Question

What are Bt-transgenic plants?

Plants that express an “antifreeze” protein that originated in bacteria that protects plants from cold stress

Plants that express a toxin that originated in the bacteria that kills insect larvae when ingested

Plants that express an herbicide resistant genes that allow them to survive when sprayed with an herbicide

Answer 1

1.Bacillus thuringiensis (Bt) crops are plants genetically engineered (modified) to contain the endospore (or crystal) toxins of the bacterium, Bt to be resistant to certain insect pests.

Bt Crops are transgenic crops that produce the same toxin as the bacterium Bacillus thuringiensis in the plant cell, thereby, protecting the crops from pests. The bacterium secretes specific proteins known as “cry proteins” that are toxic to insects.

2.Antifreeze proteins from plants are homologous to pathogenesis-related proteins and also provide protection against psychrophilic pathogens.

Transferring single genes encoding antifreeze proteins to freezing-sensitive plants lowered their freezing temperatures by approximately 1 degrees C.

These proteins bind to and inhibit the growth of ice crystals that are formed in the apoplast during subzero temperature

Biochemical characterization of plant antifreeze activity, as determined by the high ice recrystallization inhibition (IRI) activities and low thermal hysteresis (TH) of AFPs, showed that their main function is inhibition of ice crystal growth rather than the lowering of freezing temperatures.

3.When the bacteria is consumed by certain insects, the toxic crystal is released in the insects highly alkaline gut, blocking the system which protects the pest’s stomach from its own digestive juices. The stomach is penetrated, and the insect dies by poisoning from the stomach contents and the spores themselves.

Bacillus thuringiensis israelensis (Bti)

Bt-i is a highly specific biological pesticide for use against mosquito, black fly and fungus gnat larvae. It may be applied safely to irrigation and roadside ditches, pastures, marshes and ponds, water gardens, flower pots, bird baths, rain gutters…any place there is standing water! Once ingested, Bt-i kills 95-100% of mosquito larvae within 24 hours. Highly effective because it kills these pests before they become biting adults.

Bacillus thuringiensis kurstaki (Btk) is the best known and most widely used strain of Bt. It kills the larvae of many types of moths and butterflies.

4.Herbicide resistance is the inherited ability of an individual plant to survive a herbicide application that would kill a normal population of the same species.

Herbicide resistance is normally present at very low frequencies in weed populations before the herbicide is first applied. Variation exists within every population, with some individuals having the ability to survive the herbicide application.

Herbicide resistance does not equate to poor performance of a herbicide. Resistant weeds can often survive application of herbicide at rates that are much greater than the recommended rate.