Gottfried Schuster

Evidence for the Inhibition of Potato Virus X Replication at Two Stages Dependent on the Concentration of Ribavirin, 5-Azadihydrouracil as well as l,5-Diacetyl-5-azadihydrouracil

Summary The time courses of the inhibition of PVX (potato virus X) synthesis by ribavirin and 5-azadihydrouracil (= 5-ADHU = 2,4-dioxohexahydro-l,3,5-triazine) were determined in leaf disks from mechanically inoculated leaves of Nicotiana tabacum L. “Samsun” kept either at permissive temperatures (20 ± 2 °C) or for 5 days at temperatures of 5 ± 2°C followed by a shift to permissive temperatures. By both of these methods ribavirin and 5-ADHU at low concentrations (0.002 mM and 5 mM, respectively) inhibit the replication cycle of PVX at an early function prior to the period of viral RNA synthesis. In a tenfold higher concentration the two substances inhibit a later event. 1,5-Diacetyl-5-ADHU (= DA-ADHU) also inhibits the replication cycle of PVX dependent on the concentration at two stages. However, the first inhibited event is earlier and the second event later than the corresponding events acted on by ribavirin and 5-ADHU. Whereas in high doses uracil overcomes the inhibition by 5-ADHU of the early and, partially, of the late event, the inhibition caused by DA-ADHU is not reversed by uracil.

Dioxohexahydrotriazin, eine neue vollsynthetische antiphytovirale Verbindung

Summary This paper reports the first results of studies made to determine the antiviral activity of dioxo hexahydro triazine, a newly developed antiphytoviral compound. After treatment with dioxo hexahydro triazine, the concentration of helical potato virus X in leaves of Nicotiana tabacum “Samsun” was found to be considerably reduced in both the serological test and local lesion test conducted on Nicotiana glutinosa at temperatures of 14°C ± 3°C. In secondarily infected leaves, the reduction of the concentration of potato virus X in the range of from 1 mol/l to 10 −3 mol/l was so that it was no longer possible for viruses to be detected serologically. In vitro, however, dioxo hexahydro triazine, which was added to the inoculum, did not produce a significant change in the activity of the virion of potato virus X. Therefore, it is reasonable to assume that dioxo hexahydro triazine tends to affect replication steps of viruses. The use of dioxo hexahydro triazine also had the effect of greatly and highly significantly reducing the concentration of the isodiametric cucumber mosaic virus.

Wachstumsregulatorische Wirkungen von 5-Azadihydrouracil und Ribavirin

Summary Growth regulatory effects of 5-azadihydrouraeil ( = 5-ADHU = 2,4-dioxohexahydro-1,3,5-triazine), an analog of a catabolite of uracil with high activity against numerous plant viruses, and ribavirin ( = 1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxamide), an analog of an anabolite of purinbases with remarkable activities against numerous human and plant pathogenic: viruses were investigated. In several bioassays 5-ADHU as well as ribavirin exhibited considerable cytokinin-analogous activities. Generally, the cytokinin activities of 5-ADHU were obtained at higher concentrations than that of the reference cytokinins. Auxin-effects eould be proved too for both substances, using two different bioassays. But the auxin-activities of both substances remained low in comparison with the reference-IAA effects. Gibberellin-effects, tested by two gibberellin-bioassays, could not be shown. 5-ADHU and ribavirin increased the endogenous cytokinin content of healthy and PVX infected plants and the auxin content of healthy plants.

Virus-induced virus inhibitors from systemically virus-infected plants

After infection ofNicotiana tabacum cv. Samsun with tobacco mosaic virus (TMV) crude extracts from dark-green spots of upper leaves had a more strongly marked inhibitory effect upon TMV addedin vitro than crude extracts from the surrounding light-green tissue. Likewise, crude extracts from leaves ofNicotiana tabacum cv. Samsun showing recovery after infection with tobacco ringspot virus (TRV) were seen to have a marked inhibitory effect on TMV addedin vitro. The results obtained suggest that virus inhibitors are produced after virus infections not only in hypersensitive hosts but also in systemic hosts. Necrotizing processes are not an indispensable prerequisite of the production of virus-induced virus inhibitors.

Aufnahme, Transport und Persistenz der antiphytoviralen Substanz 2,4.Dioxohexahydro-l,3,5.triazin (DHT) in Nicotiana tabacum L. „Samsun“

Summary 37.1 % of the activity of [6-14C]-DHT (2,4-dioxo hexahydrotriazine = 5-azadihydrouracil) were incorporated into the plant within 24 h after application to the surface of leaves of Nicotiana tabacum L. “Samsun”. Leaves inserted above the treated leaf contain 20.9 percent of the radioactivity incorporated, whereas leaves inserted below the treated leaf, the stalk, and the root contained 18.7%, 26.7%, and 19.8 %, respectively. Accordingly, radioactivity was systemically transported both acropetally and basipetally. Experiments with nonlabeled DHT confirmed the high mobility of this substance. They also showed that DHT is readily absorbed through the root, whereas the epidermis of the leaves represents a substantial barrier of penetration. The persistence of DHT was determined in leaves, into which nonlabeled DHT had been immigrated from the root or from injected leaves. With initial concentrations between 140 and 190 ppm, the content of DHT reached in the investigated leaves its limit for detection between two and three weeks after application.

Persistenz des antiphytoviralen Präparates 2,4-Dioxohexahydro-1,3,5-triazin (DHT) in verschiedenen Böden

Summary Studies have been made to investigate the persistence of 2,4-dioxohexahydro-1,3,5-triazine (DHT), a newly developed antiphytoviral compound, in different soils. The results obtained show that the persistence of DHT is relatively low. It was above all within the first few days after incorporation into the soil that a substantial reduction in the initial amounts of DHT could be observed in all of the various experiments conducted. DHT was decomposed far more rapidly in high humus soils (compost soil, nursery bed soil) than in low humus soils (brown deep-loam similigley, black loess soil). In autoclaved soil an initial stagnation of decomposition was observed. From this the involvement of soil microorganisms in the decomposition of the active agent may by concluded.

Kinetin ( 6 Furfurylaminopurine) Inhibits the Replication Cycle of Potato Virus X at a Distinct Event

Summary The time course of inhibition of PYX (potato virus X) synthesis by kinetin was determined in synchronously infected disks from leaves of Nicotiana tabacum L. “Samsun”. Synchrony was obtained in one series of experiments by the differential temperature inoculation method. In a second series the synchrony of the first replication cycle was used. The results of both series demonstrate that kinetin (0.1 mM) inhibits an event of the replication cycle of PVX, which occurs later than the early event influenced by the reference substance 2-thioracil and earlier than the late event inhibited by the reference substance cycloheximide. It coincides with the event inhibited by the amino acid analogue ethionine. These data suggest that kinetin may inhibit the initiation of the synthesis of virus coat protein.

On in vitro and in vivo binding of tobacco mosaic virus to cytoplasmic membranes

Summary TMV contents were determined in 20 fractions separated in 10 to 50% saccharose gradients of resuspended 1,000 to 20,000 · g pellets from TMV-infected leaves of Nicotiana tabacum L. “Samsun” A maximum content was observed in the fraction containing 27 % saccharose. This fraction is characterized by a high proportion of smooth cytoplasmic (SC) membranes. These SC membranes proved are to be able in in vitro binding of considerable quantities of TMV. Bovine serum albumin (BSA) prevents the adsorption of subsequently added TMV to SC membranes but cannot detach previously bound TMV. When BSA was added before the preparation of membrane fractions, the SC membranes from TMV-infected plants remained contaminated with TMV. This results provides evidence for TMV binding to SC membranes already in vivo. Using 3 M KCl and subsequent dialysis or 0.1 % Triton X-100 suggested that ionic forces as well as hydrophobic interactions may be involved in the binding of TMV to SC membranes.

Effect of 2,4-Dioxohexahydro-l,3,5-triazine (5-Azadihydrouracil) on RNA Synthesis and Content of Tobacco Mosaic Virus and its Host Plant Nicotiana tabacum “Samsun”

Summary We studied the effect of 2,4-dioxo hexahydro-l,3,5-triazine (DHT or 5-azadihydrouracil), a newly developed antiphytoviral compound, on formation and content of tobacco mosaic virus (TMV) RNA and RNA of the host plant, Nicotiana tabacum L. “Samsun”.

Zur Wirkung von s-Triazinen auf Gewebe gesunder und virusinfizierter Kartoffelknollen

Summary Germ-free tissue cuts from healthy and virus infected potato tubers died after treatment with s-Triazine compounds. It is therefore rather improbable, that the impairment of the photosynthesis, which has been observed in green parts of plants after application of s-Triazine compounds, represents the essential or even the solitary cause of the herbicide effect. The insignificant differences in the reactions to s-Triazines by tissues of healthy and virus infected tubers can hardly be suitable as a basis for the development of techniques for virus diagnosis.