Host-specific Toxins in Relation to Pathogenesis and Disease Resistance

Scheffer, R. P.

doi:10.1007/978-3-642-66279-9_11

Cited by 38 publications

(19 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…16), but the mode of action of this compound remains unknown. As an alternative to studying the effect of HC-toxin on maize tissues, we have taken an approach that examines the effect of maize tissues on the biological activity of HCtoxin.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Enzymatic Detoxification of HC-toxin, the Host-Selective Cyclic Peptide from Cochliobolus carbonum

Meeley¹,

Walton²

1991

Plant Physiol.

View full text Add to dashboard Cite

Resistance to the fungal plant pathogen Cochliobolus carbonum race 1 and to its host-selective toxin, HC-toxin, is determined by Hm, a single dominant gene in the host plant maize, (Zea mays L). Radiolabeled HC-toxin of specific activity 70 milliCuries per millimole, prepared by feeding tritiated D,L-alanine to the fungus, was used to study its fate in maize leaf tissues. HC-toxin was converted by resistant leaf segments to a single compound, identified by mass spectrometry and nuclear magnetic resonance as the 8-hydroxy derivative of HC-toxin formed by reduction of the 8-keto group of 2-amino-9,10-epoxy-8-oxodecanoic acid, one of the amino acids in HC-toxin. Reduction of HC-toxin occurred in cell-free preparations from etiolated (Hm/ hm) maize shoots, and the activity was sensitive to heat and proteolytic digestion, dependent on NADPH, and inhibited by phydroxymercuribenzoate and disulfiram. The enzyme (from the Hm/hm genotype) was partially purified by ammonium sulfate precipitation and diethylaminoethyl-ion exchange chromatography. By gel filtration chromatography, the enzyme had a molecular weight of 42,000. NADH was approximately 30% as effective as NADPH as a hydride donor, and flavin-containing cofactors had no effect on activity. When HC-toxin was introduced to maize leaf segments through the transpiration stream, leaf segments from both resistant and susceptible maize inactivated toxin equally well over a time-course of 9 hours. Although these data suggest no relationship between toxin metabolism and host selectivity, we discuss findings in apparent conflict with the current data and describe why the relationship between enzymatic reduction of HC-toxin and Hm remains unresolved.L-Aeo2] (7,8,11,13,22). Both the terminal epoxide and vicinal ketone of Aeo are required for biological activity of HC-toxin and of its naturally-occurring analogs (1,2,9,20).Considerable research has been published on the differential effects of HC-toxin on resistant and susceptible maize (see ref.16), but the mode of action of this compound remains unknown. As an alternative to studying the effect of HC-toxin on maize tissues, we have taken an approach that examines the effect of maize tissues on the biological activity of HCtoxin. Given the requirements for the epoxy-ketone moiety of Aeo, we sought to determine if the integrity of these groups is maintained in vivo. Plants, including maize, are known to contain enzymes capable of inactivating xenobiotic compounds (10). For example, atrazine tolerance in maize is due to elevated levels of glutathione-S-transferase enzymes that inactivate atrazine by conjugation (18). Knowledge of the biochemical fate of HC-toxin within maize tissues lays the groundwork to ultimately address the hypothesis that host selectivity in maize to race 1 of C. carbonum is due to a difference in ability to detoxify HC-toxin.We introduce this topic by presenting a method to prepare tritiated HC-toxin for use in metabolic studies. The biochemical fate of HC-toxin is described as we report the conve...

show abstract

mentioning

confidence: 99%

“…A number of phytopathogenic fungi, especially in the genera Alternaria and Cochliobolus, produce low mol wt compounds known as host-selective toxins that determine their host range and contribute to their virulence (16 …”

mentioning

confidence: 99%

Enzymatic Detoxification of HC-toxin, the Host-Selective Cyclic Peptide from Cochliobolus carbonum

Meeley¹,

Walton²

1991

Plant Physiol.

View full text Add to dashboard Cite

show abstract

“…Many researchers have suggested that toxins may suppress defence mechanisms of the plants (Sheffer 1976;Hayami et al 1980;Otani et al 1980;Ouchi and Oku 1982), but there are only a few published reports supporting the hypothesis (Tietjen and Suzuki 1984;Vidhyasekaran et al 1992;Vurro and Ellis 1997). In this study, the activity of two toxin on suspension-cultured rice cells clearly shows the suppression of various defence enzymes, including phenylpropanoid metabolism, PR-proteins etc.…”

Section: Discussionmentioning

confidence: 53%

Rapid suppression of defence enzymes and compounds by sheath blight (Rhizoctonia solani) and sheath rot (Sarocladium oryzae) toxins in rice cell suspension cultures

Kandan

Commare

Nandakumar

et al. 2010

Archives Of Phytopathology And Plant Protection

View full text Add to dashboard Cite

To understand the suppression mechanisms against disease resistance in rice, we took advantage of the fact that suspension cultured cells exhibit many of the defence responses that are characteristic of intact tissues. In this study we constitutively measured the Rhizoctonia solani and Sarocladium oryzae toxins, induced and suppressed levels of phenylalanine ammonia lyase, peroxidase, superoxide dismutase, phenols, catalase, b-1,3-glucanase and chitinase in rice suspension cultured cells. The addition of Rhizoctonia solani and Sarocladium oryzae toxins separately in suspension cultured cells shows the suppression of defence enzymes and compounds at 24 h and 48 h respectively except SOD. The rice cultivar IR50 delays the disease suppression effect when compared to the other cultivars viz., Pusa Basmati and Co 43. The PR proteins (namely b-1,3-glucanase and chitinase) activities in rice suspension cultured cells were reduced during 48 h and 72 h after the addition of Rhizoctonia solani toxin, whereas the activities were suppressed only after 72 h when inoculated with Sarocladium oryzae toxin. Selective suppression of these defence enzymes and compounds by Rhizoctonia solani and Sarocladium oryzae toxin shows that toxins play a major role during pathogenesis in rice cells.

show abstract

“…Oat cultivars showed similar levels of resistance to both toxin and pathogen, indicating a genetic similarity of resistances to the pathogen and its toxin. The response of host plants to victorin is governed by a single dominant gene (Vb) and paralleles the response to the pathogen itself (Scheffer 1976). It is of interest to note that victorin can function not only as toxin, but also as a specific elicitor of phytoalexin accumulation and stress-responding genes in victorin-sensitive oatlines when applied at a low concentration (Mayama et al 1986;Tada et al 2000).…”

Section: Toxins Produced By Fungal Pathogensmentioning

confidence: 99%

Molecular Biology in Plant Pathogenesis and Disease Management

2008

View full text Add to dashboard Cite

Host-specific Toxins in Relation to Pathogenesis and Disease Resistance

Cited by 38 publications

References 52 publications

Enzymatic Detoxification of HC-toxin, the Host-Selective Cyclic Peptide from Cochliobolus carbonum

Enzymatic Detoxification of HC-toxin, the Host-Selective Cyclic Peptide from Cochliobolus carbonum

Rapid suppression of defence enzymes and compounds by sheath blight (Rhizoctonia solani) and sheath rot (Sarocladium oryzae) toxins in rice cell suspension cultures

Molecular Biology in Plant Pathogenesis and Disease Management

Contact Info

Product

Resources

About