Effect of a non‐host plant Phaseolus vulgaris on larval performance and oviposition of the oriental tobacco budworm Helicoverpa assulta (Lepidoptera: Noctuidae)

The oriental tobacco budworm, Helicoverpa assulta, is a specialist herbivore feeding on a few plants of the Solanaceae family including tobacco. Larval performance and adult oviposition of H. assulta were investigated in a non‐host plant, Phaseolus vulgaris (Fabaceae) in comparison with two solanaceous host plants, Nicotiana tabacum and Datura stramonium. Larvae provided with the P. vulgaris leaf died off at day 15, whereas 50% and 40% of larval populations fed on the leaves of N. tabacum and D. stramonium, respectively, survived at day 15. Larval growth upon feeding showed significant difference between the non‐host plant (P. vulgaris) and the host plants (N. tabacum and D. stramonium), but it was not significantly different between the two host plants. In the no‐choice experiment of oviposition, gravid females laid more eggs in N. tabacum and D. stramonium than in P. vulgaris. When the most likely acceptable host plant, N. tabacum, and the non‐host plant, P. vulgaris, were subjected to the choice experiment of oviposition, H. assulta females preferred to lay eggs in N. tabacum, where eggs were continuously laid during the whole experiment period. However, eggs in P. vulgaris were hardly detected throughout the period. This study showed that the non‐host plant, P. vulgaris, had a negative influence on the larval performance and adult oviposition of H. assulta, implying neonate stage is critical for larval survivorship, and ovipositional preference by the female is highly specialized to host plants. Further investigation is required to identify non‐host factors, which could be applied to the development of alternative pest management strategy against H. assulta.     

Dynamics and viability analysis of transplanted and natural lady's slipper (Cypripedium japonicum) populations under habitat management in South Korea

To assess the effectiveness of conservation‐based transplantation of the endangered orchid (Cypripedium japonicum), we compared the morphology, physiology, stem‐count change, and population viability of natural versus transplanted populations undergoing habitat management (repeated removal of competing understory vegetation) between 2009 and 2015 in South Korea. The restored site had lower transmitted light and soil humidity than the natural site. The natural and transplanted populations differed in leaf morphology and total chlorophyll content (natural: 1.00 ± 0.04, restored: 0.53 ± 0.06). No recruitment occurred during the monitoring period. Population viability tended to decrease in the restored population (λ_G = 0.97, μ = ?0.05, σ² = 0.036) and increase in the natural population (λ_G = 1.07, μ = 0.03, σ² = 0.075). The repeated removal of competing understory vegetation had different effects on leaf traits, abundance, and reproductive properties of the endangered orchids in both populations. Notably, habitat management increased the stem count and flowering rate in natural C. japonicum but did not increase the fruit‐setting rate. Thus, despite repeated habitat management efforts (removal of competing understory vegetation), we conclude that the population viability of transplanted populations of the endangered orchid C. japonicum had poor long‐term viability compared with naturally occurring populations, a difference that is mainly attributed to inappropriate transplant‐site selection.     

Emissive Nanoclusters Based on Subnanometer‐Sized Au38 Cores for Boosting the Performance of Inverted Organic Photovoltaic Cells

In spite of the successful enhancement of the power‐conversion efficiency (PCE) in organic bulk heterojunction (BHJ) solar cells by surface plasmon resonance (SPR), the incorporation of several tens of nanometer‐sized (25–50 nm) metal nanoparticles (NPs) has some limitations to further enhancing the PCE due to concerns related to possibly transferring nonradiative energy and disturbing the interface morphology. Instead of tens of nanometer‐sized metal NPs, here, dodecanethiol stabilized Au nanoclusters (Au:SR, R = the tail of thiolate) with sub‐nm‐sized Au38 cores are incorporated on inverted BHJ solar cells. Although metal NPs less than 5 nm in size do not show any scattering or electric field enhancement of incident light by SPR effects, the incorporation of emissive Au:SR nanoclusters provides effects that are quite similar to those of tens of nanometer‐sized plasmonic metal NPs. Due to effective energy transfer, based on the protoplasmonic fluorescence of Au:SR, the highest performing solar cells fabricated with Au:SR clusters yield a PCE of 9.15%; this value represents an ≈20% increase in the efficiency compared to solar cells without Au:SR nanoclusters.     

Synthesis and antihypertensive activity of pyrimidin-4(3H)-one derivatives as losartan analogue for new angiotensin II receptor type 1 (AT1) antagonists

The discovery, in vitro and in vivo studies of the highly potent AT(1) antagonist 12a (BR-A-657, Fimasartan) antagonists are presented. A series of pyrimidin-4(3H)-one derivatives as losartan analogue were synthesized and evaluated for a novel class of AT(1) receptor antagonists. Among them, 12a containing thioamido moiety displayed both high in vitro functional antagonism and binding affinity [IC(50)=0.42 and 0.13 nM, respectively] and inhibited strongly in vivo AngII-induced pressor response in pithed rats with an ED(50) of 0.018 mg/kg. Moreover, in vivo evaluation in furosemide-treated rat and conscious renal hypertensive rat models and the pharmacokinetic study showed that 12a is a highly potent and orally active AT(1) selective antagonist having stronger in vivo potency than losartan.     

An N-terminal sequence targets and tethers Na+ pump alpha2 subunits to specialized plasma membrane microdomains

Sodium pumps (alphabeta dimers) with the alpha1 isoform of the catalytic (alpha) subunit are expressed in all cells. Additionally, most cells express Na+ pumps with a second alpha isoform. For example, astrocytes and arterial myocytes also express Na+ pumps with the alpha2 isoform. The alpha2 pumps localize to plasma membrane (PM) microdomains overlying "junctional" sarco-/endoplasmic reticulum (S/ER), but the alpha1 pumps are more uniformly distributed. To study alpha2 targeting, we expressed alpha1/alpha2 and alpha2/alpha1 chimeras and 1-90 and 1-120 amino acid N-terminal peptides in primary cultured mouse astrocytes. Immunocytochemistry revealed that alpha2/alpha1 (but not alpha1/alpha2) chimeras markedly reduced native alpha2 (i.e. were "dominant negatives"). N-terminal (1-120 and 1-90 amino acids) alpha2 (and alpha3), but not alpha1 peptides also targeted to the PM-S/ER junctions and were dominant negative for native alpha2 in astrocytes and arterial myocytes. Thus alpha2 and alpha3 have the same targeting sequence. Ca2+ (fura-2) signals in astrocytes expressing the 1-90 alpha2 peptide were comparable to signals in cells from alpha2 null mutants (i.e. functionally dominant negative): 1 microM ATP-evoked Ca2+ transients were augmented, and 100 nM ouabain-induced amplification was abolished. Amino acid substitutions in the 1-120 alpha1 and alpha2 constructs, and in full-length alpha1, revealed that Leu-27 and Ala-35 are essential for targeting/tethering the constructs to PM-S/ER junctions.     

The C-type Arabidopsis thioredoxin reductase ANTR-C acts as an electron donor to 2-Cys peroxiredoxins in chloroplasts

2-Cys peroxiredoxins (Prxs) play important roles in the antioxidative defense systems of plant chloroplasts. In order to determine the interaction partner for these proteins in Arabidopsis, we used a yeast two-hybrid screening procedure with a C175S-mutant of Arabidopsis 2-Cys Prx-A as bait. A cDNA encoding an NADPH-dependent thioredoxin reductase (NTR) isotype C was identified and designated ANTR-C. We demonstrated that this protein effected efficient transfer of electrons from NADPH to the 2-Cys Prxs of chloroplasts. Interaction between 2-Cys Prx-A and ANTR-C was confirmed by a pull-down experiment. ANTR-C contained N-terminal TR and C-terminal Trx domains. It exhibited both TR and Trx activities and co-localized with 2-Cys Prx-A in chloroplasts. These results suggest that ANTR-C functions as an electron donor for plastidial 2-Cys Prxs and represents the NADPH-dependent TR/Trx system in chloroplasts.     

Loss of Halophytism by Interference with SOS1 Expression

The contribution of SOS1 (for Salt Overly Sensitive 1), encoding a sodium/proton antiporter, to plant salinity tolerance was analyzed in wild-type and RNA interference (RNAi) lines of the halophytic Arabidopsis (Arabidopsis thaliana)-relative Thellungiella salsuginea. Under all conditions, SOS1 mRNA abundance was higher in Thellungiella than in Arabidopsis. Ectopic expression of the Thellungiella homolog ThSOS1 suppressed the salt-sensitive phenotype of a Saccharomyces cerevisiae strain lacking sodium ion (Na⁺) efflux transporters and increased salt tolerance of wild-type Arabidopsis. thsos1-RNAi lines of Thellungiella were highly salt sensitive. A representative line, thsos1-4, showed faster Na⁺ accumulation, more severe water loss in shoots under salt stress, and slower removal of Na⁺ from the root after removal of stress compared with the wild type. thsos1-4 showed drastically higher sodium-specific fluorescence visualized by CoroNa-Green, a sodium-specific fluorophore, than the wild type, inhibition of endocytosis in root tip cells, and cell death in the adjacent elongation zone. After prolonged stress, Na⁺ accumulated inside the pericycle in thsos1-4, while sodium was confined in vacuoles of epidermis and cortex cells in the wild type. RNAi-based interference of SOS1 caused cell death in the root elongation zone, accompanied by fragmentation of vacuoles, inhibition of endocytosis, and apoplastic sodium influx into the stele and hence the shoot. Reduction in SOS1 expression changed Thellungiella that normally can grow in seawater-strength sodium chloride solutions into a plant as sensitive to Na⁺ as Arabidopsis.Accompanying the production and accumulation of osmolytes and other protective molecules, an important aspect of plant responses leading to salt stress tolerance is the regulation of uptake, reexport, and control over the distribution of sodium ions (Na⁺; Hasegawa et al., 2000; Tester and Davenport, 2003). Na⁺ appear to enter the root by several pathways (Essah et al., 2003; Pardo et al., 2006), although the nature of participating genes and their interaction in pathways require further investigation. Once Na⁺ has entered the root endodermis, a tissue that represents a barrier to ions (Peng et al., 2004), it is generally assumed that the ion enters the xylem following the movement of water to aerial parts of the plant. Despite substantial efflux of Na⁺ across the plasma membrane of root cells, the net flux of Na⁺ is unidirectional from soil to roots and then to the shoot, except for possible recirculation via the phloem (Tester and Davenport, 2003). In a range of species, the severity of damaging symptoms is positively correlated with the content of Na⁺ reaching photosynthetic tissues (Davenport et al., 2005; Ren et al., 2005; Munns et al., 2006). However, halophytic species can accumulate very high amounts of Na⁺ in vacuoles, such that Na⁺ may account for most of the total cellular osmotic potential (Tester and Davenport, 2003), and the presence of Na⁺ accelerates growth in euhalophytes to some degree (Adams et al., 1998). Emerging as the major advantage of halophytes appears to be their exceptional control over Na⁺ influx combined with export mechanisms, the ability to coordinate its distribution to various tissues, and efficient sequestration of Na⁺ into vacuoles. These characteristics are of particular advantage when plants are subjected to a sudden increase of Na⁺ salts in their environment (Hasegawa et al., 2000), whereas gradual increases in Na⁺ may be tolerated even by plants that are not halophytic in nature.Na⁺-ATPases, major Na⁺ export systems in organisms such as fungi and the moss Physcomitrella patens, have not been found in higher plants (Lunde et al., 2007). In Arabidopsis (Arabidopsis thaliana), transporters of monovalent (alkali) cations, such as HKT1 (Berthomieu et al., 2003; Rus et al., 2004), members of the NHX family (Yamaguchi et al., 2005; Pardo et al., 2006), and SOS1 (for Salt Overly Sensitive 1; Shi et al., 2000, 2002, 2003), have been shown to play roles in the movement and distribution of Na⁺ ions. Studies have shown the involvement of nonselective ion channels with roles in the transport of Na⁺ ions, but the genes encoding such function(s) have not been identified (Demidchik and Maathuis, 2007). SOS1, whose deletion resulted in a strong salt-sensitivity phenotype in Arabidopsis, encodes a plasma membrane Na⁺/H⁺ antiporter involved in removing Na⁺ ions from cells (Shi et al., 2000). This efflux strategy, which may be sufficient for the survival of unicellular organisms, must be accompanied by other means of Na⁺ confinement to avoid carryover of Na⁺ between cells in futile cycles. Hence, the physiological role of a plasma membrane Na⁺/H⁺ antiporter must be embedded in the context of tissue, organ, and whole plant distribution of ions and their transporters. A recent discovery on cell layer-specific differential responses to the salt stress of root cells supported this notion (Dinneny et al., 2008).In Arabidopsis, the SOS1 gene is most strongly expressed in the epidermis of the root tip region and in cells adjacent to vascular tissues (Shi et al., 2002). Based on the salt concentration in shoot, root, and xylem sap of wild-type Arabidopsis and its sos1 knockout mutants, the SOS1 antiporter is assumed to function in Na⁺ export under severe salt stress conditions (Shi et al., 2002). However, detailed knowledge about how a Na⁺ excluder achieves salt tolerance in a multicellular eukaryote is still missing. Significantly also, even though SOS1 has been an intensely studied component of the ion homeostasis mechanism, its involvement in the exceptional salt tolerance of halophytes is not known.Thellungiella salsuginea (salt cress), which had before been called T. halophila by us, is a close relative of Arabidopsis, which has become a model to study the genetic basis of this plant''s extreme tolerance to a variety of abiotic stress factors, including salinity (Inan et al., 2004; Gong et al., 2005; Vera-Estrella et al., 2005; Volkov and Amtmann, 2006; Amtmann, 2009). Thellungiella lacks specialized morphological structures, such as salt glands or large sodium storage cells found in other halophytes, making it a useful model for studying stress tolerance mechanisms that could be applicable to further understanding or to embark on engineering of conventional crops (Inan et al., 2004). Recently, it has been reported that Thellungiella had lower net Na⁺ uptake compared with Arabidopsis. The unidirectional influx of Na⁺ ions to roots appeared to be more restricted and/or tightly controlled in Thellungiella than in Arabidopsis. To compensate for greater influx, Arabidopsis roots showed higher Na⁺ efflux (Wang et al., 2006).Here, we wished to explore the role(s) by which ThSOS1, the SOS1 homolog in Thellungiella, could be involved in shaping the halophytic character of the species using ectopic expression of the gene in yeast and in Arabidopsis and Thellungiella SOS1-RNA interference (RNAi) lines. The results identified ThSOS1 as a genetic element whose activity limits Na⁺ accumulation and affects the distribution of Na⁺ ions at high concentration, thus acting as a major tolerance determinant.