Root Growth of Arabidopsis thaliana Is Regulated by Ethylene and Abscisic Acid Signaling Interaction in Response to HrpNEa, a Bacterial Protein of Harpin Group

HrpN_Ea is a harpin protein from Erwinia amylovora, a bacterial pathogen that causes fire blight in rosaceous plants. Treating plants with HrpN_Ea stimulates ethylene and abscisic acid (ABA) to induce plant growth and drought tolerance, respectively. Herein, we report that both growth hormones cooperate to mediate the role of HrpN_Ea in promoting root growth of Arabidopsis thaliana seedlings. Root growth is promoted coordinately with elevation in levels of ABA and ethylene subsequent to soaking of germinating seeds of wild-type (WT) Arabidopsis in a solution of HrpN_Ea. However, these responses are arrested by inhibiting WT roots from synthesizing ethylene as well as sensing of ABA and ethylene. The effects of HrpN_Ea on roots are also nullified in ethylene-insensitive etr1-1 and ein5-1 mutants and in the ABA-insensitive mutant abi2-1 of Arabidopsis. These results provide evidence for presence of a relationship between root growth enhancement and signaling by ABA and ethylene in response to HrpN_Ea. Nevertheless, when HrpN_Ea is applied to leaves, ethylene signaling is active in the absence of ABA signaling to promote plant growth. This suggests the presence of a different signaling mechanism in leaves from that in roots. X. Ren and F. Liu contributed equally to this study and are regarded as joint first authors     

Biosynthesis of glycoconjugates in mitochondrial outer membranes

The results reported in this paper show two distinct ways for the incorporation ofN-acetylglucosamine into mitochondrial outer membranes. The first one is the glycosylation of dolichol acceptors, which is indicated by the inhibition of the synthesis of these products by the inhibitors of the dolichol intermediates (tunicamycin and GDP). The second one is the incorporation ofN-acetylglucosamine into protein acceptors directly from UDP-N-acetylglucosamine. This second way of glycosylation is only localized in mitochondria outer membranes.The existence of a direct route forN-glycoprotein biosynthesis has been based on the following evidence. First, the synthesis of theN-acetylglucosaminylated protein acceptors was not inhibited by tunicamycin or GDP. Second, the addition of exogenous dolichol-phosphate did not change the rate of biosynthesis of glycosylated protein material. Third, the sequential incorporation ofN-acetylglucosamine and mannose from their nucleotide derivatives in the presence of GDP and tunicamycin led to the synthesis of glycosylated protein material which entirely bound to Concanavalin A-Sepharose. The oligosaccharide moiety of the glycosylated protein material resulting from the direct transfer of sugars from their nucleotide derivatives to the protein acceptor is of theN-glycan type. On sodium dodecylsulphate polyacrylamide gel electrophoresis, this glycosylated material migrated as a marker protein with a molecular weight between 45 000 and 63 000. HPLC chromatofocusing analysis revealed that the fraction studied was anionic. The oligosaccharide moiety of the glycoprotein material can only be elongated by the incorporation ofN-acetylglucosamine and galactose from their nucleotide derivatives.     

Expression,purification and characterization of anti-BAFF antibody secreted from the yeast <Emphasis Type="Italic">Pichia pastoris</Emphasis>

B-Cell activating factor (BAFF) is critical for B cell survival and maturation; excessive expression of it corrupts B-cell tolerance and may lead to autoimmunity. The gene, scFv-Fc, coding for the antibody of BAFF was inserted into the eukaryotic expression vector, pPICZαA, and transformed into Pichia pastoris. A high-level expression strain was obtained using a ‘yeastern blotting’ method. The scFv-Fc antibody was purified and 56 mg was obtained from 1 l of culture supernatant. It retained high binding activity to both soluble BAFF and membrane-bound BAFF.     

Different ammonia tolerances may facilitate spatial coexistence of Gammarus roeselii and the strong invader Dikerogammarus villosus

The introduction of invasive species that can replace native species is one of the most critical threats to the biodiversity of aquatic systems. Here we investigated the potential contribution of one factor to the coexistence of the indigenous amphipod Gammarus roeselii and the invasive amphipod Dikerogammarus villosus in the same ecosystem (Lake Constance) within different microhabitats. We quantitatively studied the influence of ambient ammonia concentrations on the distributions of the two amphipod species. We also assessed the ammonia tolerance ranges of both species in laboratory experiments by measuring mortality rate, precopula disruption, egg mortality, and microhabitat choice. The proportion of G. roeselii among the two amphipod species was significantly positively related to the ammonia concentration in the water, which indicated that the distribution of the invasive D. villosus was limited at high ammonia concentrations. Although the mortality rates of the two species did not significantly differ, G. roeselii was more tolerant to ammonia with regard to precopula disruption, egg mortality, and microhabitat choice. The effective ammonia concentrations that led to a significantly reduced direct reproductive success in D. villosus were within the range of the highest field concentrations measured, where only G. roeselii occurred. D. villosus may have a smaller range than the indigenous G. roeselii partially because of its lower tolerance to higher ammonia concentrations, which lead to reduced reproductive success. Beside other habitat parameters differences on ammonia tolerance between the two amphipods might allow their coexistence along a gradient of microhabitats in Lake Constance.     

The potential of click reactions for the synthesis of bioactive triterpenes

Click reactions between alkynes and azides using the privileged scaffold of triterpenes have been of interest for biological chemistry. Many publications deal with the synthesis of novel bioactive molecules; these conjugates have also been used for bioanalytical and diagnostic purposes. As a result, conjugates of better physicochemical properties were obtained; even compounds of improved solubility in water and physiological fluids were made through the introduction of a triazol residue. “Hybrid-structures“, i.e. molecules consisting of two independently bioactive subunits linked by a triazole residue were higher bioactive than their parent compounds but not as active as expected, and with a few exceptions the ultimate breakthrough has not yet been achieved. Only in the synthesis of compounds with anti-leishmanial activity some new and promising lead structures were found. As a consequence, triazole modified triterpenes seem to hold their greatest future prospect rather as diagnostic reagents and molecular probes than as drugs.     

A knee-specific finite element analysis of the human anterior cruciate ligament impingement against the femoral intercondylar notch

This work presents a finite element analysis of anterior cruciate ligament (ACL) impingement against the intercondylar notch during tibial external rotation and abduction, as a mechanism of noncontact ACL injuries. Experimentally, ACL impingement was measured in a cadaveric knee in terms of impingement contact pressure and six degrees-of-freedom tibiofemoral kinematics. Three-dimensional geometries of the ACL, femur and tibia were incorporated into the finite element model of the individual knee specimen. A fiber-reinforced model was adopted, which accounts for the anisotropy, large deformation, nonlinearity and incompressibility of the ACL. With boundary conditions specified based on the experimental tibiofemoral kinematics, the finite element analysis showed that impingement between the ligament and the lateral wall of intercondylar notch could occur when qthe knee at 45° was externally rotated at 29.1° and abducted at 10.0°. Strong contact pressure and tensile stress occurred at the impinging and nonimpinging sides of the ligament, respectively. The impingement force and contact area estimated from the model matched their counterparts from the corresponding cadaver experiment. The modeling and experimental approach provides a useful tool to characterize potential ACL impingement on a knee-specific basis, which may help elucidate the ACL injury mechanism and develop more effective treatments.