Novel strategy to reduce herbicide residue in grains by stacking detoxification and resistance genes

Weeds are the major concern in crop production, thus affecting the world economy and food security. Developing glyphosate-resistant (GR) transgenic crops has revolutionized weed management practices and significantly benefited crop production. However, the major concern is that glyphosate accumulates in the plant tissues and affects physiological functions, crop yield, and quality. Cytotoxic effects of glyphosate and their complications have been reported. Hence, removing glyphosate residues is desirable.

We characterized two different glyphosate detoxifying genes, Aldo-keto reductase (PsAKR1) and mutated glycine oxidase (mGO), and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in model plant tabcco.  Multiple genes with PsAKR1, mGO and CP4EPSPS showed an improved glyphosate tolerance with sustained physiological functions in tobacco transgenics compared to single and double gene expressing transgenic plants. Multigene expressing tobacco transgenics accumulated less glyphosate, AMPA, sarcosine (its primary metabolites) and shikimic acid upon herbicide treatment suggesting the reduced levels of cytotoxic compounds. Further, multigene expression in rice showed an improved glyphosate tolerance with no yield penalty. Our findings show evidence that glyphosate detoxification with different enzymes targeting different sites along with resistant genes is an effective approach to improve glyphosate tolerance with reduced phytotoxicity. This stratetegy provide options for the production of GR crops for the benefit of farmers and environment.

Vennapusa AR, Agarwal S, Hanumanthrao HM, Aarthy T, Babitha KC, Thulasiram HV, Kulkarni MJ, Melmaiee K, Sudhakar C, Udayakumar M & Vemanna RS. Stacking herbicide detoxification and resistant genes improves glyphosate tolerance and reduces phytotoxicity in tobacco (Nicotiana tabacum L.) and rice (Oryza sativa L.). Plant Physiology and Biochemistry. 2022. 189: 126-138. https://doi.org/10.1016/j.plaphy.2022.08.025.