DspA/E, a type III effector essential for Erwinia amylovora pathogenicity and growth in planta, induces cell death in host apple and nonhost tobacco plants

Erwinia amylovora is responsible for fire blight, a necrotic disease of apples and pears. E. amylovora relies on a type III secretion system (TTSS) to induce disease on hosts and hypersensitive response (HR) on nonhost plants. The DspA/E protein is essential for E. amylovora pathogenicity and is secreted via the TTSS in vitro. DspA/E belongs to a type III effector family that is conserved in several phytopathogenic bacteria. In E. amylovora, DspA/E has been implicated in the generation of an oxidative stress during disease and the suppression of callose deposition. We investigated the fate of DspA/E in planta. DspA/E delivered artificially to apple or tobacco cells by agroinfection induced necrotic symptoms, indicating that DspA/E was probably injected via the TTSS. We confirmed that DspA/E acts as a major cell-death inducer during disease and HR, because the dspA/E mutant is severely impaired in its ability to induce electrolyte leakage in apple and tobacco leaves. Expression of the defense marker gene PR1 was delayed when dspA/E was transiently expressed in tobacco, suggesting that DspA/E-mediated necrosis may be associated with an alteration of defense responses.     

Role of a heterotrimeric G protein in regulation of Arabidopsis seed germination

Seed germination is regulated by many signals. We investigated the possible involvement of a heterotrimeric G protein complex in this signal regulation. Seeds that carry a protein null mutation in the gene encoding the alpha subunit of the G protein in Arabidopsis (GPA1) are 100-fold less responsive to gibberellic acid (GA), have increased sensitivity to high levels of Glc, and have a near-wild-type germination response to abscisic acid and ethylene, indicating that GPA1 does not directly couple these signals in germination control. Seeds ectopically expressing GPA1 are at least a million-fold more responsive to GA, yet still require GA for germination. We conclude that the GPA1 indirectly operates on the GA pathway to control germination by potentiation. We propose that this potentiation is directly mediated by brassinosteroids (BR) because the BR response and synthesis mutants, bri1-5 and det2-1, respectively, share the same GA sensitivity as gpa1 seeds. Furthermore, gpa1 seeds are completely insensitive to brassinolide rescue of germination when the level of GA in seeds is reduced. A lack of BR responsiveness is also apparent in gpa1 roots and hypocotyls suggesting that BR signal transduction is likely coupled by a heterotrimeric G protein at various points in plant development.     

High-Resolution Two-Dimensional Atomic Localization Via Tunable Surface Plasmon Polaritons

The two-dimensional (2D) atomic localization is theoretically investigated via tunable surface plasmon polaritons (SPPs), generated on the metal (Ag) surface coupled to a quantum coherent three-level \(\lambda\)-type medium (\(^{87}\)Rb) embedded as a dielectric host. Such a useful scheme for highly precise atomic localization is reported by using the absorption spectrum of SPPs. Owing to space-dependent light–matter interaction, the sharp localized peaks are observed in a single wavelength domain of 2D space with maximum probability. By properly varying the system parameters, the precision and numbers of the localized peaks are controlled. Consequently, highly efficient and high-resolution atomic localization can be achieved in a region smaller than \(\lambda /20\times \lambda /20\). The spatial resolution of atomic localization is greatly improved as compared to the previously studied cases. These results may have potential useful applications in the fields of quantum nanoplasmonics, nanolithography, and nanophotonics.

     

Extracellular phytase (E.C. 3.1.3.8) from Aspergillus ficuum NRRL 3135: purification and characterization

Extracellular phytase from Aspergillus ficuum, a glycoprotein, was purified to homogeneity in 3 column chromatographic steps using ion exchange and chromatofocusing. Results of gel filtration chromatography and SDS-polyacrylamide gel electrophoresis indicated the approximate molecular weight of the native protein to be 85-100-KDa. On the basis of a molecular weight of 85-KDa, the molar extinction coefficient of the enzyme at 280 nm was estimated to be 1.2 X 10(4) M-1 cm-1. The isoelectric point of the enzyme, as deduced by chromatofocusing, was about 4.5. The purified enzyme is remarkably stable at 0 degree C. Thermal inactivation studies have shown that the enzyme retained 40% of its activity after being subjected to 68 degrees C for 10 minutes, and the enzyme exhibited a broad temperature optimum with maximum catalytic activity at 58 degrees C. The Km of the enzyme for phytate and p-nitrophenylphosphate is about 40 uM and 265 uM, respectively, with an estimated turnover number of the enzyme for phytate of 220 per sec. Enzymatic deglycosylation of phytase by Endoglycosidase H lowered the molecular weight of native enzyme from 85-100-KDa to about 76-KDa; the digested phytase still retained some carbohydrate as judged by positive periodic acid-Schiff reagent staining of the electrophoresed protein. Immunoblotting of the phytase with monoclonal antibody 7H10 raised against purified native enzyme recognized not only native but also partially deglycosylated protein.     

Modulating HIV-1 envelope glycoprotein conformation to decrease the HIV-1 reservoir

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Effect of desiccation on potassium and anion currents from young root hairs: Implication on tip growth

Little is known about the early response of roots to desiccation. Young growing root hairs of Arabidopsis thaliana , Vigna unguiculata and Phaseolus vulgaris were used to study the early response of roots to desiccation since they behave like sensors that are able to perceive environmental signals. In control conditions, root hairs were polarized around −120 mV and displayed inward rectifying K⁺ currents. When submitted to short-term desiccation, root hairs stopped their tip growth and their membrane became depolarized. Under these conditions, the K⁺ influx carried by the inward rectifying K⁺ channels was not maintained and instead slow deactivating anion channels were recorded. The inhibition of K⁺ influx and the large anion efflux due to the activation of slow anion currents could participate in the inhibition of tip growth.     

Soil cadmium enrichment: Allocation and plant physiological manifestations

Cadmium (Cd) in soil is enriched through several leaky management agricultural practices and natural resources. Cd enriched soil is inevitable cause of nutritional stress besides Cd induced toxicity symptoms and physiological malfunctions. Redox signals shift toward oxidative stress which accelerates cellular damage and elicits defense mechanism at the cost of growth. Plants get enriched with this toxic, abundant and undesirable element through ‘mineral uptake system’ non-specifically. Different components and pathways have been marked cooperating in cellular sequestration and systemic localization of Cd, escaped from avoidance and efflux. Cd induced metabolic alteration led to electron leakage as ROS, reduced photosynthesis and carbon fixation. Compromised primary metabolism negatively feedbacks the plant growth, result into loss of potential crop yield.     

The level of proteins and leakage of solutes in germinating fresh and stored seeds ofCicer arietinum L.

One-year-old seeds of chickpea (Cicer arietinum L. cv. C-235) lost about 23 % germinability and leaked larger quantities of N, P, K, saccharides and proteins into the soaking medium in the first 48 h, as compared with fresh seeds. The protein content in stored seeds decreased more than in fresh seeds, as the soaking progressed.