Integrins establish dendrite-substrate relationships that promote dendritic self-avoidance and patterning in drosophila sensory neurons

Dendrites achieve characteristic spacing patterns during development to ensure appropriate coverage of territories. Mechanisms of dendrite positioning via?repulsive dendrite-dendrite interactions are beginning to be elucidated, but the control, and importance, of dendrite positioning relative to their substrate is poorly understood. We found that dendritic branches of Drosophila dendritic arborization sensory neurons can be positioned either at the basal surface of epidermal cells, or enclosed within epidermal invaginations. We show that integrins control dendrite positioning on or within the epidermis in a cell autonomous manner by promoting dendritic retention on the basal surface. Loss of integrin function in neurons resulted in excessive self-crossing and dendrite maintenance defects, the former indicating a role for substrate interactions in self-avoidance. In contrast to a contact-mediated mechanism, we find that integrins prevent crossings that are noncontacting between dendrites in different three-dimensional positions, revealing a requirement?for combined dendrite-dendrite and dendrite-substrate interactions in self-avoidance.     

Weak Intra-Ring Allosteric Communications of the Archaeal Chaperonin Thermosome Revealed by Normal Mode Analysis

Chaperonins are molecular machines that use ATP-driven cycles to assist misfolded substrate proteins to reach the native state. During the functional cycle, these machines adopt distinct nucleotide-dependent conformational states, which reflect large-scale allosteric changes in individual subunits. Distinct allosteric kinetics has been described for the two chaperonin classes. Bacterial (group I) chaperonins, such as GroEL, undergo concerted subunit motions within each ring, whereas archaeal and eukaryotic chaperonins (group II) undergo sequential subunit motions. We study these distinct mechanisms through a comparative normal mode analysis of monomer and double-ring structures of the archaeal chaperonin thermosome and GroEL. We find that thermosome monomers of each type exhibit common low-frequency behavior of normal modes. The observed distinct higher-frequency modes are attributed to functional specialization of these subunit types. The thermosome double-ring structure has larger contribution from higher-frequency modes, as it is found in the GroEL case. We find that long-range intersubunit correlation of amino-acid pairs is weaker in the thermosome ring than in GroEL. Overall, our results indicate that distinct allosteric behavior of the two chaperonin classes originates from different wiring of individual subunits as well as of the intersubunit communications.     

Affordable uniform isotope labeling with <Superscript>2</Superscript>H, <Superscript>13</Superscript>C and <Superscript>15</Superscript>N in insect cells

For a wide range of proteins of high interest, the major obstacle for NMR studies is the lack of an affordable eukaryotic expression system for isotope labeling. Here, a simple and affordable protocol is presented to produce uniform labeled proteins in the most prevalent eukaryotic expression system for structural biology, namely Spodoptera frugiperda insect cells. Incorporation levels of 80 % can be achieved for ¹⁵N and ¹³C with yields comparable to expression in full media. For ²H,¹⁵N and ²H,¹³C,¹⁵N labeling, incorporation is only slightly lower with 75 and 73 %, respectively, and yields are typically twofold reduced. The media were optimized for isotope incorporation, reproducibility, simplicity and cost. High isotope incorporation levels for all labeling patterns are achieved by using labeled algal amino acid extracts and exploiting well-known biochemical pathways. The final formulation consists of just five commercially available components, at costs 12-fold lower than labeling media from vendors. The approach was applied to several cytosolic and secreted target proteins.     

Population Structure of Peronospora effusa in the Southwestern United States

Peronospora effusa is an obligate pathogen that causes downy mildew on spinach and is considered the most economically important disease of spinach. The objective of the current research was to assess genetic diversity of known historical races and isolates collected in 2014 from production fields in Yuma, Arizona and Salinas Valley, California. Candidate neutral single nucleotide polymorphisms (SNPs) were identified by comparing sequence data from reference isolates of known races of the pathogen collected in 2009 and 2010. Genotypes were assessed using targeted sequencing on genomic DNA extracted directly from infected plant tissue. Genotyping 26 historical and 167 contemporary samples at 46 SNP loci revealed 82 unique multi-locus genotypes. The unique genotypes clustered into five groups and the majority of isolates collected in 2014 were genetically closely related, regardless of source location. The historical samples, representing several races, showed greater genetic differentiation. Overall, the SNP data indicate much of the genotypic variation found within fields was produced during asexual development, whereas overall genetic diversity may be influenced by sexual recombination on broader geographical and temporal scales.     

Recovery of Lyme disease spirochetes from patients.

Since the summer of 1982, we have cultured patient specimens for Lyme disease spirochetes. Of 118 patients cultured, four specimens yielded spirochetes: two from blood, one from a skin biopsy specimen of erythema chronicum migrans (ECM), and one from cerebrospinal fluid. All four isolates appeared identical when examined with a monoclonal antibody. However, attempts to recover the spirochete from synovium or synovial fluid were unsuccessful. In addition, the organism could not be visualized in skin or synovial biopsy specimens using the avidin-biotin peroxidase complex detection system. Thus, the current yield in culturing spirochetes from patients is quite low, and it is not yet known whether the organism is still alive later in the disease when arthritis is present.     

QTLs associated with root traits increase yield in upland rice when transferred through marker-assisted selection

Altering root morphology of rice (Oryza sativa L.) cultivars could improve yields in drought-prone upland ecosystems. Marker-assisted backcross breeding was used to introgress four QTLs for root traits into an upland rice cultivar. The QTLs had previously been identified under experimental conditions in a different genetic background. The introgressed lines and the recurrent parent were grown for 6 years by resource-poor farmers in upland sites in Eastern India and yields recorded. In combination the QTLs significantly increased yield by 1 t ha^?1 under relatively favourable field conditions. In less favourable trials, the QTL effects were not detected due to greater heterogeneity in soil–water availability in very low yielding environments and consequent yield variability. Root studies under controlled conditions showed that lines with the introgressions had longer roots throughout tillering than the recurrent parent (14 cm longer 2 weeks after sowing). Therefore, both improved roots and increased yield can be attributed to the introgression of QTLs. This is the first demonstration that marker-assisted backcross breeding (MABC) to introgress multiple root QTLs identified under controlled conditions is an effective strategy to improve farmers’ yields of upland rice. The strategy was used to breed a novel upland rice cultivar that has been released in India as Birsa Vikas Dhan 111.     

Social interactions between adult male and infant rhesus monkeys in Nepal

In 1,506 hours of field observations on free-ranging rhesus monkeys in Kathmandu Valley, Nepal, in 1974 and 1975 18 cases of favorable social interactions between adult males and infants were observed. Eleven of these were brief encounters of play or grooming; seven were more extended cases of male care. One of the latter was a complete adoption of a neonatal orphan by a dominant male. This adoption was possessive and restrictive and it resulted in the death of the infant by starvation within three days. A similar adoption involving the same male occurred in 1976 and it also resulted in the death of the infant. Most of the favorable male-infant interactions occurred during the winter and spring when the infants were 6 to 12 months of age. These favorable social interactions involved eight males in six different troops, out of a total of about 48 males in 12 troops in our study population of approximately 600 monkeys. These observations are discussed in light of current sociobiological theories.