The phenylalanine ammonia-lyase inhibitor AIP induces rice defence against the root-knot nematode Meloidogyne graminicola.

The phenylalanine ammonia-lyase (PAL) enzyme catalyses the conversion of l-phenylalanine to trans-cinnamic acid. This conversion is the first step in phenylpropanoid biosynthesis in plants. The phenylpropanoid pathway produces diverse plant metabolites that play essential roles in various processes, including structural support and defence.

Strigolactone deficiency induces jasmonate, sugar and flavonoid phytoalexin accumulation enhancing rice defense against the blast fungus Pyricularia oryzae.

Strigolactones (SLs) are carotenoid-derived phytohormones that regulate plant growth and development. While root-secreted SLs are well-known to facilitate plant symbiosis with beneficial microbes, the role of SLs in plant interactions with pathogenic microbes remains largely unexplored. Using genetic and biochemical approaches, we demonstrate a negative role of SLs in rice (Oryza sativa) defense against the blast fungus Pyricularia oryzae (syn.

The diversity of salicylic acid biosynthesis and defense signaling in plants: Knowledge gaps and future opportunities.

The phytohormone salicylic acid (SA) is known to regulate plant immunity against pathogens. Plants synthesize SA via the isochorismate synthase (ICS) pathway or the phenylalanine ammonia-lyase (PAL) pathway. The ICS pathway has been fully characterized using Arabidopsis thaliana, a model plant that exhibits pathogen-inducible SA accumulation.

Constitutive expression of JASMONATE RESISTANT 1 induces molecular changes that prime the plants to better withstand drought.

In this study, we investigated Arabidopsis thaliana plants with altered levels of the enzyme JASMONATE RESISTANT 1 (JAR1), which converts jasmonic acid (JA) to jasmonoyl-l-isoleucine (JA-Ile). Analysis of a newly generated overexpression line (35S::JAR1) revealed that constitutively increased JA-Ile production in 35S::JAR1 alters plant development, resulting in stunted growth and delayed flowering. Under drought-stress conditions, 35S::JAR1 plants showed reduced wilting and recovered better from desiccation than the wild type.

Lack of antagonism between salicylic acid and jasmonate signalling pathways in poplar.

Salicylic acid (SA) and jasmonic acid (JA) often play distinct roles in plant defence against pathogens. Research from Arabidopsis thaliana has established that SA- and JA-mediated defences are more effective against biotrophs and necrotrophs, respectively. These two hormones often interact antagonistically in response to particular attackers, with the induction of one leading to suppression of the other.

Biological and biorational management of blast diseases in cereals caused by .

Blast diseases, caused by the fungal pathogen , are among the most destructive diseases that occur on at least 50 species of grasses, including cultivated cereals wheat, and rice. Although fungicidal control of blast diseases has widely been researched, development of resistance of the pathogen against commercially available products makes this approach unreliable. Novel approaches such as the application of biopesticides against the blast fungus are needed for sustainable management of this economically important disease.

The phytopathogenic fungus Sclerotinia sclerotiorum detoxifies plant glucosinolate hydrolysis products via an isothiocyanate hydrolase.

Brassicales plants produce glucosinolates and myrosinases that generate toxic isothiocyanates conferring broad resistance against pathogens and herbivorous insects. Nevertheless, some cosmopolitan fungal pathogens, such as the necrotrophic white mold Sclerotinia sclerotiorum, are able to infect many plant hosts including glucosinolate producers. Here, we show that S.

Accumulation of Catechin and Proanthocyanidins in Black Poplar Stems After Infection by : Hormonal Regulation, Biosynthesis and Antifungal Activity.

Flavan-3-ols including the monomeric catechin and the polymeric proanthocyanidins (PAs) are abundant phenolic metabolites in poplar ( spp.) previously described to protect leaves against pathogen infection. However, it is not known whether stems are also defended in this way.

Circumvents Flavonoid Defenses by Catabolizing Flavonol Glycosides and Aglycones.

Flavonols are widely distributed plant metabolites that inhibit microbial growth. Yet many pathogens cause disease in flavonol-containing plant tissues. We investigated how , a necrotrophic fungal pathogen that causes disease in a range of economically important crop species, is able to successfully infect flavonol-rich tissues of Arabidopsis ().

Strigolactones enhance root-knot nematode (Meloidogyne graminicola) infection in rice by antagonizing the jasmonate pathway.

Strigolactones (SLs) are carotenoid-derived plant hormones that also act in the rhizosphere to stimulate germination of root-parasitic plants and enhance plant symbiosis with beneficial microbes. Here, the role of SLs was investigated in the interaction of rice (Oryza sativa) roots with the root-knot nematode Meloidogyne graminicola. Genetic approaches and chemical sprays were used to manipulate SL signaling in rice before infection with M.

Flavanone-3-Hydroxylase Plays an Important Role in the Biosynthesis of Spruce Phenolic Defenses Against Bark Beetles and Their Fungal Associates.

Conifer forests worldwide are becoming increasingly vulnerable to attacks by bark beetles and their fungal associates due to the effects of global warming. Attack by the bark beetle and the blue-stain fungus it vectors () on Norway spruce () is well known to induce increased production of terpene oleoresin and polyphenolic compounds. However, it is not clear whether specific compounds are important in resisting attack.

Salicylic acid activates poplar defense against the biotrophic rust fungus Melampsora larici-populina via increased biosynthesis of catechin and proanthocyanidins.

Poplar trees synthesize flavan-3-ols (catechin and proanthocyanidins) as a defense against foliar rust fungi, but the regulation of this defense response is poorly understood. Here, we investigated the role of hormones in regulating flavan-3-ol accumulation in poplar during rust infection. We profiled levels of defense hormones, signaling genes, and flavan-3-ol metabolites in black poplar leaves at different stages of rust infection.

Flavan-3-ols Are an Effective Chemical Defense against Rust Infection.

Phenolic secondary metabolites are often thought to protect plants against attack by microbes, but their role in defense against pathogen infection in woody plants has not been investigated comprehensively. We studied the biosynthesis, occurrence, and antifungal activity of flavan-3-ols in black poplar (), which include both monomers, such as catechin, and oligomers, known as proanthocyanidins (PAs). We identified and biochemically characterized three leucoanthocyanidin reductases and two anthocyanidin reductases from involved in catalyzing the last steps of flavan-3-ol biosynthesis, leading to the formation of catechin [2,3-trans-(+)-flavan-3-ol] and epicatechin [2,3-cis-(-)-flavan-3-ol], respectively.

Acyl Sugars Protect a Wild Tobacco from Both Native Fungal Pathogens and a Specialist Herbivore.

-Acyl sugars (-AS) are abundant trichome-specific metabolites that function as indirect defenses against herbivores of the wild tobacco ; whether they also function as generalized direct defenses against herbivores and pathogens remains unknown. We characterized natural variation in AS among 26 accessions and examined their influence on two native fungal pathogens, U4 and sp. U10, and the specialist herbivore At least 15 different AS structures belonging to three classes were found in leaves.

The role of thionins in rice defence against root pathogens.

Thionins are antimicrobial peptides that are involved in plant defence. Here, we present an in-depth analysis of the role of rice thionin genes in defence responses against two root pathogens: the root-knot nematode Meloidogyne graminicola and the oomycete Pythium graminicola. The expression of rice thionin genes was observed to be differentially regulated by defence-related hormones, whereas all analysed genes were consistently down-regulated in M.