Plants Repel Insect Pests - 2 - Natural Pest Control

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Plants Repel Insect Pests - 2

Here are three more recent articles which further document the fact that plants can repel insect pests - as well as being able to mount an immune response to infections. Again, the full spectrum of the 72 trace elements is essential here - otherwise it is as if plants too have a powerful defence ring bristling with highly accurate cannons - but no ammunition.

Original Abstracts:

Herbivory-induced Volatiles Elicit Defence Genes in Lima Bean Leaves

In response to herbivore damage, several plant species emit volatiles that attract natural predators of the attacking herbivores. Using spider mites (Tetranychus urticae) and predatory mites (Phytoseiulus persimilis), it has been shown that not only the attacked plant but also neighbouring plants are affected, becoming more attractive to predatory mites and less susceptible to spider mites. The mechanism involved in such interactions, however, remains elusive.

Here we show that uninfested lima bean leaves activate five separate defence genes when exposed to volatiles from conspecific leaves infested with T. urticae, but not when exposed to volatiles from artificially wounded leaves. The expression pattern of these genes is similar to that produced by exposure to jasmonic acid. At least three terpenoids in the volatiles are responsible for this gene activation; they are released in response to herbivory but not artificial wounding. Expression of these genes requires calcium influx and protein phosphorylation/dephosphorylation.
GEN-ICHIRO ARIMURA, RIKA OZAWA, TAKESHI SHIMODA, TAKAAKI NISHIOKA, WILHELM BOLAND & JUNJI TAKABAYASHI [ Nature 406, 512 - 515 (2000) © Macmillan Publishers Ltd.]

Gene Helps Tomatoes Fight off Worms, Aphids

A single gene helps make some tomatoes resistant to two very different pests - aphids and nematodes - researchers reported Monday. They said understanding how this works could help scientists breed better pest-resistant crops in the future. Valerie Williamson of the University of California Davis and colleagues knew there was a gene, known as "Meu-1," that helps some tomatoes resist aphids. They also knew there is another gene that helps them fight off nematodes, tiny worms that kill the roots of plants. Williamson's team determined that the genes are one and the same. They have named the single gene "Mi." [ Proceedings of the National Academy of Sciences, Aug.18. '98 ]

"Footprint" Shows Master Switch Simultaneously Controls Plants' Disease Defenses

Plants respond to infections by activating one or more genetic "master switches" that in turn simultaneously control scores of genes that protect the plants against disease, scientists at the University of North Carolina at Chapel Hill have discovered.

"Because their core sets of genes are so similar, a genetic 'footprint' like the one we found could be a binding site for a universal switch for the immune system among many plant species," said Dr. Jeffery L. Dangl, John N. Couch associate professor of biology at UNC-CH. "This discovery, on this scale, is a first for plant biology."
[Nature Genetics, 11/29/2000 - Source: University Of North Carolina At Chapel Hill (http://www.unc.edu/) ]

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