Elicitor-induced metabolic changes in cell cultures of chickpea (Cicer arietinum L.) cultivars resistant and susceptible to Ascochyta rabiei

Cell-suspension cultures of two chickpea (Cicer arietinum L.) cultivars, resistant (ILC 3279) and susceptible (ILC 1929) to the fungus Ascochyta rabiei (Pass.) Lab., showed differential accumulation of the phytoalexins medicarpin and maackiain, and transient induction of related enzyme activities after application of an A. rabiei-derived elicitor. The chalcone-synthase (CHS) activity (EC 2.3.1.74) which is involved in the first part of phytoalexin biosynthesis exhibited a maximum 8–12 h after elicitation in the cells of both cultivars. Concomitant with the fivefold-higher phytoalexin accumulation, CHS activity increased twofold in the cells of the resistant cultivar. The maximum of the elicitor-induced CHS-mRNA activity was determined 4 h after onset of induction in the cultures of both cultivars, although in cells of cultivar ILC 3279 this mRNA activity was induced at a level twofold higher than that in cells of the susceptible race ILC 1929. Investigations of CHS isoenzymes by two-dimensional gel electrophoresis of immunoprecipitated in-vitro-translated protein indicated the presence of five proteins. In the cells of both cultivars only two of the isoenzymes were induced after elicitor treatment. Analysis of the total in-vitro-translated proteins by two-dimensional gel electrophoresis showed that the constitutively expressed patterns of mRNA activities in the cell cultures of the two cultivars were identical. After elicitation, considerably more translatable mRNAs were induced in the cells of cultivar ILC 3279. The few induced proteins, and their respective mRNA activities, which could be detected in the cells of the susceptible cultivar, all existed in the cells of the resistant cultivar, too. One highly induced protein (M_r 18 kDa) found in the cells of cultivar ILC 3279 reached its maximum mRNA activity 6 h after elicitor application. The amount of this protein was hardly increased in the cells of the susceptible cultivar. This protein appears to be excreted from the cells into the growth medium.Abbreviations CHS chalcone synthase - IEF isoelectric focussing - ILC international legume chickpea - PR-protein pathogenesis-related protein - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis Financial support by Deutsche Forschungsgemeinschaft and Fonds der Chemischen Industrie is gratefully acknowledged. The authors thank Dr. K. Hahlbrock (Max-Planck-Institut für Züchtungsforschung, Köln, FRG) for provision of antisera and the International Centre for Agricultural Research in the Dry Areas (Aleppo, Syria) for plant material.     

Phenotypic variation during micropropagation of the chimeralRhododendron ‘President Roosevelt’

The putative periclinal chimeraRhododendron xlimbatum President Roosevelt was used to study the origin of shoots in vitro. Genotypic segregation readily occurred in vitro. Numerous phenotypes were observed, although most shoots were either entirely green or maintained the original variegation pattern. Derivatives of the third apical layer were rarely involved in shoot formation. A reversed chimeral form was isolated. Adventitious shoots were usually miniaturized and rapidly proliferating, but axillary shoots had thicker stems, larger leaves and proliferated more slowly. Corolla tissue produced stunted, leafy shoots; no variegated shoots were produced from floret explants. In shoot tip cultures the addition of 40M 2iP without IBA resulted in the greatest number of shoots. Explant choice was the most critical factor for maintenance of foliar variegation.     

Fluorescence lifetimes of dimers and higher oligomers of bacteriochlorophyll c from Chlorobium limicola

Fluorescence lifetimes have been measured for bacteriochlorophyll (BChl) c isolated from Chlorobium limicola in different states of aggregation in non-polar solvents. Two different homologs of BChl c were used, one with an isobutyl group at the 4 position, the other with n-propyl. Species previously identified as dimers (Olson and Pedersen 1990, Photosynth Res, this issue) decayed with lifetimes of 0.64 ns for the isobutyl homolog, 0.71 ns for n-propyl. Decay-associated spectra indicate that the absorption spectrum of the isobutyl dimer is slightly red-shifted from that of the n-propyl dimer. Aggregates absorbing maximally at 710 nm fluoresced with a principal lifetime of 3.1 ns, independent of the homolog used. In CCl₄, only the isobutyl homolog forms a 747-nm absorbing oligomer spectrally similar to BChl c in vivo. This oligomer shows non-exponential fluorescence decay with lifetimes of 67 and 19 ps. Because the two components show different excitation spectra, the higher oligomer is probably a mixture of more than one species, both of which absorb at 747 nm.Abbreviations BChl bacteriochlorophyll - Chl chlorophyll - % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGGipm0dc9vqaqpepu0xbbG8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeq4Xdm2aaW% baaSqabeaacaaIYaaaaaaa!3777!\[\chi ^2 \] chi-square - FWHM full-width at half-maximum     

Phylogenetic systematic evaluation of a classification of the Zoogonidae Odhner, 1902 (Cercomeria: Trematoda: Digenea: Plagiorchiiformes)

A recent systematic study of the digenean family Zoogonidae presented a series of cladograms, which are the product of phylogenetic systematic, or cladistic, analysis. However, one of the two subfamilies and nine of the 21 genera recognised in that study lacked putative synapomorphies, a requirement for phylogenetic systematic studies. This study presents a re-analysis of the database for the zoogonids, based on rigorous application of phylogenetic systematic methods. A new phylogenetic tree is presented, which better fits the original data than the published tree (with a consistency index of 52.3% vs. 46.3%). Four subfamilies, three monophyletic and one of uncertain status, and 10 genera could be recognised phylogenetically. This would affect the nomenclatorial status of one-third (26) of the species in the family. However, it is recommended that another analysis, based on more characters, be carried out before nomenclatorial changes are proposed.     

Substance P affects the GABAergic system in the hypothalamo-pituitary axis

In the present work we examined the effect of the neutralization of endogenous substance P by the administration of an anti-substance P serum (ASPS) on GABA concentration in the anterior pituitary in hyperprolactinemic conditions induced by 5-hydroxytryptophan or by grafting anterior pituitaries. ASPS reduced the increase in the anterior pituitary GABA concentration induced by hyperprolactinemia. In vitro experiments showed that substance P inhibited K⁺-evoked GABA efflux from hypothalamic fragments and decreased GABA concentration in the anterior pituitary but ASPS increased it. Our results demonstrate that substance P modifies hypothalamic GABA release and anterior pituitary GABA concentration and suggest that an interaction exists between substance P and GABA.     

Use of an alternative method for monitoring total nitrogen concentrations in Florida lakes

We studied a recently described method for the determination of total nitrogen in natural waters involving sample oxidation with persulfate and subsequent determination of nitrate-nitrogen with second derivative spectroscopy and compared it to the USEPA approved method involving the sum of nitrate-nitrogen and Kjeldahl-nitrogen as measured with an automated analyzer. The overall objective was to determine if the two methods gave the same estimates of total nitrogen and if the detection limits, precision and accuracy of the new method were as good as those of the USEPA method. The new method was used to make measurements on replicated blanks, standards and lake water samples covering a range of concentrations. We also collaborated with certified laboratories to make comparative measurements on 5 standards and 21 lake water samples that were run by us with the new method and by them with the USEPA method. The new method had an instrument detection limit of 0.07 mg 1^–1, and the standard deviation of 20 sets of lake water samples averaged 0.03 mg 1^–1. The new method gave concentrations equivalent to those found with the USEPA method, was more sensitive, and had a higher degree of precision. We concluded that the new method is suitable as a substitute for the USEPA method. We also found that the addition of acid to lake water samples stored under refrigeration was not necessary to preserve them for later determinations of nitrate-nitrogen and total nitrogen and that freezing was an effective means of sample preservation for 90 days.     

Changes in malondialdehyde content and in superoxide dismutase, catalase and glutathione reductase activities in sunflower seeds as related to deterioration during accelerated aging

Sunflower ( Helianthus annuus L.) seeds progressively lost their ability to germinate at 25°C, the optimal temperature for germination, after accelerated aging was carried out at 45°C (a temperature too high to permit germination) in water or at 76 or 100% relative humidity (RH). The deleterious effects of the high-temperature treatment increased with increasing seed moisture content. Incubation of seeds at 45°C in water resulted in electrolyte leakage, which indicated a loss of membrane integrity. A relationship between leakage and loss of seed viability could not be assumed, since no increase in electrolyte efflux occurred after aging al 100% RH. Accelerated aging induced accumulation of malondialdehyde, suggesting that seed deterioration was associated with lipid peroxidation. However, there was no direct relationship between lipid peroxidation and deterioration in membrane integrity. Loss of seed viability was also associated with a decrease in superoxide dismutase, catalase and glutathione reductase activities. Finally, the results obtained suggest that sunflower seed deterioration during accelerated aging is closely related to a decrease in the activities of detoxifying enzymes and to lipid peroxidation.     

Induction and ionic basis of slow wave potentials in seedlings of Pisum sativum L.

Slow wave potentials (SWPs) are transient depolarizations which propagate substantial distances from their point of origin. They were induced in the epidermal cells of pea epicotyls by injurious methods such as root excision and heat treatment, as well as by externally applied defined steps in xylem pressure (Px) in the absence of wounding. The common principle of induction was a rapid increase in Px. Such a stimulus appeared under natural conditions after (i) bending of the epicotyl, (ii) wounding of the epidermis, (iii) rewatering of dehydrated roots, and (iv) embolism. The induced depolarization was not associated with a change in cell input resistance. This result and the ineffectiveness of ion channel blockers point to H(+)-pumps rather than ion channels as the ionic basis of the SWP. Stimuli such as excision, heat treatment and pressure steps, which generate SWPs, caused a transient increase in the fluorescence intensity of epicotyls loaded with the pH-indicator DM-NERF, a 2',7'-dimethyl derivative of rhodol, but not of those loaded with the pH indicator 2',7'bis(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF). Matching kinetics of depolarization and pH response identify a transient inactivation of proton pumps in the plasma membrane as the causal mechanism of the SWP. Feeding pump inhibitors to the cut surface of excised epicotyls failed to chemically simulate a SWP; cyanide, azide and 2,4-dinitrophenol caused sustained, local depolarizations which did not propagate. Of all tested substances, only sodium cholate caused a transient and propagating depolarization whose arrival in the growing region of the epicotyl coincided with a transient growth rate reduction.     

The evolution of phage lysis timing

Summary The effect of host quantity and host quality on the evolution of phage lysis timing is analysed using marginal value theorem of optimal foraging theory. Both factors have been shown to strongly influence the latent period. A high host density selects for short latent period, which is the same result as previous investigators have found. A good host quality also promotes a short latent period. However, elasticity analysis shows that these two factors exert their influences under different sets of conditions. When host density is low, the host density is more important in determining the length of latent period, whereas when host density is high, the host quality is more important.