Morphological evidence for a close interaction of chromaffin cells with cortical cells within the adrenal gland

Summary The adrenal medulla appears to exert a regulatory influence on adrenocortical steroidogenesis. We have therefore studied the morphology of rat, porcine and bovine adrenals in order to characterize the contact zones of adrenomedullary and adrenocortical tissues. The distribution of chromaffin cells located within the adrenal cortex and of cortical cells located within the adrenal medulla was investigated. Chromaffin cells were characterized by immunostaining for synaptophysin and chromogranin A, both being considered specific for neuroendocrine cells. Cortical cells were characterized by immunostaining for 17-hydroxylase, an enzyme of the steroid pathway. Cellular contacts of chromaffin cells and cortical cells were examined at the electron microscopical level. In rat and porcine adrenals, rays of chromaffin cells, small cell clusters and single chromaffin cells or small invaginations from the medulla could be detected in all three zones of the cortex. Chromaffin cells often spread in the subcapsular space of the zona glomerulosa. In porcine and bovine adrenals, 17-hydroxylase immunoreactive cells were localized within the medulla. Single cortical cells and small accumulations of cells were spread throughout this region. At the ultrastructural level, the chromaffin cells located within the cortex in pig and rat adrenals formed close cellular contacts with cortical cells in all three zones. Our morphological data provide evidence for a possible paracrine role of chromaffin cells; this may be important for the neuroregulation of the adrenal cortex.     

Cholinesterase-Aktivität im Primitivknoten,in der Schwanzknospe und bei der Chordaentwicklung des Hühnchens

Histochemistry and Cell Biology - An Hühnerkeimscheiben wurde das Verhalten der Cholinesterase bei der Caudalwanderung des Primitivknotens, bei der Chordabildung und in der Sohwanzknospe...     

Evolution of a Complex Locus for Terpene Biosynthesis in Solanum

Functional gene clusters, containing two or more genes encoding different enzymes for the same pathway, are sometimes observed in plant genomes, most often when the genes specify the synthesis of specialized defensive metabolites. Here, we show that a cluster of genes in tomato (Solanum lycopersicum; Solanaceae) contains genes for terpene synthases (TPSs) that specify the synthesis of monoterpenes and diterpenes from cis-prenyl diphosphates, substrates that are synthesized by enzymes encoded by cis-prenyl transferase (CPT) genes also located within the same cluster. The monoterpene synthase genes in the cluster likely evolved from a diterpene synthase gene in the cluster by duplication and divergence. In the orthologous cluster in Solanum habrochaites, a new sesquiterpene synthase gene was created by a duplication event of a monoterpene synthase followed by a localized gene conversion event directed by a diterpene synthase gene. The TPS genes in the Solanum cluster encoding cis-prenyl diphosphate–utilizing enzymes are closely related to a tobacco (Nicotiana tabacum; Solanaceae) diterpene synthase encoding Z-abienol synthase (Nt-ABS). Nt-ABS uses the substrate copal-8-ol diphosphate, which is made from the all-trans geranylgeranyl diphosphate by copal-8-ol diphosphate synthase (Nt-CPS2). The Solanum gene cluster also contains an ortholog of Nt-CPS2, but it appears to encode a nonfunctional protein. Thus, the Solanum functional gene cluster evolved by duplication and divergence of TPS genes, together with alterations in substrate specificity to utilize cis-prenyl diphosphates and through the acquisition of CPT genes.     

Identification and characterization of a UDP-D-glucuronate 4-epimerase in Arabidopsis

One of the major sugars present in the plant cell wall is d-galacturonate, the dominant monosaccharide in pectic polysaccharides. Previous work indicated that one of the activated precursors necessary for the synthesis of pectins is UDP-d-galacturonate, which is synthesized from UDP-d-glucuronate by a UDP-d-glucuronate 4-epimerase (GAE). Here, we report the identification, cloning and characterization of a GAE6 from Arabidopsis thaliana. Functional analysis revealed that this enzyme converts UDP-d-glucuronate to UDP-d-galacturonate in vitro. An expression analysis of this epimerase and its five homologs in the Arabidopsis genome by quantitative RT-PCR and promoter::GUS fusions indicated differential expression of the family members in plant tissues and expression of all isoforms in the developing pollen of A. thaliana.     

Reprogramming a maize plant: transcriptional and metabolic changes induced by the fungal biotroph Ustilago maydis

The fungal pathogen Ustilago maydis establishes a biotrophic relationship with its host plant maize (Zea mays). Hallmarks of the disease are large plant tumours in which fungal proliferation occurs. Previous studies suggested that classical defence pathways are not activated. Confocal microscopy, global expression profiling and metabolic profiling now shows that U. maydis is recognized early and triggers defence responses. Many of these early response genes are downregulated at later time points, whereas several genes associated with suppression of cell death are induced. The interplay between fungus and host involves changes in hormone signalling, induction of antioxidant and secondary metabolism, as well as the prevention of source leaf establishment. Our data provide novel insights into the complexity of a biotrophic interaction.     

Histochemischer Cholinesterase-Nachweis während der Abfaltungsbewegungen des Hühnerembryos

Zusammenfassung An Hühnerembryonen der Stadien 5–21 wurde das Auftreten von Cholinesterase-Aktivität in Zellverbänden verfolgt, die bei der Abfaltung des Embryos von Bedeutung sind.Im Neuroektoderm treten während der Neuralrohrbildung Cholinesterase-positive Zellen auf. Diese Aktivität verschwindet, wenn das Neuralrohr ausgebildet ist. Anschließend lassen sich Cholinesterase-positive Neuroblasten darstellen.Im Oberflächenektoderm tritt Cholinesterase-Aktivität während der Ausbildung der Kopffalte und der Grenzrinnen auf. Die Aktivität verschwindet, wenn sich die Kopfanlage vom extraembryonalen Teil der Keimblätter getrennt hat.Bei der Ausbildung der Entodermwülste und während des Einwanderns derselben zum Darmrohrschluß bilden sich palisadenartige Epithelverdickungen aus, die Cholinesterase aufweisen. Wenn das Darmrohr geschlossen ist, verschwindet die Aktivität wieder. Während der Darmrohrbildung wird das nach ventral und medial einwachsende Entoderm von palisadenartig strukturiertem Mesoderm begleitet, das Cholinesterase-Aktivität aufweist. Nach Schluß des Darmrohres löst sich die palisadenartige Anordnung auf und die Cholinesterase-Aktivität verschwindet.

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Histochemical demonstration of cholinesterase during the folding off of the chick embryo

Summary The localization of cholinesterase activity in chick embryo of stage 5 up to stage 21 has been studied in cell layers that are involved in the formation of the primitive body tube.During the formation of the neural tube, cholinesterase activity can be demonstrated in cells of the neural plate. This pattern of enzyme activity disappears after formation of the neural tube. Thereafter, the enzyme is localized in neuroblasts.In the ectodermal layer, cholinesterase activity is found during the formation of the head fold and the lateral body folds. Again, the enzyme disappears after the development of the cephalic outgrowth.Formation of the entodermal folds and their fusion in the midline — thus establishing the gut tube — is associated with cholinesterase activity in palisade cell layers. There is no enzyme activity in the completed gut.During the formation of the gut tube, the mediad invading entodermal folds are covered by mesodermal cell palisades, which are positive for cholinesterase. After the formation of the gut tube, the palisades disappear as does the enzyme activity.

     

Identification of enzyme activity quantitative trait loci in a Solanum lycopersicum x Solanum pennellii introgression line population

Activities of 28 enzymes from central carbon metabolism were measured in pericarp tissue of ripe tomato fruits from field trials with an introgression line (IL) population generated by introgressing segments of the genome of the wild relative Solanum pennellii (LA0716) into the modern tomato cultivar Solanum lycopersicum M82. Enzyme activities were determined using a robotized platform in optimized conditions, where the activities largely reflect the level of the corresponding proteins. Two experiments were analyzed from years with markedly different climate conditions. A total of 27 quantitative trait loci were shared in both experiments. Most resulted in increased enzyme activity when a portion of the S. lycopersicum genome was substituted with the corresponding portion of the genome of S. pennellii. This reflects the change in activity between the two parental genotypes. The mode of inheritance was studied in a heterozygote IL population. A similar proportion of quantitative trait loci (approximately 30%) showed additive, recessive, and dominant modes of inheritance, with only 5% showing overdominance. Comparison with the location of putative genes for the corresponding proteins indicates a large role of trans-regulatory mechanisms. These results point to the genetic control of individual enzyme activities being under the control of a complex program that is dominated by a network of trans-acting genes.