&CHAPTER 9

Marker Genes and Promoters

BRIAN MIKI

Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada

9.0. CHAPTER SUMMARY AND OBJECTIVES

9.0.1 Summary

Two essential segments of DNA are required to produce a transgenic plant that will express

the trait of interest: (1) a promoter must be fused upstream of the gene of interest to control

its expression—the choice of promoter is crucial in that it specifies when and where a trans-

gene is expressed in the plant, and (2) marker genes are needed to select transgenic plants

and/or monitor gene expression. Selectable markers typically confer antibiotic resistance so

that transgenic cells, tissues, and plants can be selected that survive antibiotic selection.

Visual marker genes often will cause a color change in the transgenic plants so that

researchers can see when and where transgenes are expressed in plant tissues.

9.0.2 Discussion Questions

1. Why use marker genes?


2. What are some differences between selectable markers and scorable markers?


3. Discuss the relative merits of GUS and GFP as reporters. Does the profile of experi-
   mentation using these reporter genes overlap directly or partially?


4. What are the advantages, if any, for the use of themanAgene over thenptIIgene as a
   selectable marker for food and feed crops, and would the use of themanAgene over-
   come public concern over the use of thenptIIgene? Conversely, what are the
   disadvantages?


5. Considering the large number of selectable marker gene systems that have been
   developed, why are so few adopted for basic research and commercialization?


6. What experimental factors should be considered for a functional genomics study of
   unknown genes if the vector employs a new selectable marker gene system in the
   base vector?

Plant Biotechnology and Genetics: Principles, Techniques, and Applications, Edited by C. Neal Stewart, Jr.

Copyright#2008 John Wiley & Sons, Inc.

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