The influence of ethylene perception on sex expression in melon (<Emphasis Type="Italic">Cucumis melo </Emphasis>L.) as assessed by expression of the mutant ethylene receptor, <Emphasis Type="Italic">At-etr1-1</Emphasis>, under the control of constitutive and floral targeted promoters

Sexual diversity expressed by Curcurbitaceae species is a primary example of developmental plasticity in plants. Ethylene, which promotes femaleness (carpel development), plays a key role in sex determination. We sought to determine the critical location for ethylene perception in developing floral primodia. The dominant negative Arabidopsis ethylene response mutant gene, etr1-1, was introduced into melon (Cucumis melo L.) plants under control of the constitutive cauliflower mosaic virus (CaMV) 35S promoter, or floral-targeted Apetela3 (AP3) and Crab’s Claw (CRC) promoters, which in Arabidopsis, promote expression in petal and stamen, and carpel and nectary primordia, respectively. Based on effects of exogenous ethylene, it was predicted that inhibition of ethylene perception by carpel primordia would inhibit carpel development. Constitutive expression of etr1-1 caused several phenotypes associated with ethylene insensitivity, verifying that etr1-1 inhibits ethylene perception in the heterologous melon system. Carpel-bearing bud production was essentially abolished in 35S::etr1-1 melons, providing direct demonstration of the requirement for ethylene perception for carpel development. CRC::etr1-1 plants, however, showed enhanced femaleness as manifested by earlier and increased number of carpel-bearing buds, and production of female (rather than bisexual) buds. Despite increased carpel-bearing bud formation, a greater proportion of the CRC::etr1-1 carpel-bearing buds aborted before anthesis. AP3::etr1-1 plants showed increased maleness by nearly exclusive staminate flower production, and poorly developed carpels in the rare bisexual flowers. These results indicate that ethylene perception by the stamen (or petal) primordia plays a critical role in promoting carpel development at the time of sex determination, while ethylene perception by the carpel is important for maturation of carpel-bearing flowers to anthesis.     

UbiProt: a database of ubiquitylated proteins

Background  

Post-translational protein modification with ubiquitin, or ubiquitylation, is one of the hottest topics in a modern biology due to a dramatic impact on diverse metabolic pathways and involvement in pathogenesis of severe human diseases. A great number of eukaryotic proteins was found to be ubiquitylated. However, data about particular ubiquitylated proteins are rather disembodied.     

A study of water diffusion into a high-amylose starch blend: the effect of moisture content and temperature

The effect of moisture content and temperature on water diffusion into a modified high amylose (< or = 90%) maize thermoplastic starch blend was investigated. Gravimetric and magnetic resonance imaging (MRI) studies were conducted to elucidate the diffusion mechanism and diffusion coefficients for this system. The diffusion coefficient data demonstrated that the rate of water diffusion into this blend was significantly dependent upon temperature and moisture content. Water diffusion was faster at higher temperatures and generally for samples stored at higher relative humidity environments. It was revealed from the gravimetric data that water diffusion into this starch blend was Fickian; however, further analysis of the MRI images found that the water diffusion mechanism was exponentially dependent on the concentration. This result was determined by comparing experimental water concentration profiles to a theoretical model calculated using the implicit Crank-Nicolson finite difference method.     

Study of Interaction of the PARP Family DNA-Dependent Proteins with Nucleosomes Containing DNA Intermediates of the Initial Stages of BER Process

Biochemistry (Moscow) - Reaction of (ADP-ribosyl)ation catalyzed by DNA-dependent proteins of the poly(ADP-ribose)polymerase (PARP) family, PARP1, PARP2, and PARP3, comprises the cellular response...     

VENOM FROM THE ECTOPARASITIC WASP Habrobracon hebetor ACTIVATES CALCIUM‐DEPENDENT DEGRADATION OF Galleria mellonella LARVAL HEMOCYTES

Ectoparasitoids inject venom into hemolymph during oviposition. We determined the influence of envenomation by the parasitoid, Habrobracon hebetor, on the hemocytes of its larval host, Galleria mellonella. An increase in both intracellular Са²⁺ content and phospholipase C activity of the host hemocytes was recorded during 2 days following envenomation by the parasitoid. The decreased hemocyte viability was detected 1, 2, and 24 h after the envenomation. Injecting of the crude venom (final protein concentration 3 μg/ml) into the G. mellonella larvae led to the reduced hemocyte adhesion. The larval envenomation caused a decrease in transmembrane potential of the hemocytes. These findings document the suppression of hemocytic immune effectors in the parasitized host larvae.     

A Flexible Nanoarray Approach for the Assembly and Probing of Molecular Complexes

Immobilization is a key step involved in probing molecular interactions using single-molecule force spectroscopy methods, including atomic force microscopy (AFM). To our knowledge, we describe a novel approach termed flexible nanoarray (FNA) in which the interaction between the two internally immobilized amyloid β peptides is measured by pulling of the tether. The FNA tether was synthesized with nonnucleotide phosphoramidite monomers using the DNA synthesis chemistry. The two anchoring points for immobilization of the peptides inside the tether were incorporated at defined distances between them and from the ends of the polymer. Decamers of amyloid β peptide capable of dimer formation were selected as a test system. The formation of the peptide dimers was verified by AFM force spectroscopy by pulling the tether at the ends. In these experiments, the thiolated end of the FNA tether was covalently immobilized on the AFM substrate functionalized with maleimide. The other end of the FNA tether was functionalized with biotin to form a noncovalent link with the streptavidin functionalized AFM tip during the approach stage. The dimers’ rupture fingerprint was unambiguously identified on the force curves by its position and the force value. The FNA design allowed reversible experiments in which the monomers were allowed to associate after the rupture of the dimers by performing the approach stage before the rupture of the biotin-streptavidin link. This suggests that the FNA technique is capable of analyzing multiple intermolecular interactions in the same molecular complex. The computational analysis showed that the tethered peptides assemble into the same dimer structure as that formed by nontethered peptides, suggesting that the FNA tether has the necessary flexibility to enable assembly of the dimer even during the course of the force spectroscopy experiment.     

Basic mechanism for biorientation of mitotic chromosomes is provided by the kinetochore geometry and indiscriminate turnover of kinetochore microtubules

Accuracy of chromosome segregation relies on the ill-understood ability of mitotic kinetochores to biorient, whereupon each sister kinetochore forms microtubule (MT) attachments to only one spindle pole. Because initial MT attachments result from chance encounters with the kinetochores, biorientation must rely on specific mechanisms to avoid and resolve improper attachments. Here we use mathematical modeling to critically analyze the error-correction potential of a simplified biorientation mechanism, which involves the back-to-back arrangement of sister kinetochores and the marked instability of kinetochore–MT attachments. We show that a typical mammalian kinetochore operates in a near-optimal regime, in which the back-to-back kinetochore geometry and the indiscriminate kinetochore–MT turnover provide strong error-correction activity. In human cells, this mechanism alone can potentially enable normal segregation of 45 out of 46 chromosomes during one mitotic division, corresponding to a mis-segregation rate in the range of 10⁻¹–10⁻² per chromosome. This theoretical upper limit for chromosome segregation accuracy predicted with the basic mechanism is close to the mis-segregation rate in some cancer cells; however, it cannot explain the relatively low chromosome loss in diploid human cells, consistent with their reliance on additional mechanisms.