Preparation and Characterization of Oligosaccharide Elicitors of Phytoalexin Accumulation

Abstract Plants utilize a variety of defence responses when confronted with invasive micro-organisms (1, 2). These defence reponses include such diverse mechanisms as the synthesis and accumulation of low molecular weight anti-microbial compounds called phytoalexins (3-6), the production of glycosyl hydrolases capable of attacking microbial surface polymers (7), the synthesis of proteins that inhibit microbial degradative enzymes (8, 9), and the modification of plant cell walls by deposition of callose (10, 11), hydroxyproline-rich glycoproteins (12, 13), and/or lignin (14).Biochemical analysis of the induction of plant defence responses has been facilitated by the recognition that cell-free extracts of microbial and plant origin are capable of inducing defence responses when applied to plant tissues. The active components in the extracts are commonly referred to as ‘elicitors’. The term ‘elicitor’ was originally used to refer to molecules and other stimuli that induce phytoalexin synthesis in plant cells (15), but the term is now used to describe molecules that elicit any of the observed plant defence responses.