Laboratory Report

Fungal Pathogen Cloaking Device

When plants and animals are challenged with fungal invaders, one of the first means of defense involves recognition of the fungus. A telltale component of fungal cell walls is chitin, which is not present in plants or humans, but alerts such hosts to a fungal presence and induces a series of defensive reactions. To avoid them, fungal pathogens produce and secrete a protein called Intercellular Protein 6 (ICP 6) during an attack that binds together their own stray chitin fragments. The fungal pathogens are essentially cloaked and unseen by their host, at least at the beginning of an infection. The tomato fungal pathogen (Cladosporium) studied in this research, when unable to produce ICP 6, was less aggressive and less able to cause disease in tomato plants. Scientists will use this information to design new ways to combat fungal infections in plants and humans.

Science, 2010; 329 (5994): 953-955

Sometimes the Textbook Explanation Is Wrong

It was assumed by many, and stated in textbooks, that the reason for tall flower stalks on insectivorous sundews (Drosera) was to keep pollinators away from the leafy traps to prevent them from being consumed. A series of experiments conducted by Bruce Anderson at the University of Stellenbosch in South Africa has shown that the real reason for the tall flower stalks is more about attracting pollinators than worrying about their safety. He chose two sundew species, one with a tall flower stalk above a rosette of traps, and the other with a shorter flower stalk on plants with an upright habit. He observed the pollination of 500 plants of each species to see if more pollinators were caught in the traps of the short-flowered plants, and checked to see what was in the traps. The pollinators of both plants were relatively large, greater than 5 mm; the trapped insects were less than 2 mm. Pollinators were not being trapped in either species. So, the first conclusion was that the length of the flower stems made no difference to the safety of the pollinators. He then cut the flowers from several plants and placed them in test tubes; some of the test tubes were buried so the flowers were barely above ground level and the others were placed so the flowers were at normal height. Pollinators visited the tall flowers ten times more frequently than the short flowers. With no other variable other than flower height, the experiment proved that taller flowers attract more pollinators to the sundew plants. Maximizing reproductive success is of paramount importance.

Annals of Botany. Volume 106, Issue 4, pp 653-657

Mathematical Model Put to the Test at Point Reyes

Tidestrom’s lupine (Lupinus tidestromii) exists in only fifteen small populations on the Point Reyes Peninsula. Before the introduction of European beachgrass (Ammophila arenaria), the lupine showed its survival advantages best after a major storm, which would blow out the dunes and most everything on them. Buried seeds of the lupine would be scarified in the process and subsequently germinate with little else around to consume or compete with them. Changes in dune habitat over the years has made it less likely for dune blowouts to occur, and Tidestrom’s lupine is suffering. The cause for the threat of extinction is more complex than one might think. European beachgrass does not directly compete with the lupine; rather, it offers protection to a little native mouse that finds shelter from predatory birds in the grass tufts. The mice feed on the seed of Tidestrom’s lupine to an extent that, if nothing is done to change the situation, the lupine will become extinct. Mathematical models have been devised by researchers at Washington University in St Louis, Missouri, to predict when this might happen and if any changes to the seed consumption rate could prevent extinction. Soon, a massive dune restoration project will be underway at Point Reyes, including the removal of over one hundred acres of European beachgrass in a 300-acre area. It will be interesting to see if the prediction of reduced seed consumption is accurate, which could aid in the survival of the lupine. Unfortunately, there is still another threat to the Tidestrom’s lupine. Silver dune lupine (L. chamissonis), which historically was separated geographically from Tidestrom’s lupine, was brought to coastal California as an ornamental. The lupines together form fertile offspring, and the hybrid plants directly compete with Tidestrom’s lupine. This little detail will need to be incorporated into a revised mathematical model.

Ecology, 2010; 91 (8): 2261-2271

Hay Fever and Dog Dander

Allergic sensitivities to family pets, such as dogs and cats, is a year-round issue for those that suffer from it. It appears that these allergies “pre-prime” the human immune system so that, when hay fever season rolls around, those already suffering from a pet or dust mite allergy are hit even harder by hay fever and may show the sneezing symptoms much sooner than those not pre-primed. Hay fever is a late summer phenomenon brought on by the pollen release of ragweed. Even if a pet allergy is only a minor nuisance, it might be worth treating that year round allergy in order to make the hay fever season a little easier to tolerate.

Annals of Allergy, Asthma & Immunology, Volume 104, Issue 4, pp 293-298 (April 2010)