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...

No abstract

No abstract

No abstract

In Oklahoma, during the late summer of 2004, an elm tree (Ulmus americanus L.) located in the Oklahoma Botanical Gardens near Stillwater showed symptoms of marginal leaf scorch bordered by a yellow band between necrotic and green tissues, indicating possible Xylella fastidiosa infection. Three leaves from the symptomatic tree and one leaf from an asymptomatic nearby elm were sampled. DNA was extracted with the Extract-N-Amp kit (Sigma, St. Louis, MO). Samples were tested for X. fastidiosa using real-time polymerase chain reaction (PCR) with Xylella genus specific primers XfF1/XfR2 and dual-labeled TaqMan probe XfP2 (2). Infected oleander from California was used as a positive control. All three samples from symptomatic leaves and the positive control were PCR positive, and the sample from the asymptomatic tree was PCR negative. Attempts to culture an isolate of the bacteria from petioles and branch tissues on PD3 and PW, media selective for X. fastidiosa, failed. For more detailed molecular characterization of the putative pathogen, DNA from additional symptomatic petioles from the same tree was isolated using the cetyltrimethylammoniumbromide (CTAB) extraction. X. fastidiosa specific primers BBXFOUTF1 (5′-AAGCGCCTCCGTGAGTTATC-3′) and BBXFOUTR1 (5′-CCTTCACGCATATCATCACC-3′) were used to PCR amplify the gyrB gene. The amplification product was recovered after gel electrophoresis with QIAquick gel extraction kit (Qiagen, Valencia, CA) and was subjected to automated sequencing (Oklahoma State University Recombinant DNA/Protein Resource Facility). BLASTN alignment (1) of the obtained 381 bp sequence revealed 100% identity with the gyrB gene from elm (GenBank Accession No. AF534966) and mulberry (GenBank Accession No. AF534965) isolates of X. fastidiosa. During 2005, petiole samples from the tree were collected and serological diagnosis was confirmed using enzyme-linked immunosorbent assay (Agdia, Inc., Elkhart, IN). Some strains of X. fastidiosa have very wide host ranges and many of the hosts may be asymptomatic. Therefore, the economic importance and implications of the detection of X. fastidiosa in the state of Oklahoma remain to be determined. To our knowledge, this is the first report of X. fastidiosa in Oklahoma. References: (1) S. F. Altschul et al. J. Mol. Biol. 215:403, 1990. (2) N. W. Schaad et al. Phytopathology 92:721, 2002.