Molecular mimicry regulates ABA signaling by SnRK2 kinases and PP2C phosphatases

Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites.     

The response of cylindrocladium conidia to soil fungistasis

Direct observation of washed conidia of Cylindrocladium scoparium on non-sterile soils, air dried and rewetted immediately before deposition of conidia, indicated that peak germination (33–58%) occurred after 24 h incubation at 26°C. Peak germination on continually moist soils was lower (18–26%) than on rewetted soils. Lysis of germ tubes and germinating conidia on continually moist soils at 26°C was evident with 48 h. Conidia did not germinate on continually moist soils at 6°C and lysis did not become apparent until 168 h. Conidia germinated at a high level (93–99%) in axenic culture in the absence of exogenous C and N sources. The inhibition of conidial germination on soils may be attributed, in part, to the presence of soil volatiles. Germination of conidia placed on washed agar disks and exposed to volatiles from four soils ranged from 51 to 86% of the no-soil controls. Addition of carbon (13 ng C per conidium as glucose) and nitrogen (65 pg N ng^?1 C as NH₄C1) nullified the inhibitory effect of the soil volatiles. Germinability assayed on a selective medium at 26°C of conidia in artificially infested soils (approximately 10⁴ conidia g^?1 soil) decreased progressively during incubation at 26°C from 1 week to 4 months. No germinable conidia were recovered from artificially infested soils after 2 months incubation at 6°C. Conidia of C. floridanum and C. crotalariae responded similarly to C. scoparium in many assays.     

Water potential and the respiration of microorganisms in the soil

The effect of soil water potential on the respiration of microorganisms in soil was studied. Bacterial respiration decreased rapidly below ?3 bar; at -20 bar it was very slight. The most rapid decline occurred above ? 6 bar. The respiration of a mixed population of microorganisms, however, was maintained at a fairly high level between ?8 and ?30 bar but subsequently declined until at ?50 bar it became negligible. At potentials below ?50 bar, additions of glucose caused no increase in respiration. The sensitivity of bacteria to relatively small negative potentials was probably due to their restricted movement as the soil pores drained.     

Effects of Co‐stocking Smallmouth Buffalo,Ictiobus bubalus,with Channel Catfish,Ictalurus punctatus

Proliferative gill disease (PGD) in catfish is caused by the myxozoan Henneguya ictaluri. The complex life cycle requires Dero digitata as the oligochaete host. Efforts to control PGD by eradicating D. digitata have been unsuccessful. Smallmouth buffalo, Ictiobus bubalus, (SMB) are opportunistic bottom feeders and a putative option for controlling D. digitata. In 2011, 15 ponds (0.4 ha) were stocked with 5000 channel catfish, Ictalurus punctatus; 7 of these 15 ponds were also stocked with 300 SMB fingerlings. There were no differences in benthic invertebrate numbers or water quality variables between ponds with or without SMB. At harvest, there were no differences in percent survival, total weight, or catfish feed conversion ratio. In the second year, 18 ponds (0.4 ha) were stocked with 6000 channel catfish. Half the ponds were also stocked with 300 SMB. Sentinel fish were used to estimate disease severity, and pond water was collected for molecular estimation of H. ictaluri actinospore concentrations. Similar to the first year, there were no differences between treatments in any variable tested, including PGD severity in sentinel fish and parasite concentrations in pond water. Under these study conditions, presence of SMB did not have a measureable effect on PGD incidence, parasite density, or overall catfish production.     

Effect of staphylococcal enterotoxin B on cardiorenal functions in rhesus macaques.

Selected cardiovascular and renal functions were measured for 5 hours in conscious, chair-restrained, female rhesus macaques (Macaca mulatta) after IV (0.05 and 1.0 mg/kg) or oral (1.0 mg/kg) administration of staphylococcal enterotoxin B (SEB). Cardiovascular functions, renal hemodynamics, and renal metabolism were also studied between 6 and 11 hours after IV SEB inoculation. Oral SEB produced few changes in cardiorenal functions. In contrast, IV SEB produced hypotension, tachycardia, increased total peripheral and renal vascular resistance, and decreased cardiac and renal functions. The early significant (P less than 0.05) renal depression was not associated with hypotension (mean arterial blood pressure greater than 100 mm of Hg). However, all measured renal functions except extraction ratio of PAH were positively correlated with decreased blood pressure (r = 0.52 - 0.71) in the later phase of SEB toxemia. It is concluded that the kidney is one of the organs affected by IV SEB. Renal impairment may partially contribute to death during SEB enterotoxemia in macaques.     

Kin discrimination and the benefit of helping in cooperatively breeding vertebrates

In many cooperatively breeding vertebrates, a dominant breeding pair is assisted in offspring care by nonbreeding helpers. A leading explanation for this altruistic behavior is Hamilton's idea that helpers gain indirect fitness benefits by rearing relatives (kin selection). Many studies have shown that helpers typically provide care for relatives, but relatively few have shown that helpers provide closer kin with preferential care (kin discrimination), fueling the suggestion that kin selection only poorly accounts for the evolution of cooperative breeding in vertebrates. We used meta-analysis to show that (i) individuals consistently discriminate between kin, and (ii) stronger discrimination occurs in species where the benefits of helping are greater. These results suggest a general role for kin selection and that the relative importance of kin selection varies across species, as predicted by Hamilton's rule.     

Isolation and differentiation of bovine mammary gland progenitor cell populations

OBJECTIVE: To isolate bovine mammary gland cells with stem cell characteristics. SAMPLE POPULATION: Monolayers of bovine mammary gland cells. PROCEDURE: Mammary gland cell populations were separated by use of selected media supplements. Phenotypic characteristics were examined via light and transmission electron microscopy. Cellular expression of casein and connexin 43 was identified immunohistochemically. A scrape-loading and dye transfer assay was used to examine the mammary gland cell populations for homogenous gap junctional intercellular communication (GJIC). RESULTS: Subpopulations of mammary gland cells grown in vitro are classified on the basis of their distinct morphologic features and ability to communicate via gap junctions. Ultrastructurally, 2 morphologically distinct cell types were classified as type I and II cells. Type I cells were small light undiffertiated cells and large light undifferentiated cells that were deficient in functional gap junctions (as is characteristic of stem cells). Type II cells included large light differentiated cells and terminally differentiated cells; GJIC was functional in type II cells. Type II cells had cytoplasmic expression of connexin 43, whereas, type I cells did not. All cells expressed casein. CONCLUSIONS AND CLINICAL RELEVANCE: Subpopulations of bovine mammary gland cells with stem cell characteristics were identified. Phenotypic differences are observed among type I bovine mammary gland cells with stem cell characteristics. Gap junctional intercellular communication may be necessary for the differentiation of stem cells. Characterization of bovine mammary gland stem cells and their progeny may provide a new tool with which to study mammary gland health.     

Transmission of Mycobacterium bovis from experimentally infected ferrets to non-infected ferrets (Mustela furo)

AIMS: To demonstrate the transmission of Mycobacterium bovis infection from experimentally infected ferrets (Mustela furo) to non-infected ferrets in a laboratory setting, using three different isotypes of M. bovis, and to observe ferret behaviour that might be implicated in disease transmission. METHODS: Three female ferrets, each experimentally infected with a unique strain of M. bovis, were housed together with six female and two male non-infected ferrets in an isolation facility. Transmission of infection was monitored clinically, serologically (using an ELISA test), bacteriologically, histologically, and by isotype analysis of M. bovis isolates using spoligotyping to determine whether or not transmission of each strain occurred. Ferret behaviour was observed using a time-lapse video recorder. RESULTS: Transmission of M. bovis infection was confirmed in two male and four female ferrets. Isotype analysis showed that of the experimentally infected females, one did not infect any other ferret, another transmitted M. bovis to one ferret before it died prematurely 49 days post-infection, and the third, which was cannibalised, appears to have transmitted M. bovis to both males and three females. However, two of these latter three females had died before the event of cannibalism took place. One female was infected with two strains. Several behavioural interactions were observed that could have resulted in M. bovis transmission, including den sharing, sniffing of orifices and faeces, cannibalism and aggressive breeding behaviour. CONCLUSIONS: Horizontal transmission of M. bovis infection was demonstrated in ferrets under experimental housing conditions. Routes of transmission may involve cannibalism and factors such as den sharing, playing, fighting, mating, and sniffing of faeces.