The phenylpropanoid pathway and plant defence—a genomics perspective

Abstract

Summary The functions of phenylpropanoid compounds in plant defence range from preformed or inducible physical and chemical barriers against infection to signal molecules involved in local and systemic signalling for defence gene induction. Defensive functions are not restricted to a particular class of phenylpropanoid compound, but are found in the simple hydroxycinnamic acids and monolignols through to the more complex flavonoids, isoflavonoids, and stilbenes. The enzymatic steps involved in the biosynthesis of the major classes of phenylpropanoid compounds are now well established, and many of the corresponding genes have been cloned. Less is understood about the regulatory genes that orchestrate rapid, coordinated induction of phenylpropanoid defences in response to microbial attack. Many of the biosynthetic pathway enzymes are encoded by gene families, but the specific functions of individual family members remain to be determined. The availability of the complete genome sequence of Arabidopsis thaliana, and the extensive expressed sequence tag (EST) resources in other species, such as rice, soybean, barrel medic, and tomato, allow, for the first time, a full appreciation of the comparative genetic complexity of the phenylpropanoid pathway across species. In addition, gene expression array analysis and metabolic profiling approaches make possible comparative parallel analyses of global changes at the genome and metabolome levels, facilitating an understanding of the relationships between changes in specific transcripts and subsequent alterations in metabolism in response to infection.

The RNA Hydrolysis and the Cytokinin Binding Activities of PR-10 Proteins Are Differently Performed by Two Isoforms of the Pru p 1 Peach Major Allergen and Are Possibly Functionally Related

“…Moreover, the promoter of aoPR1 gene contains sequence motifs similar to those found in the phenylpropanoid genes (Warner et al, 1994). These data suggest that PR-10 proteins act in concert with the phenylpropanoid pathway, which is known to be involved in several plant defense responses (Dixon et al, 2002) or that phenylpropanoid intermediates regulate PR-10 gene expression (Warner et al, 1994). PR-10 proteins have been considered a multifunctional protein family, encompassing different functional subfamilies that share homology in tertiary structure in spite of low sequence similarity.…”

Spatio Temporal Influence of Isoflavonoids on Bacterial Diversity in the Soybean Rhizosphere

“…Isoflavonoids have been implicated in nonspecific defense against plant pathogens (Dixon 2001;Dixon et al 2002). Isoflavonoids also regulate nod genes in rhizobia bacteria, specifically B. japonicum (Kosslak et al 1987).…”

On plant defense signaling networks and early land plant evolution

“…Furthermore, an ortholog of phenylalanine ammonia lyase (PAL), the enzyme catalyzing the first step in the phenylpropanoid (PP) pathway, was detected in the genome of K. nitens [121]. The PP pathway is also a source for SA biosynthesis [122]. Moreover, potential homologs for the SA receptor Nonexpressor of PR genes 1 (NPR1) [123], were reported for all land plants [113] and the putative NPR1 homolog of P. patens can partially complement defense signaling-associated phenotypes of the Arabidopsis npr1 mutant [124].…”

“…PPs and PP-derived compounds, such as lignins, lignans, flavonoids and stilbenes, are defense metabolites, because they i) can be toxic for pathogens and/or ii) reinforce cell wall structures, thereby reducing the possibility of penetration by pathogens [122,148]. PAL encodes the first enzyme in the PP pathway [122]. It shows a strong responsiveness to pathogens or exogenously applied JA in gymnosperms and JA and SA in mosses [62,63,73,143,149,150].…”