Water Deficit in Pea Root Tips: Effects on the Cell Cycle and on the Production of Dehydrin-like Proteins

Dehydrin-like proteins have been detected in nuclei and cytoplasmof meristematic root tip cells from pea seedlings subjectedto slow dehydration at 90% relative humidity for 48 h or more.Evidence was gained from Western blotting and immunocytochemicalexperiments using an antibody raised against the conserved domainof dehydrin proteins. Flow cytometer analysis has shown thatcycling cells of root tip meristems from dehydrated seedlingsare mostly arrested in G2 phase. Other stress treatments thoughtto involve water depletion (osmotic stress, cold treatment)or to modulate cell response to water deficit (abscisic acid)gave less clear-cut results with all treatments lowering theproportion of cells entering the S phase, but without a definiteand persistent arrest in any preferential phase of the cycle.Possible interrelationships between G2 arrest and dehydrin productionare discussed. Cell cycle; dehydrins; flow cytometry; nuclei; pea; Pisum sativum L.; water stress     

Conservation and versatility of a new set of primers for long‐PCR amplification of complete insect mitochondrial genomes based on Haematobia irritans mtDNA sequences

The amplification of complete mitochondrial genomes by long PCR (polymerase chain reaction) has been a major contribution to the large‐scale sequencing of arthropodan mitochondrial genomes. In this work, we designed six conserved long‐PCR primers to successfully recover the entire mitochondrial genome of the horn fly Haematobia irritans (Diptera: Muscidae) in two overlapping fragments. The conservation and versatility of these primers were tested for 17 other species from four major insect orders: Diptera (14), Coleoptera (1), Lepidoptera (1) and Hymenoptera (1). The amplification of complete mitochondrial genomes in orders other than Diptera suggested an even broader application of these primers, especially within the Hexapoda.     

Ontogenesis of internal secretory cells in leaves of Lantana camara (Verbenaceae)

Internal secretory cells may be morphologically indistinguishable from their neighbours except for the presence of secreted material, or they may differ to such an extent that could be classified as secretory idioblasts. Several authors have reported the presence of glandular trichomes secreting essential oil in Verbenaceae, including Lantana . However, none have reported internal secretory cells. Anatomical and histochemical methods applied to Lantana camara leaves revealed the occurrence of internal secretory cells whose ontogenesis and chemical nature are described in this paper. According to leaf developmental analysis, L. camara secretory cells originated from the ground meristem, started to differentiate in the third node leaves, and were actively secreting in the fourth node leaves. The content of the secretory cells was of a lipidic nature, and a terpenoid essence of their secretion was also identified. Based upon differences in size and shape from neighbouring cells and on detection of nonvolatile terpenes, they were confirmed as true internal secretory idioblasts.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 427–431.     

Enemy release or invasional meltdown? Deer preference for exotic and native trees on Isla Victoria,Argentina

Abstract How interactions between exotic species affect invasion impact is a fundamental issue on both theoretical and applied grounds. Exotics can facilitate establishment and invasion of other exotics (invasional meltdown) or they can restrict them by re‐establishing natural population control (as predicted by the enemy‐release hypothesis). We studied forest invasion on an Argentinean island where 43 species of Pinaceae, including 60% of the world's recorded invasive Pinaceae, were introduced c. 1920 but where few species are colonizing pristine areas. In this area two species of Palearctic deer, natural enemies of most Pinaceae, were introduced 80 years ago. Expecting deer to help to control the exotics, we conducted a cafeteria experiment to assess deer preferences among the two dominant native species (a conifer, Austrocedrus chilensis, and a broadleaf, Nothofagus dombeyi) and two widely introduced exotic tree species (Pseudotsuga menziesii and Pinus ponderosa). Deer browsed much more intensively on native species than on exotic conifers, in terms of number of individuals attacked and degree of browsing. Deer preference for natives could potentially facilitate invasion by exotic pines. However, we hypothesize that the low rates of invasion currently observed can result at least partly from high densities of exotic deer, which, despite their preference for natives, can prevent establishment of both native and exotic trees. Other factors, not mutually exclusive, could produce the observed pattern. Our results underscore the difficulty of predicting how one introduced species will effect impact of another one.     

Moderate heat stress reduces the pH component of the transthylakoid proton motive force in light-adapted, intact tobacco leaves

We measured the Δ Ψ and ΔpH components of the transthylakoid proton motive force ( pmf ) in light-adapted, intact tobacco leaves in response to moderate heat. The Δ Ψ causes an electrochromic shift (ECS) in carotenoid absorbance spectra. The light–dark difference spectrum has a peak at 518 nm and the two components of the pmf were separated by following the ECS for 25 s after turning the light off. The ECS signal was deconvoluted by subtracting the effects of zeaxanthin formation (peak at 505 nm) and the qE-related absorbance changes (peak at 535 nm) from a signal measured at 520 nm. Heat reduced ΔpH while Δ Ψ slightly increased. Elevated temperature accelerated ECS decay kinetics likely reflecting heat-induced increases in proton conductance and ion movement. Energy-dependent quenching (qE) was reduced by heat. However, the reduction of qE was less than expected given the loss of ΔpH. Zeaxanthin did not increase with heat in light-adapted leaves but it was higher than would be predicted given the reduced ΔpH found at high temperature. The results indicate that moderate heat stress can have very large effects on thylakoid reactions.     

FORMULATING A NEW PASSION FRUIT JUICE BEVERAGE WITH DIFFERENT SWEETENER SYSTEMS

The aim of this work was to optimize the acceptability of a natural passion fruit beverage using different levels of passion fruit pulp and sucrose, and to determine the equi-sweet concentrations of aspartame, sucralose, and a blend of 80% aspartame  +  20% acesulfame-K for the optimized formula. A 2² central composite design was used to optimize the acceptability of the sucrose-sweetened beverage, which was accessed using a 9-point structured hedonic scale. Acceptability data were fitted to a second-order model equation provided in the design. The selected pulp content and sucrose concentration were, respectively, 2.5 ° Brix and 10%. Measurements of sweetness equivalence were accomplished using two types of sensory methods: magnitude estimation and difference-from-control tests. The concentrations of aspartame, sucralose and a blend of 80% aspartame  +  20% acesulfame-K found as equi-sweet to 10% sucrose in the studied passion fruit beverage were, respectively, 0.043, 0.016 and 0.026%.

PRACTICAL APPLICATIONS

This article deals with formulating a new passion fruit juice beverage with different sweetener systems. The research makes a very important contribution to the literature on sensory science used on product development by demonstrating the necessity to study the substitution of sucrose by high-intensity sweeteners every time a formulation is changed or a new product is developed.     

Population genomics of the inbred Scandinavian wolf

The Scandinavian wolf population represents one of the genetically most well-characterized examples of a severely bottlenecked natural population (with only two founders), and of how the addition of new genetic material (one immigrant) can at least temporarily provide a 'genetic rescue'. However, inbreeding depression has been observed in this population and in the absence of additional immigrants, its long-term viability is questioned. To study the effects of inbreeding and selection on genomic diversity, we performed a genomic scan with approximately 250 microsatellite markers distributed across all autosomes and the X chromosome. We found linkage disequilibrium (LD) that extended up to distances of 50 Mb, exceeding that of most outbreeding species studied thus far. LD was particularly pronounced on the X chromosome. Overall levels of observed genomic heterozygosity did not deviate significantly from simulations based on known population history, giving no support for a general selection for heterozygotes. However, we found evidence supporting balancing selection at a number of loci and also evidence suggesting directional selection at other loci. For markers on chromosome 23, the signal of selection was particularly strong, indicating that purifying selection against deleterious alleles may have occurred even in this very small population. These data suggest that population genomics allows the exploration of the effects of neutral and non-neutral evolution on a finer scale than what has previously been possible.