Differential Effects of Phenylalanine Ammonia Lyase, Cinnamyl Alcohol Dehydrogenase, and Energetic Metabolism Inhibition on Resistance of Appropriate Host and Nonhost Cereal–Rust Interactions

Abstract

Effects of phenylpropanoid and energetic metabolism inhibition on resistance were studied during appropriate host and nonhost cereal-rust interactions. In the appropriate barley-Puccinia hordei interaction, phenylalanine ammonia lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) inhibition reduced penetration resistance in two genotypes, suggesting a role for phenolics and lignins in resistance. Interestingly, penetration resistance of the barley genotype 17.5.16 was not affected by phenylpropanoid biosynthesis but penetration resistance was almost completely inhibited by D-mannose, which reduces the energy available in plant host cells. This suggests a parallel in the cellular basis of penetration resistance between 17.5.16 rust and mlo barleys powdery mildew interaction. Results revealed differing patterns of programmed cell death (PCD) in appropriate versus nonhost rust interactions. PAL and CAD inhibitors reduced PCD (hypersensitivity) in appropriate interactions. Conversely, they had no effect in PCD of wheat to P. hordei; whereas D-mannose dramatically reduced nonhost resistance and allowed colony establishment. The differential effects of inhibitors in the expression of the different resistances and the commonalities with the cereal-powdery mildew interaction is analyzed and discussed.

Quantitative Proteomic Analysis of Bean Plants Infected by a Virulent and Avirulent Obligate Rust Fungus

“…The basal defense system as a whole is conditioned to reach a threshold inherently strong enough to create an incompatible environment for colonization of most potential pathogens (46,68,72,73). Such a response may be tied to insusceptibility and programmed cell death (19,20).…”

“…Resistant plants also had more cinnamyl alcohol dehydrogenase (CAD) at 72 hpi. Cinnamyl alcohol dehydrogenase accumulation is important for basal penetration resistance to nonadapted rusts and likely contributes to cell wall lignification and papillae formation (20). Resistant plants accumulated less 9/13 hydroperoxidase and triacylglycerol lipase, both of which are homologous to the lipoxygenases in the set of proteins defining the basal defense response.…”

“…Other processes are initiated as well, including proteolysis (11,12), fortification of cell walls (12,13), and expression of many of the same genes (14 -16). Even programmed cell death, once thought to be the final step and clear indicator of gene-forgene resistance (17), may be part of defense responses not specifically regulated by R-genes (18,19), especially against rusts (20).…”

Disruption of Poly(ADP-ribosyl)ation Mechanisms Alters Responses of Arabidopsis to Biotic Stress

“…3C). Treatment of seedlings with L-a-aminooxy-b-phenylpropionic acid (AOPP), a chemical inhibitor of PAL activity (Kudakasseril and Minocha, 1986;Prats et al, 2007;Pan et al, 2008), reduces the accumulation of this pigment ( Fig. 3D), suggesting that this pigment is likely a product of the phenylpropanoid pathway.…”

Resistance to rusts (Uromyces pisi and U. viciae-fabae) in pea

“…A relatively high proportion of germlings failing to form any haustoria in mesophyll cells causing "early aborted colonies" has been observed in some pea accessions (Table 2). Probably, epidermal cells developed papillae and/or cell wall strengthening under the site of the attempted attack avoiding the fungus penetration, as described previously in other plant-rust interactions (Prats et al 2007b;Rojas-Molina et al 2007). Further studies are currently carried out to study host cell Table 2.…”