Effects of Helminthosporium carbonum race 1 toxin on host and non-host cereal protoplasts

Wolf, S. J.; Earle, Elizabeth D.

doi:10.1016/0168-9452(91)90226-x

Cited by 17 publications

(11 citation statements)

References 36 publications

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“…Root growth, nitrate uptake, chloroplast distribution, protoplast survival, and chlorophyll synthesis are half maximally affected by HC toxin at similar concentrations (Yoder and Scheffer, 1973;Walton et al, 1982Walton et al, , 1985Rasmussen and Scheffer, 1988;Wolf and Earle, 1991). HC toxin in which the 8-ketone of Aeo has been reduced to an alcohol or in which the 9,10-epoxide of Aeo has been hydrolyzed to a diol is much less active in cellular and whole-plant bioassays (Walton and Earle, 1983;Kim etal., 1987;Meeley etal., 1992) and has greatly reduced activity against HD (Table 2).…”

Section: Discussionmentioning

confidence: 99%

“…The reason for this discrepancy is unclear but could be due to different structural properties of the active center of HDs from plants and mammalian cells. Considering their similar chemistries (Shute et al, 1988) and reciprocal biological activities in other assays (Walton et al, 1985;Wolf and Earle, 1991), it is likely that all five members of the Aeo-containing cyclic tetrapeptide family act as inhibitors of HDs, perhaps in all species.…”

Section: Discussionmentioning

confidence: 99%

“…Stimulation of nitrate uptake by HC toxin has not been shown to be due to increased nitrate reductase activity (Yoder and Scheffer, 1973), but the nitrate transporters of Arabidopsis (Tsay et al, 1993) and Aspergi//us (Unkles et al, 1991) and their mRNAs are substrate induced and nitrogen metabolite repressed. Protoplasts incubated in simple high molarity medium undergo morphological and physiological changes similar to senescence, a developmental process requiring de novo gene expression (Thomas and Stoddart, 1980;Davies and Grierson, 1989); HC toxin prevents these changes from occurring (Wolf and Earle, 1991). The step in chlorophyll biosynthesis that is blocked by HC toxin, Gaminolevulinic acid synthesis, is the sole light-inducible component of an otherwise constitutive pathway (Rasmussen and Scheffer, 1988).…”

Section: Discussionmentioning

confidence: 99%

“…HC toxin inhibits cell division in mammalian cells and kills them slowly (Walton et al, 1985); it also stimulates uptake of nitrate and some other ions (Yoder and Scheffer, 1973). Nondividing leaf mesophyll protoplasts incubated in HC toxin undergo only sÚbtle morphological changes and, over long periods of time, survive better than do control protoplasts (Wolf and Earle, 1991 Yoshida and Sugita (1992) reported that trapoxin, an analog of HC toxin with structure cyclo(L-Phe-L-Phe-D-Pip-L-Aeo), causes detransformation of sis-oncogene-transformed mammalian cells. Trichostatin, a chemically unrelated antibiotic, has the same effect.…”

Section: Introductionmentioning

confidence: 99%

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Inhibition of maize histone deacetylases by HC toxin, the host-selective toxin of Cochliobolus carbonum.

et al. 1995

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HC toxin, the host-selective toxin of the maize pathogen Cochliobolus carbonum, inhibited maize histone deacetylase (HD) at 2 pM. Chlamydocin, a related cyclic tetrapeptide, also inhibited HD activity. The toxins did not affect histone acetyltransferases. After partia1 purification of histone deacetylases HD1-A, HD1-B, and HD2 from germinating maize embryos, we demonstrated that the different enzymes were similarly inhibited by the toxins. lnhibitory activities were reversibly eliminated by treating toxins with 2-mercaptoethanol, presumably by modifying the carbonyl group of the epoxidecontaining amino acid Aeo (2-amino-9,1O-epoxy-8-oxodecanoic acid). Kinetic studies revealed that inhibition of HD was of the uncompetitive type and reversible. HC toxin, in which the epoxide group had been hydrolyzed, completely lost its inhibitory activity; when the carbonyl group of Aeo had been reduced to the corresponding alcohol, the modified toxin was less active than native toxin. In vivo treatment of embryos with HC toxin caused the accumulation of highly acetylated histone H4 subspecies and elevated acetate incorporation into H4 in susceptible-genotype embryos but not in the resistant genotype. HDs from chicken and the myxomycete Physarum polycephalum were also inhibited, indicating that the host selectivity of HC toxin is not determined by its inhibitory effect o n HD. Consistent with these results, we propose a model in which HC toxin promotes the establishment of pathogenic compatibility between C. carbonum and maize by interfering with reversible histone acetylation, which is implicated in the control of fundamental cellular processes, such as chromatin structure, cell cycle progression, and gene expression.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Inhibition of maize histone deacetylases by HC toxin, the host-selective toxin of Cochliobolus carbonum.

et al. 1995

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“…HC-toxin, for example, does not kill nondividing leaf mesophyll protoplasts but actually promotes their survival (Wolf and Earle, 1991), an effect that is perhaps related to its function as a suppressor of defense responses (see below). Light suppresses the symptoms of AM-toxin toxicity without altering the response of the host plant to the fungus (Tabira et al, 1989 Not shown is the 13.2-kD proteinaceous HST, Ptr-toxin, of Pyrenophora tritici-repentis.…”

Section: Biochemical Bases Of Hst Action and Speclflcltymentioning

confidence: 99%