Signal compound

G. Becard, L. P. Taylor, D. D. Douds, P. E. Pfeffer, and L. W. Doner. Flavonoids are not necessary plant signal compounds in arbuscular mycorrhizal symbiosis. Mol. Plant-Microbe Interact. 8 525 (1995). 

Both primitive and advanced forms have been examined for vomeronasal excitation. The turtle VN nerve was the subject of EOG recordings elicited by small organic molecules and by specific signal compounds (Tucker, 1963 Hatanaka, 1987). The simple arrangement of the chelonian accessory area (Fig. 2.8) allows air or liquid delivery hence the preferred odourant vehicle varies with habitat across the aquatic or terrestrial turtles, and the land tortoises (Chap. 1 and Halpem, 1992). 

Pollen allelopathy is phenomenon when pollen chemicals (e.g., phenols, terpenoids, sesquiterpene lactones, etc.) inhibit sexual reproduction in heterospecific individuals due to influencing of fertilization (Murphy 1992). The phenomenon includes excretion of signaling compounds from the donor cell (pollens, pistil stigma), recognition of a specific signal, transmission of information (pollen), and the development of a characteristic response in the acceptor cell. The possible mechanism of the effect was described in Roshchina (2001). 

The vapor pressure of volatile compounds, measured in atmospheres (or millimeters of mercury), varies with temperature. For example, the vapor pressure of acetone increases from 200 to 400 mmHg with a temperature rise from +20 to +40 °C, and that of w-heptane from 100 to 400 mmHg with a temperature change from +40 to +80 °C (e.g. Adams et ah, 1970). The half-lives of several acetates decreased by two- to fourfold when the temperature was raised from 20 to 30 °C (McDonough etal., 1989). In temperate latitudes, temperatures can vary from about 40 to 0 °C within 24 hours. Therefore, it is important to know the vapor pressure of a given compound for the ambient temperatures under which a particular animal species operates. Diurnal and nocturnal animals may have selected different signal compounds (or mixtures). Do polar and tropical species differ in their choice of compounds for communication. Have cold-climate... 

The odor sensitivity of an experimental animal needs to be known to appreciate communication distances and performance, but it is not easily measured. The detection thresholdhzs to be distinguished from the recognition threshold. The former is the concentration at which an odor is noticed, and the latter -typically much higher - the concentration at which behavior tests in animals or verbal responses in humans show that the odor has been recognized as a specific signal, compound, or mixture. 

It is now known that the initial interaction between plants and bacteria of the Rhizobiaceae is a chemical detection by the microbe of a susceptible host, i.e., the host produces compounds which act as signals for the microbial pathogen or symbiont. The microbe responds to these signals by expression of genes necessary in subsequent stages of the interaction. For a few of the Rhizobiaceae some signal compounds involved have been identified (1-7). 

The compounds AS and HO-AS have come to be regarded as the unique chemicals which Agrobacterium detects in nature and which trigger the initial events within the bacterium, resulting in tumor formation. However, it has yet to be shown that these acetophenones, which in fact have never previously been reported as naturally occurring phytochemicals, are the signal compounds produced by any other susceptible hosts. AS has been used to... 

Isolated compounds were collected after separation by HPLC and assayed for wr-induction in the strains described. It became apparent that the limited host range strain responded to all the substances that induced vir expression in the wide host range strain, but the LHR strain was less sensitive to the same substances and as a result was considered a less sensitive bioassay organism. Therefore work on isolation of grapevine-derived signal compounds continued using the more sensitive WHR strain and plate assay system described. 

In the case of diketopiperazine 13 and related compounds, dehydrogenation of the preceding diketopiperazine occurs in the side chain. A shift of the double bond into the central ring and dehydration may result in the formation of substituted pyrazines. Simple pyrazines are known as signaling compounds from animals. The pyrazines 16 and 17 have also been isolated from marine Streptomycetes [106]. GC/MS investigations of bacterial flavor components [951 indicate that these and others are very wide-spread. 

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