Posts Tagged: plants
You've seen honey bees buzzing past you to reach a good nectar or pollen source. But there's much more to it than that. What's in that floral nectar and pollen? Think...
What's in store for this honey bee? It is heading for an Anisodontea sp.'Strybing Beauty.' Image taken in pollinator garden in Vacaville, Calif. (Photo by Kathy Keatley Garvey)
It's a fair. It's a party. It's a pollinator party. It's the Bay Area Bee Fair in Berkeley. And it's the place to be on Sunday, Oct. 13 at the Berkeley Flea Market,...
Black-tailed bumble bee, Bombus melanopygus, nectaring on nectarine blossoms. (Photo by Kathy Keatley Garvey)
A yellow-faced bumble bee, Bombus vosnesenskii, nectaring on Mexican sunflower, Tithonia. (Photo by Kathy Keatley Garvey)
A black-tailed bee, Bombus californicus, nectaring on blanket flower, Gaillardia. (Photo by Kathy Keatley Garvey)
A bumble bee, Bombus vosnesenskii, and honey bee, Apis mellifera, sharing a purple coneflower, Echinacea purpurea. (Photo by Kathy Keatley Garvey)
How many times have you walked around the University of California, Davis campus on a weekend and wished: "If only those buildings were open--I'd love to see what's...
A walking stick being fed a leaf at the Bohart Museum of Entomology. (Photo by Kathy Keatley Garvey)
The plant-grazing bugs accomplish this by forcing the plants to create diverse natural defenses to avoid being eaten, which in turn shapes the genetic makeup of the plants in a region. The researchers discovered this by studying aphids and the broccoli-like research plant Arabidopsis thaliana. Their findings provide the first measurable evidence that this selective process is driven, in part, by the pressure that multiple natural enemies exert on plants by forcing them to create diverse natural defenses to avoid being eaten.
“Our data demonstrate that there is a link between the abundance of two types of aphids and the continental distribution of Arabidopsis plants that are genetically different in terms of the biochemicals they produce to defend against insect feeding,” said UC Davis plant scientist Dan Kliebenstein.
His laboratory is examining the naturally occurring chemicals involved with plant defenses to better to understand their role in the environment and to explore their potential for improving human nutrition and fighting cancer.
Ecologists have theorized for decades that genetic change and variation within a plant or animal species is critical to enabling the species to survive changing environmental conditions like the appearance of a new disease or pest.
They have documented that nonbiological changes, such as variations in climate and soil, can exert pressures that cause genetic variation within plant species. However there has been little evidence that biological forces, including insects feeding on plants or competition between plant species, can lead to genetic variation within a plant species across a large geographic area.
In the new study, the researchers first mapped the distribution of six different chemical profiles within Arabidopsis thaliana plants across Europe, each chemical profile controlled by the variation in three genes.
The mapping revealed a change in the function of one of these key genes across geographic areas; the gene changed from southwest to the northeast.
The researchers suspected that two aphid species — Brevicoryne brassicae and Lipaphis erysimi — were the likely causes of the geographic variation. Both are abundant in the regions and feed heavily on Arabidopsis and related plants.
The scientists then tapped data collected by British researchers for nearly 50 years on fluctuations in aphid populations in Europe. They found that distribution of the two aphids species of interest closely mirrored the geographic distribution of the different chemical types of Arabidopsis plants. Like picky restaurant goers, one aphid preferred the southwestern chemical type while the other aphid preferred the northeastern chemical type.
The next step was to determine whether the similarity between the distribution patterns of the plants and the two aphid species was more than coincidental. To do this, the researchers observed what happened when the different aphids fed on five generations of experimentally raised Arabidopsis thaliana plants.
They confirmed that the plants were genetically adapting to the aphids, with each successive plant generation showing less damage from the feeding insects. A change in the genetic makeup of the plant populations specific to each aphid accompanied this trend — and the laboratory plants evolved in a way that tracked the geographic distribution of the two aphids and the plant chemical types.
The researchers also found that when faced with feeding by aphids, the faster-growing Arabidopsis plant types fared better in the laboratory, while the slowest-growing plant types actually went experimentally extinct.
“These data make it clear that even functionally similar plant-eating pests can affect the biochemical and genetic makeup of plant populations, playing a major role in shaping and refining the plant defenses in a natural community,” Kliebenstein said.
You’ll be able to read the complete report on this study, conducted with researchers in Switzerland, Denmark, England and the United States, will appear in the Oct. 5 issue of the journal Science.
At 925 million, the number of hungry people in the world is unacceptably high.
To combat world hunger, many scientists are working on developing crops that can resist disease and withstand the elements, from drought to floods. One such scientist is Sean Cutler at UC Riverside, whose breakthrough discovery last year of pyrabactin has brought drought-tolerant crops closer to becoming reality and spawned new research in several labs around the world.
Pyrabactin is a synthetic chemical that mimics abscisic acid (ABA), a naturally produced stress hormone in plants that helps them cope with drought conditions by inhibiting growth. ABA has already been commercialized for agricultural use. But it has at least two disadvantages: it is light-sensitive and it is costly to make.
Enter pyrabactin. This chemical is relatively inexpensive, easy to make, and not sensitive to light. But is it free from drawbacks? Unfortunately, no. Unlike ABA, pyrabactin does not turn on all the “receptors” in the plant that need to be activated for drought-tolerance to fully take hold.
What does that mean? A brief lesson on receptors may be in order.
A receptor is a protein molecule in a cell to which mobile signaling molecules – such as ABA or pyrabactin, each of which turns on stress-signaling pathways in plants – may attach. Usually at the top of a signaling pathway, the receptor functions like a boss relaying orders to the team below that then proceeds to execute particular decisions in the cell.
It turns out that each receptor is equipped with a pocket, akin to a padlock, in which a chemical, like pyrabactin, can dock into, operating like a key. Even though the receptor pockets appear to be fairly similar in structure, subtle differences distinguish a pocket from its peers. The result is that while ABA, a product of evolution, can fit neatly in any of these pockets, pyrabactin is less successful. Still, pyrabactin, by being partially effective (it works better on seeds than on plant parts), serves as a leading molecule for devising new chemicals for controlling stress tolerance in plants.
Each receptor is equipped also with a lid that operates like a gate. For the receptor to be activated, the lid must remain closed. Pyrabactin is effective at closing the gate on some receptors, turning them on, but cannot close the gate on others.
Cutler and colleagues have now cracked the molecular basis of this behavior. In a receptor where the gate closes, they have found that pyrabactin fits in snugly to allow the gate to close. In a receptor not activated by pyrabactin, however, the chemical binds in a way that prevents the gate from closing and activating the receptor.
“These insights suggest new strategies for modifying pyrabactin and related compounds so that they fit properly into the pockets of other receptors,” Cutler says. “If a derivative of pyrabactin could be found that is capable of turning on all the receptors for drought tolerance, the implications for agriculture are enormous.”
So he and his colleagues continue their research on pyrabactin derivatives, having set their eyes on the prize: An ABA-mimicking, inexpensive and light-insensitive chemical that can be sprayed easily on corn, soy bean and other crops to help them survive drought – one effective approach to combating and preventing hunger worldwide. Imagine that!