Protein Targeting into Secondary Plastids1

ABSTRACT. Most of the coding capacity of primary plastids is reserved for expressing some central components of the photosynthesis machinery and the translation apparatus. Thus, for the bulk of biochemical and cell biological reactions performed within the primary plastids, many nucleus‐encoded components have to be transported posttranslationally into the organelle. The same is true for plastids surrounded by more than two membranes, where additional cellular compartments have to be supplied with nucleus‐encoded proteins, leading to a corresponding increase in complexity of topogenic signals, transport and sorting machineries. In this review, we summarize recent progress in elucidating protein transport across up to five plastid membranes in plastids evolved in secondary endosymbiosis. Current data indicate that the mechanisms for protein transport across multiple membranes have evolved by altering pre‐existing ones to new requirements in secondary plastids.     

Nest site preference and success in a gregarious, ground-nesting bee Dieunomia triangulifera

1. The characteristics of preferred nest sites of the solitary bee Dieunomia triangulifera, which nests gregariously in alluvial soil, were investigated. Nest presence was used as an indication of preference. In those cases where nests were more than a few days old, therefore, this study also investigated nest success. 2. Independent variables tested were soil surface moisture, presence of nesting conspecifics, smooth vs. irregular soil surface, distance to visual landmarks, percentage of vegetation cover, soil compaction, vehicular traffic, soil surface temperature, and light intensity. 3. Bees preferred to nest in moist, compact soil with an irregular surface. More bees nested near visual landmarks and in places with little or no vegetation. They preferred nesting in areas with warmer soil surface temperatures and brighter illumination. The presence of nesting conspecifics did not influence nesting decisions. Vehicular traffic also seemed to have no impact on nest initiation but did seem to have a negative impact on nest success. 4. Although it might seem that ground-nesting bees should not be limited by nesting sites, relatively little of the study area met all their apparent criteria. This might account, in part, for gregarious nesting in this species.     

From humoral fever to neuroimmunological control of fever

Fever is a part of the acute phase response to infection or systemic inflammation. It is thus a part of a complex physiological defence strategy against micro-organisms invading the body of the host, or against non-microbial agents recognized as foreign by mobile immune cells of the body. The fever is induced by inflammatory mediators (prostaglandins, cytokines) released by immune cells activated by contacts with foreign molecules (exogenous pyrogens). These fever-inducing mediators, produced by the host cells (endogenous pyrogens), were originally thought to be distributed by means of the bloodstream (similarly to hormones) to different tissues of the body. Although the details of their transport across the blood–brain-barrier have not been clarified, it has been assumed that they activate the local production of inflammatory mediators within the brain, inducing a change in the thermoregulatory set-range and resulting in fever (humoral theory of fever). This concept has apparently changed in the past few years. Evidence has recently been presented supporting the possibility of the transport of immune signals to the brain via vegetative and peripheral nerves. In this review an attempt is made to describe the events leading to a fever response accompanying the systemic inflammation against a background of microbiological, immunological and physiological data. The experimental evidence published during the last five years has been reviewed, and a new concept of neuroimmunological control of fever is presented. This concept suggests that the host immune defence is coordinated through an integration of the neural, immune, hemopoietic and endocrine systems. The brain seems to be informed of any damage or antigenic challenge in the periphery of the body by a sensory host-monitoring system, and this information is confirmed by immune signals delivered by the humoral transport. The combination of these signals would allow the brain to recognize the nature of the challenge, and to activate an appropriate defence strategy. Fever as a part of many successful defence strategies against infections may thus be beneficial.     

Agonistic behaviour of female Tegenaria atrica in the presence of different aged spiderlings

The agonistic behaviour of adult female T. atrica increases with increasing age of spiderlings until 80 days post-emergence, then decreases. In all cases, cannibalism of spiderlings increases markedly after completion of their pre-dispersal period with a correlation between the switch of behaviour, from tolerance to cannibalism, and a modification of individual’s cuticular compounds. Experiments that compare spiderlings weight and mobility indicate that female agonistic behaviour are always low with spiderlings in pre-dispersal period, and high with spiderlings in post-dispersal period. Female reproductive state and the weight/mobility of spiderlings are not the only factors controlling the adult female’s agonistic behaviour towards spiderlings on her web, as tactochemical information plays an important role in modulating agonistic behaviour after close contact between female spiders and spiderlings. The agonistic behaviour of females appears to correspond with a change in the increase of polar compound levels (methylesters and fatty acids) and the decrease of apolar compound levels (hydrocarbons) in spiderlings of different ages.