April 3, 2008, 8:32 PM CT

Genes key to hormone production in plants

Scientists at North Carolina State University have pinpointed a small group of genes responsible for telling plants when, where and how to produce a hormone that is key to their development. Their findings shed light on the ways in which hormone production in plants affects both a plants growth and its ability to adapt to changing environments.

Dr. Jose Alonso, assistant professor of genetics, and a team of geneticists and plant biologists from NC State, Gera number of and the Czech Republic conducted the research. Their findings appear in the April 4 edition of the journal Cell.

Plant growth and development are regulated by a small number of hormones, which plants combine in various ways so that they can adapt to and thrive in changing environmental conditions. Auxin and ethylene are two of the most important of these growth-regulating hormones.

Researchers had previously established that plants respond differently to ethylene depending upon the type of plant tissue it is applied to, the developmental stage of the plant, and the surrounding environmental conditions. They also knew that the presence of auxin, another key growth-regulator, often served as a trigger for a plant to produce more ethylene, but were unsure of the ways in which auxin was synthesized......... Posted by: Erica      Read more         Source

April 2, 2008, 10:19 PM CT

Will Avocados be Next?

Researchers with the USDA Forest Service Southern Research Station (SRS), Iowa State University, and the Florida Division of Forestry have provided the first description of a fungus responsible for the wilt of redbay trees along the coasts of South Carolina, Georgia, and Florida.

In the recent issue of Plant Disease, SRS plant pathologist Stephen Fraedrich and fellow scientists provide results from their assessment of the fungus, the beetle that carries it, and their combined effect on redbay and other members of the laurel family, including sassafras, spicebush, and avocado.

Extensive mortality of redbay, an attractive evergreen tree common along the coasts of the southeastern United States, has been observed in South Carolina and Georgia since 2003. Though the wilt was at first attributed to drought, the cause was soon found to be a fungal pathogen and the exotic redbay ambrosia beetle, Xyleborus glabratus, a native to Southeast Asia that was first found in the area in 2002. A number of ambrosia beetles carry species of fungi as food for their larvae; a previously undescribed fungus in the genus Raffaelea is a fungal symbiont of this ambrosia beetle.

To determine if the fungus was the cause of the wilt, Fraedrich and colleagues inoculated redbay trees and containerized seedlings with the Raffaelea fungus; the plants died within 5 to 12 weeks. To connect fungus and beetle, they also exposed redbay seedlings to X. glabratus beetles; the ambrosia beetles tunneled into almost all of the plants, causing 70 percent of them to die. The scientists found the fungus in 91 percent of the beetle-attacked plants......... Posted by: Erica      Read more         Source

March 31, 2008, 9:13 PM CT

Pathway plants use to fight back against pathogens

Plants are not only smart, but they also wage a good fight, as per a University of Missouri biochemist. Prior studies have shown that plants can sense attacks by pathogens and activate their defenses. However, it has not been known what happens between the pathogen attacks and the defense activation, until now. A new MU study revealed a very complex process that explains how plants counter attack pathogens. This discovery could potentially lead to crops with enhanced disease resistance.

There is a chemical warfare between plants and pathogens, said Shuqun Zhang, associate professor of biochemistry in the College of Agriculture, Food and Natural Resources and the College of Medicine. Normally, plants put effort into growth and development. However, when plants sense pathogens, they have to use some of their energy and resources to make secondary metabolites to fight disease. Until now, very little has been known about how this process is regulated.

As per the study, plants first sense the attack of a pathogen, and then activate defense responses by triggering a complex signaling cascade in plants. One of the defense responses is the induction and accumulation of anti-microbial defense chemicals, known as phytoalexins.

In his study, Zhang found the specific signaling path, known as a mitogen-activated protein kinase (MAPK) cascade, in the plants that ends when the defense chemical camalexin is created. Camalexin is essential for resistance to some plant diseases. Zhang used Arabidopsis, a small flowering plant and the first to have its entire genome sequenced, and Botrytis cinera, a fungal pathogen that causes grey mold disease in many plants including grapes and strawberries......... Posted by: Erica      Read more         Source

Mon, 31 Mar 2008 00:08:48 GMT

Cnidoscolus stimulosus

Todays Botany Photo of the Day comes courtesy of Bruce Vanderveen aka duneaster@Flickr (original via UBCBG BPotD pool). Check out his collection of native plant photos from Florida.

Who could suspect this dainty member of the Euphorbiaceae of being such a menace? A flower has never looked so appetizing, bearing such close resemblance to a piece of floral confectionary from some wedding cake. However, with such suggestive common names as finger rot and tread softly, it''s no surprise that this plant isn''t found on cakes or in bouquets. As can be seen from today''s image, Cnidoscolus stimulosus is covered in trichomes. In the case of Cnidoscolus stimulosus, these small hairs will irritate the skin upon contact. Regarding tread softly and other plants which possess such weaponry, Nancy C. Coile writes,

"The urticating hair or trichome has a bulbous and very fragile tip which breaks off at an angle and results in a perfect tool for piercing skin. Basically, the shaft of the hair resembles a glass tube due to the deposition of silica in the cell wall during formation (Thurston 1974). When the urticating hair tip is broken, it has the action of a hypodermic needle and injects the urticating substances which cause the intense pain and result in irritated skin rashes." (from Florida''s Department of Agriculture - Urtica chamaedryoides Pursh: a Stinging Nettle, or Fireweed and Some Related Species - PDF).

Cnidoscolus stimulosus is often mistaken for the true stinging nettle, Urtica dioica. The latter has a near world-wide distribution while finger-rot is confined to the southeastern United States. As far as the urticating substances in Cnidoscolus stimulosus are concerned, I can only guess that they might include those found in Urtica dioica such as histamine, acetylcholine, and serotonin (from the previously mentioned article). Posted by: Daniel Mosquin      Read more     Source

March 27, 2008, 9:21 PM CT

Can you rescue a rainforest?

Half a century after most of Costa Rica's rainforests were cut down, scientists from the Boyce Thompson Institute took on a project that a number of thought was impossible - restoring a tropical rainforest ecosystem.

When the scientists planted worn-out cattle fields in Costa Rica with a sampling of local trees, native species began to move in and flourish, raising the hope that destroyed rainforests can one day be replaced.

Carl Leopold and his partners in the Tropical Forestry Initiative began planting trees on worn-out pasture land in Costa Rica in 1992. For 50 years the soil was compacted under countless hooves, and its nutrients washed away. When it rained, Leopold says, red soil appeared to bleed from the hillsides.

The group chose local rainforest trees, collecting seeds from native trees in the community. "You can't buy seeds," Leopold says. "So we passed the word around among the neighbors." When a farmer would notice a tree producing seeds, Leopold and his wife would ride out on horses to find the tree before hungry monkeys beat them to it.

The group planted mixtures of local species, trimming away the pasture grasses until the trees could take care of themselves. This was the opposite of what commercial companies have done for decades, planting entire fields of a single type of tree to harvest for wood or paper pulp......... Posted by: Erica      Read more         Source

March 24, 2008, 8:25 PM CT

Corn's roots dig deeper into South America

Corn has long been known as the primary food crop in prehistoric North and Central America. Now it appears it may have been an important part of the South American diet for much longer than previously thought, as per new research by University of Calgary archaeologists who are cobbling together the ancient history of plant domestication in the New World.

In a paper reported in the March 24 advanced online edition of the Proceedings of the National Academy of Sciences (PNAS), U of C PhD student Sonia Zarrillo and archaeology professor Dr. Scott Raymond report that a new technique for examining ancient cooking pots has produced the earliest directly dated examples of domesticated corn (maize) being consumed on the South American continent. Their discovery shows the spread of maize out of Mexico more than 9,000 years ago occurred much faster than previously believed and provides evidence that corn was likely a vital food crop for villages in tropical Ecuador at least 5,000 years ago.

The domestication and dispersal of maize has been a hot topic in archaeology for decades and these are the earliest indisputable dates for its presence in South America, Raymond said. It has long been thought that maize may have been used south of Panama at this time for ritual purposes but this shows it was also being consumed as food......... Posted by: Erica      Read more         Source

Wed, 19 Mar 2008 01:54:27 GMT

Arabidopsis thaliana

Today''s entry, organized by Connor Fitzpatrick, is the fourth in a BPotD series for UBC Research Week. The photographs and write up come courtesy of Dr. Fred Sack, Professor and Head, Department of Botany.

Each leaf contains thousands of pores, stomata, which allow gas exchange between the atmosphere and the shoot. Stomata are cellular valves central to plant survival because they allow carbon dioxide to enter leaves where it is used to make sugars in photosynthesis. Stomata are also adaptive because they close down when water loss becomes too great. Efficient gas exchange seems to require that valves be spaced apart from each other since it is rare in nature to find two stomata in direct contact.

My lab pioneered the discovery of genes required for stomatal formation and spacing. We first determined how stomata develop and are distributed in the model eudicot Arabidopsis. As in all plants, stomatal formation requires an initial division that is unequal in size and fate, generating a smaller cell and a larger cell. After the smaller cell becomes oval in profile, it divides equally thus producing the two young guard cells that develop into the stoma. Meanwhile the larger cell produced by the unequal division can in turn divide asymmetrically. Normally this "piggyback" (iterative) division is oriented so that the new small precursor cell does not contact the previously formed one, a placement that generates the minimal one-celled separation between stomata. This placement probably requires intercellular communication, a conclusion reinforced when we identified the TOO MANY MOUTHS gene which encodes a probable receptor. Defects in TMM induce spacing violations, suggesting that it normally receives spatial cues used to correctly orient "piggyback" divisions. TOO MANY MOUTHS acts exclusively in the cells that form stomata as shown by the distribution of green fluorescent protein in the accompanying picture (red shows the cell walls; note that stomata are still forming in this picture; reproduced from Nadeau and Sack, Science). Thus this gene, which is conserved in monocots as well, controls the division behavior of islands of stem cells distributed throughout the epidermis of the developing shoot.

We also found that a different gene, FOUR LIPS, is required to ensure that there is only one equal division of the GMC (the guard mother cell is a precursor to guard cells). Mutations in FLP induce extra, abnormal, equal divisions resulting in four guard cells (lips) in a row ("stoma" comes from the Greek for "mouth"). We found that FLP is a transcription factor that regulates genes involved in cell cycling. Additional genes in this pathway are being identified in collaboration with Erich Grotewold at Ohio State University. It is likely that restricting GMC divisions to one (failsafe) would be strongly selected for in evolution since the control of water loss and the efficiency of carbon dioxide uptake are critical for plant survival.

The first photograph was taken using cryoscanning electron microscopy. The second photograph was taken using confocal laser scanning microscopy. The red channel shows the cell outlines (cell walls labeled with propidium iodide), and the green channel shows where the gene TMM is expressed. Posted by: Daniel Mosquin      Read more     Source

March 16, 2008, 9:48 PM CT

Nutrient regulation of biological clock in plants

Using a systems biological analysis of genome-scale data from the model plant Arabidopsis, an international team of scientists identified that the master gene controlling the biological clock is sensitive to nutrient status. The study will appear in the latest issue of the Proceedings of the National Academy of Sciences. This hypothesis derived from multi-network analysis of Arabidopsis genomic data, and validated experimentally, has shed light on how nutrients affect the molecular networks controlling plant growth and development in response to nutrient sensing.

The study was conducted by a team of scientists at New York Universitys Center for Genomics and Systems Biology, Chiles Pontificia Universidad Catlica de Chile, Dartmouth College, and Cold Spring Harbor Labs. The studys lead authors are Rodrigo A. Gutirrez of the Pontificia Universidad Catlica de Chile and Gloria Coruzzi of NYUs Center for Genomics and Systems Biology. They note that the systems biology approach to uncovering nutrient regulated gene networks provides new targets for engineering traits in plants of agronomic interest such as increased nitrogen use efficiency, which could lead to reduced fertilizer cost and lowering ground water contamination by nitrates.

Researchers have previously studied how nitrogen nutrients affect gene expression as a way to understand the mechanisms that control plant growth and development. Nitrogen is an essential nutrient and a metabolic signal that is sensed and converted, resulting in the control of gene expression in plants. In addition, nitrate has been shown to serve as a signal for the control of gene expression in Arabidopsis, the first flowering plant to have its entire genome sequenced. There is current evidence, on a gene-by-gene basis, that products of nitrogen assimilation, the amino acids glutamate (Glu) or glutamine (Gln), might serve as signals of organic nitrogen status that are sensed and in turn regulate gene expression......... Posted by: Erica      Read more         Source

Thu, 13 Mar 2008 02:58:13 GMT

Lotus japonicus and Lotus berthelotii

Connor''s been gathering entries for a new series on BPotD, and it starts today. Connor writes:

Research Week has officially begun at UBC. This year''s Research Week is particularly special as it marks UBC''s 100th anniversary. Events are taking place from March 4-15 that celebrate the research conducted by all of UBC''s faculties, departments, schools and partner institutions.

From March 4 to March 15, Botany Photo of the Day will feature research from the Department of Botany, the Faculty of Forestry and the Faculty of Land and Food Systems.

Dr. Quentin Cronk, a professor in the Faculty of Land and Food Systems and Director of the UBC Botanical Garden and Centre for Plant Research, shares with us today his research on the evolution of bird pollination:

These two photographs show two species of the legume genus Lotus. The yellow flower is Lotus japonicus, a "model organism" for legume biology. Its genome is being sequenced to aid the study of legume biology, particularly nodulation, the process by which legumes partner with nitrogen-fixing bacteria to produce their own fertilizer (a major source of nitrogen in the best agricultural systems). In order to separate the genetic components of nodulation, many mutants have been raised. You can see a fanciful animation of how these mutants are created and screened by the "magical mutation machine". Lotus japonicus, as the name implies, comes from Japan, but there are a number of closely related species throughout temperate Eurasia, including the familiar Lotus corniculatus ("bacon and eggs") which is widely introduced in North America (and can be seen all over the UBC campus).

The red flower is a narrow Canary Island endemic called Lotus berthelotii, sometimes grown in warmer gardens under the name "parrot vine". It makes a low, mounded, trailing bush with grey leaves. It looks so different from Lotus japonicus because it is bird-pollinated (Lotus japonicus, like most Lotus species, is bee pollinated).

The flowers are shown side-by-side to illustrate the different pollination mechanisms (for convenience the larger Lotus berthelotii flowers are shown the same size as the Lotus jaonicus flower). Bees are attracted to the flat upright "standard" petal of the yellow flower and land on the closed wing and keel petals, which they have to open to get at the pollen. In consequence the flowers are held horizontally. In Lotus berthelotii, ground perching birds probe down into the flowers from above and therefore the flowers are held in an upright position. Bird pollinated flowers are often red, both to attract birds and to help bird flowers avoid the attentions of bees. For animals like birds, with good colour vision, red contrasts well with green foliage. However, it is camouflaged from bees, as insect eyes are insensitive to the red end of the spectrum.

Together with graduate student Isidro Ojeda, my laboratory is investigating the evolution of bird pollination in Lotus and the gene expression changes that are associated with the very different flower type. The project fits well with our interest both in the evolution and biology of island plants and also in flower development. We are collaborating with the Jardín botanico canario Viera y Clavijo in Gran Canaria and with Arnoldo Santos Guerra of the Jardín de aclimatacion de La Orotava in Tenerife.

Incidentally, one mystery we have not yet solved is how we can persuade Lotus berthelotii to flower reliably in western Canada. Whether under glass or outside it remains stubbornly vegetative. We have tried hormone treatments, light treatments, various temperature regimes, not to mention various fertilizer treatments, and yet we only get the occasional flower here in Vancouver. In the Canary Islands, the plants are covered with flowers in April and May. Posted by: Daniel Mosquin      Read more     Source

March 11, 2008, 10:38 PM CT

New twist on life's power source

A startling discovery by researchers at the Carnegie Institution puts a new twist on photosynthesis, arguably the most important biological process on Earth. Photosynthesis by plants, algae, and some bacteria supports nearly all living things by producing food from sunlight, and in the process these organisms release oxygen and absorb carbon dioxide. But two studies by Arthur Grossman and his colleagues*+ reported in Biochimica et Biophysica Acta and Limnology and Oceanography suggest that certain marine microorganisms have evolved a way to break the rulesthey get a significant proportion of their energy without a net release of oxygen or uptake of carbon dioxide. This discovery impacts not only researchers basic understanding of photosynthesis, but importantly, it may also impact how microorganisms in the oceans affect rising levels of atmospheric carbon dioxide.

Grossmans team investigated photosynthesis in a marine Synechococcus, a form of photosynthetic bacteria called cyanobacteria (formerly blue-green algae). These single-celled organisms dominate phytoplankton populations over much of the worlds oceans and are important contributors to global primary productivity. Grossman and colleagues wanted to understand how Synechococcus could thrive in the iron-poor waters that cover large areas of the ocean, since certain activities of normal photosynthesis require high levels of iron. While others had suggested a potential role of oxygen as accepting electrons from the photosynthetic apparatus in place of carbon dioxide, the studies by Grossmans group show that this activity is significant in the oligotrophic (nutrient-poor) oceans, which cover about half the oceans area......... Posted by: Erica      Read more         Source