Effect of flower traits and hosts on the abundance of parasitoids in perennial multiple species wildflower strips sown within oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis>) crops

Reducing the use of insecticides is an important issue for agriculture today. Sowing wildflower strips along field margins or within crops represents a promising tool to support natural enemy populations in agricultural landscapes and, thus, enhance conservation biological control. However, it is important to sow appropriate flower species that attract natural enemies efficiently. The presence of prey and hosts may also guide natural enemies to wildflower strips, potentially preventing them from migrating into adjacent crops. Here, we assessed how seven flower traits, along with the abundance of pollen beetles (Meligethes spp., Coleoptera: Nitidulidae) and true weevils (Ceutorhynchus spp., Coleoptera: Curculionidae), affect the density of parasitoids of these two coleopterans in wildflower strips sown in an oilseed rape field in Gembloux (Belgium). Only flower traits, not host (i.e. pollen beetles and true weevils) abundance, significantly affected the density of parasitoids. Flower colour, ultraviolet reflectance and nectar availability were the main drivers affecting parasitoids. These results demonstrate how parasitoids of oilseed rape pests react to flower cues under field conditions. Similar analyses on the pests and natural enemies of other crops are expected to help to develop perennial flower mixtures able to enhance biological control throughout a rotation system.     

Pollen-vegetation richness and diversity relationships in the tropics

Tracking changes in biodiversity through time requires an understanding of the relationship between modern diversity and how this diversity is preserved in the fossil record. Fossil pollen is one way in which past vegetation diversity can be reconstructed. However, there is limited understanding of modern pollen-vegetation diversity relationships from biodiverse tropical ecosystems. Here, pollen (palynological) richness and diversity (Hill N₁) are compared with vegetation richness and diversity from forest and savannah ecosystems in the New World and Old World tropics (Neotropics and Palaeotropics). Modern pollen data were obtained from artificial pollen traps deployed in 1-ha vegetation study plots from which vegetation inventories had been completed in Bolivia and Ghana. Pollen counts were obtained from 15 to 22 traps per plot, and aggregated pollen sums for each plot were >?2,500. The palynological richness/diversity values from the Neotropics were moist evergreen forest?=?86/6.8, semi-deciduous dry forest?=?111/21.9, wooded savannah?=?138/31.5, and from the Palaeotropics wet evergreen forest?=?144/28.3, semi-deciduous moist forest?=?104/4.4, forest-savannah transition?=?121/14.1; the corresponding vegetation richness/diversity was 100/36.7, 80/38.7 and 71/39.4 (Neotropics), and 101/54.8, 87/45.5 and 71/34.5 (Palaeotropics). No consistent relationship was found between palynological richness/diversity, and plot vegetation richness/diversity, due to the differential influence of other factors such as landscape diversity, pollination strategy, and pollen source area. Palynological richness exceeded vegetation richness, while pollen diversity was lower than vegetation diversity. The relatively high global diversity of tropical vegetation was found to be reflected in the pollen rain.     

Pattern of shift rota modulates oral temperature circadian rhythm and sleep-wakefulness profiles in shift workers

Twenty four shift workers (8 from a steel industry and 16 from a Government hospital) participated in the study. The subjects were instructed to self-measure oral temperature, 4 6 times a day for about three weeks. Sleep quantity and quality for each subject were analysed with the help of an appropriate inventory. The data were analysed by cosinor and power spectrum methods. The frequency of circadian rhythm detection was in the order of 48% in senior nurses, 29% in steel plant workers and 14% in junior nurses. These were also complemented by the results of power spectrum analysis. Present results suggest that rhythms of subjective fatigue and subjective drowsiness are governed neither by oral temperature oscillator nor by the sleep/wake cycle oscillator. The results show that shift rotation pattern chiefly modulates the circadian time structure of shift workers. It is also suggested that the phenomenon of circadian rhythm desynchronization in oral temperature appears to be independent of per day total sleep length.     

Increased gene expression of plasminogen activators and inhibitors in left ventricular hypertrophy

In the early stages of left ventricular hypertrophy (LVH) acute adaptive changes occur in the coronary vasculature as it remodels. Plasminogen activators (PAs) and inhibitors (PAIs) have the potential effects of proteolytic degradation that is relevant to tissue remodeling and angiogenesis. Our study focused on the possible roles of PAI-1, PAI-2, uPA and tPA in myocyte hypertrophy and angiogenesis in the early and late stages of pressure overload induced left ventricular hypertrophy (LVH). We divided seventeen adult swine, weighing 24.2 ± 6.5 kg, into four groups: control, sham-operated, early LVH and late heart failure LVH group. At surgery we placed a fixed constrictor on the ascending aorta immediately above the aortic valve. This increased LV systolic pressure from 133 ± 15 to 193 ± 24 mm Hg after the surgery. We subdivided the early group into groups of 3 animals each that we euthanized at 8, 24 and 72 h after operation and obtained heart samples for analysis. In the late heart failure group individual animals were euthanized at 55, 59, 62 and 72 days after the detection of congestive heart failure. We also obtained tissue samples from the control and sham-operated swine. Sections for histologic analysis were fixed in 10% buffered formalin. We isolated RNA, size fractionated it using 1% formaldehyde-agarose gel electrophoresis and then did Northern blots. The mRNAs from both PAI-1 and PAI-2 showed a remarkable increase at 8 and 24 h after acute aortic constriction and returned to control by 72 h. Regional differences showed that most of the increases were in the endocardium. Three animals in the late heart failure LVH group were determined to be in congestive heart failure at about 2 months after the onset of aortic constriction. In these animals PAI-1 and PAI-2 were increased in both the left and right ventricles but remained low in an animal of the same elevation in aortic pressure seen by the LV who did not have congestive failure. These data suggest that PA and PAI gene expressions change before morphologic changes occur in the early stages of developing LVH. Also at the time of onset of congestive heart failure this increased expression reappears. PAs and PA inhibitors mRNA levels vary in the different regions of the heart reflecting changing wall stresses. Thus, the PAs and PA inhibitors may play an important role in angiogenesis that occurs during the early stages of LVH. The increased expression in the late stage of LVH may reflect further changes in wall stresses since these animals also showed overt clinical signs of heart failure.     

Identification of a Novel, Putative Rho-specific GDP/GTP Exchange Factor and a RhoA-binding Protein: Control of Neuronal Morphology

The small GTP-binding protein Rho has been implicated in the control of neuronal morphology. In N1E-115 neuronal cells, the Rho-inactivating C3 toxin stimulates neurite outgrowth and prevents actomyosin-based neurite retraction and cell rounding induced by lysophosphatidic acid (LPA), sphingosine-1-phosphate, or thrombin acting on their cognate G protein–coupled receptors. We have identified a novel putative GDP/GTP exchange factor, RhoGEF (190 kD), that interacts with both wild-type and activated RhoA, but not with Rac or Cdc42. RhoGEF, like activated RhoA, mimics receptor stimulation in inducing cell rounding and in preventing neurite outgrowth. Furthermore, we have identified a 116-kD protein, p116^Rip, that interacts with both the GDP- and GTP-bound forms of RhoA in N1E-115 cells. Overexpression of p116^Rip stimulates cell flattening and neurite outgrowth in a similar way to dominant-negative RhoA and C3 toxin. Cells overexpressing p116^Rip fail to change their shape in response to LPA, as is observed after Rho inactivation. Our results indicate that (a) RhoGEF may link G protein–coupled receptors to RhoA activation and ensuing neurite retraction and cell rounding; and (b) p116^Rip inhibits RhoA-stimulated contractility and promotes neurite outgrowth.     

LhcaR1 of the red alga Porphyridium cruentum encodes a polypeptide of the LHCI complex with seven potential chlorophyll a-binding residues that are conserved in most LHCs

The accessory light-harvesting polypeptides associated with photosystem I (LHCI) in Porphyridium cruentum bind chlorophyll a, zeaxanthin and -carotene. A cDNA library of P. cruentum was screened with an antiserum specific to the LHCI polypeptides, and an 0.9 kb fragment was identified as coding for an LHCI polypeptide. This cDNA, which we named LhcaR1, has an open reading frame encoding 222 amino acid residues including a putative transit peptide of 28 amino acids. Hydropathy analysis suggests that there are three transmembrane helices in the mature polypeptide. Each of the amino acid residues that bind chlorophyll (six residues) and serve in stabilizing the helices in higher-plant LHCs are conserved in helices 1 and 3 of P. cruentum LhcaR1. The N-terminal flanking regions of these two helices also show high sequence conservation with other LHCs. Helix 2 contains a seventh putative chlorophyll-binding site, but resembles helix 2 of higher-plant LHCs to a lesser degree. A sequence motif of 11 residues found near the N-terminus and in each of the three helices suggests the possibility that the red algal LhcaR1 derives from a gene duplication. Polypeptides of the expected molecular weight in six other red algae (Achrochaetium, Bangia, Callithamnion, Cyanidium, Polysiphonia, Spermothamnion) were recognized by the antiserum to P. cruentum LHCI, indicating a wide distribution of LHCI in rhodophytes.     

Analogues of tentoxin: Tools for mechanistic investigations

Summary Tentoxin [cyclo-(MeAla¹-Leu²-MeΔPhe³-Gly⁴] is a metabolite isolated from a phytopathogenic fungusAlternaria alternata, which induces chlorosis of many plants. This potential natural herbicide binds specifically to the soluble part CF₁ of the chloroplastic coupling factor, which is a proton ATP-synthase. The effect of the toxin is concentration dependent: at low concentration it is a powerful inhibitor, while at higher concentration, it stimulates the enzyme. We synthesized tentoxin and we designed new analogues in order to vary the hydrophobicity on the side chain and to study the structure activity relationships. Comparative activities suggest that it is possible to separate inhibitory and activating effects using tentoxin analogues, showing some evidence for the existence of two binding sites with different affinity constant.     

Mimosine, the Allelochemical from the Leguminous Tree Leucaena leucocephala, Selectively Enhances Cell Proliferation in Dinoflagellates

Mimosine, the allelochemical from the leguminous tree Leucaena leucocephala, is toxic to most terrestrial animals and plants. We report here that while mimosine inhibits major phytoplankton groups, it enhances cell proliferation in dinoflagellates. On addition to coastal seawater samples, mimosine is able to confer a growth advantage to dinoflagellates. The use of mimosine will promote the isolation and culture of this group of phytoplankton.