Bacillus thuringiensis Gene Inserted in Corn Plants

The advent of genetic engineering technology has provided scientists with the capability of developing plants with the ability to make this bacterial protein in the desired plant tissues. In the late 1980’s, scientists were able to isolate and clone the gene coding for one of the Bt proteins toxic to ECB. By 1996 the first Bt corn hybrid was on the market (Witkowski, et al., 1997). Once the Bt gene was successfully inserted into corn the level of toxicity to insects increased making the final expression of the toxic crystalline protein higher than the level in Bt insecticide sprays. There are five different Bt CRY genes that have been inserted into corn grown commercially. (See Table 2, National Corn Growers Association, 2005, and Wright, et al., 2000).

Table 2 - Transgenic Events Designed to Control ECB

Event	Gene Coding Region	Promoter	Characteristics	US EPA Approval (as of 2001)**	Trade Name
Mon 810	CRY 1Ab	CaMV 35S	Bt expressed in all plant tissues, controls both 1st and 2nd generation ECB	food and livestock feed	YieldGard
Bt-11	CRY 1Ab	CaMV 35S	Bt expressed in all plant tissues, controls both 1st and 2nd generation ECB, glufosinate herbicide tolerance	food and livestock feed	YieldGard
E-176	CRY 1Ab	PEP Carboxylase	Bt expressed in only green plant tissue and pollen, controls both 1st and 2nd generation ECB	food and livestock feed	Knockout or Naturegard
DBT-418	CRY 1Ac	CaMV 35S	Bt expressed at some level in all plant tissues, controls 1st generation ECB	food and livestock feed	Bt-Xtra
TC1507	CRY 1F	Ubiquitin/CaMV 35S	Bt expressed at some level in all plant tissues, controls 1st and 2nd generation ECB, glufosinate herbicide tolerance	food and livestock feed	Herculex I
CBH-351	CRY 9C	CaMV 35S	different protein from 1A, Bt expressed in all plant tissue, controls 1st and 2nd generation ECB	livestock feed only	StarLink

**For approval status in other countries, including the European Union, refer to http://ec.europa.eu/food/dyna/gm_register/index_en.cfm .

As of April 1, 2001 the registration on Syngenta’s Knockout (Cry 1Ab, Event 176), expired and was not renewed. On June 30, 2001, the registration for Naturegard (Cry 1Ab, Event 176) by Mycogen expired and a request to renew the registration was not made. Aventis voluntarily cancelled the registration of StarLink (Cry 9c) as of February 20, 2001. (Biopesticides, 2001) Due to Monsanto’s aquisition of Dekalb, the registration of Bt-Xtra (Cry 1Ac, Event DBT-418) was voluntarily cancelled on February 20, 2001. (Sloderbeck, 2004)

For more information on how promoters, events, and Bt genes are actually inserted into corn, please refer to the following Library of Crop Technology Website lessons: Gene design 1, Gene design 2, Transformation 1, Transformation 2, Transformation 3.

Quiz

Question

What gene construct (promoter + coding region) would be most likely to target ECB at an early larval stage?

PEP Carboxylase - CRY 1Ab

Incorrect: PEP Carboxylase - CRY 1Ab is expressed only in green leaf tissue. CaMV 35S - CRY 1Ac is expressed in all plant tissues. Therefore, both of these gene constructs would effectively target control of young ECB larva.

CaMV 35S - CRY 1Ac

Both the above

Correct: PEP Carboxylase - CRY 1Ab is expressed only in green leaf tissue. CaMV 35S - CRY 1Ac is expressed in all plant tissues. Therefore, both of these gene constructs would effectively target control of young ECB larva.

Looks Good! Correct: PEP Carboxylase - CRY 1Ab is expressed only in green leaf tissue. CaMV 35S - CRY 1Ac is expressed in all plant tissues. Therefore, both of these gene constructs would effectively target control of young ECB larva.

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