Cell type-specific gene expression in the Drosophila melanogaster male accessory gland.

The accessory gland of the male Drosophila melanogaster plays a vital role in reproduction. This secretory organ synthesizes products that are transferred to the female and are necessary to elicit the proper physiological and behavioral responses in the female. The accessory gland is composed of two morphologically distinct secretory cell types, the main cells and the secondary cells. Previous studies identified some genes expressed in main cells or in all accessory gland cells. In this paper we use P-element mediated enhancer traps to examine gene expression in the accessory gland. We show that, in addition to genes expressed in main cells only or in all accessory gland secretory cells, there are genes expressed specifically in secondary cells. Each cell type is uniform in the expression of its genes. Our results demonstrate that the two cell types are not only morphologically distinct but also biochemically distinct. We also show that the two cell types differ in their regulation of gene expression in response to mating activity.     

The Crystal Structure and Small-Angle X-Ray Analysis of CsdL/TcdA Reveal a New tRNA Binding Motif in the MoeB/E1 Superfamily

Cyclic N⁶-threonylcarbamoyladenosine (‘cyclic t⁶A’, ct⁶A) is a non-thiolated hypermodification found in transfer RNAs (tRNAs) in bacteria, protists, fungi and plants. In bacteria and yeast cells ct⁶A has been shown to enhance translation fidelity and efficiency of ANN codons by improving the faithful discrimination of aminoacylated tRNAs by the ribosome. To further the understanding of ct⁶A biology we have determined the high-resolution crystal structures of CsdL/TcdA in complex with AMP and ATP, an E1-like activating enzyme from Escherichia coli, which catalyzes the ATP-dependent dehydration of t⁶A to form ct⁶A. CsdL/TcdA is a dimer whose structural integrity and dimer interface depend critically on strongly bound K⁺ and Na⁺ cations. By using biochemical assays and small-angle X-ray scattering we show that CsdL/TcdA can associate with tRNA with a 1:1 stoichiometry and with the proper position and orientation for the cyclization of t⁶A. Furthermore, we show by nuclear magnetic resonance that CsdL/TcdA engages in transient interactions with CsdA and CsdE, which, in the latter case, involve catalytically important residues. These short-lived interactions may underpin the precise channeling of sulfur atoms from cysteine to CsdL/TcdA as previously characterized. In summary, the combination of structural, biophysical and biochemical methods applied to CsdL/TcdA has afforded a more thorough understanding of how the structure of this E1-like enzyme has been fine tuned to accomplish ct⁶A synthesis on tRNAs while providing support for the notion that CsdA and CsdE are able to functionally interact with CsdL/TcdA.     

Growth forms and life-history strategies predict the occurrence of aquatic macrophytes in relation to environmental factors in a shallow peat lake complex

Hydrobiologia - Aquatic ecosystems provide vital services, and macrophytes play a critical role in their functioning. Conceptual models indicate that in shallow lakes, plants with different growth...     

Impact of participant and interventionist race concordance on weight loss outcomes

Objective:

We have previously shown that racial composition of behavioral intervention groups does not affect achieved weight loss. However, it is unclear if the race of the interventionist affects intervention outcomes. The objective of this analysis is to estimate the impact of race concordance between participant and interventionist on weight change in the initial weight loss phase (phase I) of the Weight Loss Maintenance trial (WLM).

Design and Methods:

A total of 1,685 overweight or obese adults (BMI 25‐45 kg/m²) who were taking medication for hypertension and/or dyslipidemia participated in phase I of the WLM trial. All participants received a 6‐month intensive behavioral intervention in groups of 15‐20 facilitated by a trained interventionist. The main outcome is change in weight at 6 months.

Results:

Participants were on average 55 years of age, 67% female and 44% African American (AA). Three of seventeen interventionists were AA, 14 were non‐AA. Seventy‐three percent of participants shared race concordance with the interventionist. There was a small but statistically significant difference in weight change of participants who were the same race as the interventionist (?5.84 kg, s.e. 0.17) as compared with those who were not race concordant (?5.04 kg, s.e. 0.33), a difference of 0.8 kg, (P = 0.04). The impact of concordance on weight change differed by race (i.e., interaction of race and concordance was significant, P = 0.02).

Conclusions:

In a post hoc analysis of a group‐based behavioral intervention, race concordance for non‐AA participants was associated with slightly greater weight loss. Race concordance was not associated with weight loss for AA participants.

     

Estimating and Analyzing Savannah Phenology with a Lagged Time Series Model

Savannah regions are predicted to undergo changes in precipitation patterns according to current climate change projections. This change will affect leaf phenology, which controls net primary productivity. It is of importance to study this since savannahs play an important role in the global carbon cycle due to their areal coverage and can have an effect on the food security in regions that depend on subsistence farming. In this study we investigate how soil moisture, mean annual precipitation, and day length control savannah phenology by developing a lagged time series model. The model uses climate data for 15 flux tower sites across four continents, and normalized difference vegetation index from satellite to optimize a statistical phenological model. We show that all three variables can be used to estimate savannah phenology on a global scale. However, it was not possible to create a simplified savannah model that works equally well for all sites on the global scale without inclusion of more site specific parameters. The simplified model showed no bias towards tree cover or between continents and resulted in a cross-validated r² of 0.6 and root mean squared error of 0.1. We therefore expect similar average results when applying the model to other savannah areas and further expect that it could be used to estimate the productivity of savannah regions.     

Disentangling the effects of drought,salinity, and sulfate on baldcypress growth in a coastal plain restored wetland

Because of their dominance in swamps of the southeastern United States, baldcypress (Taxodium distichum) trees are commonly used in wetland restoration. Though baldcypress are known to tolerate moderate flooding and salinity, their growth has been shown to decrease when they experience drought and high salinity. This study examined the effects of drought and elevated salinity on the growth of baldcypress seedlings and saplings. In a restored wetland in North Carolina, we examined the growth of 8‐year‐old baldcypress by measuring height and diameter at breast height (DBH) along salinity, nutrient, and flooding gradients. In a greenhouse, we placed 1‐year‐old baldcypress seedlings in either drought or saturated conditions and applied different water treatments: fresh water, sulfate, and artificial salt water (5 ppt [parts per thousand]). Over 26 weeks, we measured diameter at root collar, height, and biomass. In the field, chloride concentrations in soil solution had a negative effect on DBH and height (51 and 36% decrease, respectively); high water levels had a negative effect on height (47% decrease) and DBH (46% decrease). In the greenhouse, both drought and salinity decreased diameter growth (43 and 61% decline, respectively) and height (64 and 43% decline, respectively). Sulfate did not have a significant effect on diameter growth, but caused a 14% decrease in height. Our results suggest that both drought and salinity (even as low as 1 ppt) can lead to a 20–60% decline in baldcypress growth. Restoration practitioners should consider the negative consequences of both drought and increased salinity on baldcypress growth when planning for wetland restoration.     

Effects of a reimbursement incentive on enrollment in a weight control program

Objective: The objective was to examine the effect of offering a reimbursement incentive on the percentage of inquirers who enrolled in a weight control program and on weight loss and program attendance among enrollees. Research Methods and Procedures: We used a sequential control‐intervention design to observe how inquirers of the University of Alabama at Birmingham EatRight Lifestyle Program responded to an enrollment incentive for potential 50% ($150) reimbursement of the total program fee if they attended 10 of 12 classes and lost at least 6% of their current body weight. Inquirers had to be adults with a BMI ≥30 kg/m², seeking information about a weight control program, and informed of the program cost. Outcomes included proportion of inquirers enrolled, overall number of classes attended, and weight loss. Results: Of the 401 people who inquired during the study periods, 24.5% and 25.0% enrolled in the intervention and control periods, respectively. There was a trend toward higher attendance in the intervention group, compared with the control group; there were no differences in percentage of weight loss. The odds of attending ≥10 classes were 2.4 times as high, and both losing >6% body weight and attending ≥10 classes were three times as high in the intervention subjects compared with controls, although non‐significant. Discussion: The potential of earning a performance‐based reimbursement incentive did not affect enrollment in the EatRight Lifestyle Program. Performance‐based incentives may be an ideal mechanism for extending coverage of weight‐loss interventions by insurers because of limited financial risk and improved adherence.     

Structures of the Substrate-free and Product-bound Forms of HmuO,a Heme Oxygenase from Corynebacterium diphtheriae: X-RAY CRYSTALLOGRAPHY AND MOLECULAR DYNAMICS INVESTIGATION*?

Heme oxygenase catalyzes the degradation of heme to biliverdin, iron, and carbon monoxide. Here, we present crystal structures of the substrate-free, Fe³⁺-biliverdin-bound, and biliverdin-bound forms of HmuO, a heme oxygenase from Corynebacterium diphtheriae, refined to 1.80, 1.90, and 1.85 Å resolution, respectively. In the substrate-free structure, the proximal and distal helices, which tightly bracket the substrate heme in the substrate-bound heme complex, move apart, and the proximal helix is partially unwound. These features are supported by the molecular dynamic simulations. The structure implies that the heme binding fixes the enzyme active site structure, including the water hydrogen bond network critical for heme degradation. The biliverdin groups assume the helical conformation and are located in the heme pocket in the crystal structures of the Fe³⁺-biliverdin-bound and the biliverdin-bound HmuO, prepared by in situ heme oxygenase reaction from the heme complex crystals. The proximal His serves as the Fe³⁺-biliverdin axial ligand in the former complex and forms a hydrogen bond through a bridging water molecule with the biliverdin pyrrole nitrogen atoms in the latter complex. In both structures, salt bridges between one of the biliverdin propionate groups and the Arg and Lys residues further stabilize biliverdin at the HmuO heme pocket. Additionally, the crystal structure of a mixture of two intermediates between the Fe³⁺-biliverdin and biliverdin complexes has been determined at 1.70 Å resolution, implying a possible route for iron exit.     

Flavour formation by amino acid catabolism

Microbial catabolism of amino acids produces flavour compounds of importance for foods such as cheese, wine and fermented sausages. Lactic acid bacteria are equipped with enzyme systems for using the amino acids in their metabolism and are useful for flavour formation of foods. Branched-chain amino acids (Leu, Ile, Val) are converted into compounds contributing to malty, fruity and sweaty flavours; catabolism of aromatic amino acids (Phe, Tyr, Trp) produce floral, chemical and faecal flavours; aspartic acid (Asp) is catabolised into buttery flavours and sulphuric amino acids (Met, Cys) are transferred into compounds contributing to boiled cabbage, meaty and garlic flavours.