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Biomedical subjects

R P Doss

Publications and source records attributed to R P Doss.

14 recordsLinked to original sources
PubMed2005

Application of Bruchin B to pea pods results in the up-regulation of CYP93C18, a putative isoflavone synthase gene, and an increase in the level of pisatin, an isoflavone phytoalexin.

Bruchins, mono and bis (3-hydroxypropanoate) esters of long chain alpha,omega-diols, are a recently discovered class of insect elicitors that stimulate cell division and neoplasm formation when applied to pods of peas and certain other legumes. Differential display analysis resulted in the identification of an mRNA whose level was increased by the application of Bruchin B to pea pods. The corresponding amplification product was cloned and sequenced and a full length cDNA sequence was obtained. This cDNA and the gene from which it was derived were assigned the name CYP93C18 based upon sequence similarities to the cytochrome P450 mono-oxygenase CYP93C subfamily, which contains isoflavone synthase genes from legumes. RNA gel blots and quantitative RT-PCR demonstrated that expression of CYP93C18 increased within 8 h of bruchin treatment to a maximum of 100-200-fold of the level in untreated pods, and then declined. The up-regulation of CYP93C18 was followed by an increase in the level of the isoflavone phytoalexin, pisatin. Pisatin was detectable in the bruchin-treated pods after 16 h and reached a maximum between 32 h and 64 h. This, the first report of induction of phytoalexin biosynthesis by an insect elicitor, suggests that Bruchin B not only stimulates neoplasm formation, but also activates other plant defence responses.

Amino Acid Sequence↗
PubMed2000

Bruchins: insect-derived plant regulators that stimulate neoplasm formation.

Pea weevil (Bruchus pisorum L.) oviposition on pods of specific genetic lines of pea (Pisum sativum L.) stimulates cell division at the sites of egg attachment. As a result, tumor-like growths of undifferentiated cells (neoplasms) develop beneath the egg. These neoplasms impede larval entry into the pod. This unique form of induced resistance is conditioned by the Np allele and mediated by a recently discovered class of natural products that we have identified from both cowpea weevil (Callosobruchus maculatus F.) and pea weevil. These compounds, which we refer to as "bruchins," are long-chain alpha,omega-diols, esterified at one or both oxygens with 3-hydroxypropanoic acid. Bruchins are potent plant regulators, with application of as little as 1 fmol (0.5 pg) causing neoplastic growth on pods of all of the pea lines tested. The bruchins are, to our knowledge, the first natural products discovered with the ability to induce neoplasm formation when applied to intact plants.

Animals↗
PubMed2000

Lipid composition of the extracellular matrix of Botrytis cinerea germlings.

Six simple lipid classes (mono-, di- and tri-acylglycerols, free fatty acids, free fatty alcohols and wax esters) were identified by TLC in the extracellular matrix of Botrytis cinerea germlings and the molecular components of each class were characterized using GC-MS. The relative amounts of fatty acids and fatty alcohols within each lipid class were determined by GC-FID. Over all the lipid classes, the most abundant saturated fatty acids were palmitic (ca. 30%) and stearic acid (ca. 22%). Palmitoleic and oleic acids made up ca. 21% and 24% (respectively) of the free fatty acids, while erucic (ca. 4.1%) and linoleic (ca. 3.6%) acids were the most abundant unsaturated fatty acids in the acylglycerides. The acylglycerides also contained almost 35% long chain fatty acids (C20:0 to C28:0). Six fatty acids were identified which had odd-numbered carbon chain lengths (C15:0, C17:0, C19:0, C21:0, C23:0 and C25:0). Of these, pentacosanoic acid made up almost 14% of the fatty acids in the acylglycerides. Three methyl-branched chain fatty acids, namely isopalmitic, isoheptadecanoic and anteisopalmitic, were identified in the ECM, all in small amounts. Of the fatty alcohols identified, only palmityl and stearyl alcohols were found in the free form (ca. 57% and 43%, respectively) but arachidyl alcohol (ca. 47%) and 1-octacosanol (ca. 30%) were the most abundant fatty alcohols found in the wax ester fraction.

Botrytis↗
PubMed1999

Composition and enzymatic activity of the extracellular matrix secreted by germlings of botrytis cinerea.

Germlings of Botrytis cinerea, an important fungal pathogen of plants, produce an extracellular matrix (ECM), or ensheathing film, that serves, in part, in their attachment (R. P. Doss, et al., Appl. Environ. Microbiol. 61:260-265, 1995). The composition of this film has been ascertained by using samples obtained by growing germlings on a glass surface, removing the fungal mycelium by vigorous washing, and collecting the tightly attached film by scraping the substratum with a razor blade. Slightly over half of the dry weight of the ECM was found to be carbohydrates (about 20%), proteins (about 28%), and lipids (about 6%). Hydrolysis of the carbohydrate portion of the ECM revealed that glucose was the most prominent monosaccharide present, comprising about 60% of the total monosaccharides. Also present were mannose (about 35%) and myo-inositol (about 5%). The proteinaceous fraction of the ECM was made up of a number of polypeptides separable by polyacrylamide gel electrophoresis. The lipid fraction of the ECM, analyzed by thin-layer chromatography, was made up of several simple lipid components, including free fatty acid, mono- and triacylglycerol, wax ester, fatty alcohol, and several unidentified components. No complex lipids were detected. Isolated ECM exhibited polygalacturonase and laccase activity and was able to catalyze the hydrolysis of p-nitrophenyl butyrate, a model substrate for assessing cutinase activity. Cellulase, pectin lyase, and pectin methyl esterase activities were noted with both heated and unheated ECM preparations. Proteinase activity was not detected.

Journal Article↗
PubMed1995

Adhesion of germlings of Botrytis cinerea.

Adhesion of conidia and germlings of the facultative plant parasite Botrytis cinerea occurs in two distinct stages. The first stage, which occurs immediately upon hydration of conidia and is characterized by relatively weak adhesive forces, appears to involve hydrophobic interactions (R. P. Doss, S. W. Potter, G. A. Chastagner, and J. K. Christian, Appl. Environ. Microbiol. 59:1786-1791, 1993). The second stage of adhesion, delayed adhesion, occurs after viable conidia have been incubated for several hours under conditions that promote germination. At this time, the germlings attach strongly to either hydrophobic or hydrophilic substrata. Delayed adhesion involves secretion of an ensheating film that remains attached to the substratum upon physical removal of the germlings. This fungal sheath, which can be visualized by using interference-contrast light microscopy, scanning electron microscopy, or atomic force microscopy, is 25 to 60 nm thick in the region immediately adjacent to the germ tubes. Germlings are resistant to removal by boiling or by treatment with a number of hydrolytic enzymes, 2.0 M periodic acid, or 1.0 M sulfuric acid. They are readily removed by brief exposure to 1.25 N NaOH. A base-soluble material that adheres to culture flask walls in short-term liquid cultures of B. cinerea is composed of glucose (about 30%), galactosamine (about 3%), and protein (30 to 44%).

Cell Adhesion↗
PubMed1993

Adhesion of Nongerminated Botrytis cinerea Conidia to Several Substrata.

Conidia of the plant pathogenic fungus Botrytis cinerea adhered to tomato cuticle and to certain other substrata immediately upon hydration. This immediate adhesion occurred with both living and nonliving conidia. Adhesion was not consistently influenced by several lectins, sugars, or salts or by protease treatment, but it was strongly inhibited by ionic or nonionic detergents. With glass and oxidized polyethylene, substrata whose surface hydrophobicities could be conveniently varied, there was a direct relationship between water contact angle and percent adhesion. Immediate adhesion did not involve specific conidial attachment structures, although the surfaces of attached conidia were altered by contact with a substratum. Freshly harvested conidia were very hydrophobic, with more than 97% partitioning into the organic layer when subjected to a phase distribution test. Percent adhesion of germinated conidia was larger than that of nongerminated conidia. Evidence suggests that immediate adhesion of conidia of B. cinerea depends, at least in part, on hydrophobic interactions between the conidia and substratum.

Journal Article↗
PubMed1990

Cicatricial ectropion in lamellar ichthyosis.

A 35-year-old woman presented with bilateral lower lid ectropion associated with lamellar ichthyosis. She was successfully treated with postauricular skin grafts and horizontal lid shortenings. This report reviews the literature on the surgical management of this condition and suggests several modifications to prevent recurrence.

Adult↗
PubMed1989

Fibrous capsule from extruded implant used as graft material in cul-de-sac reconstruction.

A 74-year-old woman underwent radiation therapy for ocular malignant melanoma. The eye was subsequently enucleated. Three years later, implant migration and conjunctival contracture necessitated a socket reconstruction. The fibrous capsule that formed around the migrated implant proved to be an easily harvested and effective tissue for expanding the contracted socket.

Aged↗
PubMed1983

Endogenous levels of abscisic Acid and decanoic Acid in dutch iris bulbs and the influence of abscisic Acid and decanoic Acid on iris meristems cultured in vitro.

Abscisic acid (ABA) and decanoic acid inhibited shoot elongation and floral development of Dutch iris (Iris hollandica Hoog. cv Ideal) meristems cultured in vitro. No synergism with respect to inhibition of leaf growth between ABA and decanoic acid was observed. With monthly harvest dates, from July 10, 1981 to October 10, 1981, there was a progressive decrease in endogenous level of free ABA in ;Ideal' iris bulbs. Bulbs subjected to a full set of the usual preplanting storage conditions flowered, on average, 46 days after planting versus 194 days after planting for bulbs planted directly after harvest. ABA levels at harvest were 4- to 5-fold those after the preplanting storage treatment. In general, ABA levels did not correlate well with the length of time from planting until flowering of iris bulbs. Endogenous decanoic acid levels did not follow any pattern with respect to harvest date or postharvest treatment. After the postharvest high temperature treatment, there was about a 3-fold increase in nonscale decanoic acid concentration. Decanoic acid levels, in nonscale tissue, remained high after each of the other postharvest treatments. It is concluded that there is no good evidence to support the contention that either ABA or decanoic acid is directly involved in iris bulb dormancy.

Journal Article↗
PubMed1975

Influence of Temperature on the Flowering of Lemna perpusilla 6746 Grown under Skeleton Photoperiods.

The flowering of Lemna perpusilla Torr. strain 6746 grown under 24-hour skeleton photoperiods consisting of 13- and 10.5-hour dark periods separated by 0.25-hr light pulses is strongly dependent on temperature. When plants are cultured in 50-ml Erlenmeyer flasks containing 20 ml of half-strength Hutner's medium supplemented with 1% (w/v) sucrose maximum, per cent, flowering occurs at 23 C. At temperatures above and below 23 C a marked decline in per cent flowering is seen.

Journal Article↗
PubMed1975

Influence of timing and number of consecutive inductive photoperiodic cycles on the flowering of lemna.

Requirements for flowering of the short day plant Lemna perpusilla Torr. strain 6746 can be studied by interposition of varying numbers of consecutive short days during 7 days of continuous light. A single inductive cycle can cause the formation of few flowers if it comes during the middle of a 7-day period of continuous light. Three inductive cycles cause 30% or more of the fronds to flower if the cycles are properly spaced in the 7-day period. The fact that timing of the inductive photoperiodic cycles is critical indicates the importance of development time and abortion of evoked floral primordia in the flowering response. These results are particularly useful in studies of processes occurring during induction.

Journal Article↗
PubMed1975

Influence of Short Term Inhibitor Treatment on the Flowering of Lemna perpusilla 6746.

Short term inhibitor treatment can be used to examine the processes that occur during an inductive dark period in the short day plant Lemna perpusilla Torr., strain 6746. Several inhibitors of protein biosynthesis are most effective in reducing per cent flowering when treatment occurs over the 2-hour intervals beginning at the 12th hour or the 14th hour of a 8 (16) photoperiodic cycle. The antimetabolite, 5-fluorouracil, is most effective when treatment occurs early in the dark period. Evidence is cited suggesting that distilled water incubation inhibits flowering by interfering with protein biosynthesis.

Journal Article↗