Chloroplast Engineering for Herbicide Resistance via Phytoene Desaturase

Introduction

Carotenoids are essential isoprenoids in photosynthetic organisms and can play important functions as antioxidants, photosynthetic pigments and plant hormone precursors. Phytoene desaturase (PDS), an enzyme involved in carotenoid biosynthesis, protects plants from photooxidative damage. At present, PDS has become the main target of herbicides to inhibit carotenoid biosynthesis pathway. PDS-inhibiting herbicides like pyrazinone, mefluoperazine, and defluoperazine inhibit carotenoid biosynthesis by specifically blocking desaturation, resulting in phytoene accumulation, which leads to chlorophyll degradation and chloroplast membrane disruption. PDS encoded by crtI gene was isolated from Erwinina uredovora and engineered into tobacco nuclear genome. The protein was targeted to the chloroplast where carotenoid biosynthesis takes place and it could confer a good level of tolerance to the herbicides.

Fig. 1. Crystal Structure of Phytoene Desaturase of Oryza sativa. (Brausemann A, et al., 2017)

Solutions

A natural mutation in amino acid 304 of the PDS of the zooxanthellae can confer herbicide resistance. Our engineers have successfully isolated the phytoene desaturase gene from plants. In addition, Lifeasible is commmitted to improving crop tolerance to PDS-inhibiting herbicides by overexpressing PDS genes in plant chloroplast genomes and selecting resistant mutants. The PDS gene has potential value as a selectable marker. We successfully introduced the PDS gene into the chloroplast genome of crops to obtain resistance to PDS family herbicides such as pyrazinone, pyridinecarboxamide and phenoxybutyramide. We are very mature in developing solutions for crops that are resistant to PDS inhibitors.

Here, we replaced 304 amino acids of Verticillium wilt PDS with 19 other major amino acids and tested its enzymatic activity against flusalidone in vitro. Our available solutions for herbicide resistant via PDS include:

• Analysis of nucleotide sequences of higher plant ene desaturases.
• To analyze the mutation sites that increase the resistance of Synechococcus to herbicides.
• Construction of crop transformation using PDS gene vector.
• Cross-resistance of the T3 generation of transgenic plants.
• Maximum resistance to fluridone and defluoperazine.
• Evaluation of strain biometric parameters.

Features of Our Strategy

• Successful evolution of resistance to PDS inhibitors in higher plants by somatic mutation.
• Plants mutated in Hydrala pds containing Cys, Ser, His, and Thr at position 304 were determined to be highly resistant to fluoroketone and desfluoperazine.
• Helping eliminate undesired genetically modified plants in the wild instead of creating highly resistant weeds.
• Plant herbicide resistance engineering is the most effective way to obtain extremely high selectivity between crops and weeds. Expression of PDS genes in plants renders crops insensitive to PDS inhibitors.

Plants transformed with the mutated higher plant PDS showed an interesting herbicide resistance profile. Lifeasible has extensive knowledge and experience in the engineering of herbicide resistance via herbicide-insensitive enzymes. Our mission is to provide customers with comprehensive, reliable, professional solutions to accelerate your research. If you are interested in our solutions, please contact us at any time.

References

1. Brausemann A, Gemmecker S, Koschmieder J, et al. (2017) Structure of phytoene desaturase provides insights into herbicide binding and reaction mechanisms involved in carotene desaturation[J]. Structure. 25(8): 1222-1232. e3.
2. Arias R S, Dayan F E, Michel A, et al. (2006) Characterization of a higher plant herbicide‐resistant phytoene desaturase and its use as a selectable marker[J]. Plant biotechnology journal. 4(2): 263-273.