Transgenic Expression of Antimicrobial Peptides in Plants: Strategies for Enhanced Disease Resistance, Improved Productivity, and Production of Therapeutics

Abstract

Antimicrobial peptides represent a diverse group of small membrane-active molecules that are essential components of the innate defense system of, probably, all living organisms. In this chapter, we demonstrate that the transformation of plants with genes encoding for antimicrobial peptides have enabled the development of plants with enhanced and durable resistance to many diseases, increased crop yields, and reduced post-harvest losses. In vitro, the peptides inhibited plant-specific pathogens at micromolar concentrations that were not toxic to plant protoplasts or mammalian cells. The majority of the antimicrobial peptides retained their activities in heterologous plant systems. Most importantly, the expression level of antimicrobial peptides in transgenic plants, regulated by promoters with appropriate level of spatiotemporal activity, was sufficient to confer resistance against a variety of pathogenic fungi, oomycetes, and bacteria. The accumulation of antimicrobial peptides in transgenic plants did not alter normal plant growth or development, even in the lines with the highest level of transgene expression. These studies are greatly expanding our knowledge of the interactions between antimicrobial peptides, phytopathogens, and host plants. In turn, this is helping the development of novel strategies for sustainable agriculture, including the engineering of new crop varieties with broad-spectrum disease resistance that will require fewer pesticide applications, reduce the associated environmental risks, and provide higher yields. In addition, the transgenic expression of antimicrobial peptides in plants is emerging as one of the most promising platforms for the cost-effective production of tomorrow’s therapeutics.