No evidence for learned mating discrimination in male Drosophila pseudoobscura

Background  

Since females often pay a higher cost for heterospecific matings, mate discrimination and species recognition are driven primarily by female choice. In contrast, frequent indiscriminate matings are hypothesized to maximize male fitness. However, recent studies show that previously indiscriminate males (e.g., Drosophila melanogaster and Poecilia reticulata) can learn to avoid heterospecific courtship. This ability of males to discriminate against heterospecific courtship may be advantageous in populations where two species co-occur if courtship or mating is costly.     

Adaptive evolution of G-protein coupled receptor genes

The phylogeny and patterns of nucleotide substitutions in the visual pigment genes, adrenergic receptor genes, muscarinic receptor genes, and in the human mas oncogene were studied by comparing their DNA sequences. The evolutionary tree obtained shows that the visual pigment genes and mas oncogene form one cluster and that the receptor genes form another. In the evolution of rhodopsin genes, synonymous substitutions outnumber nonsynonymous substitutions. This is consistent with the neutral theory of molecular evolution. However, the early evolutionary stages of alpha- and beta-adrenergic and muscarinic receptors are notable for significantly more nonsynonymous substitutions than synonymous substitutions, suggesting the acquisition of novel functional adaptations. Variable rates of nonsynonymous changes in different domains of these proteins reveal DNA segments that might have been important in their functional adaptations.      

Changes in photosynthetic metabolism induced by tobamovirus infection in Nicotiana benthamiana studied in vivo by thermoluminescence

* In thylakoids from Nicotiana benthamiana infected with the pepper mild mottle virus (PMMoV), a decreased amount of the PsbP and PsbQ proteins of photosystem II and different proteins of the Calvin cycle have been previously observed. We used thermoluminescence to study the consequences in vivo. * Measurements on unfrozen discs from symptomatic and asymptomatic leaves of plants infected by two tobamovirus PMMoV-S and PMMoV-I strains were compared with homologous samples in control plants. * Thermoluminescence emission did not reveal noticeable alteration of PSII electron transfer activity in infected symptomatic leaves. In these leaves, the relative intensity of the 'afterglow' emission indicated an increase of the NADPH + ATP assimilatory potential, contrasting with its decrease in asymptomatic leaves. High-temperature thermoluminescence, as a result of peroxides, increased in symptomatic and asymptomatic leaves. * In young infected leaves, PSII activity is preserved, producing a high assimilatory potential. Older asymptomatic leaves export more nutrients towards young infected leaves. This depresses their assimilatory potential and weakens their defence mechanisms against reactive oxygen species, resulting in higher peroxide content.     

Aspergillus terreus and its toxic metabolites as a food contaminant in some Egyptian Bakery products and grains

A. terreus isolates isolated from some bakery products, corn and rice were found to be able to produce territrems. 90% of theA. terreus isolated from bakery products were able to produce territrem A, with a mean of 0.09 ppm, while 80% ofA. terreus isolates produce territrem B with a mean of 0.24 ppm. On the other hand 31.8% of the isolates ofA. terreus from corn were able to produce territrem A with a mean of 0.44 ppm. ConcerningA. terreus isolates from rice, 66.7% were found to produce territrem A, with a mean of 5.28 ppm, and 77.8% of the isolates produced territrem B with a mean of 1.79 ppm.     

Thermoluminescence studies on the facultative crassulacean-acid- metabolism plant Mesembryanthemum crystallinum L.

Thermoluminescence (TL) signals were measured from leaves of the facultative CAM (crassulacean acid metabolism) plant Mesembryanthemum crystallinum L.. Following the induction of CAM by salt treatment, a TL band at 46 °C was induced, which was charged by a single-turnover flash. The intensity of the 46 °C-band depends on the number of excitation flashes and oscillates with a period of four. A similar band was induced in C₃ plants by far-red illumination. Under CAM conditions, the intensity of the 46 °C-band underlies a diurnal rhythm. The maximal intensity of the 46 °C-band is observed in the morning after onset of the light and in the evening. At around 12 a.m. it is suppressed. The intensity of the 46 °C-band relates to diurnal changes in the ratio of dihydroxy acetone phosphate/3-phosphoglycerate (DHAP/PGA) which is an indicator of the energy status of the chloroplast. During high-intensity illumination, the 46 °C-band disappears, but it is restored in the dark. We propose that the 46 °C-band is an indicator of the metabolic state of the leaf, originating from photosystem II centres initially in the S₂(S₃)Q_B oxidation state, in which the electron acceptor Q_B becomes reduced either by reverse electron flow or reduction of the plastoquinone pool via an NAD(P)H plastoquinone oxidoreductase. We present evidence that the redox state of the electron-transport chain is different under conditions of CAM compared to C₃ metabolism and that changes induced by CAM can be monitored by measuring the amplitude of the 46 °C-band after flash excitation. Received: 7 August 1997 / Accepted: 22 December 1997