The AtNHX1 exchanger mediates potassium compartmentation in vacuoles of transgenic tomato

NHX‐type antiporters in the tonoplast have been reported to increase the salt tolerance of various plants species, and are thought to mediate the compartmentation of Na⁺ in vacuoles. However, all isoforms characterized so far catalyze both Na⁺/H⁺ and K⁺/H⁺ exchange. Here, we show that AtNHX1 has a critical involvement in the subcellular partitioning of K⁺, which in turn affects plant K⁺ nutrition and Na⁺ tolerance. Transgenic tomato plants overexpressing AtNHX1 had larger K⁺ vacuolar pools in all growth conditions tested, but no consistent enhancement of Na⁺ accumulation was observed under salt stress. Plants overexpressing AtNHX1 have a greater capacity to retain intracellular K⁺ and to withstand salt‐shock. Under K⁺‐limiting conditions, greater K⁺ compartmentation in the vacuole occurred at the expense of the cytosolic K⁺ pool, which was lower in transgenic plants. This caused the early activation of the high‐affinity K⁺ uptake system, enhanced K⁺ uptake by roots, and increased the K⁺ content in plant tissues and the xylem sap of transformed plants. Our results strongly suggest that NHX proteins are likely candidates for the H⁺‐linked K⁺ transport that is thought to facilitate active K⁺ uptake at the tonoplast, and the partitioning of K⁺ between vacuole and cytosol.     

Reduced fitness of the leafhopper vector Scaphoideus titanus exposed to Flavescence dorée phytoplasma

Scaphoideus titanus Ball (Homoptera: Cicadellidae), a specialist and univoltine leafhopper on grapevine (Vitis vinifera L.) (Vitaceae), is a vector of Flavescence dorée phytoplasma (FDP) in vineyards of European temperate areas. Males and females of the leafhopper were exposed to FDP by feeding on infected broad bean (Vicia faba L.) (Fabaceae). Detection of FDP by the amplification of phytoplasma DNA with polymerase chain reaction assays of individual insects revealed an acquisition rate of 91.4% (96/105) after an acquisition access period of 13 days. The adult life span of FD‐exposed males and females was much less than that of leafhoppers fed on healthy broad bean, as revealed by ANOVA on the quartiles of survival distribution and Weibull scale parameter. The progeny of exposed females (number of nymphs emerging from eggs deposited on woody cane segments) was significantly less than the progeny of unexposed females. Eggs produced by FD‐exposed females were slightly but significantly delayed in hatching. Reduced fecundity was confirmed by dissecting FD‐exposed and non‐exposed 42‐day‐old females and counting the number of fully sized eggs in each leafhopper. There was no evidence of transovarial passage of FDP in the offspring of infected females after 72 nymphs were reared on a healthy grapevine until the fifth instar or adult appearance and then confined on broad bean seedlings.     

d-Xylose detection in Escherichia coli by a xylose binding protein-dependent response

A gene circuit for the controlled expression of a marker gene and for the assay of xylose concentration in Escherichia coli has been designed and tested. The xylF coding sequence for the xylose binding protein (XBP) was cloned in pT7T318U downstream from the promoter for xylanase A from B. subtilis (Pbsu), together with the GFP coding sequence (gfp) under the control of the xylF promoter, forming the pT7T3-GFP-XBP construct. GFP fluorescence in Escherichia coli JW3538-1 xylF—transformed with pT7T3-GFP-XBP was approximately 1.4× higher after 520 min growth in the presence of 5 mM xylose than in cells transformed with pT7T3-GFP. Under saturating xylose concentration, flow cytometry analysis showed that all cells resulted in homogeneous populations, and the population with XBP showed a fluorescence greater than that without XBP. Activity of the xylF promoter in cells transformed with pT7T3-GFP-XBP was ∼40% higher than with the pT7T3-GFP. No response was observed with arabinose and ribose, showing that the expression effects were specific for xylose, demonstrating the potential use of the gene circuit as a biosensor.     

Inventario delle Corallinales del Mar Mediterraneo: considerazioni tassonomiche

Abstract

Inventory of Corallinales of the Mediterranean Sea: taxonomic aspects. - The aim of the present work is the drawing up of a critical inventory of Corallinales of the Mediterranean Sea. This research has been based upon a census of 320 works published since 175 years, upon direct collections and sample exchanges. A census of 88 species of Corallinales (with forms and varieties), made up on the basis of about 5000 records, has been taken. 34 of the 88 species are considered “species dubiae aut rariter inventae”, it has been reported also “species inquirendae” and “species addendae”. From this census it results that there are some taxonomic problems about genera attributions (Lithophyllum, Pseudolithophyllum, Titanoderma, Neogoniolithon, Spongites, Goniolithion, Leptophytum), species attributions of articulated Corallinales (Corallina elongata, C. officinalis e Haliptilon squamatum) and non-articulated Corallinales (Fosliella ischitana, Lithophyllum (Titanoderma) trochanter, Spongites fruticulosus). Definition of these taxonomic attributions might condition not only studies of phytogeographical distribution of these algae but also every successive interpretation.     

Affinità floristica dei tipi di vegetazione bentonica della Cala di Mitigliano (Massa Lubrense,Napoli)

Abstract

Floristic affinity of bentonic vegetational types of Cala di Mitigliano (Massa Lubrense Napoli). — We have studied the bentonic plants community in the Cala di Mitigliano. It appears that some species compositions repeat themselves with a certain regularity. This fact lets us recognize and consequently classify them. In Cala di Mitigliano we took an interest and considered only such species compositions. We calculated, in them and between them, the coefficient of affinity by SÖRENSEN (1948). The cluster analysis by average linkage and the use of an index of «individualisation» (Feoli, ined.) based on floristic comparison showed that the species compositions, although we chose such ones to describe the vegetation, equally change gradually from place to place.     

Osservazioni sugli stadi iniziali della morfogenesi in coltura di alcune specie del genere Peyssonnelia Decaisne

Abstract

Researches on the morphogenesis of the genus Peyssonnelia Decaisne. — This paper reports the first result on morphogenetic researches in cultures of 3 species of the genus Peyssonnelia Decne. The development of Peyssonnelia rubra (Grev.) J. Ag. is of «Dumontia type »(CHEMIN, 1937) that one of Peyssonnelia squamaria (Gmelin) Decne. and of Peyssonnelia inamoena Pilger of «Naccaria type». According to our cultures results the morphogenesis of genus Peyssonnelia is of two type. Sample of P. squamaria and P. inamoena are collected in the gulf of Trieste (Nord Adriatic Sea) those of P. cfr. rubra in the Morlaix Bay (English Channel). Taxonomic value of the results are discussed.     

Bacterial communities of two parthenogenetic aphid species cocolonizing two host plants across the Hawaiian Islands

Aphids (Hemiptera: Aphididae) have been the focus of several studies with respect to their interactions with inherited symbionts, but bacterial communities of most aphid species are still poorly characterized. In this research, we used bar-coded pyrosequencing to characterize bacterial communities in aphids. Specifically, we examined the diversity of bacteria in two obligately parthenogenetic aphid species (the melon aphid, Aphis gossypii, and the cardamom aphid, Pentalonia caladii) cocolonizing two plant species (taro, Colocasia esculenta, and ginger, Alpinia purpurata) across four Hawaiian Islands (Hawaii, Kauai, Maui, and Oahu). Results from this study revealed that heritable symbionts dominated the bacterial communities for both aphid species. The bacterial communities differed significantly between the two species, and A. gossypii harbored a more diverse bacterial community than P. caladii. The bacterial communities also differed across aphid populations sampled from the different islands; however, communities did not differ between aphids collected from the two host plants.     

Nine new polymorphic microsatellite loci for the amplification of archived otolith DNA of Atlantic cod,Gadus morhua L.

Nine out of 22 microsatellite primers tested were successfully amplified on three samples of cod Gadus morhua L. (two contemporary and one archived otolith samples). All loci were polymorphic (5–23 alleles/locus). The average observed heterozygosity across loci and samples was 0.625, ranging from 0.294 to 0.895 at each locus. All loci were under Hardy–Weinberg equilibrium, except PGmo56 that showed significant excess of heterozygotes in all studied samples. The isolated loci were suitable for degraded DNA and therefore useful for conducting a long‐term temporal study with DNA obtained from archived otoliths of cod.     

Seed weevils living on the edge: pressures and conflicts over body size in the endoparasitic Curculio larvae

Abstract 1. Body size in parasitic insects can be subjected to contrasting selective pressures, especially if they complete their development within a single host. On the one hand, a larger body size is associated with a higher fitness. On the other hand, the host offers a discrete amount of resources, thus constraining the evolution of a disproportionate body size. 2. The present study used the weevil Curculio elephas as a study model. Larvae develop within a single acorn, feeding on its cotyledons, and larval body size is strongly related to individual fitness. 3. The relationship between larval and acorn size was negatively exponential. Larval growth was constrained in small acorns, which did not provide enough food for the weevils to attain their potential size. Larval size increased and levelled off in acorns over a certain size (inflexion point), in which cotyledons were rarely depleted. When there were more than one larva per acorn, a larger acorn was necessary to avoid food depletion. 4. The results show that C. elephas larvae are sometimes endoparasitic, living on the edge of host holding capacity. If they were smaller they could avoid food depletion more easily, but the fitness benefits linked to a larger size have probably promoted body size increase. The strong negative effects of conspecific competition may have possibly influenced female strategy of laying a single egg per seed. 5. Being larger and fitter, but always within the limits of the available host sizes, may be one main evolutionary dilemma in endoparasites.