Sick plant? Take two aspirin and....Thanks to the immune system immune system Cells, cell products, organs, and structures of the body involved in the detection and destruction of foreign invaders, such as bacteria, viruses, and cancer cells. Immunity is based on the system's ability to launch a defense against such invaders. , diseases such as measles make people sick just once, and then the body develops a lifelong resistance to the infection. Plants, too, possess similar defenses. Something called "systemic acquired resistance In plants, systemic acquired resistance (SAR) is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen. SAR is analogous to the innate immune system found in animals, and there is evidence that SAR in plants and innate immunity in " allows plants to fight off subsequent attacks not only by the original pathogen but by other infections as well. For years scientists have suspected that salicylic acid salicylic acid or 2-hydroxybenzoic acid, C6H4(OH)CO2H, a colorless, crystalline organic carboxylic acid that melts at 159°C;; it is soluble in ethanol and ether but is only slightly soluble in water. , a chemical similar to aspirin's active ingredient An active ingredient, also active pharmaceutical ingredient (or API), is the substance in a drug that is pharmaceutically active. Some medications may contain more than one active ingredient. , helped plants develop this resistance. New research has confirmed that hunch and shown that the amount of this chemical in a plant determines the degree to which it fights off current and future infections. Thomas Gaffney and his colleagues at Ciba-Geigy in Research Triangle Park Research Triangle Park, research, business, medical, and educational complex situated in central North Carolina. It has an area of 6,900 acres (2,795 hectares) and is 8 × 2 mi (13 × 3 km) in size. Named for the triangle formed by Duke Univ. , N.C., and Basel, Switzerland, report their findings in the Aug. 6 Science. To assess the importance of salicylic acid, the researchers created "transgenic" tobacco plants. The plants contain a bacterial gene, which codes for a protein that breaks down salicylic acid. The researchers infected three lower leaves of these plants with a tobacco virus. A week later, they observed brown spots at the site of infection and measured the amount of the bacterial gene, its protein, and salicylic acid. At the same time, the investigators infected plants that lacked the gene. Leaves from those plants increased their salicylic acid production 185-fold. In contrast, infected leaves from plants with a lot of this protein had just two to three times more salicylic acid, the group reports. Moderate amounts of the bacterial protein Bacterial protein a protein formed by bacterial activity.[1]. Examples
[2] led to moderate increases in salicylic acid. Next, the researchers put virus on the upper leaves of these plants and, six days later, measured the size of the brown spots that developed. They observed that the less salicylic acid the plant possessed, the larger the spots. "It was nice that everything correlated so well," says Leslie Friedrich, a geneticist ge·net·i·cist n. A specialist in genetics. geneticist a specialist in genetics. geneticist at Ciba-Geigy. Also, plants with a lot of the bacterial protein developed larger brown spots at the site of the first infection than did the unmodified plants. This indicates that salicylic acid plays a role in neutralizing the initial viral attack, she and her colleagues suggest. Ultimately, the researchers would like to understand enough about how systemic acquired resistance develops to create a "vaccine" that would mobilize this defense system prior to any infection, she adds. |
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