metallothionein and Wounds-and-Injuries

The cloning and characterization of genes expressed in plant disease resistance could be an initial step toward understanding the molecular mechanisms of disease resistance. A metallothionein-like gene that is inducible by tobacco mosaic virus and by wounding was cloned in the process of subtractive cloning of disease resistance-response genes in Nicotiana glutinosa. One 530-bp cDNA clone (KC9-10) containing an open reading frame of 81 amino acids was characterized. Genomic Southern blot hybridization with the cDNA probe revealed that tobacco metallothionein-like genes are present in few or in one copy per diploid genome. Northern blot hybridization detected strong induction of a 0.5-kb mRNA by wounding and tobacco mosaic virus infection, but only mild induction was detected when copper was tested as an inducer. Methyl jasmonate, salicylic acid, and ethylene were also tested as possible inducers of this gene, but they had no effect on its expression. The possible role of this gene in wounded and pathogen-stressed plants is discussed.

Topics: Amino Acid Sequence; Base Sequence; Cloning, Molecular; DNA, Complementary; Ethylenes; Genes, Plant; Immunity, Innate; Metallothionein; Molecular Sequence Data; Nicotiana; Open Reading Frames; Plant Diseases; Plant Proteins; Plants, Toxic; Sequence Homology, Amino Acid; Tobacco Mosaic Virus; Transcription, Genetic; Wounds and Injuries

Transgenic mice expressing v-jun under the control of the H-2K promoter develop dermal fibrosarcomas and rhabdomyosarcomas via a multistep process following wounding. To assess the relative roles that wounding and the H-2K promoter play in this process, we compared the phenotype of H-2K-v-jun mice with that of animals expressing v-jun under the control of the metallothionein I (MTI) promoter. MT-v-jun animals also develop wound-induced neoplasms by a multistage process. Both early and late features of tumorigenesis in MT-v-jun mice are different, however, from what is observed in H-2K-v-jun animals. First, the acute hyperplastic response that is characteristic of H-2K-v-jun granulation tissue is not observed in MT-v-jun wounds. Second, the myogenic components that are readily detected in the majority of late stage H-2K neoplasms are never observed in their MT counterparts. Moreover, analysis of wound tumours arising in animals expressing both MT-v-jun and H-2K-v-jun reveals that the two transgenes are not expressed in identical malignant cell populations. These results imply that mesenchymal granulation tissue is heterogeneous in composition and that the different cellular phenotypes of MT-v-jun and H-2K-v-jun malignancies result from oncogenic activation of wound-derived cells which differ in their differentiation potential. Thus, whereas the wounding component of multistage tumorigenesis is attributable to the action of v-jun, the transcriptional regulatory elements which drive its expression determine the nature of the target cells which give rise to wound-induced neoplasms.

Topics: Animals; Gene Expression; Genes, jun; H-2 Antigens; Metallothionein; Mice; Mice, Transgenic; Muscles; Sarcoma, Experimental; Skin Neoplasms; Tumor Cells, Cultured; Wounds and Injuries

A striking radioresistance has been found in mice which were subjected to various pretreatments to induce metallothionein synthesis in the liver prior to irradiation. The tolerance to lethal damage from an LD50 level of radiation during a 30-day postirradiation period was demonstrated by a highly significant difference (P less than 0.01) in mortality rate between mice given subcutaneously manganese, cadmium, or zinc injection or surgical skin excision of mice and the control mice (no pretreatment). A typical loss in body weight that generally reached a peak 2 weeks after irradiation was observed in the control mice, but mice given a dose of 10 mg manganese per kilogram body weight showed a steady weight increase even a few days after irradiation. The normal level of metallothionein in mouse liver is 20 micrograms/g tissue. This level increased up to 70 micrograms/g tissue following irradiation at 6.3 Gy. Among irradiated mice, metallothionein levels in the liver increased approximately 200-800% after cadmium, manganese, or zinc injection compared to levels of irradiated mice without pretreatment. Mice undergoing 2 X 2-cm2 dermal excision also demonstrated a similar reduction of mortality and high metallothionein contents in liver, i.e., 150-400 micrograms/g. The present results, together with our previous findings (Matsubara et al., 1982, 1983, 1984; Matsubara, 1986), suggest that the body's protective mechanism against radiation strongly correlates with the biosynthesis of metallothionein or metallothionein itself acting as a scavenger of radiation-induced peroxides.

Topics: Acetates; Acetic Acid; Animals; Body Weight; Cadmium; Cadmium Chloride; Chlorides; Cold Temperature; Liver; Male; Manganese; Manganese Compounds; Metallothionein; Mice; Radiation Tolerance; Whole-Body Irradiation; Wounds and Injuries