Festkolloquium and Symposium "Präadaptation in der Evolution von Pflanze and Tier"

Zum Gelingen dieses Symposiums haben viele entscheidend beigetragen. Tatkräftige Hilfe bei der Organisation habe ich vielen Mitgliedern des Institutes zu verdanken. Stellvertretend für alle sollen nur Frau Dr. C. Gack and meine technische Assistentin, Frau Christine Gutmann , besonders crwähnt werden. Großzügige finanzielle Unterstützung erhielten wir von der Fa. Goedecke (Freiburg) und dem Herder-Verlag (Freiburg).     

Feinstruktur des ventralen mandibulären Muskelrezeptors bei Liposcelis bostrichophilus (Insecta,Psocoptera)

Zusammenfassung Der ventrale Mandibel-Muskelrezeptor wird im Kopf von Liposcelis bostrichophilus (Psocoptera) nachgewiesen. Er zieht, median der Mandibel-Gelenkachse gelegen, vom vorderen Tentorium-Arm zur hinteren Mandibel-Basis und wird also während der Abduktion der Mandibel gedehnt. Der Rezeptor besteht aus einer motorisch und sensorisch innervierten Muskelfaser und 10 bipolaren, multiterminalen Sinneszellen. Einige der Sinneszellen senden ihre Dendriten ins Innere des Rezeptor-Muskels, wo sie sich verzweigen und jeweils an den Z-Scheiben enden. Die übrigen Sinneszellen bilden mit ihren Dendriten ein Bündel, das der Oberfläche des Rezeptor-Muskels anliegt. Nur die ins Innere ziehenden Dendriten weisen in ihren Endigungen Tubularkörper-ähnliche Strukturen auf. Sowohl die Sinneszellen als auch der Rezeptor-Muskel werden von Hüllzell-Wicklungen eng umhüllt.

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Summary The ventral mandibular muscle receptor in the head of Liposcelis bostrichophilus (Psocoptera) is described. It is located median to the mandibular hinge axis, extending from the front tentorium to the dorsal mandibular basis, and is stretched according to the movements of the mandible. The receptor consists of a sensorily and a motor-stimulated muscle fibre and ten bipolar multiterminal neurons. Some of the neurons send their dendrites into the inner part of the receptor muscle, where they branch and terminate at the level of the Z discs. The other neurons build a dendritic bunch, which runs parallel to the muscle fibre surface. Only the dendrites located close to the Z discs show tubular-body-like structures in their terminal ends. The multiterminal neurons and the receptor muscle are covered with glial cells.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft     

The chemical compound ‘Heatin’ stimulates hypocotyl elongation and interferes with the Arabidopsis NIT1-subfamily of nitrilases

Temperature passively affects biological processes involved in plant growth. Therefore, it is challenging to study the dedicated temperature signalling pathways that orchestrate thermomorphogenesis, a suite of elongation growth-based adaptations that enhance leaf-cooling capacity. We screened a chemical library for compounds that restored hypocotyl elongation in the pif4-2–deficient mutant background at warm temperature conditions in Arabidopsis thaliana to identify modulators of thermomorphogenesis. The small aromatic compound ‘Heatin’, containing 1-iminomethyl-2-naphthol as a pharmacophore, was selected as an enhancer of elongation growth. We show that ARABIDOPSIS ALDEHYDE OXIDASES redundantly contribute to Heatin-mediated hypocotyl elongation. Following a chemical proteomics approach, the members of the NITRILASE1-subfamily of auxin biosynthesis enzymes were identified among the molecular targets of Heatin. Our data reveal that nitrilases are involved in promotion of hypocotyl elongation in response to high temperature and Heatin-mediated hypocotyl elongation requires the NITRILASE1-subfamily members, NIT1 and NIT2. Heatin inhibits NIT1-subfamily enzymatic activity in vitro and the application of Heatin accordingly results in the accumulation of NIT1-subfamily substrate indole-3-acetonitrile in vivo. However, levels of the NIT1-subfamily product, bioactive auxin (indole-3-acetic acid), were also significantly increased. It is likely that the stimulation of hypocotyl elongation by Heatin might be independent of its observed interaction with NITRILASE1-subfamily members. However, nitrilases may contribute to the Heatin response by stimulating indole-3-acetic acid biosynthesis in an indirect way. Heatin and its functional analogues present novel chemical entities for studying auxin biology.     

Decreased cerebral Irp‐1B limits impact of social isolation in wild type and Alzheimer's disease modeled in Drosophila melanogaster

Environmental factors, such as housing conditions and cognitively stimulating activities, have been shown to affect behavioral phenotypes and to modulate neurodegenerative conditions such as Alzheimer's disease (AD). AD is a progressive neurodegenerative disorder affecting cognitive functions. Epidemiological evidence and experimental studies using rodent models have indicated that social interaction reduces development and progression of disease. Drosophila models of Aβ42‐associated AD lead to AD‐like phenotypes, such as long‐term memory impairment, locomotor and survival deficits, while effects of environmental conditions on AD‐associated phenotypes have not been assessed in the fly. Here, we show that single housing reduced survival and motor performance of Aβ42 expressing and control flies. Gene expression analyses of Aβ42 expressing and control flies that had been exposed to different housing conditions showed upregulation of Iron regulatory protein 1B (Irp‐1B) in fly brains following single housing. Downregulating Irp‐1B in neurons of single‐housed Aβ42 expressing and control flies rescued both survival and motor performance deficits. Thus, we provide novel evidence that increased cerebral expression of Irp‐1B may underlie worsened behavioral outcome in socially deprived flies and can additionally modulate AD‐like phenotypes.