Salicylate Activity. 3
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Figure 3. Tobacco mosaic virus (TMV) lesion diameter reduction by
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) 0.10; n ) 4 plants). Means with the same letter are not
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10) Vernooij, B.; Friedrich, L.; Morse, A.; Reist, R.; Kolditz-Jawhar,
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the salicylates (Tables 1 and 2), is more persistent and effective
at a lower rate than SA.
The effect of structure modification on salicylate activity has
been examined previously in other systems. These include
studies on the reduction of inflammation (22, 23), inhibition of
the mammalian endothelin ETA receptor (24), heat production
in Arum lily (25), NOx emission by soybean (26), glucosyl-
transferase activity in TMV infected tobacco (27), TMV lesions
size reduction, PR-1 protein induction, catalase activity, and
SA binding inhibition (28), and herbicide modulation (29, 30).
The structure-activity relationship of salicylates is dependent
on the assay system. For example, 5-(2,4-difluorophenyl)-
salicylic acid (diflunisal) is a very effective anti-inflammatory
drug (22), but was inactive as an inducer of PR-1a proteins
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(Table 2). In contrast, 3-, 4-, and 5-substituted chlorosalicylates
and 5-fluorosalicylate were active NOx inducers (26) and also
induced PR-1a and TMV resistance in our studies. Moreover,
the halogenated salicylates were among the most active poten-
tiators of atrazine, even through atrazine potentiation is inde-
pendent of SAR (30). The protection from the herbicide paraquat
also demonstrates the superior biological activity of the halo-
genated salicylates over that of other derivatives (29).
(
15) Weidner-Wells, M. A.; Fraga-Spano, S. A. An improved method
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In summary, we have shown that the induction of tobacco
PR-1a is of value in predicting the ability of substituted
salicylates and related compounds to induce disease resistance
in plants. Among the compounds tested, we have determined
that only fluorinated or chlorinated salicylates in the 3- and/or
1
5, 633-638.
(
18) Baizer, M.; Dub, M.; Gister, S.; Steinberg, N. Synthesis of
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5-ring position were more active than SA at inducing PR-1a
protein. We have also demonstrated that the ability of a
compound to induce PR-1a correlates with its ability to induce
resistance of tobacco to TMV.
8
09-818.
20) Parent, J.; Asselin, A. Detection of pathogenesis-related proteins
PR or b) and of other proteins in the intercellular fluid of
(
(
hypersensitive plants infected with tobacco mosaic virus. Can.
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