Identification of a host 14-3-3 Protein that Interacts with Xanthomonas effector AvrRxv

AvrRxv is a member of a family of pathogen effectors present in pathogens of both plant and mammalian species. Xanthomonas campestris pv. vesicatoria strains carrying AvrRxv induce a hypersensitive response (HR) in the tomato cultivar Hawaii 7998. Using a yeast two-hybrid screen, we identified a 14-3-3 protein from tomato that interacts with AvrRxv called AvrRxv Interactor 1 (ARI1). The interaction was confirmed in vitro with affinity chromatography. Using mutagenesis, we identified a 14-3-3-binding domain in AvrRxv and demonstrated that a mutant in that domain showed concomitant loss of interaction with ARI1 and HR-inducing activity in tomato. These results demonstrate that the AvrRxv bacterial effector recruits 14-3-3 proteins for its function within host cells. AvrRxv homologues YopP and YopJ from Yersinia do not have AvrRxv-specific HR-inducing activity when delivered into tomato host cells by Agrobacterium. Although YopP itself cannot induce HR, its C-terminal domain containing the catalytic residues can replace that of AvrRxv in an AvrRxv-YopP chimera for HR-inducing activity. Phylogenetic analysis indicates that the sequences encoding the C-termini of family members are evolving independently from those encoding the N-termini. Our results support a model in which there are three functional domains in proteins of the family, translocation, interaction, and catalytic.     

Dietary lycopene supplementation on Nile Tilapia (Oreochromis niloticus) juveniles submitted to confinement: effects on cortisol level and antioxidant response

This study evaluates the inclusion of lycopene in the commercial diet for Nile Tilapia exposured to a stressor. For 60 days, fish diet was supplemented with lycopene (600 mg kg^?1 diet) and at the end, subjected to confinement for 90 min. Zootechnical parameters (weight gain, specific growth rate and intake), hormonal (cortisol level), biochemical {enzyme activity and lipid peroxidation level [thiobarbituric acid (TBARS)]} and physical (instrumental colour) parameters were also evaluated. Supplementation with lycopene did not alter zootechnical parameters. In unconfined fish, catalase (CAT) activity was reduced in the white muscle of fish fed with lycopene; however, in red muscle, it was not altered. In fish under confinement, plasma cortisol increased as well as CAT, glutathione reductase (GR) and lactate dehydrogenase (LDH) activity in both muscles. Lipid peroxidation of the fillet also displayed higher values. However, the lycopene supplementation abolished the effects of confinement available through cortisol levels, remaining unchanged in the above parameters, activity of CAT, GR and LDH in both muscles and TBARS content of the fillet; in addition, it did not induce alteration of fillet coloration. Inclusion of lycopene in commercial feed reduces the impact of confinement and does not alter the zootechnical parameters; additionally, no modification of the fillet colour from juvenile Nile tilapia was observed.     

A fast generation cycling system for oat and triticale breeding

A fast generation cycling system (FGCS) was developed in oat and triticale, allowing the production of pure line populations of the crops within 1‐year timeframe. Twelve oat and 12 triticale cultivars were tested using the FGCS, and most of them completed a generation cycle within 48–61 days under the system achieving up to seven generations a year. This system involves growing plants under stressed conditions to promote reproduction and in vitro culture of immature embryos bypassing full seed maturation. The developed system could be widely adopted in breeding and genetic studies of crops for producing desired segregating pure line populations, which could significantly shorten the breeding cycles.     

Copper Release, Speciation, and Toxicity Following Multiple Floodings of Copper Enriched Agriculture Soils: Implications in Everglades Restoration

This study characterizes the effects of water–soil flooding volume ratio and flooding time on copper (Cu) desorption and toxicity following multiple floodings of field-collected soils from agricultural sites acquired under the Comprehensive Everglades Restoration Plan (CERP) in south Florida. Soils from four field sites were flooded with three water–soil ratios (2, 4, and 6 [water] to 1 [soil]) and held for 14 days to characterize the effects of volume ratio and flooding duration on Cu desorption (volume ratio and flooding duration study). Desorption of Cu was also characterized by flooding soils four times from seven field sites with a volume ratio of 2 (water) to 1 (soil) (multiple flooding study). Acute toxicity tests were also conducted using overlying waters from the first flooding event to characterize the effects of Cu on the survival of fathead minnows (Pimephales promelas), cladocerans (Daphnia magna), amphipods (Hyalella azteca), midges (Chironomus tentans), duckweed (Lemna minor), and Florida apple snails (Pomacea paludosa). Acute tests were also conducted with D. magna exposed to overlying water from the second and third flooding events. Results indicate that dissolved Cu concentrations in overlying water increased with flooding duration and decreased with volume ratio. In the multiple flooding study, initial Cu concentrations in soils ranged from 5 to 223 mg/kg (dw) and were similar to Cu concentration after four flooding events, indicating retention of Cu in soils. Copper desorption was dependent on soil Cu content and soil characteristics. Total Cu concentration in overlying water (Cu_w) was a function of dissolved organic carbon (DOC), alkalinity, and soil Cu concentration (Cu_s): log(Cu_w)?=?1.2909?+?0.0279 (DOC)?+?0.0026 (Cu_s)???0.0038 (alkalinity). The model was validated and highly predictive. Most of the desorbed Cu in the water column complexed with organic matter in the soils and accounted for 99% of the total dissolved Cu. Although total dissolved Cu concentrations in overlying water did not significantly decrease with number of flooding events, concentrations of free Cu²⁺ increased with the number of flooding events, due to a decrease in DOC concentrations. The fraction of bioavailable Cu species (Cu²⁺, CuOH⁺, CuCO₃) was also less than 1% of the total Cu. Overlying water from the first flooding event was only acutely toxic to the Florida apple snail from one site. However, overlying water from the third flooding of six out of seven soils was acutely toxic to D. magna. The decrease in DOC concentrations and increase in bioavailable Cu²⁺ species may explain the changes in acute toxicity to D. magna. Results of this study reveal potential for high Cu bioavailability (Cu²⁺) and toxicity to aquatic biota overtime in inundated agricultural lands acquired under the CERP.     

Application of Statistical Inference for Analysis of Heavy Metal Variability in Roadside Soil

Previous studies have found there are a variety of factors that influence heavy metal concentrations and Pb isotope ratios in roadside soil. One issue in assessing these factors is the need to distinguish between the natural sample variability at a single site and the variability between different sites. Data constraint often results in the lack of an adequate number of samples and hence is often a constraint on statistical reliability. Presented herein is a regionalisation approach that can be used to overcome the data constraint. This approach was used to analyse data collected at Miranda Park, Sydney, for assessment of the influence of rainfall, distance, depth and soil types. Application of the regionalisation approach enabled discrimination between natural sample variability and that from changes in the factors being considered. The regionalisation approach mitigates the data constraint and may assist researchers in their analysis of constrained data sets enabling more efficient monitoring of potential environmental issues. Additionally, it was found that the primary factors for heavy metal concentrations were rainfall, distance and soil types while depth was a secondary factor. A similar result was determined for the anthropogenic Pb component but not for the natural Pb component.     

Acute and chronic effects of honey and its carbohydrate constituents on calcium absorption in rats

The effects of honey and its carbohydrate constituents (glucose, fructose, and raffinose) on calcium absorption in rats were investigated in acute and chronic feeding studies. In the acute study, rats ( n = 120) were gavaged with an oral solution consisting of (a) 10 microCi (45)Ca, (b) 25 mg of calcium as calcium acetate, and (c) one of the following: 0 mg of honey (control), or 200, 500, or 800 mg of honey, a glucose-fructose mixture, 10.75 mg of raffinose, or 200 mg of raffinose. Another group received (45)Ca intraperitoneally. Femurs were collected 2 days later and analyzed for (45)Ca content. Rats given 500 and 800 mg of honey showed 25.5 and 33.6% increases in calcium absorption ( P<0.05), respectively, over the control group. Groups given the glucose-fructose mixture or 200 mg of raffinose had a significantly higher increase in calcium absorption than the control group (17.1 and 25.6%, respectively). In the chronic study, rats (n=96) were fed for 8 weeks with either 0% honey (control), 5% honey, 10% honey, or a glucose-fructose-raffinose (GFR) mixture. Femurs of GFR-fed rats had significantly lower calcium content, (45)Ca absorption, width, and BMD (at distal region) than control rats. Groups fed honey did not show the negative effects of GFR on bone, but had no advantage over the control group. No significant differences were observed in femur length, density, strength, or BMC among any treatment group compared to the control group. These results indicate that although a positive dose-response effect of honey and its carbohydrate constituents on calcium absorption was observed in the acute study, this effect disappeared upon long-term feeding in rats, implying adaptation had occurred.     

Evaluation of a Rapid Reagent Strip Test for Blood Glucose Determination in Diarrheic Calves

Sixty-three blood samples from 10 diarrheic calves were tested for glucose concentration by two methods. Plasma glucose concentration was measured by the conventional glucose-6-phosphate dehydrogenase method in the clinical laboratory, and the results compared to those obtained using a rapid reagent strip test for blood glucose concentration measurement. The rapid reagent strip test result could not be used to make an accurate prediction of the actual plasma glucose concentration as determined by the conventional method, due to the wide variability in actual plasma glucose concentrations corresponding to each rapid test result.