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.