Steuerung und potentielle Evolutionsgeschwindigkeit des obligaten Teilzieherverhaltens: Ergebnisse eines Zweiweg-Selektionsexperiments mit der M?nchsgrasmücke (Sylvia atricapilla)

Zusammenfassung 1. In Südfrankreich lebt eine obligat teilziehende Population der Mönchsgrasmücke (Sylvia atricapilla) mit rund drei Vierteln Zugvögeln und einem Viertel Standvögeln. Das Teilzugverhalten dieser Population wird in beträchtlichem Umfang von genetischen Faktoren gesteuert (Berthold &Querner 1982). Der starke Selektionserfolg eines Zweiweg-Selektionsexperiments bis zur F₁-Generation ließ eine hohe potentielle Evolutionsgeschwindigkeit des obligaten Teilzieherverhaltens vermuten (2). Wir haben das Evolutionspotential in einem Langzeit-Selektionsversuch experimentell untersucht.2. Wir zogen insgesamt 267 Individuen der freilebenden Mönchsgrasmückenpopulation in fünf Gruppen von Hand auf, und alle fünf Stichproben zeigten entsprechende Verhältnisse von Ziehern und Nichtziehern. Wir konnten das Langzeit-Zweiweg-Selektionsexperiment bis zu einer F₆-Generation durchführen und konnten dabei insgesamt 455 Mönchsgrasmücken in Volieren züchten.3. Das Zweiweg-Selektionsexperiment zeigt, daß die untersuchte teilziehende Mönchsgrasmückenpopulation bereits nach drei Generationen eine ausschließlich ziehende und nach vier bis sechs Generationen eine fast nicht mehr ziehende Population werden kann.4. Das Zweiweg-Selektionsexperiment zeigt starken Selektionserfolg und hohe Heritabilitätswerte (ca. 0,6–1), die deutlich höher liegen als bisher für das Verhalten von (meist domestizierten) Wirbeltieren angegeben. Demnach sind genetische Faktoren für die Steuerung dieses obligaten Teilzugs sehr bedeutsam und wahrscheinlich dominant über Umwelteinflüsse.5. Die Versuchsergebnisse lassen im Falle von schnellen Umweltveränderungen und der Wirkung von starken Selektionsfaktoren ein enorm großes Evolutionspotential des obligaten Teilzieherverhaltens annehmen und damit allgemein eine schnelle Mikroevolution der Ortsbewegung von Vögeln. Sollten die von Meteorologen prophezeiten Klimaänderungen in Bälde eintreten (Erwärmung aufgrund von Verunreinigungen der Atmosphäre durch den Menschen, Treibhauseffekt), dann könnten viele obligate Teilzieher auf genetischer Basis rasch zu Standvögeln werden und wenig ausgeprägte Zieher rasch zu Teilziehern. Unter diesem allgemeinen Anwachsen von Standvögeln könnten ausgeprägte Zugvögel mehr und mehr zu leiden haben.6. Eine genetische Kontrolle obligaten Teilzugs scheint weit verbreitet zu sein, und sie stellt wohl auch für alle Individuen den zuverlässigsten Steuerungsmechanismus dar. Beim fakultativen Teilzug hingegen dürften Umweltfaktoren mehr unmittelbar steuernd wirken.

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Control and evolutionary potential of obligate partial migration: results of a two-way selective breeding experiment with the Blackcap (Sylvia atricapilla)

Summary 1. In southern France breeds an obligate partially migratory population of the Blackcap with about three quarters of migrants and one quarter of residents. Partial migration of this population is considerably controlled by genetic factors (Berthold &Querner 1982). The large selection response of a two-way selective breeding experiment up to F₁-generations suggested a high evolutionary potential of obligate partial migration (2). We have this evolutionary potential experimentally investigated in a long-term selective breeding study.2. We raised by hand a total of 267 individuals of the free-living Blackcap population in five groups, and all five samples showed corresponding ratios of migrants and nonmigrants. We were able to conduct the long-term selective breeding experiment up to a F₆-generation, and thereby a total of 455 Blackcaps could be bred in aviaries.3. The two-way selective breeding experiment shows, that the investigated partially migratory Blackcap population can become completely migratory in just three generations and almost exclusively sedentary in just four to six generations.4. The two-way selective breeding experiment yielded large selection responses and high heritability values (about 0.6–1) which are distinctly higher than those previously reported for behavioural traits of (mostly domesticated) vertebrates. Hence, genetic factors are very important for the control of this obligate partial migration and are presumedly dominant over environmental influences.5. In case of rapid environmental changes and the effect of strong selection factors the experimental results suggest a strikingly high evolutionary potential of obligate partial migration and thus in general a rapid microevolution of bird movements. If climatic changes would occur in the near future as they are predicted by meteorologists (rise in temperature due to man-made pollution of the atmosphere, greenhouse-effect) then many obligate partial migrants could rapidly become sedentary on a genetic basis and many less typical migrants could then considerably suffer from the general increase of residents.6. A genetic control of obligate partial migration appears to be widespread and it also appears to be the most reliable control mechanism for all individuals of such a partially migratory population. Facultative partial migration, however, appears to be controlled more directly by environmental factors.

     

Permeabilization of yeast for in situ determination of α-glucosidase

A quantitative in situ assay of yeast α-glucosidase involving permeabilization of the cells by freezing and thawing is described. The assay was applied to different strains in different physiological states and was shown to give results comparable to those obtained with total cell homogenates. The primary advantage of the in situ assay was the possibility of analyzing a large number of samples from the same culture during a growth curve using a very reduced cell mass.     

An analysis of the action of light on betalain synthesis in the seedling of Amaranthus caudatus,var. viridis

Accumulation of betalain (amaranthin) in the seedling of Amaranthus caudatus, var. viridis, is inducible by light. Since the apparent lag-phase of amaranthin accumulation after the onset of light is of the order of 3 h, light induction experiments could be performed up to 3 h after the onset of light without interference with actual synthesis. The intricate induction phenomena can be explained as follows: The inductive light operates through phytochrome and through a blue/UV photoreceptor (cryptochrome). A phytochrome-dependent High Irradiance Reaction is of minor importance. However, there is a strong, specific interaction between the light effects mediated through phytochrome and cryptochrome in the sense that the extent of the reversible response — (response obtained with a particular light treatment terminated with a saturating red light pulse) minus (response obtained with the same light treatment when terminated with a saturating 756 nm light pulse) —increases with increasing P_fr level and total fluence rate during the induction period. It is concluded that light induced amaranthin synthesis is, in fact, a convenient biochemical model system of photomorphogenesis in the case when phytochrome and cryptochrome operate simultaneously in mediating photomorphogenesis. Abbreviations: see Table 1 and 2 Materials and Medthods     

The involvement of phytochrome in controlling chlorophyll and 5-aminolevulinate formation in a gymnosperm seedling (Pinus sylvestris)

Chlorophyll a (Chl a) accumulation in the cotyledons of Scots pine seedlings (Pinus sylvestris L.) is much higher in the light than in darkness where it ceases 6 days after germination. When these darkgrown seedlings are treated with continuous white light (3,500 lx) a 3 h lag phase appears before Chl a accumulation is resumed. The lag phase can be eliminated by pretreating the seedlings with 7 h of weak red light (0.14 Wm^-2) or with 14 red light pulses separated by relatively short dark periods (<100 min). The effect of 15s red light pulses can be fully reversed by 1 min far-red light pulses. This reversibility is lost within 2 min. In addition, the amount of Chl a formed within 27 h of continuous red light is considerably reduced by the simultaneous application of far-red (RG 9) light. It is concluded that phytochrome (P_fr) is required not only for the elimination of the lagphase but also to maintain a high rate of Chl a accumulation in continuous light. Since accumulation of 5-aminolevulinate (ALA) responds in the same manner as Chl a accumulation to a red light pretreatment it is further concluded that ALA formation is the point where phytochrome regulates Chl biosynthesis in continuous light. No correlation has been found between ALA and Chl a formation in darkness. This indicates that in a darkgrown pine seedling ALA formation is not rate limiting for Chl a accumulation.Abbreviations Chl chlorophyll(ide) - PChl protochlorophyll(ide) - ALA 5-aminolevulinate - P_r the red absorbing form of phytochrome - P_fr the far-red absorbing form of phytochrome - P_tot total phytochrome ([P_r]+[P_fr])     

Cellulose and 1,3-glucan synthesis during the early stages of wall regeneration in soybean protoplasts

Protoplasts isolated from cultured soybean cells (Glycine max (L.) Merr., cv. Mandarin) were used to study polysaccharide biosynthesis during the initial stages of cell wall-regeneration. Within minutes after the protoplasts were transferred to a wall-regeneration medium containing [¹⁴C]glucose, radioactivity was detected in a product which was chemically characterized as cellulose. The onset and accumulation of radioactivity into cellulose coincided with the appearance fibrils on the surface of protoplasts, as seen under the electron microscope. At these early stages, a variety of polysaccharide-containing polymers other than cellulose were also synthesized. Under conditions where the protoplasts were competent to synthesize cellulose from glucose, uridine diphosphate-[¹⁴C]glucose and guanosine diphosphate-[¹⁴C]glucose did not serve as effective substrates for cellulose synthesis. However, substantial amounts of label from uridine diphosphate glucose were incorporated into 1,3-glucan.Abbreviations ECM extracellular material - GLC gas liquid chromatography - GDP-glucose guanosine diphosphate glucose - UDP-glucose uridine diphosphate glucose - U enzyme units as defined by Sigma Chemical Corp., St. Louis, Mo., USA     

Crystal structure studies and inhibition kinetics of tripeptide chloromethyl ketone inhibitors with Streptomyces griseus protease B

The bacterial serine protease, SGPB, was inhibited by two specific tripeptide chloromethyl ketones, N-t-butyloxycarbonyl-l-alanylglycyl-l-phenylalanine chloromethyl ketone (BocAGFCK) and N-t-butyloxycarbonyl-glycyl-l-leucyl-l-phenylalanine chloromethyl ketone (BocGLFCK). Crystals of the inhibited complexes were grown and examined by X-ray crystallographic methods. The peptide backbone of each inhibitor is bound by three hydrogen bonds to the main chain of residues Ser214 to Gly216. There are two well-characterized hydrophobic pockets, S₁ and S₂, on the surface of SGPB which accommodate the P₁ and P₂ side-chains of the BocGLFCK inhibitor. A conformational change of Tyr171 is induced by the binding of this inhibitor. Both inhibitors make two covalent bonds to the SGPB enzyme. The imidazole ring of His57 is alkylated at the N^?2 atom and O^γ of Ser195 forms a hemiketal bond with the carbonyl-carbon atom of the inhibitor. Comparison of the binding modes of the two tripeptides in conjunction with the differences in their inhibition constants (K_I) allows one to estimate the binding energy of the leucyl side-chain as ?2.6 kcal mol^?1. The importance of an electrophilic component in the serine protease mechanism, which involves the polarization of the susceptible carbonyl bond of a substrate or inhibitor by the peptide NH groups of Gly193 and Ser195 is discussed.