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Agricultural crops suffer losses due to diseases and pests. Chemical and biological insecticides have been in use for a long time to minimize yield losses due to insect pests. Traditionally, these are externally applied as formulations on crops. The most common biological pesticides used include Cry proteins from Bacillus thuringiensis (Bt), which is a soil bacterium. Bt has a vast collection of cry genes. The encoded proteins vary widely with respect to their insect control efficacy and target insect specificity. It produces crystalline inclusions containing these proteins during sporulation. When ingested by insect larvae, these crystalline inclusions dissociate into monomers in the alkaline insect gut. The monomers further undergo proteolytic cleavage which results in an activated insecticidal protein. This protein binds to the larval gut lining and damages it inducing an antifeeding behavior in the larvae and eventually death. The cry protein binds to the larval gut lining at specific host-encoded receptors. One of the first genes to be commercially exploited for trait development in crops is the Bt cry. This was the advent of plant produced pesticides. A few genes like cry1Ac, cry1F, cry2Ab, have been effectively incorporated into plants for control of insect pests.

Bt Cotton
Bt cry1C Highlights

  Cry1Ca1 630 amino acid residues
  The active toxin alone has been expressed
  Cry1Ca1 has effective control of Spodoptera litura
  Cry1Ca1 has an alternative mode of action for control of Helicoverpa
  The gene is completely codon optimized for cotton
  Event ID: The selected cotton event for further evaluations is MLS9124
 
Metahelix has developed two versions of Bt cotton with proprietary cry1C (Spodoptera control) and cry1Ac (Bollworm control) based genes. The combination of cry1C and cry1Ac is also being developed as a stack. The Bt Cotton expressing cry1C is currently at the stage of regulatory approvals for Large Scale Trials (LST) for agronomic and trait evaluation. The biosafety studies for the Cry1C protein have been completed and the event MLS9124 is found to be safe.

Metahelix candidate genes cry1Ac and cry1C have different modes of action on bollworms. While cry1Ac has no activity against Spodoptera litura, cry1C is highly effective in its control. These two genes were chosen for controlling the bollworms and Spodoptera litura and also delay resistance development among the bollworm populations.
 
 
The biosafety of Bt cotton expressing Metahelix gene cry1C event MLS9124

The table below provides details of all the biosafety studies that have been conducted for establishing the biosafety of the Cry1C protein and the event MLS9124.


  Name of the study   Agency conducting the   Study   Status of the   study
  Acute oral toxicity of transgenic seed in rat   Shriram Research Institute   Completed
  Sub-chronic oral toxicity study of transgenic   seed in rats (90 days)   Shriram Research Institute   Completed
  Primary Skin Irritation test in rabbits   Shriram Research Institute   Completed
  Irritation to mucous membrane test of   transgenic seed in female rabbit   Shriram Research Institute   Completed
  Skin sensitization test of transgenic seed in   guinea pigs   Shriram Research Institute   Completed
  Allerginicity studies   Shriram Research Institute   Completed
  Feeding studies with laying hens   Shriram Research Institute   Completed
  Feeding studies in catfish   Shriram Research Institute   Completed
  Sub chronic oral toxicity in goats-90 days   study for genetically engineered seed   Shriram Research Institute   Completed
  Feeding studies in lactating crossbred cows   National Dairy Research   Institute, Karnal   Completed
  Pollen flow studies   Metahelix trials  2 years completed
  Baseline susceptibility studies of Spodoptera  to Bt Cry1C protein   Project Directorate for   Biological Control, Bangalore   Completed
  Studies on Soil microbiota
  1. Soil microflora
  University of Agricultural   Sciences, Bangalore   Completed
  
 2. Soil fauna   Metahelix Life Sciences,   Bangalore  Completed
  Biochemical equivalence studies   University of Agricultural   Sciences, Bangalore   Completed
  Aggressiveness, germination, weediness   Metahelix Life Sciences,   Bangalore  Completed
 Study on beneficial fauna   Metahelix Bt cotton trials  2-year study completed
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