The root-colonizing endophyte Pirifomospora indica confers drought tolerance in Arabidopsis by stimulating the expression of drought stress-related genes in leaves

Piriformospora indica is an endophytic fungus that colonizes the roots of many plant species, including Arabidopsis. We exposed 18-day-old Arabidopsis seedlings, which were either cocultivated with the fungus or mock-treated for the last 9 days, to mild drought stress for 84 h. During the first 36 to 48 h, seedlings cocultivated with the fungus continued to grow, while the uncolonized controls did not. This results in a threefold difference in the fresh weight and a more than twofold difference in the chlorophyll content. The photosynthetic efficiency was only slightly reduced in the colonized (F variable/F maximum [Fv/Fm] at t(0 h) = 0.82 and t(36 h) = 0.79) and was severely impaired in the uncolonized (Fv/Fm at t(0 h) = 0.81 and (t)(36 h) = 0.49) seedlings, which also showed symptoms of withering. When seedlings exposed to drought stress for 72 or 84 h were transferred to soil, 10% (72 h) and none (84 h) of uncolonized seedlings reached the flowering stage and produced seeds, while 59% (72 h) and 47% (84 h) of the colonized seedlings flowered and produced seeds. After exposure to drought stress for 3 h, the message levels for RESPONSE TO DEHYDRATION 29A, EARLY RESPONSE TO DEHYDRATION1, ANAC072, DEHYDRATION-RESPONSE ELEMENT BINDING PROTEIN2A, SALT-, AND DROUGHT-INDUCED RING FINGER1, phospholipase Ddelta, CALCINEURIN B-LIKE PROTEIN (CBL)1, CBL-INTERACTING PROTEIN KINASE3, and the histone acetyltransferase (HAT) were upregulated in the leaves of P. indica-colonized seedlings. Uncolonized seedlings responded 3 to 6 h later, and the message levels increased much less. We identified an Arabidopsis ethylmethane-sulfonate mutant that is less resistant to drought stress and in which the stress-related genes were not upregulated in the presence of P. indica. Thus, P. indica confers drought-stress tolerance to Arabidopsis, and this is associated with the priming of the expression of a quite diverse set of stress-related genes in the leaves. Transfer to soil was again associated with a faster and stronger upregulation of the message levels for phospholipase Ddelta, CBL1, and HAT in P. indica-colonized seedlings, indicating that this response might also contribute to better survival on soil.     

Measurement of Elastic Modulus of Collagen Type I Single Fiber

Collagen fibers are the main components of the extra cellular matrix and the primary contributors to the mechanical properties of tissues. Here we report a novel approach to measure the longitudinal component of the elastic moduli of biological fibers under conditions close to those found in vivo and apply it to type I collagen from rat tail tendon. This approach combines optical tweezers, atomic force microscopy, and exploits Euler-Bernoulli elasticity theory for data analysis. This approach also avoids drying for measurements or visualization, since samples are freshly extracted. Importantly, strains are kept below 0.5%, which appear consistent with the linear elastic regime. We find, surprisingly, that the longitudinal elastic modulus of type I collagen cannot be represented by a single quantity but rather is a distribution that is broader than the uncertainty of our experimental technique. The longitudinal component of the single-fiber elastic modulus is between 100 MPa and 360 MPa for samples extracted from different rats and/or different parts of a single tail. Variations are also observed in the fibril-bundle / fibril diameter with an average of 325±40 nm. Since bending forces depend on the diameter to the fourth power, this variation in diameter is important for estimating the range of elastic moduli. The remaining variations in the modulus may be due to differences in composition of the fibril-bundles, or the extent of the proteoglycans constituting fibril-bundles, or that some single fibrils may be of fibril-bundle size.     

Crystal structure of the streptococcal superantigen SpeI and functional role of a novel loop domain in T cell activation by group V superantigens

Superantigens (SAgs) are potent microbial toxins that bind simultaneously to T cell receptors (TCRs) and class II major histocompatibility complex molecules, resulting in the activation and expansion of large T cell subsets and the onset of numerous human diseases. Within the bacterial SAg family, streptococcal pyrogenic exotoxin I (SpeI) has been classified as belonging to the group V SAg subclass, which are characterized by a unique, relatively conserved ∼15 amino acid extension (amino acid residues 154 to 170 in SpeI; herein referred to as the α3-β8 loop), absent in SAg groups I through IV. Here, we report the crystal structure of SpeI at 1.56 Å resolution. Although the α3-β8 loop in SpeI is several residues shorter than that of another group V SAg, staphylococcal enterotoxin serotype I, the C-terminal portions of these loops, which are located adjacent to the putative TCR binding site, are structurally similar. Mutagenesis and subsequent functional analysis of SpeI indicates that TCR β-chains are likely engaged in a similar general orientation as other characterized SAgs. We show, however, that the α3-β8 loop length, and the presence of key glycine residues, are necessary for optimal activation of T cells. Based on Vβ-skewing analysis of human T cells activated with SpeI and structural models, we propose that the α3-β8 loop is positioned to form productive intermolecular contacts with the TCR β-chain, likely in framework region 3, and that these contacts are required for optimal TCR recognition by SpeI, and likely all other group V SAgs.     

Postnatal glucocorticoid exposure alters the adult phenotype

We examined the effect of six doses of dexamethasone (Dex) administered daily (2-7 days of age) to postnatal rats on body weight gain, food and water intake, peripheral hormonal/metabolic milieu, and hypothalamic neuropeptides that regulate food intake. We observed a Dex-induced acute (3 days of age) suppression of endogenous corticosterone and an increase in circulating leptin concentrations that were associated with a decrease in body weight in males and females. Followup during the suckling, postsuckling, and adult stages (7-120 days of age) revealed hypoleptinemia in males and females, and hypoinsulinemia, a relative increase in the glucose-to-insulin ratio, and a larger increase in skeletal muscle glucose transporter (GLUT 4) concentrations predominantly in the males, reflective of a catabolic state associated with a persistent decrease in body weight gain. The increase in the glucose-to-insulin ratio and hyperglycemia was associated with an increase in water intake. In addition, the changes in the hormonal/metabolic milieu were associated with an increase in hypothalamic neuropeptide Y content in males and females during the suckling phase, which persisted only in the 120-day-old female with a transient postnatal decline in alpha-melanocyte-stimulating hormone and corticotropin-releasing factor. This increase in neuropeptide Y (NPY) during the suckling phase in males and females was associated with a subsequent increase in adult food intake that outweighed the demands of body weight gain. In contrast to the adult hypothalamic findings, cerebral ventricular dilatation was more prominent in adult males. We conclude that postnatal Dex treatment causes permanent sex-specific changes in the adult phenotype, setting the stage for future development of diabetes (increased glucose:insulin ratio), obesity (increased NPY and food intake), and neurological impairment (loss of cerebral volume).     

Cutaneous manifestations in non-Hodgkin's lymphoma

OBJECTIVE: To examine and subtype cutaneous lymphoma specimens for diagnosis. STUDY DESIGN: Aspiration smears from skin lesions and lymph nodes diagnosed as non-Hodgkin's lymphoma (NHL) on cytology in 6 cases over a period of 1 year were reviewed. Two were follow-up cases of nodal lymphoma and were receiving chemotherapy, during which they developed skin lesions. In 4, the patients had cutaneous lesions as a presenting manifestation. Cytologic findings were correlated with histologic and hematologic findings and immunocytochemical markers for subtyping. RESULTS: Patients ranged from 14 to 50 years, with equal sex ratio. All presented with 0.5-5 cm multiple nodular, ulcerated and fungating skin lesions at various body sites. The aspirate was satisfactory in all cases. Cytologically, all cases were diagnosed as NHL. They were then immunocytochemistry subtyped as various lymphomas. CONCLUSION: Cutaneous lymphoma should always be considered in the presence of predominantly atypical lymphoid cells in smears from nodular and fungating skin lesions, even in the absence of a definitive clinical diagnosis.     

Dynein: An ancient motor protein involved in multiple modes of transport

Cytoplasmic dynein has long been thought to be responsible for retrograde axonal transport. As the number of cellular roles for this multifunctional protein has expanded, the complexity of its contribution to axonal transport has increased. In this article the increasing evidence for a role for cytoplasmic dynein in anterograde as well as retrograde transport is discussed. The current status of the complex dynein cargo-binding mechanism is evaluated. Finally, recent genetic evidence supporting a role in axonal transport and revealing a role in neurodegenerative conditions is reviewed.     

Threads that Guide or Ties that Bind: William Kirby and the Essentialism Story

Nineteenth-century British entomologist William Kirby is best known for his generic division of bees based on tongues and his vigorous defence of natural theology. Focusing on these aspects of Kirby’s work has lead many current scholars to characterise Kirby as an “essentialist.” As a result of this characterisation, many important aspects of his work, Monographia Apum Angliæ (1802) have been over-looked or misunderstood. Kirby’s religious devotion, for example, have lead some scholars to assume Kirby used the term “type” for connecting an ontological assumption about essences with a creationist assumption about species fixity, which I argue conceals a variety of ways Kirby employed the term. Also, Kirby frequently cautioned against organising a classification system exclusively by what he called “analytic reasoning,” a style of reasoning 20th century scholars often associate with Aristotelian logic of division. I argue that Kirby’s critique of analytic reasoning brought the virtues of his own methodological agenda into sharp relief. Kirby used familiar metaphors in the natural history literature – Ariadne’s thread, the Eleusinian mysteries, and Bacon’s bee and spider metaphors – to emphasise the virtues of building tradition and cooperation in the goals and methodological practices of 19th century British naturalists.     

The role ofRhipicephalus appendiculatus andR. evertsi evertsi males in inducing resistance in laboratory animals: preliminary studies

Guinea-pigs infested with male ticks of the speciesRhipicephalus appendiculatus, and rabbits infested withR. evertsi evertsi, acquired immunity to conspecific female ticks. The hosts were first infested with male ticks and thereafter were challenged with males and females of the same species. The mean weight of the engorged females ofR. appendiculatus fed on guinea pigs previously infested with male ticks was 509.0 (±41.4) mg compared with that of females fed on control guinea pigs (651.2±31.8 mg). Similar weight differences were observed forR.e. evertsi females which fed on rabbits previously infested three times with male ticks. The mean weight of the female ticks which fed on these rabbits was 520.1 (±29.8) mg compared with 640.7 (±30.2) mg ofR.e. evertsi females which fed on control hosts. The concentration of gammaglobulins in the sera of rabbits was monitored at various intervals after the first infestation. It was found, for the first time, that infestation of laboratory animals with male ticks conferred immunity, but to a lesser degree than infestation with both sexes. It was also shown that the level of gammaglobulins increased from 3.4±0.28 g l^–1 to 7.3±0.24 g l^–1 in sera of rabbits hosts as a result of the feeding activity of males, but to a lesser extent than in sera of rabbits on which both sexes had fed (10.8±2.4 g l^–1).     

Gel beads composed of collagen reconstituted in alginate

Spherical gel beads of collagen/alginate were prepared by discharging droplets of a mixture containing collagen (1.07-1.9 mg/ml) and alginate (1.2-1.5% w/v) into 1.5% w/v CaCl2 solution at 4°C. Collagen in the gel beads was reconstituted by raising the temperature to 37°C after alginate was liquefied by citrate. Scanning electron microscopy of the beads revealed the characteristic fibrous structure of collagen. To demonstrate the application of this new technique in cell culture, GH3 rat pituitary tumor cells were entrapped and grown in the gel beads. The immobilized cells proliferated to a density of 1.95 x 106 cell/ml which is about an order of magnitude higher than that grown in the alginate beads.     

Phosphorylation of deinococcal RecA affects its structural and functional dynamics implicated for its roles in radioresistance of Deinococcus radiodurans

Abstract

Deinococcus RecA (DrRecA) protein is a key repair enzyme and contributes to efficient DNA repair of Deinococcus radiodurans. Phosphorylation of DrRecA at Y77 (tyrosine 77) and T318 (threonine 318) residues modifies the structural and conformational switching that impart the efficiency and activity of DrRecA. Dynamics comparisons of DrRecA with its phosphorylated analogues support the idea that phosphorylation of Y77 and T318 sites could change the dynamics and conformation plasticity of DrRecA. Furthermore, docking studies showed that phosphorylation increases the binding preference of DrRecA towards dATP versus ATP and for double-strand DNA versus single-strand DNA. This work supporting the idea that phosphorylation can modulate the crucial functions of this protein and having good concordance with the experimental data. Abbreviations DrRecA Deinococcus RecA

DSB DNA double-strand breaks

hDNA heteroduplex DNA

STYPK serine/threonine/tyrosine protein kinase

T318 threonine 318

Y77 tyrosine 77

Communicated by Ramaswamy H. Sarma