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.

Cinnamate-CoA ligase is involved in biosynthesis of benzoate-derived biphenyl phytoalexin in Malus × domestica 'Golden Delicious' cell cultures.

Abstract: Apple (Malus sp.) and other genera belonging to the sub‐tribe Malinae of the Rosaceae family produce unique benzoic acid‐derived biphenyl phytoalexins. Cell cultures of Malus domestica cv. ‘Golden Delicious’ accumulate two biphenyl phytoalexins, aucuparin and noraucuparin, in response to the addition of a Venturia inaequalis elicitor (VIE). In this study, we isolated and expressed a cinnamate‐CoA ligase (CNL)‐encoding sequence from VIE‐treated cell cultures of cv. ‘Golden Delicious’ (M. domestica CNL; MdCNL). MdCNL catalyses the conversion of cinnamic acid into cinnamoyl‐CoA, which is subsequently converted to biphenyls. MdCNL failed to accept benzoic acid as a substrate. When scab‐resistant (cv. ‘Shireen’) and moderately scab‐susceptible (cv. ‘Golden Delicious’) apple cultivars were challenged with the V. inaequalis scab fungus, an increase in MdCNL transcript levels was observed in internodal regions. The increase in MdCNL transcript levels could conceivably correlate with the pattern of accumulation of biphenyls. The C‐terminal signal in the MdCNL protein directed its N‐terminal reporter fusion to peroxisomes in Nicotiana benthamiana leaves. Thus, this report records the cloning and characterisation of a cinnamoyl‐CoA‐forming enzyme from apple via a series of in vivo and in vitro studies. Defining the key step of phytoalexin formation in apple provides a biotechnological tool for engineering elite cultivars with improved resistance.

Agent for enhancing allelopathy effect and/or phytoalexin production of plant

Abstract: PROBLEM TO BE SOLVED: To provide an allelopathy effect or phytoalexin production enhancing agent, increasing allelopathy effect or phytoalexin production like weeding effect and antibacterial action by performing foliar application or rhizosphere fertilization for grains, vegetables, fruit vegetables and plants such as garden plants, and maintaining an environment where weeds hardly grow, and to provide a method for enhancing allelopathy effect or phytoalexin production, using the agent.SOLUTION: This plant allelopathy effect or phytoalexin production enhancing agent which includes an amino acid fermentation byproduct, a nucleic acid fermentation byproduct, amino acid or nucleic acid is applied to plants when cultivating the plants to suppress sprouting and growth of other plants at the periphery of the plants.

Glucan Elicitor-Binding Proteins and Signal Transduction in the Activation of Plant Defence

Abstract: Soybean (Glycine max L.) tissues respond to infection with the fungus Phytophthora megasperma f. sp. glycinea, the pathogen causing stem and root rot in this plant, by the rapid, cultivar-specific activation of a phytoalexin defence response. The phytoalexin response is also expressed in cultured soybean cells following treatment with an elicitor derived from the cell walls of the fungus. The best characterized elicitors for soybean are the branched (1→3)- and (1→6)-linked s-glucans from the fungus. The glucans are naturally released during the early stages of germination of the fungal cysts in a host-independent manner. Surface-localized glucan-binding proteins exist in soybean cells which display high affinity and specificity for the fungal s-glucans, including an elicitor-active hepta-s-glucoside fragment derived from the polysaccharide, suggesting that elicitor perception involves a receptor-mediated process on the host cell membrane. The main component of the s-glucan-binding sites is a 70-kDa protein in SDS/PAGE, as identified by photoaffinity labelling and glucan-affinity chromatography of detergent-solubilized binding proteins. The elicitor-mediated transmembrane signalling process which leads to the activation of the phytoalexin response very likely involves Cat2+. Purified P. megasperma s-glucans and synthetic hepta-s-glucoside showed differential elicitor activity when tested in different experimental systems. In contrast to bioassays utilizing cotyledons, cell cultures responded only weakly to the presence of these carbohydrates. A strong and synergistic response, however, was observed when the cells were simultaneously treated with glucan elicitors and compound K-252a, a known inhibitor of mammalian protein kinases.

Two Chalcone Synthase Isozymes Participate Redundantly in UV-Induced Sakuranetin Synthesis in Rice

Abstract: Chalcone synthase (CHS) is a key enzyme in the flavonoid pathway, participating in the production of phenolic phytoalexins. The rice genome contains 31 CHS family genes (OsCHSs). The molecular characterization of OsCHSs suggests that OsCHS8 and OsCHS24 belong in the bona fide CHSs, while the other members are categorized in the non-CHS group of type III polyketide synthases (PKSs). Biochemical analyses of recombinant OsCHSs also showed that OsCHS24 and OsCHS8 catalyze the formation of naringenin chalcone from p-coumaroyl-CoA and malonyl-CoA, while the other OsCHSs had no detectable CHS activity. OsCHS24 is kinetically more efficient than OsCHS8. Of the OsCHSs, OsCHS24 also showed the highest expression levels in different tissues and developmental stages, suggesting that it is the major CHS isoform in rice. In oschs24 mutant leaves, sakuranetin content decreased to 64.6% and 80.2% of those in wild-type leaves at 2 and 4 days after UV irradiation, respectively, even though OsCHS24 expression was mostly suppressed. Instead, the OsCHS8 expression was markedly increased in the oschs24 mutant under UV stress conditions compared to that in the wild-type, which likely supports the UV-induced production of sakuranetin in oschs24. These results suggest that OsCHS24 acts as the main CHS isozyme and OsCHS8 redundantly contributes to the UV-induced production of sakuranetin in rice leaves.