Induction of antimicrobial 3-deoxyflavonoids in pome fruit trees controls fire blight

Fire blight, a devastating bacterial disease in pome fruits, causes severe economic losses worldwide. Hitherto, an effective control could only be achieved by using antibiotics, but this implies potential risks for human health, livestock and environment. A new approach allows transient inhibition of a step in the flavonoid pathway, thereby inducing the formation of a novel antimicrobial 3-deoxyflavonoid controlling fire blight in apple and pear leaves. This compound is closely related to natural phytoalexins in sorghum. The approach does not only provide a safe method to control fire blight: Resistance against different pathogens is also induced in other crop plants.     

Comparative potency of different plant growth retardants in cell cultures and intact plants

A comparison of the efficiency of a broad range of plant growth retardants on cell division growth of 13 cell suspension cultures is presented. The results show that (1) the new plant bioregulator tetcyclacis (NDA) is the compound with the highest activity in inhibiting cell division of all cultures tested, and (2) cell cultures react species-specifically to various compounds. Significant correlations between the results from suspension cultures and intact seedlings of the same plant species demonstrate the usefulness of cell cultures for identifying substances with a growth-regulating potency. Futhermore, the usefulness of cell cultures for establishing structure-activity relationships was shown with structural analogues of chlormequat and mepiquat chloride.     

Optimal nitrogen supply as a key to increased and sustained production of a monoclonal full‐size antibody in BY‐2 suspension culture

Plant cell cultures have been used as expression hosts for recombinant proteins for over two decades. The quality of plant cell culture‐produced proteins such as full‐size monoclonal antibodies has been shown to be excellent in terms of protein folding and binding activity, but the productivity and yield fell short of what was achieved using mammalian cell culture, in which the key to gram‐per‐liter expression levels was strain selection and medium/process optimization. We carried out an extensive media analysis and optimization for the production of the full‐size human anti‐HIV antibody 2G12 in N. tabacum cv. BY‐2. Nitrogen source and availability was found to be one key factor for the volumetric productivity of plant cell cultures. Increased amounts of nitrate in the culture medium had a dramatic impact on protein yields, resulting in a 10–20‐fold increase in product accumulation through a combination of enhanced secretion and higher stability. The results were scalable from shake flasks to stirred‐tank bioreactors, where the maximum yield per cultivation volume was 8 mg L^?1 over 7 days. During the stationary phase, antibody levels were 150‐fold higher in nitrogen‐enriched medium compared to standard medium. The enhanced medium appeared not to affect antibody quality and activity, as determined by Western blots, surface plasmon resonance binding assays and N‐glycan analysis. Biotechnol. Bioeng. 2010;107: 278–289. © 2010 Wiley Periodicals, Inc.     

The synaptic scaffold protein MPP2 interacts with GABAA receptors at the periphery of the postsynaptic density of glutamatergic synapses

Recent advances in imaging technology have highlighted that scaffold proteins and receptors are arranged in subsynaptic nanodomains. The synaptic membrane-associated guanylate kinase (MAGUK) scaffold protein membrane protein palmitoylated 2 (MPP2) is a component of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor–associated protein complexes and also binds to the synaptic cell adhesion molecule SynCAM 1. Using superresolution imaging, we show that—like SynCAM 1—MPP2 is situated at the periphery of the postsynaptic density (PSD). In order to explore MPP2-associated protein complexes, we used a quantitative comparative proteomics approach and identified multiple γ-aminobutyric acid (GABA)_A receptor subunits among novel synaptic MPP2 interactors. In line with a scaffold function for MPP2 in the assembly and/or modulation of intact GABA_A receptors, manipulating MPP2 expression had effects on inhibitory synaptic transmission. We further show that GABA_A receptors are found together with MPP2 in a subset of dendritic spines and thus highlight MPP2 as a scaffold that serves as an adaptor molecule, linking peripheral synaptic elements critical for inhibitory regulation to central structures at the PSD of glutamatergic synapses.

This study shows that the MAGUK scaffold protein MPP2 is located at the periphery of postsynaptic densities in excitatory neurons, where it interacts with GABA-A receptors, thereby serving as a functional adaptor that links excitatory and inhibitory components of synaptic transmission at glutamatergic synapses.     

Effects of NDA,a new plant growth retardant,on cell culture growth ofZea mays L.

A new plant growth retardant, the norbornenodiazetine derivative 5-(4-chlorophenyl) - 3,4,5,9,10 - pentaaza - tetracyclo - 5,4,1,0^2.6,0^8.11- dodeca - 3,9 - diene (NDA) was tested for its effects on growth ofZea mays suspension cultures. It was shown that NDA could inhibit cell division almost completely at a concentration of 5× 10^?5 M, while 80% of cells could be considered viable. Tracer experiments revealed that NDA inhibited thymidine, uridine, and leucine uptake into cells after 30 min of application. In contrast, amino acid incorporation into proteins was reduced only after one day of treatment and incorporation of precursors into DNA and RNA still later. Since NDA stimulated DNase, RNase, and protease activity in the cells simultaneously, an enhancement of DNA and RNA in cells possibly was prevented. That NDA affected protein synthesis indirectly seemed to be proved by the late point in time of its action on leucine incorporation and by only slight effects on cell free translation. An explanation of these findings could be an alteration in or inhibition of sterol biosynthesis caused by NDA, because it is known that sterols play an important role in controlling permeability of plant membranes as well as in maintaining normal protein synthesis. Thus we tested NDA for its effects on sterol production in maize cells and demonstrated that the composition of the sterol fraction, mainly stigmasterol and β-sitosterol, was clearly changed qualitatively as well as quantitatively.     

Characterization of photodamage to escherichia coli in optical traps

Optical tweezers (infrared laser-based optical traps) have emerged as a powerful tool in molecular and cell biology. However, their usefulness has been limited, particularly in vivo, by the potential for damage to specimens resulting from the trapping laser. Relatively little is known about the origin of this phenomenon. Here we employed a wavelength-tunable optical trap in which the microscope objective transmission was fully characterized throughout the near infrared, in conjunction with a sensitive, rotating bacterial cell assay. Single cells of Escherichia coli were tethered to a glass coverslip by means of a single flagellum: such cells rotate at rates proportional to their transmembrane proton potential (. J. Mol. Biol. 138:541-561). Monitoring the rotation rates of cells subjected to laser illumination permits a rapid and quantitative measure of their metabolic state. Employing this assay, we characterized photodamage throughout the near-infrared region favored for optical trapping (790-1064 nm). The action spectrum for photodamage exhibits minima at 830 and 970 nm, and maxima at 870 and 930 nm. Damage was reduced to background levels under anaerobic conditions, implicating oxygen in the photodamage pathway. The intensity dependence for photodamage was linear, supporting a single-photon process. These findings may help guide the selection of lasers and experimental protocols best suited for optical trapping work.