Plasticity of metabolic pathways – Investigating a novel biosynthetic step in the formation of 2-phenylnitroethane in the Salicaceae

• Applicant: Professorin Dr. Nathalie Lackus
• Subject Area: Plant Biochemistry and Biophysics ; Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 543671286

N-containing compounds produced by plants are ecologically important and can often be used as pharmacological compounds. The pharmacological benefits as well as the chemical ecological functions of N-containing compounds are enormous, but due to their huge structural diversity, limited occurrence and low abundance, the natural biosynthetic pathways are often not well understood and knowledge about these compounds is still limited. The N-containing volatile 2-phenylnitroethane is a characteristic component of the herbivore-induced volatile bouquet of poplars and a floral component of about 200 plant species. However, the biosynthesis of this compound, and in particular of the rather unusual nitro group, is not yet known. Thus, the aim of this research project is to elucidate the biosynthesis of 2-phenylnitroethane and its ecological function in plant defense responses using the plant family Salicaceae as an example. Preliminary experiments have shown that herbivore-induced 2-phenylnitroethane emission is conserved within the Salicaceae plant family by studying herbivore-induced volatile emission in different species of the monophyletic Populus-Salix lineage and its sister lineage Idesia. Multiple transcriptome analyses allowed the identification of cytochrome P450 monooxygenases of the CYP76 family in black cottonwood (Populus trichocarpa), basket willow (Salix viminalis) and Japanese orange cherry (Idesia polycarpa). Cloning and heterologous expression of the corresponding poplar CYP76 candidate revealed its previously undescribed enzymatic activity in the monooxygenation of (E/Z)-phenylacetaldoxime to 2-phenylnitroethane in vitro. Future experiments will characterize all identified CYP76 candidates from different Salicaceae species in vitro and confirm their respective activities in vivo using stable and transient RNAi-mediated knockdown approaches. In addition, a comparative approach will be used to investigate the enzymatic properties of the newly identified and previously described CYP76 monooxygenases from other plant families to understand the enzymatic mechanisms and properties that enable the newly identified enzymatic activity. Moreover, the ecological function of 2-phenylnitroethane as aherbivore-induced defense compound will be investigated by testing its effect on herbivore performance and as an antimicrobial compound.

• DFG Programme: Research Grants