Pathogenesis-Related Proteins and Plant Defense

The families of pathogenesis-related proteins, their activities, and comparative analysis of PR-1 type proteins

“…SAR, likewise, is a generally occurring phenomenon, that engenders an enhancement of the defensive capacity of plants in response to * All correspondence to be addressed to : L. C. van necrotizing infections [70]. Since some of the tobacco PRs were identified as chitinases [45] and β-1,3-glucanases [38] with potential antifungal activity, it has often been suggested that the collective set of PRs may be effective in inhibiting pathogen growth, multiplication and\or spread, and be responsible for the state of SAR [42,65].…”

“…For the majority of the PR families, activities are known or can be inferred [42,46]. Thus, the PR-2 family consists of endo-β-1,3-glucanases, and PR-3, -4, -8 and -11 are all classified as endochitinases, even though their specific activities on colloidal chitin vary over 100-fold [12].…”

“…Substrate preferences of ten tobacco chitinases purified to homogeneity from tobacco leaves reacting hypersensitively to tobacco mosaic virus (TMV) and belonging to five distinct structural classes, were suggested to represent complementary enzymes which may have synergistic effects on their substrates [12]. Several glucanases and chitinases have been shown to have antifungal properties, although these appear to be restricted to certain fungi [42].…”

Class I β-1,3-Glucanase and Chitinase Are Expressed in the Micropylar Endosperm of Tomato Seeds Prior to Radicle Emergence

“…Both ␤-1,3-glucanase and chitinase are well known as PR proteins, belonging to the PR-2 and PR-3 families, respectively (van Loon, 1999). They are strongly induced when plants respond to wounding or infection by fungal, bacterial, or viral pathogens, and there is compelling evidence that ␤-1,3-glucanase and chitinase, acting alone and particularly in combination, contribute to plant defenses against fungal infection (for review, see Kombrink and Somssich, 1997;Leubner-Metzger and Meins, 1999;Neuhaus, 1999).…”

Snakin-2, an Antimicrobial Peptide from Potato Whose Gene Is Locally Induced by Wounding and Responds to Pathogen Infection

“…Expression of this gene is also up-regulated after infection of potato tubers with the compatible fungus Botritys cinerea and down-regulated by the virulent bacteria Ralstonia solanacearum and Erwinia chrysanthemi. These observations are congruent with the hypothesis that the StSN2 is a component of both constitutive and inducible defense barriers.An important component of plant defense is a diverse set of constitutive and pathogen-inducible antimicrobial compounds that includes the so-called pathogenesis-related proteins, several families of antimicrobial peptides, a variety of chemically diverse organic compounds classified as phytoalexins and phytoanticipins, and certain active oxygen and nitrogen species (Osbourn, 1996(Osbourn, , 1999 Broekaert et al, 1997;Kombrink and Somssich, 1997; García-Olmedo et al, 1998). Accumulation of these compounds and the ability of a given pathogen to deal with them may be decisive for the outcome of the interaction (Titarenko et al, 1997a;Ló pez-Solanilla et al, 1998Miguel et al, 2000; Alamillo and García-Olmedo, 2001;García-Olmedo et al, 2001).…”