This year, the ZQT-China team focused on addressing two key agricultural challenges: chlorimuron-ethyl herbicide residue and crop growth promotion. Using E. coli as a chassis, we engineered multiple functional modules including herbicide-degrading enzymes, indole-3-acetic acid (IAA) biosynthesis enzymes, a cell-surface display system, and a cold-inducible biosafety module. Our project aims to provide a dual-function synthetic biology solution for soybean–wheat crop rotation in North China, combining efficient herbicide degradation with plant growth promotion. Altogether, we contributed 7 new basic parts and 1 composite part, covering herbicide degradation, auxin biosynthesis, protein surface display, and biosafety.
Core Contributions
Basic Parts
- BBa_25F26ZPS (GST, 660 bp) – Glutathione S-transferase, catalyzing GSH-dependent nucleophilic substitution reactions to break sulfonylurea herbicides such as chlorimuron-ethyl, serving as a complementary detoxification pathway. (Silver Prize)
- BBa_256OWE6C (SulE, 945 bp) – A carboxylesterase from Hansschlegelia zhihuaiae, capable of hydrolyzing ester bonds in chlorimuron-ethyl and initiating degradation.
- BBa_K4695010 (PnbA, 957 bp) – A carboxylesterase from Chenggangzhangella methanolivorans CHL1, demonstrating the highest degradation efficiency (>60%) toward chlorimuron-ethyl.
- BBa_K523013 (INP, 357 bp) – An ice nucleation protein anchor sequence, enabling the stable localization of fusion proteins on the E. coli outer membrane for whole-cell catalysis.
- BBa_25I91ENZ (IaaM, 1032 bp) – Tryptophan 2-monooxygenase, converting tryptophan to IAM, the first step of IAA biosynthesis.
- BBa_25C6MDDL (IaaH, 900 bp) – IAM hydrolase, converting IAM to IAA, completing the auxin biosynthetic pathway.
- BBa_25I88Y9O (INP-PnbA, 1284 bp) – A fusion protein displaying PnbA on the cell surface via INP anchoring, enabling E. coli to directly degrade chlorimuron-ethyl as a whole-cell biocatalyst. (Gold Prize)
Composite Part
- BBa_25R1N9DT (PcspA–T4 Holin–T4 Lysozyme) – A cold-inducible lysis system in which PcspA drives the expression of T4 Holin and T4 Lysozyme at 16 °C, providing an environmentally responsive safety mechanism to eliminate engineered strains outside laboratory conditions. (Gold Prize)
Benefits for Future iGEM Teams
Our project demonstrates how synthetic biology can be harnessed for pesticide residue remediation and plant growth promotion in agricultural systems. The contributed parts provide reusable tools in several areas:
- Herbicide degradation modules – GST, SulE, and PnbA enzymes collectively offer complementary enzymatic strategies for sulfonylurea herbicide breakdown.
- Surface display toolkit – INP and INP-PnbA modules enable whole-cell catalysis applications without the need for enzyme purification.
- IAA biosynthesis pathway – IaaM and IaaH parts establish a microbial auxin production system to enhance plant root development and stress tolerance.
- Environmental safety design – PcspA–T4 Holin–T4 Lysozyme provides a cold-triggered containment mechanism, ensuring biosafety in open-field applications.
Taken together, these innovations extend beyond our project’s focus on soybean–wheat rotations, offering valuable design strategies and functional parts for future iGEM teams working on pesticide degradation, plant hormone production, cell-surface display, and biosafety control.
