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Chapter 18
Engineering Disease Resistance in Plants: An Overview
Richard A. Dixon, Nancy L. Paiva, and Madan K. Bhattacharyya
TABLE OF CONTENTS
I. Introduction and Scope ............................................................................................................. 249
II. Molecular Features of Plant-Pathogen Interactions ................................................................. 249
III. Choice of Promoters ................................................................................................................. 250
IV. Manipulation of Single Gene Traits to Directly Confer Antimicrobial Activity ................... 252
A. Pathogenesis-Related Proteins ........................................................................................... 252
B. Novel Antimicrobial Proteins ............................................................................................ 253
C. Engineered Toxin Insensitivity .......................................................................................... 253
D. Engineered Toxin Detoxification ...................................................................................... 254
E. Expression of Antibodies in Plants ................................................................................... 254
V. Manipulation of Phytoalexins to Increase Disease Resistance ............................................... 255
A. Introducing New Phytoalexins .......................................................................................... 255
B. Modifying Existing Phytoalexins ...................................................................................... 255
C. Altering the Amount or Timing of Phytoalexin Production ............................................ 258
D. Concerns Regarding Phytoalexin Manipulations .............................................................. 259
VI. Potential for Manipulation of Disease-Resistance Genes ....................................................... 260
A. Genetics of Host-Pathogen Interactions ............................................................................ 260
B. Genetics of Nonhost Resistance and Evolution of Host-Pathogen Specificity ............... 260
C. Engineering Disease-Resistance Genes for Crop Improvement...................... 261
Acknowledgments ............................................................................................................................... 262
Notes Added in Proof ......................................................................................................................... 262
References ........................................................................................................................................... 262
Further Reading .................................................................................................................................. 270
1. INTRODUCTION AND SCOPE
The goal of genetically manipulating disease resistance in plants has become a reality in the last 3 or
4 years. This is primarily due to advances in two areas: the technology of plant transformation and our
better understanding of the molecular basis of plant-pathogen interactions. Transgenic plants expressing
either novel proteins from foreign organisms or overexpressing a part of their own defensive arsenal
have been engineered, tested in both laboratory and field situations, and evaluated for disease resistance.
Engineered viral resistance through expression of viral coat protein genes,' replicase components,2 or
antisense RNA3 has proved effective in several instances. To date, there are fewer reports on engineered
resistance against fungi and bacteria. However, we believe that the next 5 years will witness a number
of successes in this area, utilizing a range of different, and often ingenious, strategies. The purpose of
this chapter is to outline the principles upon which strategies for fungal and bacterial resistance may
be based, to evaluate the types of genetic manipulations which may lead to increased resistance, and
to review those examples in which success has already been reported.
II. MOLECULAR FEATURES OF PLANT-PATHOGEN INTERACTIONS
The processes of plant-pathogen coevolution have led in many cases to interactions in which the outcome
(compatibility or incompatibility) is determined by a single dominant gene for resistance in the host,
the functional realization of which is determined by the presence of a corresponding, dominant avirulence
gene in the fungal or bacterial pathogen.4 In such gene-for-gene interactions, incompatibility is associated
with the rapid activation of a battery of defense-response genes, whose products may include biosynthetic
enzymes for the production of antimicrobial phytoalexins and wall-bound phenolics, hydrolytic enzymes
and other so-called pathogenesis-related (PR) proteins, and hydroxyproline-rich glycoproteins.5 These
products usually accumulate locally around the site of attempted microbial ingress. In compatible
0-87371-877-1/95/$0.00+$.50 249
0 1995 by CRC Press, Inc.
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Dixon, R. A.; Paiva, Nancy L. & Bhattacharyya, Madan Kumar. Engineering Disease Resistance in Plants: An Overview, chapter, 1995; [Boca Raton, Florida]. (https://digital.library.unt.edu/ark:/67531/metadc674022/m1/3/?rotate=270: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT College of Arts and Sciences.