Genetic variation for foot-rot and Fusarium head-blight resistances among full-sib families of a self-incompatible winter rye (Secale cereale L.) population

The amount of genetic variation for resistance to foot rot caused by Pseudocercosporella herpotrichoides, Fusarium spp., and Microdochium nivale and for resistance to head blight caused by Fusarium culmorum are important parameters when estimating selection gain from recurrent selection in winter rye. One-hundred and eighty-six full-sib families of the selfincompatible population variety Halo, representing the Petkus gene pool, were tested for foot-rot resistance at five German location-year combinations (environments) and for head-blight resistance in three environments with artificial inoculation in all but one environment. Foot-rot rating was based on 25 stems per plot scored individually on a 1–9 scale. Head-blight resistance was plotwise scored on a 1–9 scale and, additionally, grain-weight per spike was measured relative to the non-inoculated control plots. Significant estimates of genotypic variance and medium-sized heritabilities (h ²=0.51–0.69) were observed in the combined analyses for all resistance traits. In four out of five environments, the amount of genetic variance was substantially smaller for foot-rot than for head-blight rating. Considerable environmental effects and significant genotype-environment interactions were found for both foot-rot and head-blight resistance. Coefficients of error-corrected correlation among environments were considerably closer than phenotypic correlations. No significant association was found between the resistances to both diseases (r=-0.20 to 0.17). In conclusion, intra-population improvement by recurrent selection should lead to substantial higher foot-rot and head-blight resistances due to significant quantitative genetic variation within Halo. Selection should be carried out in several environments. Lack of correlation between foot-rot and head-blight resistance requires separate infection tests for improving both resistances.     

Endocytosis and Exocytosis Events Regulate Vesicle Traffic in Endothelial Cells

We used water-soluble styryl pyridinium dyes that fluoresce at the membrane-water interface to study vesicle traffic in endothelial cells. Cultured endothelial cells derived from bovine and human pulmonary microvessels were incubated in styryl probes, washed to remove dye from the plasmalemmal outer face, and observed by digital fluorescence microscopy. Vesicles that derived from plasmalemma by endocytosis were filled with the styryl dye. These vesicles were distributed throughout the cytosol as numerous particles of heterogeneous diameter and brightness. Vesicle formation was activated 2-fold following addition of extracellular albumin whereas a control protein, immunoglobulin G, had no effect. Dye uptake was abrogated by labeling at low temperatures and inhibitors of phosphoinositide-3-kinase (PI 3-kinase). Tyrosine kinase inhibitors (genistein and herbimycin A) prevented the albumin-induced vesicle formation. Cytochalasin B prevented vesicle redistribution indicating involvement of actin filaments in translocation of endosomes away from sites of vesicle formation. Styryl dye was lost from cells by exocytosis as evident by the disappearance of discrete fluorescent particles. N-ethylmaleimide and botulinum toxin types A and B caused cells to accumulate increased number of vesicles suggesting that exocytosis was regulated by NSF-dependent SNARE mechanism. The results suggest that phosphoinositide metabolism regulates endocytosis in endothelial cells and that extracellular albumin activates endocytosis by a mechanism involving tyrosine phosphorylation, whereas exocytosis is a distinct process regulated by the SNARE machinery. The results support the hypothesis that albumin regulates its internalization and release in vascular endothelial cells via activation of specific endocytic and exocytic pathways.     

Field Hypothesis on the Self-regulation of Gene Expression

The mechanism of the self-regulation of gene expression in living cells is generally explained by considering complicated networks of key-lock relationships, and in fact there is a large body of evidence on a hugenumber of key-lock relationships. However, in the present article we stress that with the network hypothesis alone it is impossible to fully explain the mechanism of self-regulation in life. Recently, it has been established that individual giant DNA molecules, larger than several tens of kilo base pairs, undergo a large discrete transition in their higher-order structure. It has become clear that nonspecific weak interactions with various chemicals, suchas polyamines, small salts, ATP and RNA, cause on/off switching in the higher-order structure of DNA. Thus, the field parameters of the cellular environment should play important roles in the mechanism of self-regulation, in addition to networks of key and locks. This conformational transition induced by field parameters may be related to rigid on/off regulation, whereas key-lock relationships may be involved in a more flexible control of gene expression.     

Fairy wrasses perceive and respond to their deep red fluorescent coloration

Fluorescence enables the display of wavelengths that are absent in the natural environment, offering the potential to generate conspicuous colour contrasts. The marine fairy wrasse Cirrhilabrus solorensis displays prominent fluorescence in the deep red range (650–700 nm). This is remarkable because marine fishes are generally assumed to have poor sensitivity in this part of the visual spectrum. Here, we investigated whether C. solorensis males can perceive the fluorescence featured in this species by testing whether the presence or absence of red fluorescence affects male–male interactions under exclusive blue illumination. Given that males respond aggressively towards mirror-image stimuli, we quantified agonistic behaviour against mirrors covered with filters that did or did not absorb long (i.e. red) wavelengths. Males showed significantly fewer agonistic responses when their fluorescent signal was masked, independent of brightness differences. Our results unequivocally show that C. solorensis can see its deep red fluorescent coloration and that this pattern affects male–male interactions. This is the first study to demonstrate that deep red fluorescent body coloration can be perceived and has behavioural significance in a reef fish.     

Photosynthetic pigment concentration, organization and interconversions in a pale green Syrian landrace of barley (Hordeum vulgare L., Tadmor) adapted to harsh climatic conditions

Tadmor is a Syrian barley landrace that has adapted to semi-arid environments. Its leaves are pale green because of a 30% decrease in the chlorophyll and the carotenoid content of the chloroplasts (leading to a 7·5% decrease in light absorption) compared with barley genotypes that are not adapted to harsh Mediterranean climatic conditions (e.g. Plaisant). This difference in pigment content was attenuated during growth of the plants in strong light, but was strongly amplified when strong light was combined with a high growth temperature. The low pigment content of Tadmor leaves was not associated with significant changes in the pigment distribution between the photosystems or between the reaction centres of the photosystems and their associated chlorophyll antennae. No significant difference in the photosynthetic activity (O₂ production per unit absorbed light) was observed between Tadmor and Plaisant. The conversion of violaxanthin to zeaxanthin in strong light and its reversal in darkness were much faster and operated at a higher capacity in Tadmor leaves compared with Plaisant leaves, resulting in an increased photostability of photosystem II in the former leaves. The accelerated xanthophylls interconversion in the Syrian landrace was associated with, and possibly related to, an increased fluidity of the thylakoid membranes. The lipid peroxide level was lower in Tadmor compared with Plaisant. In contrast, no difference was found in the non-photochemical quenching of chlorophyll fluorescence between the two barley genotypes. The data indicate that the pale green Syrian landrace is equipped to survive excessive irradiance through a passive reduction of the light absorptance of its leaves, which mitigates the heating effects of strong light, and through the active protection of its photochemical apparatus by a rapid xanthophyll cycling.     

Influence of chlorophyll concentrations on the reliability of measurements with an oxygen electrode when studying photosynthetic efficiency in bioassays using microalgae

Euglena gracilis and Chlamydomonas reinhardtii were used as model organisms to establish the best conditions for studying photosynthetic efficiency using the Light Pipette – experimental system, which enables sensitive detection of changes in oxygen evolution/consumption and an easy collection and digitalisation of data. Chlorophyll concentrations of 0.005, 0.025, 0.050 and 0.075 mgmL^-1 were investigated using different light regimes. Cultures of E. gracilis at the same chlorophyll concentration absorbed more light(measured at 580 μmol m^-2 s^-1) than those of C. reinhardtii. Cell density had a considerable effect on the reliability of measurements. Chlorophyll concentrations between 0.025 mg_Chl ml^-1 and 0.050 mg_Chlml^-1 can be recommended when applying the Light Pipette system in bioassays using microalgae. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fluorescence induction in the phycobilisome-containing cyanobacterium Synechococcus sp PCC 7942: Analysis of the slow fluorescence transient

At room temperature, the chlorophyll (Chl) a fluorescence induction (FI) kinetics of plants, algae and cyanobacteria go through two maxima, P at ∼ 0.2-1 and M at ∼ 100-500 s, with a minimum S at ∼ 2-10 s in between. Thus, the whole FI kinetic pattern comprises a fast OPS transient (with O denoting origin) and a slower SMT transient (with T denoting terminal state). Here, we examined the phenomenology and the etiology of the SMT transient of the phycobilisome (PBS)-containing cyanobacterium Synechococcus sp PCC 7942 by modifying PBS → Photosystem (PS) II excitation transfer indirectly, either by blocking or by maximizing the PBS → PS I excitation transfer. Blocking the PBS → PS I excitation transfer route with N-ethyl-maleimide [NEM; A. N. Glazer, Y. Gindt, C. F. Chan, and K.Sauer, Photosynth. Research 40 (1994) 167-173] increases both the PBS excitation share of PS II and Chl a fluorescence. Maximizing it, on the other hand, by suspending cyanobactrial cells in hyper-osmotic media [G. C. Papageorgiou, A. Alygizaki-Zorba, Biochim. Biophys. Acta 1335 (1997) 1-4] diminishes both the PBS excitation share of PS II and Chl a fluorescence. Here, we show for the first time that, in either case, the slow SMT transient of FI disappears and is replaced by continuous P → T fluorescence decay, reminiscent of the typical P → T fluorescence decay of higher plants and algae. A similar P → T decay was also displayed by DCMU-treated Synechococcus cells at 2 °C. To interpret this phenomenology, we assume that after dark adaptation cyanobacteria exist in a low fluorescence state (state 2) and transit to a high fluorescence state (state 1) when, upon light acclimation, PS I is forced to run faster than PS II. In these organisms, a state 2 → 1 fluorescence increase plus electron transport-dependent dequenching processes dominate the SM rise and maximal fluorescence output is at M which lies above the P maximum of the fast FI transient. In contrast, dark-adapted plants and algae exist in state 1 and upon illumination they display an extended P → T decay that sometimes is interrupted by a shallow SMT transient, with M below P. This decay is dominated by a state 1 → 2 fluorescence lowering, as well as by electron transport-dependent quenching processes. When the regulation of the PBS → PS I electronic excitation transfer is eliminated (as for example in hyper-osmotic suspensions, after NEM treatment and at low temperature), the FI pattern of Synechococcus becomes plant-like.     

Photodesorption of mitochondria

Photodesorption of mitochondria absorbed on a quartz plate was discovered. The rate of photodesorption of mitochondria from the plate into solution depends on the wavelength, intensity, and irradiation period. The maximum rate of photodesorption was detected upon irradiation with UV light at the mitochondrial protein tryptophan absorption band. UV photodesorption is presumably caused by a local photothermal effecth—eating of photoexcited proteins at the membrane surface that attach mitochondria to the plate. Preliminary fixation of a smear with isopropanol or acetone drastically decreased photodesorption and spontaneous desorption. No photodesorption of either mitochondria or formazan was observed upon illumination with green light of formazan granules formed in mitochondria as a product of reductase reaction. These data are important for elaborating a technique of immobilizing mitochondria for enzyme assays and biosensors.     

Time-resolved fluorescence spectroscopy of hematoporphyrin-derivative in human lymphocytes

This paper reports on time-resolved microfluorimetric measurements on hematoporphyrin-derivative (HpD)-treated lymphocytes. HpD is at present widely used as a tumor-locating and photosensitizing drug. It is therefore of great importance to study the extent to which the HpD uptake process depends on cell functional and structural properties. Time-resolved fluorescence measurements in single cells are very useful in this respect, since they give information on the content of fluorescent molecules through fluorescence peak-intensity, and, indirectly, on the binding properties through the fluorescence decay times. In particular, we studied the dependence of HpD fluorescence on the cellular functional state. To this end, we performed in-cell fluorescence measurements on human lymphocytes, both in quiescent conditions and in the pre-replicative phase, after stimulation with phytohemagglutinin (PHA). We found a higher HpD content in stimulated lymphocytes. Moreover, we found a spectral band around 575 nm, corresponding to a particular porphyrin species, in which the differences between normal and stimulated lymphocytes are more striking. The porphyrin species emitting in this band seems to play a role in the specific interaction of HpD with tumors, since a similar emission band has also been found in tumor cells containing HpD.