Nutrient sensitivity of the cost of male function in gynodioecious Phacelia linearis (Hydrophyllaceae)

Allocation trade-offs should be measured as opportunity costs, estimating what individuals sacrifice in one function by allocating to others. We investigated opportunity costs of male function in gynodioecious Phacelia linearis, asking whether nutrient limitation contributes to them. This hypothesis predicts that hermaphrodites experience greater nutrient stress than females, and that hermaphrodite disadvantages in production might decrease with nutrient supply. We cultivated hermaphrodites and females at two nutrient levels, scoring individuals for prereproductive leaf number at 5 wk, and biomass, nitrogen concentration, and fruit and seed production at 16 wk. Nutrient treatments caused final growth differences of two orders of magnitude. No gender difference appeared at 5 wk, but at 16 wk hermaphrodites produced less stem, leaf, and inflorescence biomass than females, and made fewer fruits. Hermaphrodites' shoot-size disadvantage was marginally significantly more severe at low nutrients than high nutrients. Significant gender x nutrient interactions for root fraction and whole-plant nitrogen concentration indicate greater nutrient stress in hermaphrodites than females. Hermaphrodites also acquired less total nitrogen than females. Nutrient limitation contributes to opportunity costs of male function, but there must be other contributors. Possibilities include limitations in other resources, gender effects on morphology, and genetic trade-offs not directly involving allocation or morphology.     

Development of a qPCR assay for specific quantification of Botrytis cinerea on grapes

The aim of this study was to develop a system for rapid and accurate real-time quantitative PCR (qPCR) identification and quantification of Botrytis cinerea, one of the major pathogens present on grapes. The intergenic spacer (IGS) region of the nuclear ribosomal DNA was used to specifically detect and quantify B. cinerea. A standard curve was established to quantify this fungus. The qPCR reaction was based on the simultaneous detection of a specific IGS sequence and also contained an internal amplification control to compensate for variations in DNA extraction and the various compounds from grapes that inhibit PCR. In these conditions, the assay had high efficiency (97%), and the limit of detection was estimated to be 6.3 pg DNA (corresponding to 540 spores). Our method was applied to assess the effects of various treatment strategies against Botrytis in the vineyard. Our qPCR assay proved to be rapid, selective and sensitive and may be used to monitor Botrytis infection in vineyards.     

Alterations in pp60c-src accompany differentiation of neurons from rat embryo striatum.

Cultured neurons from rat embryo striatum were found to contain two structurally distinct forms of pp60c-src. The 60-kilodalton (kDa) form appeared similar to pp60c-src from cultured rat fibroblasts or astrocytes. The 61-kDa form was specific to neurons and differed in the NH2-terminal 18 kDa of the molecule. In undifferentiated neurons the predominant phosphorylated species of pp60c-src was the fibroblast form. Upon differentiation, a second phosphorylated form of pp60c-src was detected. This form had two or more additional sites of serine phosphorylation within the NH2-terminal 18-kDa region of the molecule, one of which was Ser-12. The specific protein-tyrosine kinase activity of the total pp60c-src population increased 14-fold, as measured by autophosphorylation, or 7-fold, as measured by phosphorylation of an exogenous substrate, as striatal neurons differentiated. This elevation in protein kinase activity occurred without a detectable decrease in Tyr-527 phosphorylation or increase in Tyr-416 phosphorylation. Our results support the idea that the expression of the neuron-specific form of pp60c-src and the increase in specific protein kinase activity may be important for neuronal differentiation.     

C-terminal Src kinase associates with ligand-stimulated insulin-like growth factor-I receptor

Increased expression of the insulin-like growth factor-I receptor (IGF-IR) protein-tyrosine kinase occurs in several kinds of cancer and induces neoplastic transformation in fibroblast cell lines. The transformed phenotype can be reversed by interfering with the function of the IGF-IR. The IGF-IR is required for transformation by a number of viral and cellular oncoproteins, including SV40 large T antigen, Ras, Raf, and Src. The IGF-IR is a substrate for Src in vitro and is phosphorylated in v-Src-transformed cells. We observed that the IGF-IR and IR associated with the C-terminal Src kinase (CSK) following ligand stimulation. We found that the SH2 domain of CSK binds to the tyrosine-phosphorylated form of IGF-IR and IR. We determined the tyrosine residues in the IGF-IR and in the IR responsible for this interaction. We also observed that fibroblasts stimulated with IGF-I or insulin showed a rapid and transient decrease in c-Src tyrosine kinase activity. The results suggest that c-Src and CSK are involved in IGF-IR and IR signaling and that the interaction of CSK with the IGF-IR may play a role in the decrease in c-Src activity following IGF-I stimulation.     

Afferent connections of physiologically identified neuronal complexes in the paraventricular nucleus of conscious Pekin ducks involved in regulation of salt- and water-balance

Summary The afferent connections of the paraventricular nucleus (PVN) of the domestic mallard (Pekin duck), Anas platyrhynchos, were demonstrated by means of microiontophoretic injection of horseradish peroxidase (HRP). To place the HRP injection exactly into the PVN, its location was identified prior to the injection by observing antidiuretic reactions to electrostimulations within the rostral hypothalamus of conscious, hydrated animals. Antidiuresis was induced only when electrostimulation was applied to a distinct hypothalamic area. Two different patterns of antidiuresis were observed: (i) an immediate reduction in rate of production of urine, and (ii) antidiuresis preceded by a period of increase in production of urine. Repeated stimulation of the same site with the same parameters resulted in decreasing antidiuretic effects. At the site where stimulation had elicited the most pronounced antidiuresis of either response type, HRP was injected microiontophoretically.Histological examination after 3–8 days of survival revealed delicate injection sites located exclusively in the periventricular portion of the PVN. Adjacent to the dorsal portion of the PVN retrogradely labeled tanycytes and intraependymal neurons were scattered in the ventricular wall. As demonstrated in neurohistological and electron-microscopic investigations, this ependymal region exhibits a particular arrangement of tanycytes and small neurons (10–15 m in diameter), some of which belong to the neurosecretory type.Additional HRP-labeled neuronal perikarya afferent to the PVN were demonstrated in the contralateral PVN, and on the ipsilateral side in the lateral septum, lateral hypothalamic area and locus coeruleus. Within the nuclei of the solitary tract, stained nerve cells were found ipsilateral as well as contralateral to the injection site.Several of the neurons demonstrated may be considered as candidates for the transmission of signals originating from various receptive structures relevant for the control of avian salt- and water-balance. The physiological results conform to the concept that neurons of the PVN influence urine formation by controlling the release of arginine-vasotocin (AVT). Evidence that suggests additional modes of control exerted by these neurons in salt- and water-balance is presented.Supported by grants from the Deutsche Forschungsgemeinschaft (Ko 758/1; Si 230/4-4)Portions of these results were presented on the occasion of the 54th Meeting of the Deutsche Physiologische Gesellschaft (Korf et al. 1981 a) and the 76th Meeting of the Anatomische Gesellschaft (Korf et al. 1981 b)