Importance of juvenile hormone signaling arises with competence of insect larvae to metamorphose

AbstractJuvenile hormone (JH) postpones metamorphosis of insect larvae until they have attained an appropriate stage and size. Then, during the final larval instar, a drop in JH secretion permits a metamorphic molt that transforms larvae to adults either directly (hemimetaboly) or via a pupal stage (holometaboly). In both scenarios, JH precludes metamorphosis by activating the Kr-h1 gene through a JH receptor, Methoprene-tolerant (Met). Removal of Met, Kr-h1, or JH itself triggers deleterious precocious metamorphosis. Although JH is thought to maintain the juvenile status throughout larval life, various methods of depleting JH failed to induce metamorphosis in early-instar larvae. To determine when does JH signaling become important for the prevention of precocious metamorphosis, we chose the hemimetabolous bug, Pyrrhocoris apterus, and the holometabolous silkworm, Bombyx mori. Both species undergo a fixed number of five larval instars. Pyrrhocoris larvae subjected to RNAi-mediated knockdown of Met or Kr-h1 underwent precocious adult development when treated during the fourth (penultimate) instar, but younger larvae proved increasingly resistant to loss of either gene. The earliest instar developing minor signs of precocious metamorphosis was the third. Therefore, the JH-response genes may not be required to maintain the larval program during the first two larval instars. Next, we examined Bombyx mod mutants that cannot synthesize authentic, epoxidized forms of JH. Although mod larvae expressed Kr-h1 mRNA at severely reduced levels since hatching, they only entered metamorphosis by pupating after four, rarely three instars. Based on findings in Pyrrhocoris and Bombyx, we propose that insect postembryonic development is initially independent of JH. Only later, when larvae gain competence to enter metamorphosis, JH signaling becomes necessary to prevent precocious metamorphosis and to optimize growth

In Hungary, Czech Republic, Poland, Romania, Slovakia, and East Germany (including Berlin)

With the integration of post-communist countries into the European and global economy after 1990, there was strong research interest into the role of multinational enterprises (MNEs) for economic restructuring and technological catching-up. Most of the existing empirical studies on locational determinants of FDI and host country effects did not take account of East Germany. This might be for different reasons: Firstly, theoretical and empirical difficulties derive from the fact that East Germany followed a distinct transition pattern as it became a region subsumed in a larger and more mature economy. Secondly, East Germany received private investment from foreign as well as West German firms. Only the first can be considered as a foreign direct investment (FDI). Finally, there had long been a lack of micro data to adequately analyse the activities of corresponding firms from a production as well as technological perspective

Functional Upgrading and Productivity Growth of Multinational Subsidiaries in European Transition Economies

With economic transformation and European integration Central and Eastern European countries (CEECs) have been inserted into European and global production networks. The literature on global value chains (GVCs) suggests that firms’ performance in terms of value creation and capture crucially depends upon their ability to ‘upgrade’. Apart from product and process upgrading this refers to ‘functional upgrading’ i.e. the changing portfolio and nature of business functions executed by firms within the GVC. In principal this should hold also for multinational affiliates. They participate in GVCs through vertically integrated and specialized forms of organization. Their ability to upgrade is closely linked with their position, mandate and power asymmetries within the multinational network. Recent case study evidence documents functional upgrading in multinational subsidiaries located in CEECs. Yet, their ability to increase value capture through these processes has been contested. This paper tests the relationship between functional upgrading and productivity growth of multinational subsidiaries. We exploit a unique firm level dataset that matches state-of-the-art survey-based business function indicators with times-series accounting data for a representative sample of multinational subsidiaries in selected CEECs. The estimation results indicate that functional upgrading has a positive effect on foreign subsidiaries’ average productivity growth. The effect is higher for subsidiaries with more recent entries of foreign investors. This finding is robust to different measures for functional upgrading. The positive effect of functional upgrading seems to be mainly confined to foreign subsidiaries in manufacturing industries

Common and Distinct Roles of Juvenile Hormone Signaling Genes in Metamorphosis of Holometabolous and Hemimetabolous Insects

Insect larvae metamorphose to winged and reproductive adults either directly (hemimetaboly) or through an intermediary pupal stage (holometaboly). In either case juvenile hormone (JH) prevents metamorphosis until a larva has attained an appropriate phase of development. In holometabolous insects, JH acts through its putative receptor Methoprene-tolerant (Met) to regulate Krüppel-homolog 1 (Kr-h1) and Broad-Complex (BR-C) genes. While Met and Kr-h1 prevent precocious metamorphosis in pre-final larval instars, BR-C specifies the pupal stage. How JH signaling operates in hemimetabolous insects is poorly understood. Here, we compare the function of Met, Kr-h1 and BR-C genes in the two types of insects. Using systemic RNAi in the hemimetabolous true bug, Pyrrhocoris apterus, we show that Met conveys the JH signal to prevent premature metamorphosis by maintaining high expression of Kr-h1. Knockdown of either Met or Kr-h1 (but not of BR-C) in penultimate-instar Pyrrhocoris larvae causes precocious development of adult color pattern, wings and genitalia. A natural fall of Kr-h1 expression in the last larval instar normally permits adult development, and treatment with an exogenous JH mimic methoprene at this time requires both Met and Kr-h1 to block the adult program and induce an extra larval instar. Met and Kr-h1 therefore serve as JH-dependent repressors of deleterious precocious metamorphic changes in both hemimetabolous and holometabolous juveniles, whereas BR-C has been recruited for a new role in specifying the holometabolous pupa. These results show that despite considerable evolutionary distance, insects with diverse developmental strategies employ a common-core JH signaling pathway to commit to adult morphogenesis

FDI in hot labour markets: The implications of the war for talent

This paper highlights an inherent contradiction that exists within investment promotion activities in rich countries. Since the financial crisis, many inward investment agencies have shifted their activities from job creation per se to seeking to attract investment in high-tech activities. Such knowledge-intensive sectors are engaged in what has become referred to as “the war for talent”, so locations need to understand their value proposition to firms, especially where labour is tight. This paper explores the implications of this, in terms of the impact on employment and earnings of high skilled labour. We show that, because skill shortages already exist in many of these sectors, seeking to attract inward investment in these sectors simply causes the earnings of such workers to be bid up, and employment in the incumbent sector to fall. We highlight the over-riding importance that firms place on the availability of skilled labour when determining locations, and how policies which promote labour market flexibility, particularly through investment in skills to address skill shortages, can significantly mitigate the adverse effects, which tend to be more keenly felt in poorer regions of Europe where skilled labour is in even shorter supply

Počítačový řídící systém s využitím jednočipových mikroprocesorů

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta elektrotechniky a informatiky. Katedra (454) elektroniky a telekomunikační technik