Modulating plant ubiquitination system to increase leafy biomass

Overview

This biotechnology platform addresses the challenge of increasing leafy biomass in plants by targeting the ubiquitination system through a novel molecular mechanism. The approach exploits Membrane-anchored Ubiquitin-fold (MUB) proteins, specifically non-prenylated isoforms that inhibit Group VI Ubiquitin Conjugating Enzymes (UBCs). By blocking these UBCs, vegetative meristems become overactive, resulting in plants with substantially increased leaf number and biomass. This has potential applications in agricultural productivity, leafy crop yield enhancement, and biomass production for food, feed, and bioenergy markets.

Technical specifications

Core mechanism:

• Non-prenylated MUB isoforms inhibit Group VI UBC enzymes, which normally regulate meristem activity
• Loss of the native farnesyl lipid anchor (normally added via protein prenylation) converts MUB from a membrane-anchored inhibitor into a soluble, broadly active form
• A conserved alternative splicing switch naturally produces non-prenylated MUB isoforms across diverse plant species

Key discoveries supporting the platform:

• In vitro biochemical and structural studies confirmed specific MUB-UBC interactions
• A 2.8 angstrom co-crystal structure of the MUB:UBC complex was solved and validated through directed mutagenesis
• Transgenic plants expressing non-prenylated MUB proteins showed large increases in leaf number
• The leafiness phenotype depends on UBC binding, as mutagenizing the UBC binding site abolishes the effect
• Surveys of 30 major model and non-model plant transcriptomes revealed strong conservation of the alternative splicing pattern across the MUB gene family

Validation approaches in development:

• Artificial microRNAs (amiRNAs) targeting the conserved seven-membered Group VI UBC family to phenocopy MUB inhibition
• UBC mutants resistant to MUB binding but enzymatically active, designed to rescue and suppress the leafiness phenotype

Technology readiness level

The technology is at an early-to-mid stage of research validation. In vitro biochemical and structural characterization is complete, including a high-resolution co-crystal structure. In planta validation has demonstrated proof-of-concept through transgenic expression studies showing increased leaf biomass. Future work focuses on confirming the mechanism through targeted UBC knockdowns and rescue experiments in whole plants. The conserved splicing switch observed across 30 plant species suggests broad applicability, though commercial-scale development and field validation remain to be conducted.