Pathogen-induced biosynthetic pathways encode defense-related molecules in bread wheat

Wheat is a widely grown food crop that suffers major yield losses due to attack by pests and pathogens. A better understanding of biotic stress responses in wheat is thus of major importance. The recently assembled bread wheat genome coupled with extensive transcriptomic resources provides unprecedented new opportunities to investigate responses to pathogen challenge. Here, we analyze gene coexpression networks to identify modules showing consistent induction in response to pathogen exposure. Within the top pathogen-induced modules, we identify multiple clusters of physically adjacent genes that correspond to six pathogen-induced biosynthetic pathways that share a common regulatory network. Functional analysis reveals that these pathways, all of which are encoded by biosynthetic gene clusters, produce various different classes of compounds—namely, flavonoids, diterpenes, and triterpenes, including the defense-related compound ellarinacin. Through comparative genomics, we also identify associations with the known rice phytoalexins momilactones, as well as with a defense-related gene cluster in the grass model plant Brachypodium distachyon. Our results significantly advance the understanding of chemical defenses in wheat and open up avenues for enhancing disease resistance in this agriculturally important crop. They also exemplify the power of transcriptional networks to discover the biosynthesis of chemical defenses in plants with large, complex genomes

The 'Solanum pimpinellifolium' 'Cf-ECP1' and 'Cf-ECP4' genes for resistance to 'Cladosporium fulvum' are located at the 'Milky Way' locus on the short arm of chromosome 1

The interaction between tomato and the leaf mould pathogen Cladosporium fulvum is an excellent model to study gene-for-gene interactions and plant disease resistance gene evolution. Most Cf genes were introgressed into cultivated tomato (Solanum lycopersicum) from wild relatives such as S. pimpinellifolium and novel Cf-ECP genes were recently identified in this species. Our objective is to isolate Cf-ECP1, Cf-ECP2, Cf-ECP4 and Cf-ECP5 to increase our understanding of Cf gene evolution, and the molecular basis for recognition specificity in Cf proteins. The map locations of Cf-ECP2 and Cf-ECP5 have been reported previously and we report here that Cf-ECP1 and Cf-ECP4 map to a different locus on the short arm of chromosome 1. The analysis of selected recombinants and allelism tests showed both genes are located at Milky Way together with Cf-9 and Cf-4. Our results emphasise the importance of this locus in generating novel Cf genes for resistance to C. fulvum. Candidate genes for Cf-ECP1 and Cf-ECP4 were also identified by DNA gel blot analysis of bulked segregant pools. In addition, we generated functional cassettes for expression of the C. fulvum ECP1, ECP2, ECP4 and ECP5 proteins using recombinant Potato Virus X, and three ECPs were also expressed in stable transformed plants. Using marker-assisted selection we have also identified recombinants containing Cf-ECP1, Cf-ECP2, Cf-ECP4 or Cf-ECP5 in cis with a linked T-DNA carrying the non-autonomous Zea mays transposon Dissociation. Using these resources it should now be possible to isolate all four Cf-ECPs using transposon tagging, or a candidate gene strategy

Caractéristiques du fumier et du compost équins

National audienceLes effluents équins sont des amendements organiques assez proches des effluents bovins très pailleux. Ils apporteront en particulier du phosphore, du potassium, du soufre ainsi que de la matière organique. L’azote est présent essentiellement sous la forme organique et peu mobilisable à court terme par la plante. L’apport de fumier ou de compost équin contribue à améliorer la structure et la rétention en eau des sols en augmentant le taux de matières organiques (stockage de carbone).Le compost est préféré au fumier car :- Il est hygiénisé si l’on respecte bien les phases de montée entempérature et de maturation avant son épandage.- Il est plus homogène et stable avec une teneur en paille réduitece qui lui confère un effet amendant plus rapide après épandage.Des pratiques raisonnées de traitements médicamenteux des chevaux sont à privilégier pour limiter l’impact sur les sols lors du recyclage du fumier ou du compost équin

Caractéristiques du fumier et du compost équins

National audienceLes effluents équins sont des amendements organiques assez proches des effluents bovins très pailleux. Ils apporteront en particulier du phosphore, du potassium, du soufre ainsi que de la matière organique. L’azote est présent essentiellement sous la forme organique et peu mobilisable à court terme par la plante. L’apport de fumier ou de compost équin contribue à améliorer la structure et la rétention en eau des sols en augmentant le taux de matières organiques (stockage de carbone).Le compost est préféré au fumier car :- Il est hygiénisé si l’on respecte bien les phases de montée entempérature et de maturation avant son épandage.- Il est plus homogène et stable avec une teneur en paille réduitece qui lui confère un effet amendant plus rapide après épandage.Des pratiques raisonnées de traitements médicamenteux des chevaux sont à privilégier pour limiter l’impact sur les sols lors du recyclage du fumier ou du compost équin

Discovery of isoflavone phytoalexins in wheat reveals an alternative route to isoflavonoid biosynthesis

Abstract Isoflavones are a group of phenolic compounds mostly restricted to plants of the legume family, where they mediate important interactions with plant-associated microbes, including in defense from pathogens and in nodulation. Their well-studied health promoting attributes have made them a prime target for metabolic engineering, both for bioproduction of isoflavones as high-value molecules, and in biofortification of food crops. A key gene in their biosynthesis, isoflavone synthase, was identified in legumes over two decades ago, but little is known about formation of isoflavones outside of this family. Here we identify a specialized wheat-specific isoflavone synthase, TaCYP71F53, which catalyzes a different reaction from the leguminous isoflavone synthases, thus revealing an alternative path to isoflavonoid biosynthesis and providing a non-transgenic route for engineering isoflavone production in wheat. TaCYP71F53 forms part of a biosynthetic gene cluster that produces a naringenin-derived O-methylated isoflavone, 5-hydroxy-2′,4′,7-trimethoxyisoflavone, triticein. Pathogen-induced production and in vitro antimicrobial activity of triticein suggest a defense-related role for this molecule in wheat. Genomic and metabolic analyses of wheat ancestral grasses further show that the triticein gene cluster was introduced into domesticated emmer wheat through natural hybridization ~9000 years ago, and encodes a pathogen-responsive metabolic pathway that is conserved in modern bread wheat varieties