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Glucosinolates are defense-related secondary metabolites found in Brassicaceae. When Brassicaceae come under attack, glucosinolates are hydrolyzed into different forms of glucosinolate hydrolysis products (GHPs). Among the GHPs, isothiocyanates are the most comprehensively characterized defensive compounds, whereas the functional study of nitriles, another group of GHP, is still limited. Therefore, this study investigates whether 3-butenenitrile (3BN), a nitrile, can trigger the signaling pathways involved in the regulation of defense responses in Arabidopsis thaliana against biotic stresses. Briefly, the methodology is divided into three stages, (i) evaluate the physiological and biochemical effects of exogenous 3BN treatment on Arabidopsis, (ii) determine the metabolites involved in 3BN-mediated defense responses in Arabidopsis, and (iii) assess whether a 3BN treatment can enhance the disease tolerance of Arabidopsis against necrotrophic pathogens. As a result, a 2.5 mM 3BN treatment caused lesion formation in Arabidopsis Columbia (Col-0) plants, a process found to be modulated by nitric oxide (NO). Metabolite profiling revealed an increased production of soluble sugars, Krebs cycle associated carboxylic acids and amino acids in Arabidopsis upon a 2.5 mM 3BN treatment, presumably via NO action. Primary metabolites such as sugars and amino acids are known to be crucial components in modulating plant defense responses. Furthermore, exposure to 2.0 mM 3BN treatment began to increase the production of salicylic acid (SA) and jasmonic acid (JA) phytohormones in Arabidopsis Col-0 plants in the absence of lesion formation. The production of SA and JA in nitrate reductase loss-of function mutant (nia1nia2) plants was also induced by the 3BN treatments, with a greater induction for JA. The SA concentration in nia1nia2 plants was lower than in Col-0 plants, confirming the previously reported role of NO in controlling SA production in Arabidopsis. A 2.0 mM 3BN treatment prior to pathogen assays effectively alleviated the leaf lesion symptom of Arabidopsis Col-0 plants caused by Pectobacterium carotovorum ssp. carotovorum and Botrytis cinerea and reduced the pathogen growth on leaves. The findings of this study demonstrate that 3BN can elicit defense response pathways in Arabidopsis, which potentially involves a coordinated crosstalk between NO and phytohormone signaling.

Y2O3 was in situ deposited on a freshly grown molecular beam epitaxy GaAs(001)-4 × 6 surface by atomic layer deposition (ALD). In situ synchrotron radiation photoemission was used to study the mechanism of the tris(ethylcyclopentadienyl)yttrium [Y(CpEt)3] and H2O process. The exponential attenuation of Ga 3d photoelectrons confirmed the laminar growth of ALD-Y2O3. In the embryo stage of the first ALD half-cycle with only Y(CpEt)3, the precursors reside on the faulted As atoms and undergo a charge transfer to the bonded As atoms. The subsequent ALD half-cycle of H2O molecules removes the bonded As atoms, and the oxygen atoms bond with the underneath Ga atoms. The product of a line of Ga–O–Y bonds stabilizes the Y2O3 films on the GaAs substrate. The resulting coordinatively unsaturated Y–O pairs of Y2O3 open the next ALD series. The absence of Ga2O3, As2O3, and As2O5 states may play an important role in the attainment of low interfacial trap densities (Dit) of

The Interface of Ag with p -type α2 GaAs(001)-2 × 4 has been studied to further understand the formation mechanism of the Schottky barrier height (SBH). In the initial phase of Ag deposition, high-resolution core-level data show that Ag adatoms effectively passivate the surface As-As dimers without breaking them apart. The Ag(+)-As(−) dipoles are thus generated with a maximal potential energy of 0.26 eV; a SBH of 0.38 eV was measured. Greater Ag coverage causes elemental segregation of As/Ga atoms, reversing the direction of the net dipole. The band bending effect near the interface shows a downward shift of 0.08 eV, and the final SBH is similar to the value as measured at the initial Ag deposition. Both parameters are secured at 0.25 A of Ag thickness prior to the observation of metallic behavior of Ag. Inadequacy of the metal-induced gap-state model for explaining SBH is evident.

In this paper, we investigate the embryonic stage of oxidation of an epi Ge(001)-2 &times, 1 by atomic oxygen and molecular O2 via synchrotron radiation photoemission. The topmost buckled surface with the up- and down-dimer atoms, and the first subsurface layer behaves distinctly from the bulk by exhibiting surface core-level shifts in the Ge 3d core-level spectrum. The O2 molecules become dissociated upon reaching the epi Ge(001)-2 &times, 1 surface. One of the O atoms removes the up-dimer atom and the other bonds with the underneath Ge atom in the subsurface layer. Atomic oxygen preferentially adsorbed on the epi Ge(001)-2 &times, 1 in between the up-dimer atoms and the underneath subsurface atoms, without affecting the down-dimer atoms. The electronic environment of the O-affiliated Ge up-dimer atoms becomes similar to that of the down-dimer atoms. They both exhibit an enrichment in charge, where the subsurface of the Ge layer is maintained in a charge-deficient state. The dipole moment that was originally generated in the buckled reconstruction no longer exists, thereby resulting in a decrease in the ionization potential. The down-dimer Ge atoms and the back-bonded subsurface atoms remain inert to atomic O and molecular O2, which might account for the low reliability in the Ge-related metal-oxide-semiconductor (MOS) devices.

Ethylene response factors (ERFs) are a large plant-specific transcription factor family and play diverse important roles in various plant functions. However, most tomato ERFs have not been characterized. In this study, we showed that the expression of an uncharacterized member of the tomato ERF-IX subgroup, ERF68, was significantly induced by treatments with different bacterial pathogens, ethylene (ET) and salicylic acid (SA), but only slightly induced by bacterial mutants defective in the type III secretion system (T3SS) or non-host pathogens. The ERF68-green fluorescent protein (ERF68-GFP) fusion protein was localized in the nucleus. Transactivation and electrophoretic mobility shift assays (EMSAs) further showed that ERF68 was a functional transcriptional activator and was bound to the GCC-box. Moreover, transient overexpression of ERF68 led to spontaneous lesions in tomato and tobacco leaves and enhanced the expression of genes involved in ET, SA, jasmonic acid (JA) and hypersensitive response (HR) pathways, whereas silencing of ERF68 increased tomato susceptibility to two incompatible Xanthomonas spp. These results reveal the involvement of ERF68 in the effector-triggered immunity (ETI) pathway. To identify ERF68 target genes, chromatin immunoprecipitation combined with high-throughput sequencing (ChIP-seq) was performed. Amongst the confirmed target genes, a few genes involved in cell death or disease defence were differentially regulated by ERF68. Our study demonstrates the function of ERF68 in the positive regulation of hypersensitive cell death and disease defence by modulation of multiple signalling pathways, and provides important new information on the complex regulatory function of ERFs.

Global water shortage seriously threatens rice growth especially in irrigated production areas. Association of plants with beneficial soil microbes is one strategy for plant adaption to environmental stresses. In this study, rice (Oryza sativa L.) plants were colonized by the beneficial root-colonizing endophytic fungus Piriformospora indica (P. indica). We demonstrate that grain yield were higher in P. indica-colonized rice plants compared to the uncolonized plants grown in soil. Moreover, P. indica effect on improving water stress tolerance in rice and its physiological mechanism were investigated in a hydroponic culture system. Polyethylene glycol (PEG) was applied to the culture solution to conduct the water stress condition. Water stress-induced leaf wilting and impairments in photosynthetic efficiency were diminished in P. indica-colonized plants. Furthermore, P. indica colonization promotes stomata closure and increases the leaf surface temperature under water stress. The malondialdehyde level (as an indicator for oxidative stress) was lower and the reduced to oxidized glutathione ratio was higher in P. indica-colonized and PEG-exposed rice plants compared to the uncolonized plants. Furthermore, the activities of the antioxidant enzymes catalase and glutathione reductase were up-regulated in inoculated rice seedlings under water stress. In conclusion, P. indica promotes rice performance under water stress by stomata closure and lower oxidative stress.

The electronic structure of rubrene doped with various concentrations of Na was studied by synchrotron-radiation photoemission. Three stages of development were found with increasing Na concentration; Na penetrating deep into the organic film, followed by development of gap states, and ended with a metallic Na film. The charge transfer from Na to rubrene resulted in a vacuum-level shift. By doping Na into rubrene, we could control the IP of the organic molecule, which is favorable for application in organic semiconductor devices.

During the last 20 years, beamline BL08B has been upgraded step by step from a photon beam-position monitor (BPM) to a testing beamline and a single-grating beamline that enables experiments to record X-ray photo-emission spectra (XPS) and X-ray absorption spectra (XAS) for research in solar physics, organic semiconductor materials and spinel oxides, with soft X-ray photon energies in the range 300–1000 eV. Demands for photon energy to extend to the extreme ultraviolet region for applications in nano-fabrication and topological thin films are increasing. The basic spherical-grating monochromator beamline was again upgraded by adding a second grating that delivers photons of energy from 80 to 420 eV. Four end-stations were designed for experiments with XPS, XAS, interstellar photoprocess systems (IPS) and extreme-ultraviolet lithography (EUVL) in the scheduled beam time. The data from these experiments show a large count rate in core levels probed and excellent statistics on background normalization in theL-edge adsorption spectrum.

Y2O3 was in situ deposited on a freshly grown molecular beam epitaxy GaAs(001)-4 × 6 surface by atomic layer deposition (ALD). In situ synchrotron radiation photoemission was used to study the mechanism of the tris(ethylcyclopentadienyl)yttrium [Y(CpEt)3] and H2O process. The exponential attenuation of Ga 3d photoelectrons confirmed the laminar growth of ALD-Y2O3. In the embryo stage of the first ALD half-cycle with only Y(CpEt)3, the precursors reside on the faulted As atoms and undergo a charge transfer to the bonded As atoms. The subsequent ALD half-cycle of H2O molecules removes the bonded As atoms, and the oxygen atoms bond with the underneath Ga atoms. The product of a line of Ga–O–Y bonds stabilizes the Y2O3 films on the GaAs substrate. The resulting coordinatively unsaturated Y–O pairs of Y2O3 open the next ALD series. The absence of Ga2O3, As2O3, and As2O5 states may play an important role in the attainment of low interfacial trap densities (Dit) of

Plant defensins (PDFs) are cysteine-rich peptides that have a range of biological functions, including defence against fungal pathogens. However, little is known about their role in defence against bacteria. In this study, we showed that the protein encoded by ARABIDOPSIS THALIANA PLANT DEFENSIN TYPE 1.1 (AtPDF1.1) is a secreted protein that can chelate apoplastic iron. Transcripts of AtPDF1.1 were induced in both systemic non-infected leaves of Arabidopsis thaliana plants and those infected with the necrotrophic bacterium Pectobacterium carotovorum subsp. carotovorum (Pcc). The expression levels of AtPDF1.1 with correct subcellular localization in transgenic A. thaliana plants were positively correlated with tolerance to Pcc, suggesting its involvement in the defence against this bacterium. Expression analysis of genes associated with iron homeostasis/deficiency and hormone signalling indicated that the increased sequestration of iron by apoplastic AtPDF1.1 overexpression perturbs iron homeostasis in leaves and consequently activates an iron-deficiency-mediated response in roots via the ethylene signalling pathway. This in turn triggers ethylene-mediated signalling in systemic leaves, which is involved in suppressing the infection of necrotrophic pathogens. These findings provide new insight into the key functions of plant defensins in limiting the infection by the necrotrophic bacterium Pcc via an iron-deficiency-mediated defence response.

Genes encoding phytoalexin biosynthesis enzymes are transcriptionally regulated and are required for defense against fungi and oomycetes. Here, we studied the regulation of tobacco 5-epi-aristolochene synthase 4 (EAS4) promoters on bacterial infection and investigated the roles of tomato and Arabidopsis phytoalexin biosynthesis genes in defense against pathogenic bacteria. Our results showed that the Nicotiana glutinosa EAS4 (NgEAS4) promoter was significantly induced by treatments with several bacteria in treated and systemic leaves of transgenic plants. This promoter was also partially induced by treatments with type-III secretion-deficient mutants and total lysate of R. solanacearum (Rs), revealing that both bacterial pathogen-associated molecular patterns (PAMPs) and effectors are involved in R. solanacearum-induced local and systemic activation of the NgEAS4 promoter. Furthermore, the absence of a cis-element GT-1 box in the NgEAS4 promoter abolished systemic activation in non-treated leaves, whereas disruption of the GT-1 box of the N. tabacum EAS4 (NtEAS4) promoter led to constitutive expression. Moreover, silencing of tomato sesquiterpene synthase genes and disruption of the key gene PAD3 for Arabidopsis camalexin biosynthesis resulted in decreased tolerance to R. solanacearum. These results together, reveal the varied function of GT-1 boxes in regulating tobacco EAS4 promoters and the involvement of phytoalexin-biosythesis genes in plant defense against R. solanacearum.

Lipopolysaccharides (LPS) are critical components for the fitness of most gram-negative bacteria. Ralstonia solanacearum causes a deadly wilting disease in many crops; however, the pathogenic roles of different forms of LPS and their pathways of biogenesis remain unknown. By screening for phage-resistant mutants of R. solanacearum Pss4, whose genome sequence is unavailable, mutants with various types of structural defects in LPS were isolated. Pathogenesis assays of the mutants revealed that production of rough LPS (R-LPS), which does not contain O-polysaccharides, was sufficient to cause necrosis on Nicotiana benthamiana and induce the hypersensitive response on N. tabacum. However, biosynthesis of smooth LPS (S-LPS), which contains O-polysaccharides, was required for bacterial proliferation at infection sites on N. benthamiana leaves and for proliferation and causing wilt on tomato. Complementation tests confirmed the involvement of the previously unidentified cluster RSc2201 to RSc2204 in the formation of R. solanacearum S-LPS. With these data and the availability of the annotated genomic sequence of strain GMI1000, certain loci involved in key steps of R. solanacearum LPS biosynthesis were identified. The strategy of this work could be useful for similar studies in other bacteria without available genome sequences.

Previously, we have identified an avirulent Ralstonia solanacearum mutant carrying a transposon insertion in RSc0411, a gene homologous to the Escherichia coli LPS-transporting protein LptC. However, how the disruption of RSc0411 affects the bacterium-plant interactions and leads to decreased pathogenicity was not known. Here we show that the disruption of RSc0411 leads to pleiotropic defects, including reducing bacterial motility, biofilm formation, root attachment, rough-form LPS production and virulence in tomato and increasing membrane permeability. Disruption of the orthologous RSc0411 present in other R. solanacearum strains proves that most of these functions are conserved in the species. In contrast, trans-complementation analyses show that only RSc0411 orthologues from closely related bacteria can rescue the defects of the disruption mutant. These results enable us to propose a function for RSc0411, and for the clustered genes, in LPS biogenesis, and for the first time, to our knowledge, also a role of a gene from the DUF1239 gene family in bacterial pathogenicity. In addition and notably, the RSc0411 mutant displays a strain-specific phenotype for hypersensitive response (HR), in which the RSc0411 disruption impairs the HR caused by strain Pss190 but not that by strain Pss1308. Consistent with this strain-specific defect, the mutation clearly affects expression of the type III secretion system (T3SS) in Pss190 but not in other strains, suggesting that the HR-deficient phenotype of the RSc0411 mutant in Pss190 is due to impairment of the T3SS and thus RSc0411 has a strain-specific role in the T3SS activity of R. solanacearum.

article présenté lors du congrès Plant Biology 2015 ; Minneapolis (Etats-Unis) - (2015-07-26 - 2015-07-30); International audience; The soil-borne pathogen Ralstonia solanacearum causes bacterial wilt in a broad range of plants. The main virulence determinants of R. solanacearum are the type III secretion system (T3SS) and its associated type III effectors (T3Es), translocated into the host cells. Of the conserved T3Es among R. solanacearum strains, the Fbox protein RipG7 is required for R. solanacearum pathogenesis on Medicago truncatula. In this work, we describe the natural ripG7 variability existing in the R. solanacearum species complex. We show that eight representative ripG7 orthologues have different contributions to pathogenicity on M. truncatula: only ripG7 from Asian or African strains can complement the absence of ripG7 in GMI1000 (Asian reference strain). Nonetheless, RipG7 proteins from American and Indonesian strains can still interact with M. truncatula SKP1-like/MSKa protein, essential for the function of RipG7 in virulence. This indicates that the absence of complementation is most likely a result of the variability in the leucine-rich repeat (LRR) domain of RipG7. We identified 11 sites under positive selection in the LRR domains of RipG7. By studying the functional impact of these 11 sites, we show the contribution of five positively selected sites for the function of RipG7CMR15 in M. truncatula colonization.This work reveals the genetic and functional variation of the essential core T3E RipG7 from R. solanacearum.This analysis is the first of its kind on an essential disease-controlling T3E, and sheds light on the co-evolutionary arms race between the bacterium and its hosts.

Ralstonia solanacearum is a soil-borne xylem-inhibited pathogen and causes a deadly wilting disease on a wide range of crops. This bacterium can also colonize many weeds and native plants without necessarily causing symptoms, leading to devastating epidemiological consequences; however, little is known about the biology. A R. solanacearum mutant harbouring a transposon insertion in the annotated gene RSc1206 was previously shown to retain virulence in tomato but displayed reduced virulence in model weed host Arabidopsis. In this study, we investigated the function of RSc1206 in bacterial pathogenesis in weed hosts. RSc1206 encodes a putative protein that is homologous to E. coli NlpD, and the organization of RSc1206-related gene cluster is mostly conserved among representative gram-negative bacteria analyzed. We therefore designate it R. solanacearum gene nlpD. Microscopic data revealed that the nlpD mutant had defects in cell separation and envelope integrity. An increased sensitivity to hydrophobic toxic chemicals confirmed that the cell integrity of the nlpD mutant was damaged. In addition, the activity of the nlpD mutant in biofilm formation and motility was reduced. However, enzymatic activity and tobacco pathogenesis assays revealed that this mutant functioned normally in the Type II and III secretion systems. Trans-mutation and trans-complementation analyses further verified that disruption of nlpD function was responsible for the observed defects. Our study provides evidence that NlpD contributes to R. solanacearum cell integrity and pathogenesis in weed host Arabidopsis.

A microscopic view of O2 adsorption on an epi Ge(001)-2 × 1 surface at room temperature, as studied by synchrotron radiation photoemission, is presented. One of the dissociated O atoms etches off the up-dimer atom to form the GeO species. The other dissociated O atom fills the vacancy and bonds with the underneath Ge atom in the subsurface layer. The down-dimer atom and its backbond with the subsurface atom remain inert to O2. The present investigation reports the notorious effect of O2 on the Ge surface, which should not be overlooked in Ge metal–oxide–semiconductor (MOS) device development.

Using in situ synchrotron-radiation photoelectron spectroscopy, the band offsets and the surface dipole potential energy for cycle-by-cycle atomic layer deposited (ALD) Y2O3 on p-type GaAs(0 0 1)-4 × 6 were studied. We have characterized the electronic property for laminar films. The valence- and conduction-band offsets and interfacial dipole potential energy are approximately 1.75, 2.4, and 0.46 eV, respectively. The dipole direction points outward, showing that Y(+) is located at the topmost layer and the O(−) ions participate in the bonding with the GaAs surface atoms.

Abiotic stresses such as cold, water deficit, and salt stresses severely reduce crop productivity. Tomato (Solanum lycopersicum) is an important economic crop; however, not much is known about its stress responses. To gain insight into stress-responsive gene regulation in tomato plants, we identified transcription factors from a tomato cDNA microarray. An ABA-responsive element binding protein (AREB) was identified and named SlAREB. In tomato protoplasts, SlAREB transiently transactivated luciferase reporter gene expression driven by AtRD29A (responsive to dehydration) and SlLAP (leucine aminopeptidase) promoters with exogenous ABA application, which was suppressed by the kinase inhibitor staurosporine, indicating that an ABA-dependent post-translational modification is required for the transactivation ability of SlAREB protein. Electrophoretic mobility shift assays showed that the recombinant DNA-binding domain of SlAREB protein is able to bind AtRD29A and SlLAP promoter regions. Constitutively expressed SlAREB increased tolerance to water deficit and high salinity stresses in both Arabidopsis and tomato plants, which maintained PSII and membrane integrities as well as water content in plant bodies. Overproduction of SlAREB in Arabidopsis thaliana and tomato plants regulated stress-related genes AtRD29A, AtCOR47, and SlCI7-like dehydrin under ABA and abiotic stress treatments. Taken together, these results show that SlAREB functions to regulate some stress-responsive genes and that its overproduction improves plant tolerance to water deficit and salt stress.

Protease inhibitors provide a promising means of engineering plant resistance against attack by insects and pathogens. Sporamin (trypsin inhibitor) from sweet potato and CeCPI (phytocystatin) from taro were stacked in a binary vector, using pMSPOA (a modified sporamin promoter) to drive both genes. Transgenic tobacco lines of T0 and T1 generation with varied inhibitory activity against trypsin and papain showed resistance to both insects and phytopathogens. Larvae of Helicoverpa armigera that ingested tobacco leaves either died or showed delayed growth and development relative to control larvae. Transgenic tobacco-overexpressing the stacked genes also exhibited strong resistance against bacterial soft rot disease caused by Erwinia carotovora and damping-off disease caused by Pythium aphanidermatum. Thus, stacking protease-inhibitor genes, driven by the wound and pathogen responsive pMSPOA promoter, is an effective strategy for engineering crops to resistance against insects and phytopathogens.

Microbes encounter various environmental factors which frequently cause detrimental effects on their population dynamics. Ralstonia solanacearum is a devastating bacterium causing a deadly and very complex disease of many agronomically important crops. To better control the disease, information about responses of distinct strains of this bacterium to environmental factors is certainly important but still insufficient. In this study, effects of salinity, excess copper, extreme pHs, drought and light on the propagation and survival of a representative of R. solanacearum strains in Taiwan, Pss4, were assessed. Our results showed that salinity negatively affected Pss4 multiplication in rich media at a dose-dependent manner, but resulted in negligent effects on its survival in sand and in water. In the presence of excess copper, similar negative effects on Pss4 culturability in rich media and at a less level on that in sand occurred. Additionally, Pss4 multiplication in rich media was substantially reduced at pH 9.0 and at a less degree at pH 5.0. Moreover, the survival of this bacterium in sand was sensitive to drought, but it sustained under incident light in water. The results were compared with previous studies on distinct R. solanacearum strains prevalent in different geographic regions and discussed in detail. The information gathered from this study would pave to the way for future studies on field samples to advance disease epidemiology and develop feasible strategies for disease control in Taiwan.

Ralstonia solanacearum causes a deadly wilting disease on a wide range of crops. To elucidate pathogenesis of this bacterium in different host plants, we set out to identify R. solanacearum genes involved in pathogenesis by screening random transposon insertion mutants of a highly virulent strain, Pss190, on tomato and Arabidopsis thaliana. Mutants exhibiting various decreased virulence levels on these two hosts were identified. Sequence analysis showed that most, but not all, of the identified pathogenesis genes are conserved among distinct R. solanacearum strains. A few of the disrupted loci were not reported previously as being involved in R. solanacearum pathogenesis. Notably, a group of mutants exhibited differential pathogenesis on tomato and Arabidopsis. These results were confirmed by characterizing allelic mutants in one other R. solanacearum strain of the same phylotype. The significantly decreased mutants' colonization in Arabidopsis was found to be correlated with differential pathogenesis on these two plants. Differential requirement of virulence genes suggests adaptation of this bacterium in different host environments. Together, this study reveals commonalities and differences of R. solanacearum pathogenesis on single solanaceous and nonsolanaceous hosts, and provides important new insights into interactions between R. solanacearum and different host plants.

Ralstonia solanacearum, the causing agent of crop bacterial wilt, is a devastating bacterium with an unusually wide host range. To effectively integrate durable resistance to R. solanacearum into crops, comprehensive and global information on pathogenesis mechanisms employed by this pathogen is important. In this study, we report the development of an efficient Arabidopsis-based bioassay system useful for screening of large number of bacterium mutants with altered virulence. The effectiveness and uniqueness of this system was further demonstrated by the isolation of R. solanacearum mutants exhibiting differential pathogenesis and in vitro characteristics, and by the identification of mutants with the transposon inserted in known and novel loci. This highly efficient bioassay system, together with the accompanying in planta and in vitro bioassay systems described here, would facilitate comprehensive study on R. solanacearum pathogenesis mechanisms.

Plant root is a unique organ conferring various important functions but lacks comprehensive studies. To identify genes that may contribute to root functions, we searched for genes specifically or abundantly expressed in root, but not in fruit tissues. A family of tomato transcripts (designated as LeGRP ), sharing a high degree of nucleotide sequence identity in their 3′-regions, was identified. Southern blot analysis revealed the presence of multiple copies of LeGRP homologues in tomato, as well as in other dicot or monocot plant species tested. Comparative genomic Southern and polymerase chain reaction (PCR) analyses indicated that some LeGRP genes could be cultivar-specific. An open-reading frame (ORF) was identified in the sequence of one of the LeGRP genes ( LeGRP2 ), with the predicted protein sharing good sequence homology with a few known and putative plant structural signal peptide-containing glycine-rich proteins (GRPs). However, the patterns and modulation of LeGRP gene expression were distinct from those of known plant GRP genes identified to date. LeGRP transcripts predominately accumulated in roots at different developmental stages, but not in leaves or ripe fruit tissues, and their levels declined gradually during plant development. Accumulation of LeGRP transcripts was effectively reduced by treatment with hydrogen peroxide and completely suppressed by salinity and application of sodium salicylate, however significantly enhanced with nutrient supplements such as HYPONeX solutions. To our knowledge, this is the first study to report down-regulation of plant GRP expression by salinity and hydrogen peroxide. Possible roles of LeGRP genes in plant growth, development and response to environmental stimuli are discussed.

Development of effective disease-resistance to a broad-range of pathogens in crops usually requires tremendous resources and effort when traditional breeding approaches are taken. Genetic engineering of disease-resistance in crops has become popular and valuable in terms of cost and efficacy. Due to long-lasting and broad-spectrum of effectiveness against pathogens, employment of systemic acquired resistance (SAR) for the genetic engineering of crop disease-resistance is of particular interest. In this report, we explored the potential of using SAR-related genes for the genetic engineering of enhanced resistance to multiple diseases in tomato. The Arabidopsis NPR1 (nonexpresser of PR genes) gene was introduced into a tomato cultivar, which possesses heat-tolerance and resistance to tomato mosaic virus (ToMV). The transgenic lines expressing NPR1 were normal as regards overall morphology and horticultural traits for at least four generations. Disease screens against eight important tropical diseases revealed that, in addition to the innate ToMV-resistance, the tested transgenic lines conferred significant level of enhanced resistance to bacterial wilt (BW) and Fusarium wilt (FW), and moderate degree of enhanced resistance to gray leaf spot (GLS) and bacterial spot (BS). Transgenic lines that accumulated higher levels of NPR1 proteins exhibited higher levels and a broader spectrum of enhanced resistance to the diseases, and enhanced disease-resistance was stably inherited. The spectrum and degree of these NPR1-transgenic lines are more significant compared to that of transgenic tomatoes reported to date. These transgenic lines may be further explored as future tomato stocks, aiming at building up resistance to a broader spectrum of diseases.

Photoemission from an epi Ge(001)-2 × 1 surface is presented using synchrotron radiation as a probe. The topmost surface atoms are buckled with the up-dimer and down-dimer atoms exhibiting surface core-level shifts (SCLSs) of −0.492 and −0.178 eV, respectively. The subsurface layer shows a +0.083 eV SCLS. The final-state effect suffices to explain the sign of the shift. The electron affinity and ionization potential for the epi Ge surface are 4.36 and 5.09 eV, respectively. An argument contrasting the current results with those of existing reports with non-epi surfaces is also given. Non-epi surfaces possess Ge surfaces with isolated single atoms or small droplets that affect Ge's contact with dielectric layers and the electric performances of the Ge metal–oxide–semiconductor structure.

Using synchrotron-radiation photoemission spectroscopy, we have studied the electronic structure of a Cs-doped rubrene surface. The doping induces the energy level shift and molecular orbital change at different doping level that can be separated into four different stages. In the first stage, the Cs atoms continuously diffuse into the substrate, and the Fermi level moves in the energy gap as a result of the doping of electrons from the Cs to the rubrene. The second stage, in which the shifts of the spectra are interrupted, is characterized by the introduction of two gap states. As increasing doping of Cs into the third stage, the spectra move again. In the fourth stage, the movement of the spectra almost stops and the third gap state appears in the former forbidden region. A pronounced shift of the vacuum level was observed, indicating the formation of an interfacial dipole.

Summary Pattern-triggered immunity (PTI) is broad spectrum and manipulation of PTI is believed to represent an attractive way to engineer plants with broad-spectrum disease resistance. PTI is activated upon perception of microbe-associated molecular patterns (MAMPs) by pattern-recognition receptors (PRRs). We have recently demonstrated that the L-type lectin receptor kinase-VI.2 (LecRK-VI.2) positively regulates Arabidopsis thaliana PTI. Here we show through in vitro pull-down, bimolecular fluorescence complementation and co-immunoprecipitation analyses that LecRK-VI.2 associates with the PRR FLS2. We also demonstrated that LecRK-VI.2 from the cruciferous plant Arabidopsis remains functional after interfamily transfer to the Solanaceous plant Nicotiana benthamiana. Wild tobacco plants ectopically expressing LecRK-VI.2 were indeed more resistant to virulent hemi-biotrophic and necrotrophic bacteria, but not to the fungal pathogen Botrytis cinerea suggesting that, as with Arabidopsis, the LecRK-VI.2 protective effect in N. benthamiana is bacteria specific. Ectopic expression of LecRK-VI.2 in N. benthamiana primed PTI-mediated reactive oxygen species production, mitogen-activated protein kinase (MAPK) activity, callose deposition and gene expression upon treatment with the MAMP flagellin. Our findings identified LecRK-VI.2 as a member of the FLS2 receptor complex and suggest that heterologous expression of components of PRR complexes can be used as tools to engineer plant disease resistance to bacteria.

Ralstonia solanacearum causes deadly wilting on many crops worldwide. However, the information on its components important for cell integrity and interactions with phages is limited. By systematically characterizing mutants resistant to a T7-like phage, we showed that the biosynthesis of rough lipopolysaccharides (R-LPS) was crucial for maintaining the membrane integrity, while the production of smooth LPS (S-LPS) was required for the resistance to polymyxin B and phage adsorption. Furthermore, RSc0154/ampG disruption did not affect LPS production and phage adsorption but may have caused aberrant release of peptidoglycan fragments, thus hindering phage DNA injection into or virion release from the cell. Mutations in the RSc2958–RSc2962/mla cluster, although not affecting LPS production, may have caused elevated phospholipid level in the outer leaflet of the outer membrane, consequently sheltering the mutants from phage adsorption on the O-antigen. These results specify important roles of the biogenesis and homeogenesis of envelope components for R. solanacearum-phage interaction.

Twelve nodule isolates from Canavalia rosea, an indigenous leguminous halophyte growing in the seaside areas of southern Taiwan, were effective symbionts for the original host and able to grow at NaCl concentrations up to 3-3.5% (w/v). The taxonomy of these isolates was investigated using a polyphasic approach, including phenotypic characteristics, banding patterns of total proteins from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), genomic fingerprint patterns from random amplified polymorphic DNA (RAPD) analysis, pulsed-field gel electrophoresis (PFGE) analysis, amplified 16S rDNA restriction analysis (ARDRA), 16S rRNA gene sequencing, and nifH gene sequencing. Based on the SDS-PAGE, RAPD, PFGE and ARDRA results, the 12 isolates are highly diverse. The 16S rRNA and nifH gene sequences were determined for isolates with distinct ARDRA patterns and compared with other members of the rhizobial species. We propose these isolates should be classified into the genus Sinorhizobium and distinguished from the current species of this genus.

Analysis of high-resolution Si 2p photoemission spectra recorded from a clean Si(001)2×1 surface clearly reveals seven components. Four of them are surface-related emission with core-level binding-energy shifts (SCLS) of −500, 278, −200, and 138 meV, which are associated with up and down atoms in the dimers, atoms in symmetric dimers, and subsurface atoms, respectively. The other two loss components appear at 1.3 and 1.75 eV, associated with the bulk and surface, respectively. The latter loss structure corresponds to the transitions of dimer-related electronic states. The components assigned to the surface dimer show significant line shifts and broadenings upon C 60 adsorption, whereas the component to the subsurface layer does not. The present result from a modified model function supports the predominance of the initial charge-transfer effect to the SCLS in Si, as in the case of Si(111)7×7.

The evolution of the valence band spectra of K doped μm thick C60 film is presented. The data shows directly that there exists a threshold concentration before the first stable phase, K3C60, starts to appear. Below the threshold concentration, no Fermi emission is seen and the K atoms distributed randomly in the bulk retain their 4s electron whose binding energy is at 0.9 eV below the Fermi level. This finding differs from all the previous experiments, which reported the immediate appearance of the K3C60 phase with a distinct Fermi cutoff upon K doping. A second stable phase, K6C60, evolves upon further doping with two characteristic states at 0.5 and 2.0 eV and coexists with the K3C60 phase. Our work also demonstrates for the first time that the superfulleride phase which arises from the filling of the t1g band can be obtained at high doping. This phase is found on the surface.

A synchrotron-radiation photoemission study of Ba deposited on a clean $\mathrm{Si}(001)2\ifmmode\times\else\texttimes\fi{}1$ surface at room temperature is presented. Upon Ba adsorption, the maximum drop in work function is about 2.3 eV. At submonolayer coverage, the asymmetric dimers on the surface are preserved. Near to one monolayer, however, they become symmetric. In the meantime, barium silicides start to form, first the monosilicide followed by the disilicide with increasing coverage. The Si $2p$ core-level photoemission spectra clearly exhibit these monosilicide and disilicide components having a surface core-level shift of 1.05 and 1.84 eV, respectively.

Tubular structures containing bacilliform virions were observed in cell-free extracts of Commelina diffusa infected with Commelina yellow mottle badnavirus (CoYMV). The exterior of the tubule reacted with antibodies to CoYMV movement protein, but not with antibodies to virus coat protein. Similar tubular structures containing bacilliform particles were also observed in ultrathin sections of CoYMV-infected C. diffusa. These tubular structures traversed the cell wall at points where this was thickened or protruded. No similar structures were observed in healthy C. diffusa. These observations support the hypothesis that the virion-containing tubular structures observed in cell-free extracts are the same as those observed in situ, that these structures are composed, at least in part, of virus movement protein, and that they play a role in the cell-to-cell trafficking of virions of CoYMV.