Induction of pathogen resistance and pathogenesis-related genes in tobacco by a heat-stable Trichoderma mycelial extract and plant signal messengers

Abstract

1997. Induction of pathogen resistance and pathogenesis-related genes in tobacco by a heat-stable Trichoderma mycelial extract and plant signal messengers. -Physiol. Plant. 100: 341-352.Heat-stable mycelial extracts of the nonpathogenic fungus Trichoderma longibrachiatum induced resistance in tobacco seedlings {Nicotiana tabacum L. cv. Wisconsin 38) to the pathogen Phytophthora parasitica var. nicotianae (race 0), which did not involve a hypersensitive response. Resistance could not be induced with mycelial extract prepared in the same manner from P. parasitica. The nonpathogenic mycelial extract induced expression of PR-lb and osmotin (PR-5) genes to a higher level than did mycelial extract from the pathogenic fungus. The tissue-specific pattem of PR gene induction by the nonpathogenic mycelial extract was different from that of the pathogenic mycelial extract and was consistent with the ability of the former to cause disease resistance. The expression pattems of these two PR genes and the accumulations of their encoded proteins also were affected by salicylic acid (SA), methyl jasmonate (MeJA), ethylene (E) and combinations of these plant signal messengers. However, only combined SA and MeJA treatment mimicked the pattem of PR gene mRNA and protein accumulation induced by the nonpathogenic mycelial extract. E inhibitors blocked both mycelial extract-induced and SA/MeJA-induced PR gene expression, and the cis pattem of responsiveness on the osmotin promoter was the same for the mycelial extract, SA, E, or E/MeJA. Seedlings treated with P. parasitica spores in the presence of SA/MeJA were protected from pathogen colonization. However, these seedlings exhibited symptoms of cell death (disease symptoms) both in the absence and presence of P. parasitica spores, in contrast to seedlings treated with nonpathogenic mycelial extract, which remained healthy. These results suggest that the signal transduction pathways for elicitation of defense responses by exogenously applied heat-stable nonpathogenic mycelial extract and SA/MeJA overlap at the point of PR protein induction but are not identical.

A PR‐5 gene promoter from Asparagus officinalis (AoPRT‐L) is not induced by abiotic stress, but is activated around sites of pathogen challenge and by salicylate in transgenic tobacco

“…Basic PR-5 proteins include osmotins, which accumulate following a variety of osmotic stresses, but which also exhibit a high degree of constitutive and developmental expression (Leone et al , 1994;Linthorst, 1991;Stinzi et al , 1993;Van Kan et al , 1995). Both acidic and basic PR-5s are expressed following pathogen challenge (Boyd et al , 1994;Bryngelsson and Green, 1989;Chang et al , 1997;Jacobs et al , 1999;Reiss & Bryngelsson, 1996;Vale et al , 1994;Zhu et al , 1995a,b). Individual PR-5s may be up-regulated in a pathogenspecific fashion.…”

“…A number of PR-5 proteins, notably osmotins, accumulate following exposure to a variety of environmental stresses and the signals associated with these stresses. Thus osmotins accumulate in response to desiccation, wounding, temperature, cytokinins and ethylene treatment (Chang et al , 1997;Grillo et al , 1995;Raghothama et al , 1993;Thomas and Bohnert, 1993;Zhu et al , 1995b). Similarly, acid PR-5 protein accumulation has been detected in sunflower treated with ethephon, and exposed to UV light (Jung et al , 1995).…”

“…Both acidic and basic PR‐5s are expressed following pathogen challenge (Boyd et al. , 1994; Bryngelsson and Green, 1989; Chang et al. , 1997; Jacobs et al.…”

“…A number of PR‐5 proteins, notably osmotins, accumulate following exposure to a variety of environmental stresses and the signals associated with these stresses. Thus osmotins accumulate in response to desiccation, wounding, temperature, cytokinins and ethylene treatment (Chang et al. , 1997; Grillo et al.…”

Protein pattern changes induced by culture filtrate of Pseudomonas syringae pv. phaseolicola in bean (Phaseolus vulgaris L.) explants cultured in vitro

“…In bean, PR proteins have been induced in french bean (Phaseolus vulgaris) and lima bean (P. lunatus) leaves infected with a virus [8,27,34] and fungi [5,7]. The induction of PR proteins is not an exclusive pathogen-specific response because these proteins are synthesized under different stress conditions, and the elicitoractive molecules are chemically diverse: glycans, glycoproteins and lipids isolated from fungal and bacterial cell walls and culture filtrates, and a variety of structurally unrelated, artificial inducers [6,10]. In fact, exposure of bean leaves to mercuric chloride or ethylene induces PR proteins [8,38].…”