Molecular response of plants to infection

Abstract

Plants exhibit resistance to disease involving inducible defenses including phytoalexin and hydroxyproline-rich glycoprotein (HRGP) accumulation, lignin deposition and increased activity of certain hydrolytic enzymes. Treatment of suspension-cultured cells of Phaseolus vulgaris L. with fungal elicitors redirects RNA synthesis leading to induction of mRNAs encoding phytoalexin biosynthetic enzymes such as phenylalanine ammonia-lyase and chalcone synthase; the lignin precursor biosynthetic enzyme cinnamyl alcohol dehydrogenase and HRGP. Accumulation of defense mRNAs is also observed during race:cultivar specific interactions between the fungus Colletotrichum lindemuthianum and P. vulgaris hypocotyls. There are clear temporal and spatial differences in the pattern of mRNA accumulation between incompatible (host resistant) and compatible (host susceptible) interactions. The data suggest that specific activation of plant defense genes is a key early component in the sequence of events leading to expression of defense reponses during race:cultivar specific interactions and that an elicitation signal is transmitted intercellularly to pre-activate defense genes in hitherto uninfected tissue. These observations indicate a number of potential sites for biotechnological manipulation and enhancement of disease resistance.