Mode of Pisatin Induction

Abstract

Increases in phenylalanine ammonia lyase activity and pisatin synthesis were induced in excised pea pods (a) by basic polypeptides such as protamine, histone, lysozyme, cytochrome c, and ribonuclease; (b) by the polyamines spermine, spermidine, cadaverine, and putrescine, and (c) by the synthetic oligopeptides poly-L-lysine, poly-DL-ornithine, and poly-Poly-L-lysine (1 milligram per milliliter, molecular weight 7,200) was utilized as a model inducer of pisatin and phenylalanine ammonia lyase. The poly-L-lysine-induced responses could be inhibited by adding the RNA synthesis inhibitors cordycepin or a-amanitin to the pods prior to or at the time of inducer application. Cordycepin added 1.5 hours after inducer no longer completely inhibited induction. The application of poly-L-lysine was shown to characteristically change the rate of RNA synthesis within 30 minutes. Ultrastructural changes in pea nuclei were detected within 3 hours, and gross changes in nuclear morphology were apparent at 14 hours after inducer application. The physical appearance of uranyl acetate-stained chromatin isolated from poly-L-lysine 2 hours after inducer application differed from that of water-treated tissues. The template properties of chromatin extracted from pods 3 hours after inducer application were consistently superior to control chromatin when assayed with Escherichia coli RNA polymerase (without sigma factor). Chromatin from poly-L-lysine-induced tissue also bound 49% more actinomycin D-'H.The DNA-complexing properties of inducer compounds and the induced changes in the template and dye-binding properties of pea chromatin formed the basis for a proposed mode of action for phytoalexin induction.The functions of numerous polypeptide hormones (5) have been characterized in animal systems; however, interest in the potential role of polypeptides in regulating plant processes is still limited. There is reason to believe that numerous polypeptide components remain to be discovered which can influence plant cell processes (46). Phytoalexin induction in pea tissue has been employed as one measure of the effects of chemically defined compounds on the regulation of cell processes (12,(15)(16)(17)(18)(19)(20)(21)38). We now report that basic peptides can induce gene-controlled responses, and we demonstrate that this gene-activating potential exists for basic compounds (2, 41, 47) which occur in plants and other higher organisms.The synthetic compound, poly-L-lysine, was chosen as a model inducer because of its amino acid residue uniformity and chemical simplicity. This paper examines the phytoalexininducing effect of poly-L-lysine in relation to (a) alteration of the fine structure of nuclei and cell membranes, (b) template activity and dye-binding capacity of isolated chromatin, (c) the in vivo rate of RNA synthesis, and (d) the dependency of the induction process on RNA and protein synthesis.Our previous hypothesis (20, 38) that regulation of gene expression can occur as a result of changes in the conformation of specific segment...

Localization of Fungal Components in the Pea-Fusarium Interaction Detected Immunochemically with Anti-chitosan and Anti-fungal Cell Wall Antisera

“…nucleus is compatible with our recent studies on phytoalexin induction which indicate that this response is induced by compounds which initially and specifically modify the pea DNA (8,11,12,20).…”

Chitosan as a Component of Pea-Fusarium solani Interactions

“…DNA Specificity of Chitosan. Since chitosan mimics the action of fungi in inducing phytoalexin production and many of the compounds known to induce pisatin are highly DNA-specific (12,17,18,23), the affmity of chitosan for DNA was evaluated with comparable affinity columns prepared from cellulose and chitosan. Short fragments of calf thymus DNA were differentially retained by the chitosan column at salt concentrations up to 4.0 M. These same fragments were completely recovered from cellulose columns eluted with 100 mm NaCl (Fig.…”

“…The components involved with the spontaneous communication of these effects have not been identified. There are, however, numerous pure chemicals and chromatographically characterized cell fractions which can substitute for the fungal cell in eliciting phytoalexin production (2,4,8,9,12,(17)(18)(19), a biochemical monitor of the host response, which starts within 6 h in most legumes (13,20). Many fractions of the fungal cell can elicit phytoalexin production in peas (R. Dobson and L. A. Hadwiger, unpublished); however, those eliciting components derived from the fungal cell wall are regarded as functionally important because of their immediate proximity to the plant cell.…”

Host-Pathogen Interactions

“…These include treatment of the plant tissues with UV light (10,19) and freezing (32). Phytoalexin synthesis is stimulated, too, by the application to plant tissues of many chemicals such as polyamines (16,17), antibiotics (4,35,36), DNA intercalating agents (18,20), and salts of heavy metals (11,34,35). However, the concentrations of these reagents required to stimulate phytoalexin synthesis (10-3-10' M) are higher than those (10-b-10`M) required for the pathogen-produced elicitors.…”