Involvement of RTE1 in conformational changes promoting ETR1 ethylene receptor signaling in Arabidopsis

Ethylene is an important regulator of plant growth, development and responses to environmental stresses. Arabidopsis perceives ethylene through five homologous receptors that negatively regulate ethylene responses. RTE1, a novel gene conserved in plants, animals and some protists, was recently identified as a positive regulator of the ETR1 ethylene receptor. Here, we genetically analyze the dependence of ETR1 on RTE1 in order to obtain further insight into RTE1 function. The function of RTE1 was found to be independent and distinct from that of RAN1, which encodes a copper transporter required for ethylene receptor function. We tested the ability of an rte1 loss-of-function mutation to suppress 11 etr1 ethylene-binding domain mis-sense mutations, all of which result in dominant ethylene insensitivity due to constitutive signaling. This suppression test uncovered two classes of etr1 mutations -RTE1-dependent and RTE1-independent. The nature of these mutations suggests that the ethylene-binding domain is a possible target of RTE1 action. Based on these findings, we propose that RTE1 promotes ETR1 signaling through a conformational effect on the ethylene-binding domain.     

Social,Educational, and Psychological Correlates of Weight Status in Adolescents

Objectives: The purpose of this research was to examine the social, educational, and psychological correlates of weight status in an adolescent population. It was hypothesized that obese adolescents would differ on psychological, social, and educational variables compared with their non‐overweight peers. Research Methods and Procedures: In this cross‐sectional study, a population‐based sample of 4742 male and 5201 female public school students in the 7th, 9th, and 11th grades responded anonymously to a classroom administered questionnaire. Body mass index was calculated from self‐reported height and weight and categorized into four classes of weight status: underweight (<15th percentile), average weight (15th to 85th percentile), overweight (>85th to 95th percentile), and obese (>95th percentile). The questionnaire also included questions about social experiences, psychological well‐being, educational experiences, and future goals. Associations of weight status with social, psychological, and educational variables and future goals were explored. Results: After adjustment for grade level, race, and parental socioeconomic status, obese girls, when compared with their average weight counterparts, were 1.63 (95% confidence interval [CI]: 1.16, 2.30) times less likely to hang out with friends in the last week, 1.49 (95% CI: 1.12, 1.98) times more likely to report serious emotional problems in the last year, 1.79 (95% CI: 1.20, 2.65) times more likely to report hopelessness, and 1.73 (95% CI: 1.21, 1.98) times more likely to report a suicide attempt in the last year. Obese girls were also 1.51 (95% CI: 1.09, 2.10) times more likely to report being held back a grade and 2.09 (95% CI: 1.35, 3.24) times more likely to consider themselves poor students compared with average weight girls. Compared with their average weight counterparts, obese boys were 1.91 (95% CI: 1.43, 2.54) times less likely to hang out with friends in the last week, 1.34 (95% CI: 1.06, 1.70) times more likely to feel that their friends do not care about them, 1.38 (95% CI: 1.08, 1.76) times more likely to report having serious problems in the last year, 1.46 (95% CI: 1.05, 0.03) times more likely to consider themselves poor students, and 2.18 (95% CI: 1.45, 3.30) times more likely to expect to quit school. Compared with average weight boys, underweight boys were 1.67 (95% CI: 1.30, 2.13) times more likely to report hanging out with friends in the last week, 1.22 (95% CI: 1.01, 1.49) times more likely to report disliking school, and 1.40 (95% CI: 1.06, 1.86) times more likely to consider themselves poor students. Discussion: Associations of weight status with social relationships, school experiences, psychological well‐being, and some future aspirations were observed. Among girls, the pattern of observations indicates that obese girls reported more adverse social, educational, and psychological correlates. Obese as well as underweight boys also reported some adverse social and educational correlates. These findings contribute to an understanding of how adolescent experiences vary by weight status and suggest social and psychological risks associated with not meeting weight and body shape ideals embedded in the larger culture.     

Differential suppression of DNA repair deficiencies of Yeast rad50, mre11 and xrs2 mutants by EXO1 and TLC1 (the RNA component of telomerase).

Rad50, Mre11, and Xrs2 form a nuclease complex that functions in both nonhomologous end-joining (NHEJ) and recombinational repair of DNA double-strand breaks (DSBs). A search for highly expressed cDNAs that suppress the DNA repair deficiency of rad50 mutants yielded multiple isolates of two genes: EXO1 and TLC1. Overexpression of EXO1 or TLC1 increased the resistance of rad50, mre11, and xrs2 mutants to ionizing radiation and MMS, but did not increase resistance in strains defective in recombination (rad51, rad52, rad54, rad59) or NHEJ only (yku70, sir4). Increased Exo1 or TLC1 RNA did not alter checkpoint responses or restore NHEJ proficiency, but DNA repair defects of yku70 and rad27 (fen) mutants were differentially suppressed by the two genes. Overexpression of Exo1, but not mutant proteins containing substitutions in the conserved nuclease domain, increased recombination and suppressed HO and EcoRI endonuclease-induced killing of rad50 strains. exo1 rad50 mutants lacking both nuclease activities exhibited a high proportion of enlarged, G2-arrested cells and displayed a synergistic decrease in DSB-induced plasmid:chromosome recombination. These results support a model in which the nuclease activity of the Rad50/Mre11/Xrs2 complex is required for recombinational repair, but not NHEJ. We suggest that the 5'-3' exo activity of Exo1 is able to substitute for Rad50/Mre11/Xrs2 in rescission of specific classes of DSB end structures. Gene-specific suppression by TLC1, which encodes the RNA subunit of the yeast telomerase complex, demonstrates that components of telomerase can also impact on DSB repair pathways.     

Photoreactivation and Gene Dosage in Yeast

The amount of photoreactivating enzyme in tetraploid cells of Saccharomyces cerevisiae and the ability of the cells to be photoreactivated after ultraviolet irradiation are directly proportional to the number of genes per cell involved in the synthesis of photoreactivating enzyme.     

Yeast ARMs (DNA at-risk motifs) can reveal sources of genome instability

The genomes of all organisms contain an abundance of DNA repeats which are at-risk for causing genetic change. We have used the yeast Saccharomyces cerevisiae to investigate various repeat categories in order to understand their potential for causing genomic instability and the role of DNA metabolism factors. Several types of repeats can increase enormously the likelihood of genetic changes such as mutation or recombination when present either in wild type or mutants defective in replication or repair. Specifically, we have investigated inverted repeats, homonucleotide runs, and short distant repeats and the consequences of various DNA metabolism mutants. Because the at-risk motifs (ARMs) that we characterized are sensitive indicators, we have found that they are useful tools to reveal new genetic factors affecting genome stability as well as to distinguish subtle differences between alleles.     

Evidence for diet partitioning among three coexisting native freshwater fishes in South Africa's Cape Fold Ecoregion

The partitioning of limited resources commonly explains how different species can coexist within the same ecological community. In this 2010 study, the diets of three coexisting freshwater fishes (Cape galaxias Galaxias zebratus, n = 27; Cape kurper Sandelia capensis, n = 60; Breede River redfin Pseudobarbus burchelli, n = 77) were characterised and compared in three headwater streams in South Africa's Cape Fold Ecoregion using gut contents and stable isotope analyses. These data were analysed to ascertain whether the three species exploit distinct trophic niches. Both approaches provided evidence that these species occupy different trophic niches, though with some overlap. However, dietary differences among sites were not consistent and were probably influenced by site-specific factors like resource availability. Pseudobarbus burchelli had a broader niche breadth at Tierkloof Stream than the other two species, but not at Waaihoek or Tierstel Streams. Our results also suggest that P. burchelli consumed a more omnivorous diet than do the other two species, whereas S. capensis occupied a higher trophic position than the other two species and consumed vertebrates. Our findings suggest that these species occupy non-equivalent feeding niches in Cape Fold Ecoregion headwater streams, and that diet partitioning might facilitate their coexistence in these systems.     

Effects of synergistic signaling by phytochrome A and cryptochrome1 on circadian clock-regulated catalase expression.

Persistent oscillation in constant conditions is a defining characteristic of circadian rhythms. However, in plants transferred into extended dark conditions, circadian rhythms in mRNA abundance commonly damp in amplitude over two or three cycles to a steady state level of relatively constant, low mRNA abundance. In Arabidopsis, catalase CAT3 mRNA oscillations damp rapidly in extended dark conditions, but unlike catalase CAT2 and the chlorophyll a/b binding protein gene CAB, in which the circadian oscillations damp to low steady state mRNA abundance, CAT3 mRNA oscillations damp to high steady state levels of mRNA abundance. Mutational disruption of either phytochrome- or cryptochrome-mediated light perception prevents damping of the oscillations in CAT3 mRNA abundance and reveals strong circadian oscillations that persist for multiple cycles in extended dark conditions. Damping of CAT3 mRNA oscillations specifically requires phytochrome A but not phytochrome B and also requires the cryptochrome1 blue light receptor. Therefore, we conclude that synergistic signaling mediated through both phytochrome A and cryptochrome1 is required for damping of circadian CAT3 mRNA oscillations in extended dark conditions.     

A Comparison of Body Size Evaluations of Obesity Surgery Patients and General Population Adults

RAND, COLLEEN S. W., JAQUELYN LISS RESNIK, AND ALEX M. C. MACGREGOR. A comparison of body size evaluations of obesity surgery patients and general population adults. Obes Res. Objective: To compare post-operative obesity surgery patients and general population adults in their assessments of a wide range of body sizes. Research Methods and Procedures: Obesity surgery patients (n = 274) and general population adults (n = 326) rated ideal and socially acceptable body sizes in separate arrays of babies, children, young adults, and middle-aged and older adults. Nine line figure drawings ranging from very thin to very obese were rated for each array. Results: Both groups selected the same ideal body size for all arrays except for babies. Both groups rejected obese and very thin body sizes as socially acceptable. However, the obesity surgery patients were more restrictive than general population adults in their ratings of socially acceptable body sizes. Current obesity status did not impact ratings for the patient or general population subjects. In the patient sample, time since surgery did not influence body size evaluations. Discussion: The study of body size ratings limited only to the “ideal” size may be misleading because it may mask subtle but meaningful differences between groups. The consistent difference in more restrictive ratings of obesity surgery patients compared to general population adults may be due to patients' greater psychological investment in endorsing the societal ideal body size. It may also be due to patients' status as peripheral group members of the normal weight community. The inability of some patients to maintain their post-operative weight loss may be particularly problematic for those who have defined “socially acceptable” body size most narrowly.     

The ecological integrity of the lower Olifants River,Limpopo province,South Africa: 2009–2015 – Part B: Tributaries of the Olifants River

Monitoring on the Lowveld reaches of the Olifants River, Limpopo River System, and its Steelpoort, Blyde, Klaserie and Selati tributaries was initiated in 2009. Analysis of the 2009–2015 data from four Olifants River sites showed deterioration in the river’s ecological condition between where it enters the Lowveld and where it enters the Kruger National Park, with a slight recovery within the Kruger National Park. Physico-chemical, aquatic macroinvertebrate and fish data collected in 2009–2015 at six sites on the Steelpoort, Blyde, Klaserie and Selati tributaries of the Olifants River corroborated the ecological condition of these tributaries. The Selati was the most polluted and was in a critically modified condition, whereas the Klaserie and Steelpoort were in fair condition and the Blyde was in good condition. The Selati appeared to have a significant negative impact on the water quality, macroinvertebrates and fish of the Olifants River within the Kruger National Park.