Dual-target fungicides inhibiting alternative oxidase and cytochrome bc1 for resistant plant pathogens

Overview

Fungal pathogens cause major crop losses worldwide, and the effectiveness of leading fungicides is declining as resistance spreads. This research addresses that challenge by targeting two complementary branches of the mitochondrial respiratory chain at once: the alternative oxidase (AOX) pathway and the cytochrome bc1 complex. Existing QoI fungicides act only on cytochrome bc1, allowing stress-induced AOX expression to rescue the pathogen and drive resistance. By blocking both pathways with a single class of inhibitors, this approach aims to deliver more reliable eradication of phytopathogenic fungi and reduce the emergence of resistant strains.

The work is relevant to agrochemical companies, crop protection developers, and agricultural biotechnology partners seeking next-generation fungicide chemistries with novel modes of action. Compounds have demonstrated potent activity against AOX from multiple fungal species and encouraging selectivity between fungal and mammalian targets.

Technical specifications

Core innovation:

• Dual-mode inhibitors designed to engage both AOX and the cytochrome bc1 complex in a single molecule
• Binding pocket identified through crystallographic analysis and homology modelling of AOX
• Preliminary structure–activity relationship (SAR) studies completed, yielding lead compounds

Key performance data:

• pIC50 values in the nanomolar range against AOX from Candida spp., Trypanosoma brucei, and Moniliophthora perniciosa
• Cytochrome bc1 inhibition in the 1–50 µM range using rat liver mitochondria, indicating meaningful fungal-versus-mammalian discrimination
• Mitochondrial targeting strategies under investigation, including phosphonium moiety modifications informed by activity against Cryptococcus neoformans AOX

Validation platform:

• Recombinant AOX expressed in E. coli membrane fractions for kinetic and inhibition studies
• 96-well plate spectrophotometric kinetic assay enabling rapid compound screening
• Planned testing against agriculturally relevant targets including Blumeria graminis, Zymoseptoria tritici, and Botrytis cinerea

Technology readiness level

The program is at an early-to-mid stage of preclinical chemistry development. Lead compounds have been synthesized and characterized, with demonstrated in vitro potency against multiple fungal AOX enzymes and preliminary selectivity data against mammalian mitochondria. Remaining work includes expanding efficacy testing to key phytopathogens, refining mitochondrial uptake through chemical modification, and completing kinetic characterization of inhibitor binding. The investigators estimate 3–6 months to complete the next validation milestone, after which the chemistry would be positioned for partnership with an agrochemical organization for further lead optimization, formulation, and field-relevant testing.