), so selecting varieties that are more reflective will enhance this cooling effect. Since arable agriculture is a global industry, such cooling could be extensive.

Reporting today [15 January] in Current Biology, Dr Andy Ridgwell and his colleagues at the University of Bristol argue that we should select crop varieties in order to exert a control on the climate, in the same way that we currently cultivate specific varieties to maximize and fine-tune food production.

Dr Ridgwell said: "We have reviewed the effect of our approach in a global climate model. By choosing from among current crop varieties, our best estimate for how much reflectivity might be increased leads us to predict that summer-time temperatures could be reduced by more than 1C throughout much of central North America and mid-latitude Eurasia. Ultimately, further regional cooling of the climate could be made through selective breeding or genetic modification to optimise crop plant albedo"......... Posted by: Erica      Read more         Source

January 15, 2009, 7:31 PM CT

Plant flowering in different environments

It has been known for some time that plants respond to environmental cues that guide their flowering. Chief among these signals are light, temperature and vernalization, when flowering is promoted by prolonged exposure to cold temperatures.

In some plants, researchers have identified particular genes that deal with each of these environmental signals. But they haven't fully grasped how plants integrate these signals in nature. For example, when day length and temperature are combined in different ways, plants outdoors may not respond the same way as plants in the lab.

Through a series of field experiments at five European sites, a Brown University-led research team has charted the internal and external signals that guide the life cycle of one plant species, Arabidopsis thaliana, across its native climate range. The team has created a model that shows the importance of the genetic and environmental cues for key genotypes of Arabidopsis and how these signals vary depending on the plant's location and seasonal environment.

"This is a powerful tool to predict how this plant species and other species will respond to climate change and which genetic pathways are important in different environments," said Amity Wilczek, a postdoctoral research associate in ecology and evolutionary biology at Brown and the paper's main author......... Posted by: Erica      Read more         Source

January 8, 2009, 8:46 PM CT

Shade coffee provides genetic diversity

Here's one more reason to say "shade grown, please" when you order your morning cup of coffee. Shade coffee farms, which grow coffee under a canopy of multiple tree species, not only harbor native birds, bats and other beneficial creatures, but also maintain genetic diversity of native tree species and can act as focal points for tropical forest regeneration.

The finding comes from a study published by University of Michigan scientists Shalene Jha and Christopher Dick in the Dec. 23 issue of the journal Current Biology.

Jha, a graduate student whose main interest is insects, initially wanted to find out whether shade coffee farms nurture native pollinators such as stingless bees. When she began her fieldwork in Chiapas, Mexico, she focused on a particular tree, Miconia affinis, which is pollinated by an unusual method known as buzz pollination. In order to release pollen from its flowers, bees grab hold and vibrate their flight muscles, shaking the pollen free. Non-native species such as Africanized honeybees don't perform buzz pollination, but native bees do, said Jha, "so I thought Miconia, which requires buzz pollination and is common both in forests and on coffee farms, could be a bio-indicator of how well native bees are pollinating native plants".

As she spent time in the field, however, Jha realized that the story of how Miconia trees spread into coffee farms and how their dispersal affects the tree population's genetic diversity begged to be addressed before she proceeded with the pollen studies. With guidance from Dick, an assistant professor of ecology and evolutionary biology who studies genetic diversity patterns in tropical tree species, Jha collected and analyzed DNA samples from Miconia trees growing in a network of coffee farms and forest fragments......... Posted by: Erica      Read more         Source