Are 'Pathogenesis-related' Proteins Involved in Acquired Systemic Resistance of Tobacco Plants to Tobacco Mosaic Virus?

Abstract

SUMMARYFour host-coded 'pathogenesis-related' proteins accumulate systemically in locallesion-forming varieties of tobacco after infection with tobacco mosaic virus. It has been suggested that they are involved in the acquired systemic resistance of plants to a second inoculation. Pathogenesis-related protein concentration and amount of resistance (reduction in size and number of lesions formed in the second inoculation) were measured at various times after the first inoculation. The results showed no quantitative or temporal relationship between amounts of resistance and pathogenesis-related proteins. In particular, resistance could be demonstrated in leaves before detectable accumulation of pathogenesis-related protein. Abscisic acid sprayed on plants induced an apparent resistance without inducing pathogenesisrelated proteins. Low doses of methyl benzimidazol-2yl-carbamate caused accumulation of pathogenesis-related protein but not resistance. Nicotiana glutinosa plants accumulated large amounts of a similar protein after infection, but became more susceptible to a second inoculation. All these results suggest that the pathogenesis-related proteins do not play a central role in the mechanism of acquired systemic resistance.

Arbuscular Mycorrhizal Symbiosis Limits Foliar Transcriptional Responses to Viral Infection and Favors Long-Term Virus Accumulation

“…In tomato, high ABA levels are predominantly associated with high susceptibility but, in Arabidopsis, both positive and negative effects have been reported (Asselbergh et al 2008a). It is known that TMV infection is able to increase ABA concentration in tobacco (Fraser 1982;Whenham et al 1986) and that infecting bacteria enhance ABA levels in early stages of interaction in order to promote plant infection (Maksimov 2009). Mutants unable to synthesize ABA show enhanced resistance to several biotrophic and necrotrophic fungi (Maksimov 2009;Mauch-Mani and Mauch 2005).…”

Abscisic acid enhances resistance to Alternaria solani in tomato seedlings

“…Fraser found that treatment with ABA causes a 70% reduction in lesion number [17]. Treatment of barley roots with ABA activated resistance in response to Blumeria graminis f. sp.…”

Pathogenesis-related Proteins

“…Compounds known to enhance resistance to viruses in animal systems, such as 2-thiouracil and dioxohydrotriazine, were found to induce PRS in plants (White et al, 1986). Methylbenzimidazol-2-yl-carbonate, which has cytokinin-like properties (Fraser, 1982), and a number of amino acids and their analogues (Asselin, et al,.1985) exhibited some degree of PR gene induction, as did several metal ions such as silver, cadmium, manganese, and barium (Asselin et al,1985;White et al, 1986). Two compounds associated with phosphatidylinositol metabolism, phytic acid (Maiss and Poehling, 1983) and arachidonic acid (Malamy et al, 1991) also stimulate PR gene expression.…”