In defense against pathogens. Both plant sentinels and foot soldiers need to know the enemy

Abstract

Plants are major targets of microbes seeking a source of nutrition. A complex array of interactions between plants and microbes has evolved that reflects both the nutrient acquisition strategies of microbes and defense strategies of plants. Part of plant defense strategy includes an active offense against invading microbes using an array of antimicrobial gene products. Within the context of the overall plant-microbe interaction, we attempt here to emphasize the role of antimicrobial proteins (typically, over 100 amino acid residues) and peptides (typically, 30–60 amino acid residues) in plant defense.

The majority of plant-microbe encounters do not result in disease. Preformed factors including constitutively expressed waxes, cell wall components, antimicrobial peptides, proteins, and non-proteinaceous secondary metabolites that deter invasion have been proposed to contribute significantly to the host range of pathogens (Garcia-Olmedo et al., 1998; Morrisey and Osbourn, 1999; Heath, 2000). The importance of preformed defenses has been inferred from the observation that plants can be rendered susceptible by a deficiency in the production of these secondary metabolites or by the abilities of pathogens to degrade them (Morrisey and Osbourn, 1999; Papadopoulou et al., 1999).