Engineered Agrobacterium Strains for Improved Crop Transformation

Overview

Our group develops engineered Agrobacterium strains to improve crop transformation by modifying the bacterial side of plant–bacterium interactions.

Super-Agrobacterium ver. 4 expresses ACC deaminase and GABA transaminase in Agrobacterium tumefaciens GV2260. These enzymes metabolise the ethylene precursor ACC and GABA, respectively, addressing inhibitory factors associated with plant–Agrobacterium interactions. In tomato ‘Micro-Tom’, the strain increased stable transformation frequency approximately 3.6-fold relative to the matched GV2260 control.

We seek partners to evaluate this technology in commercial crops and genotypes. Performance in each new host or genotype would be established through comparative testing.

What we bring

• Published stable transformation data: In tomato ‘Micro-Tom’, stable transformation frequency was 15.2 ± 1.1% with ver. 4 versus 4.3 ± 1.9% with the matched control. These values reflect recovery of independent diploid plants classified as carrying a single T-DNA copy by Southern blot analysis.

• Improved transient expression: In Erianthus ravennae calli, GUS-positive spots per gram increased approximately 7.2-fold relative to the matched control. In tomato cotyledons, the proportion of explants with GUS staining over more than 20% of their area increased approximately 3.9-fold. These are transient expression indicators used to assess T-DNA delivery, not stable transformation frequencies.

• A bacterial modification system: The acdS and gabT expression system is carried on a helper plasmid and could be evaluated in other Agrobacterium backgrounds. Each strain–vector combination requires testing.

• Evaluation across transformation stages: Our published work assessed transient expression, callus induction, shoot regeneration, rooting, and stable plant recovery.

Transient expression was also evaluated in Nicotiana benthamiana and Solanum torvum. Responses varied by species, and ver. 4 did not consistently outperform earlier Super-Agrobacterium versions.

Partnership opportunities

We welcome seed, vegetable, fruit, and agricultural biotechnology companies interested in: • Comparative testing in elite or proprietary genotypes with low transformation efficiency • Evaluating effects on delivery and plant recovery • Testing additional bacterial backgrounds or partner-supplied constructs • Extending the approach to hosts with suitable regeneration systems

We welcome partners contributing crop-specific knowledge, plant material, and regeneration expertise to jointly define tests and success criteria.

Readiness and timeline

The strain has been constructed, with published evidence of stable transformation and whole-plant recovery in tomato ‘Micro-Tom’. Stable transformation in other crops and commercial genotypes remains to be established. DNA-free or transgene-free editing and the maintenance and intact integration of constructs of 60 kb or larger have not been demonstrated in this study.

Study scope and timing would be agreed based on material availability, institutional arrangements, and culture cycles.

Funding and contracting

We seek industry-supported feasibility studies and collaborative research. Scope, budget, material transfer, intellectual property, and contracts would be discussed with partners and the relevant University of Tsukuba offices.

Publication

Nonaka et al. (2019). Super-Agrobacterium ver. 4. Frontiers in Plant Science, 10, 1204. https://doi.org/10.3389/fpls.2019.01204