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.

Tomato‐Fusarium oxysporum f. sp. lycopersici Interaction: “in vitro” Analysis of Several Possible Pathogenic Factors

Abstract: The behaviour of Tomato cultures from known resistant and susceptible cultivars and lines was examined for callus growth on culture media containing increasing concentrations of Fusarium oxysporum f. sp. lycopersici race 1 culture filtrate and phytoalexin synthesis elicited by Fusarium cell wall components. A strict correlation was found between in vivo resistance to the fungus and in vitro hypersensitive response and phytoalexin induction. On the other hand in vitro tolerance to toxic filtrate does not seem in this case a good indicator of in vivo resistance to the pathogen.

Biosynthesis of Phenylamide Phytoalexins in Pathogen-Infected Barley.

Abstract: Phytoalexins are inducible antimicrobial metabolites in plants, and have been indicated to be important for the rejection of microbial infection. HPLC analysis detected the induced accumulation of three compounds 1–3 in barley (Hordeum vulgare) roots infected by Fusarium culmorum, the causal agent of Fusarium root rot. Compounds 1–3 were identified as cinnamic acid amides of 9-hydroxy-8-oxotryptamine, 8-oxotryptamine, and (1H-indol-3-yl)methylamine, respectively, by spectroscopic analysis. Compounds 1 and 2 had been previously reported from wheat, whereas 3 was an undescribed compound. We named 1–3 as triticamides A–C, respectively, because they were isolated from barley and wheat, which belong to the Triticeae tribe. These compounds showed antimicrobial activities, indicating that triticamides function as phytoalexins in barley. The administration of deuterium-labeled N-cinnamoyl tryptamine (CinTry) to barley roots resulted in the effective incorporation of CinTry into 1 and 2, which suggested that they were synthesized through the oxidation of CinTry. Nine putative tryptamine hydroxycinnamoyl transferase (THT)-encoding genes (HvTHT1–HvTHT9) were identified by database search on the basis of homology to known THT gene sequences from rice. Since HvTHT7 and HvTHT8 had the same sequences except one base, we measured their expression levels in total by RT-qPCR. HvTHT7/8 were markedly upregulated in response to infection by F. culmorum. The HvTHT7 and HvTHT8 enzymes preferred cinnamoyl- and feruloyl-CoAs as acyl donors and tryptamine as an acyl acceptor, and (1H-indol-3-yl)methylamine was also accepted as an acyl acceptor. These findings suggested that HvTHT7/8 are responsible for the induced accumulation of triticamides in barley.

Scopolin, a glycoside form of the phytoalexin scopoletin, is likely involved in the resistance of nicotiana attenuata against alternaria alternata

Abstract: Phenolic coumarins are secondary metabolites playing an important role in plant-environment interaction. Previously, we have shown that wild tobacco Nicotiana attenuata accumulates high amounts of the jasmonate (JA)-dependent phenolic coumarin, scopoletin, as a phytoalexin to defend itself against a necrotic fungal pathogen, Alternaria alternata (tobacco pathotype). Scopolin, a s-glycoside form of scopoletin, was strongly elicited and to a level even higher than that of scopoletin in host plants after A. alternata infection. However, it was not known whether scopolin functioned as a phytoalexin playing a role in the resistance or simply as a storage form of scopoletin. When supplied in PDA medium, scopolin exhibited a moderate but slightly weaker anti-fungal activity against A. alternata than that of scopoletin. In addition, A. alternata-elicited scopolin level was dramatically decreased in JA deficient plants. Thus, all the data suggest that scopolin is also a JA-dependent phytoalexin likely involved in the resistance of N. attenuata against A. alternata.

Inhibitors of the Detoxifying Enzyme of the Phytoalexin Brassinin Based on Quinoline and Isoquinoline Scaffolds

Abstract: The detoxification of the phytoalexin brassinin to indole-3-carboxaldehyde and S-methyl dithiocarbamate is catalyzed by brassinin oxidase (BOLm), an inducible fungal enzyme produced by the plant pathogen Leptosphaeria maculans. Twenty-six substituted quinolines and isoquinolines are synthesized and evaluated for antifungal activity against L. maculans and inhibition of BOLm. Eleven compounds that inhibit BOLm activity are reported, of which 3-ethyl-6-phenylquinoline displays the highest inhibitory effect. In general, substituted 3-phenylquinolines show significantly higher inhibitory activities than the corresponding 2-phenylquinolines. Overall, these results indicate that the quinoline scaffold is a good lead to design paldoxins (phytoalexin detoxification inhibitors) that inhibit the detoxification of brassinin by L. maculans.