Effects of diapause duration on future reproduction in the cabbage beetle,Colaphellus bowringi: positive or negative?

Abstract.  Cabbage beetles, Colaphellus bowringi , undergoing an imaginal summer and winter diapause in the soil, show a great difference in diapause duration (from several months to more than 3 years) under natural conditions. The effects of diapause duration on future reproduction in the beetle are investigated at 25 °C with an LD 14 : 10 h photoperiod and under natural conditions. The fecundity of postdiapause adults with a short diapause of 5 months and nondiapause adults is similar, showing that a short diapause has no affect on reproduction, whereas the longevity of postdiapause adults with a short diapause of 5 months is significantly shorter than nondiapause adults, showing that a short diapause has a negative affect on longevity. The mean total egg production per female and longevities of postdiapause adults with long diapause periods of 16, 22, 29 and 34 months are similar to nondiapause adults, but the mean daily egg production per female is significantly higher than nondiapause adults, showing that extended diapause has a positive effect on postdiapause reproduction. The offspring of postdiapause parents require a relatively shorter time for egg development compared with the offspring of nondiapause parents, showing that diapause has a positive effect on their offspring's performance. However, there are no significant differences among offspring performance in terms of survival, adult longevity, mean egg production per female and mean daily egg production per female.     

The selective basis for increased egg retention: early incubation temperature determines hatchling phenotype in wall lizards (Podarcis muralis)

The thermal environment during development influences many aspects of the phenotype of hatchling reptiles. We hypothesized that temperature should differentially affect early incubation stages, in which differentiation dominates over growth, and late incubation stages, characterized by high growth rates. To test this idea, we incubated eggs of wall lizard ( Podarcis muralis ) under three regimes with the same mean temperature (29 °C), one constant and two variable with opposite sequences: first cold (25 °C) and then hot (32 °C), and vice versa. Hatchlings incubated at high temperature during the initial period had shorter hindlimbs and tails than those incubated under the other two temperature regimes and shorter heads than those incubated initially at low temperature. Thus, temperature experienced by embryos during the early external incubation period produced similar phenotypic responses compared to those reported in previous studies for the same constant temperature applied over the whole incubation period. Because female wall lizards select lower body temperatures during pregnancy, an increase of intrauterine retention would extend the time of exposure of developing embryos to suitable temperatures. Diminution of body temperature during pregnancy is contrary to the expected pattern under the hypothesis that egg retention has evolved to accelerate development, as proposed by the cold-climate model for evolution of viviparity in squamates, and the results of the present study support the alternative hypothesis of developmental optimization as a special case of the broader maternal manipulation view.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 441–447.     

Hepatocyte growth factor at S phase induces G2 delay through sustained ERK activation

The effect of growth factors on the cell cycle progression, except G1/S transition, is poorly understood. Herein, we examined the effect of hepatocyte growth factor (HGF) treated at S phase on the cell cycle progression of HeLa cells. Interestingly, the treatment resulted in G2 delay, evidenced by flow cytometric and mitotic index analyses. The delay corresponded with the delay of degradation of cyclin A and cyclin B, and the delay of decrease of Cdk1/cyclin B and Cdk2/cyclin A kinase activities. As for the signaling responsible, sustained activation of ERK, but neither of p38MAPK nor of JNK, was observed after HGF treatment at S phase. Furthermore, U0126, an inhibitor of MEK1, and DN-MEK partially abrogated the G2 delay, indicating that activation of MEK-ERK pathway is involved. Taken together, HGF treatment of HeLa cells at S phase induces G2 delay partially through sustained activation of ERK signaling.     

Key developmental regulators change during hyperoxia-induced injury and recovery in adult mouse lung

Developmentally important genes have recently been linked to tissue regeneration and epithelial cell repair in neonatal and adult animals in several organs, including liver, skin, prostate, and musculature. We hypothesized that developmentally important genes play roles in lung injury repair in adult mice. Although there is considerable information known about these processes, the specific molecular pathways that mediate injury and regulate tissue repair are not fully elucidated. Using a hyperoxic injury model to study these mechanisms of lung injury and tissue repair, we selected the following genes based upon their known or putative roles in lung development and organogenesis: TTF-1, FGF9, FGF10, BMP4, PDGF-A, VEGF, Ptc, Shh, Sca-1, BCRP, CD45, and Cyclin-D2. Our findings demonstrate that several developmentally important genes (Sca-1, Shh, PDGF-A, VEGF, BCRP, CD45, BMP4, and Cyclin-D2) change during hyperoxic injury and normoxic recovery in mice, suggesting that adult lung may reactivate key developmental regulatory pathways for tissue repair. The mRNA for one gene (TTF-1), unchanged during hyperoxia, was upregulated late in recovery phase. These novel findings provide the basis for testing the efficacy of post-injury lung repair in animals genetically modified to inactivate or express individual molecules.     

Analysis of the effects of firing rate and synchronization on spike-triggered averaging of multidirectional motor unit torque

Spike-triggered averaging (STA) of muscle force transients has often been used to estimate motor unit contractile properties, using the discharge of a motor unit within the muscle as the triggering events. For motor units that exert torque about multiple degrees-of-freedom, STA has also been used to estimate motor unit pulling direction. It is well known that motor unit firing rate and weak synchronization of motor unit discharges with other motor units in the muscle can distort STA estimates of contractile properties, but the distortion of STA estimates of motor unit pulling direction has not been thoroughly evaluated. Here, we derive exact equations that predict that STA decouples firing rate and synchronization distortion when used to estimate motor unit pulling direction. We derive a framework for analyzing synchronization, consider whether the distortion due to synchronization can be removed from STA estimates of pulling direction, and show that there are distributions of motor unit pulling directions for which STA is insensitive to synchronization. We conclude that STA may give insight into how motoneuronal synchronization is organized with respect to motor unit pulling direction. Action Editor: David Terman     

Sparse cerebellar innervation can morph the dynamics of a model oculomotor neural integrator

The oculomotor integrator is a brainstem neural network that converts velocity signals into the position commands necessary for eye-movement control. The cerebellum can independently adjust the amplitude of eye-movement commands and the temporal characteristics of neural integration, but the percentage of integrator neurons that receive cerebellar input is very small. Adaptive dynamic systems models, configured using the genetic algorithm, show how sparse cerebellar inputs could morph the dynamics of the oculomotor integrator and independently adjust its overall response amplitude and time course. Dynamic morphing involves an interplay of opposites, in which some model Purkinje cells exert positive feedback on the network, while others exert negative feedback. Positive feedback can be increased to prolong the integrator time course at virtually any level of negative feedback. The more these two influences oppose each other, the larger become the response amplitudes of the individual units and of the overall integrator network. Action Editor: Jonathan D. Victor     

The role of two LEAFY paralogs from Idahoa scapigera (Brassicaceae) in the evolution of a derived plant architecture

Idahoa scapigera produces solitary flowers in the axils of rosette leaves without elongation of the shoot axis, a rosette-flowering architecture. Previous work with one of the two I. scapigera LFY paralogs, IscLFY1, showed that this gene caused aerial flowering rosettes in Arabidopsis thaliana. In this paper, we report that after three generations IscLFY1 transgenic lines are phenotypically indistinguishable from wild-type Arabidopsis, indicating that IscLFY1 protein is able to replace normal LFY function. Additionally, we found that ectopic LFY expression late in development can phenocopy aspects of the aerial rosette phenotype, suggesting that shoot compression caused by IscLFY1 could be caused by localized overexpression of a functional IscLFY protein. We also characterized the expression and function of the second I. scapigera LFY paralog, IscLFY2, in A. thaliana. In contrast to IscLFY1, this paralog was expressed in floral meristems and the shoot apical meristem (SAM). In I. scapigera, LFY-specific antibodies detected high protein levels in developing flowers but not in the apex, suggesting trans-regulatory differences between I. scapigera and A. thaliana. Most IscLFY2 transgenic A. thaliana plants were indistinguishable from wild type, but in a minority of lines the SAM was converted to a terminal flower as would be expected from the reporter-expression pattern. Taken together these results show that both I. scapigera paralogs have conserved LFY function, both proteins can rescue lfy and both can modify inflorescence architecture in an A. thaliana background: either by affecting internode elongation (IscLFY1) or by causing homeotic conversion of shoots into flowers (IscLFY2).     

A primary role of developmental instability in sexual selection

In evolutionary biology, fluctuating asymmetry (FA) is thought to reveal developmental instability (DI, inability to buffer development against perturbations), but its adaptive and genetic bases are being debated. In other fields, such as human clinical genetics, DI is being assessed as incidence of minor morphological abnormalities (MMAs) and used to predict certain fitness outcomes. Here, for the first time, we combine these complementary measures of DI in sexual selection and quantitative genetic studies of a natural population. Comprehensive multivariate analyses demonstrate that FA and MMAs in a condition-dependent sexual ornament, the male Drosophila bipectinata sex comb used in courtship, are sole significant targets of selection favouring their reduced expression in New Caledonia. Comb FA and MMAs are positively correlated, confirming that each are linked to a common buffering system. Ornament size and DI (as FA and MMAs) are positively correlated, genetically and phenotypically, contrary to theoretical expectation of negative size-FA scaling under the assumption that FA reveals overall genetic quality. There exists significant additive genetic variance for MMAs, demonstrating their evolutionary potential. Ornament DI in New Caledonia is markedly elevated compared with populations where such selection was not detected, suggesting that the increased population-level DI is capacitating adaptive evolution.