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 1Gene design 2Transformation 1Transformation 2Transformation 3.

Quiz

Question

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

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.