Fatal attraction of Caenorhabditis elegans to predatory fungi through 6-methyl-salicylic acid

Salicylic acid is a phenolic phytohormone which controls plant growth and development. A methyl ester (MSA) derivative thereof is volatile and involved in plant-insect or plant-plant communication. Here we show that the nematode-trapping fungus Duddingtonia flagrans uses a methyl-salicylic acid isomer, 6-MSA as morphogen for spatiotemporal control of trap formation and as chemoattractant to lure Caenorhabditis elegans into fungal colonies. 6-MSA is the product of a polyketide synthase and an intermediate in the biosynthesis of arthrosporols. The polyketide synthase (ArtA), produces 6-MSA in hyphal tips, and is uncoupled from other enzymes required for the conversion of 6-MSA to arthrosporols, which are produced in older hyphae. 6-MSA and arthrosporols both block trap formation. The presence of nematodes inhibits 6-MSA and arthrosporol biosyntheses and thereby enables trap formation. 6-MSA and arthrosporols are thus morphogens with some functions similar to quorum-sensing molecules. We show that 6-MSA is important in interkingdom communication between fungi and nematodes.

Salicylic and Methyl Salicylic Acid Affect Quality and Phenolic Profile of Apple Fruits Three Weeks before the Harvest

Effects of spraying over apple trees (Malus domestica; 'Topaz') with methyl salicylic acid (MeSA) and SA during fruit maturation were investigated for quality parameters (weight, firmness, hue angle, red blush, yield) and phenolic profile of the peel and pulp (HPLC–mass spectrometry). These treatment effects were also investigated for activities of the phenylpropanoid pathway enzymes phenylalanine ammonia-lyase, chalcone synthase and isomerase (combined), and flavanone-3β-hydroxylase. The MeSA and SA treatments resulted in poor fruit peel coloration, with higher hue angles and 20% and 10% lower red blush, respectively. Anthocyanin levels were also significantly lower (56%) for MeSA treatment. MeSA stimulated activities of phenylalanine ammonia-lyase and chalcone synthase/isomerase, which resulted in higher levels of flavanols (to 34%), flavonols (to 33%), and hydroxycinnamic acids (to 29%), versus control. Therefore, while these salicylate treatments improve levels of some beneficial polyphenols, they also have negative effects on the external quality characteristics of the fruit.

Light-responsive fluids based on reversible wormlike micelle to rodlike micelle transitions

A new family of rheological responsive fluids based on azobenzene surfactant and 5-methyl salicylic acid binary mixtures is developed due to the light-induced reversible transitions between wormlike micelles and rodlike micelles.

Role of Salicylic Acid in Tomato Defense against Cotton Bollworm, Helicoverpa armigera Hubner

We investigated the role of the salicylic acid (SA) signaling pathway in defense responses of tomato plants to the herbivore, cotton bollworm. After exposure to the cotton bollworm, tomato leaves rapidly accumulated a high level of SA. The transcription of PR1 and BGL2 genes, the marker genes of SA pathway, was up-regulated. An enhanced endogenous SA level was accompanied by an increase in the endogenous H2O2 level as compared with controls. Spraying tomato plants with a solution containing either SA or methyl salicylic acid (Me-SA), the H2O2 level dramatically increased. These data proved that the SA pathway was involved in the tomato plant defense responses to the herbivore.

METABOLIC DEVELOPMENT AND SECONDARY BIOSYNTHESIS IN PENICILLIUM URTICAE

In cultures of Penicillium urticae Bainier, two successive physiological phases are distinguished. In the first, or trophophase, mycelial N, P, RNA, and —SH and the utilization of acetate for synthesis reach maximum values while glucose oxidation, mainly by the hexose monophosphate pathway, is most rapid. In the second, or idiophase, assimilation of N and P is reduced, RNA and —SH levels are lower, glucose is oxidized more slowly and mainly by glycolysis, fatty acids or mannitol accumulate, and special phenolic metabolites derived from 6-methyl-salicylic acid appear. The phase transition occurs sharply, with a minimum of respiratory activity and of acetate utilization; thereafter the pattern of secondary metabolism is established in a stepwise manner. The observations are interpreted in terms of sequential enzyme induction initiated by metabolic dislocation, and the generalized applications of such an hypothesis are considered.