Phytoalexin

About: Phytoalexin is a research topic. Over the lifetime, 1161 publications have been published within this topic receiving 63405 citations. The topic is also known as: phytoalexins.

Inactivation of UDP-Glucose Sterol Glucosyltransferases Enhances Arabidopsis Resistance to Botrytis cinerea

Abstract: Free and glycosylated sterols are both structural components of the plasma membrane that regulate their biophysical properties and consequently different plasma membrane-associated processes such as plant adaptation to stress or signaling. Several reports relate changes in glycosylated sterols levels with the plant response to abiotic stress, but the information about the role of these compounds in the response to biotic stress is scarce. In this work, we have studied the response to the necrotrophic fungus Botrytis cinerea in an Arabidopsis mutant that is severely impaired in steryl glycosides biosynthesis due to the inactivation of the two sterol glucosyltransferases (UGT80A2 and UGT80B1) reported in this plant. This mutant exhibits enhanced resistance against B. cinerea when compared to wild-type plants, which correlates with increased levels of jasmonic acid (JA) and up-regulation of two marker genes (PDF1.2 and PR4) of the ERF branch of the JA signaling pathway. Upon B. cinerea infection, the ugt80A2;B1 double mutant also accumulates higher levels of camalexin, the major Arabidopsis phytoalexin, than wild-type plants. Camalexin accumulation correlates with enhanced transcript levels of several cytochrome P450 camalexin biosynthetic genes, as well as of their transcriptional regulators WRKY33, ANAC042, and MYB51, suggesting that the Botrytis-induced accumulation of camalexin is coordinately regulated at the transcriptional level. After fungus infection, the expression of genes involved in the indole glucosinolate biosynthesis is also up-regulated at a higher degree in the ugt80A2;B1 mutant than in wild-type plants. Altogether, the results of this study show that glycosylated sterols play an important role in the regulation of Arabidopsis response to B. cinerea infection and suggest that this occurs through signaling pathways involving the canonical stress-hormone JA and the tryptophan-derived secondary metabolites camalexin and possibly also indole glucosinolates.

The role of lipid and non-lipid components of Phytophthora infestans in the elicitation of the hypersensitive response in potato tuber tissue

Abstract: The hypersensitive reaction of potato tuber tissue, measured by necrosis and phytoalexin accumulation, was elicited by lipids and lipid-containing and lipid-free fractions extracted from mycelium of Phytophthora infestans . The most active fraction extracted after homogenization in phosphate buffer was composed of carbohydrate, protein and lipid. A heat-released preparation containing very low levels of eicosapentaenoic, arachidonic and dihomo-γ-linolenic acids was more active than a lipid extract of the mycelium. The majority of the elicitor of the mycelium remained associated with the wall residue after extraction. No relation was found between the activity of the fractions and their content of specific fatty acid elicitors. The activity of most fractions could not be explained by synergism between the eliciting fatty acids and mycelial carbohydrate. Furthermore, the activity of the lipid fractions appeared to be attenuated by some fungal component. Many of the fractions were shown by analytical isoelectric focussing to contain carbohydrate and protein bands also present in an elicitor obtained from culture filtrates of P. infestans . It is suggested that both lipid and non-lipid materials in the mycelium of P. infestans are able to elicit the hypersensitive response in potato tuber tissue.

Method for production of phytoalexins

Abstract: The invention relates to a topical composition, in particular a cosmetic rich in metabolites produced by dedifferentiated plant cells elicited in vitro, then dried, milled and dispersed in said composition. The invention further relates to a method for preparation of phytoalexin(s).

Further studies on induction of enzymes of phytoalexin synthesis in soybean and cultured soybean cells

Abstract: Abstract The glucan elicitor from cell walls o f the fungal pathogen, Phytophthora megasperma f. sp. glycinea, caused a decrease in activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase in wounded soybean cotyledons, whereas wounding alone led to an increase in the activity of this enzyme. A decrease o f HMG -CoA reductase activity after elicitor treatment was also found in soybean hypocotyls and soybean cell cultures. In contrast to the activity o f HMG -CoA reductase, the activity of dimethylallylpyrophosphate: 3,6a,9-trihydroxypterocarpan dimethylallyltransferase increases after elicitor challenge of soybean cell cultures and after inoculation of soybean hypocotyls (cv Amsoy 71) with mycelium of either race 1 (incompatible) or race 3 (compatible) of P. megasperma.