Soil water content, maize yield and its stability as affected by tillage and crop residue management in rainfed semi-arid highlands

Rainfed crop management systems need to be optimized to provide more resilient options to cope with projected climatic scenarios forecasting a decrease in mean precipitation and more frequent extreme drought periods in Mexico. Soil water content (0?C60 cm) was measured during three crop cycles in maize plots with different agronomic management practices in a long-term rainfed experiment (established in 1991) in the highlands of Mexico. Maize yields of 1997?C2009 were reported. Crop management practices varied in (1) tillage (conventional [CT] vs. zero tillage [ZT]) and (2) residue management (full or partial retention and removal). ZT with residue retention had higher soil water content than management practices involving CT and ZT with residue removal which provided a buffer for drought periods during the growing seasons. In 2009, a cycle with a prolonged drought during vegetative growth, this resulted in yield differences of up to 4.7 Mg ha^?1 between ZT with (partial) residue retention and the other practices. Averaged over 1997?C2009, these practices had a yield advantage of approximately 1.5 Mg ha^?1 over practices involving CT and ZT with residue removal. ZT with (partial) residue retention used rainfall more efficiently and resulted in a more resilient agronomic system than practices involving either CT or ZT with residue removal.     

Costs and benefits of induced resistance in a clonal plant network

Plant defense theory suggests that inducible resistance has evolved to reduce the costs of constitutive defense expression. To assess the functional and potentially adaptive value of induced resistance it is necessary to quantify the costs and benefits associated with this plastic response. The ecological and evolutionary viability of induced defenses ultimately depends on the long-term balance between advantageous and disadvantageous consequences of defense induction. Stoloniferous plants can use their inter-ramet connections to share resources and signals and to systemically activate defense expression after local herbivory. This network-specific early-warning system may confer clonal plants with potentially high benefits. However, systemic defense induction can also be costly if local herbivory is not followed by a subsequent attack on connected ramets. We found significant costs and benefits of systemic induced resistance by comparing growth and performance of induced and control plants of the stoloniferous herb Trifolium repens in the presence and absence of herbivores.     

Structural insight into the altered substrate specificity of human cytochrome P450 2A6 mutants

Human P450 2A6 displays a small active site that is well adapted for the oxidation of small planar substrates. Mutagenesis of CYP2A6 resulted in an increased catalytic efficiency for indole biotransformation to pigments and conferred a capacity to oxidize substituted indoles (Wu, Z.-L., Podust, L.M., Guengerich, F.P. J. Biol. Chem. 49 (2005) 41090-41100.). Here, we describe the structural basis that underlies the altered metabolic profile of three mutant enzymes, P450 2A6 N297Q, L240C/N297Q and N297Q/I300V. The Asn297 substitution abolishes a potential hydrogen bonding interaction with substrates in the active site, and replaces a structural water molecule between the helix B'-C region and helix I while maintaining structural hydrogen bonding interactions. The structures of the P450 2A6 N297Q/L240C and N297Q/I300V mutants provide clues as to how the protein can adapt to fit the larger substituted indoles in the active site, and enable a comparison with other P450 family 2 enzymes for which the residue at the equivalent position was seen to function in isozyme specificity, structural integrity and protein flexibility.     

Delayed behavioral effects of postnatal exposure to corticosterone in the zebra finch (Taeniopygia guttata)

Early developmental conditions can significantly influence the growth and survival of many animal species. We studied the consequences of exposure to corticosterone (CORT), a stress hormone, during the nestling stage on two behavioral traits (neophobia, social dominance) measured when the birds had reached independence. Nestling zebra finches (Taeniopygia guttata) were exposed twice daily to exogenous CORT via oral administration for a 12-day period up until fledging. Experimental CORT administration depressed nestling growth rates, confirming results previously obtained in this species. Our data on neophobic behavior revealed a significant interaction between sex and treatment, with CORT-dosed males showing reduced latencies to approach a novel object, while there was little effect of corticosterone treatment on female neophobia. There was no significant effect of age (30 or 50 days), however, there was a non-significant trend towards an interaction between treatment and age, with neophobia increasing with age in the CORT-dosed birds, but decreasing in controls. At 50 days of age previous exposure to corticosterone resulted in reduced success in competitions for a non-food-based resource (a perch) in both sexes. There were no effects of brood size on any behavioral traits measured here, but this may be due to the small range in brood size used. Our results show that elevated levels of stress hormones during postnatal development can have significant effects on important behavioral traits, i.e., neophobia and dominance. Moreover, they confirm the importance of rearing conditions in shaping adult phenotypes.     

Adaptations for the oxidation of polycyclic aromatic hydrocarbons exhibited by the structure of human P450 1A2

Microsomal cytochrome P450 family 1 enzymes play prominent roles in xenobiotic detoxication and procarcinogen activation. P450 1A2 is the principal cytochrome P450 family 1 enzyme expressed in human liver and participates extensively in drug oxidations. This enzyme is also of great importance in the bioactivation of mutagens, including the N-hydroxylation of arylamines. P450-catalyzed reactions involve a wide range of substrates, and this versatility is reflected in a structural diversity evident in the active sites of available P450 structures. Here, we present the structure of human P450 1A2 in complex with the inhibitor alpha-naphthoflavone, determined to a resolution of 1.95 A. alpha-Naphthoflavone is bound in the active site above the distal surface of the heme prosthetic group. The structure reveals a compact, closed active site cavity that is highly adapted for the positioning and oxidation of relatively large, planar substrates. This unique topology is clearly distinct from known active site architectures of P450 family 2 and 3 enzymes and demonstrates how P450 family 1 enzymes have evolved to catalyze efficiently polycyclic aromatic hydrocarbon oxidation. This report provides the first structure of a microsomal P450 from family 1 and offers a template to study further structure-function relationships of alternative substrates and other cytochrome P450 family 1 members.     

Nuclear accumulation of plasmid DNA can be enhanced by non-selective gating of the nuclear pore

One of the major obstacles in non-viral gene transfer is the nuclear membrane. Attempts to improve the transport of DNA to the nucleus through the use of nuclear localization signals or importin-β have achieved limited success. It has been proposed that the nuclear pore complexes (NPCs) through which nucleocytoplasmic transport occurs are filled with a hydrophobic phase through which hydrophobic importins can dissolve. Therefore, considering the hydrophobic nature of the NPC channel, we evaluated whether a non-selective gating of nuclear pores by trans-cyclohexane-1,2-diol (TCHD), an amphipathic alcohol that reversibly collapses the permeability barrier of the NPCs, could be obtained and used as an alternative method to facilitate nuclear entry of plasmid DNA. Our data demonstrate for the first time that TCHD makes the nucleus permeable for both high molecular weight dextrans and plasmid DNA (pDNA) at non-toxic concentrations. Furthermore, in line with these observations, TCHD enhanced the transfection efficacy of both naked DNA and lipoplexes. In conclusion, based on the proposed structure of NPCs we succeeded to temporarily open the NPCs for macromolecules as large as pDNAs and demonstrated that this can significantly enhance non-viral gene delivery.     

Personality and basal metabolic rate in a wild bird population

Personality and metabolic rate are predicted to show covariance on methodological and functional grounds, but empirical studies at the individual level are rare, especially in natural populations. Here we assess the relationship between exploration behaviour, an important axis of personality, and basal metabolic rate (BMR) for 680 free‐living great tits Parus major, studied over three years. We find that exploration behaviour is weakly negatively related to BMR among female, but not male, birds. Moreover, we find exploration behaviour to be independent of methodological aspects of BMR measurements (e.g. activity levels, time to acclimatize) which have been suggested to be indicative of personality‐related activity or stress levels during measurement. This suggests that the weak link between exploration behaviour and BMR found here is functional rather than methodological. We therefore test the hypothesis that selection favours covariance between exploration behaviour and metabolic rate, but find no evidence for correlational survival or fecundity selection. Our data therefore provide at best only very weak evidence for a functional link between personality and metabolic rate, and we suggest that studies of personality and metabolic strategies, or personality and daily energy expenditure, are required to further resolve the link between personality and metabolic rate.     

Childhood Internalizing and Externalizing Problems Predict the Onset of Clinical Panic Attacks over Adolescence: The TRAILS Study

Background

Panic attacks are a source of individual suffering and are an independent risk factor for later psychopathology. However, much less is known about risk factors for the development of panic attacks, particularly during adolescence when the incidence of panic attacks increases dramatically. We examined whether internalizing and externalizing problems in childhood predict the onset of panic attacks in adolescence.

Method

This study is part of the TRacking Adolescents’ Individual Lives Survey (TRAILS), a Dutch longitudinal population cohort study (N = 1,584). Internalizing and Externalizing Problems were collected using the Youth Self-Report (YSR) and the parent-report Child Behavior Checklist (CBCL) at baseline (age 10–12). At age 18–20, DSM-IV defined panic attacks since baseline were assessed with the Composite International Diagnostic Interview (CIDI). We investigated whether early adolescent Internalizing and Externalizing Problems predicted panic attacks between ages 10–20 years, using survival analysis in univariate and multivariate models.

Results

There were N = 314 (19.8%) cases who experienced at least one DSM-IV defined panic attack during adolescence and N = 18 (1.2%) who developed panic disorder during adolescence. In univariate analyses, CBCL Total Problems, Internalizing Problems and three of the eight syndrome scales predicted panic attack onset, while on the YSR all broad-band problem scales and each narrow-band syndrome scale predicted panic attack onset. In multivariate analyses, CBCL Social Problems (HR 1.19, p<.05), and YSR Thought Problems (HR 1.15, p<.05) and Social Problems (HR 1.26, p<.01) predicted panic attack onset.

Conclusion

Risk indicators of panic attack include the wide range of internalizing and externalizing problems. Yet, when adjusted for co-occurring problem behaviors, Social Problems were the most consistent risk factor for panic attack onsets in adolescence.     

Bill redness is positively associated with reproduction and survival in male and female zebra finches

Sexual traits can serve as honest indicators of phenotypic quality when they are costly. Brightly coloured yellow to red traits, which are pigmented by carotenoids, are relatively common in birds, and feature in sexual selection. Carotenoids have been linked to immune and antioxidant function, and the trade-off between ornamentation and these physiological functions provides a potential mechanism rendering carotenoid based signals costly. Mutual ornamentation is also common in birds and can be maintained by mutual mate choice for this ornament or by a correlated response in one sex to selection on the other sex. When selection pressures differ between the sexes this can cause intralocus sexual conflict. Sexually antagonistic selection pressures have been demonstrated for few sexual traits, and for carotenoid-dependent traits there is a single example: bill redness was found to be positively associated with survival and reproductive output in male zebra finches, but negatively so in females. We retested these associations in our captive zebra finch population without two possible limitations of this earlier study. Contrary to the earlier findings, we found no evidence for sexually antagonistic selection. In both sexes, individuals with redder bills showed higher survival. This association disappeared among the females with the reddest bills. Furthermore, females with redder bills achieved higher reproductive output. We conclude that bill redness of male and female zebra finches honestly signals phenotypic quality, and discuss the possible causes of the differences between our results and earlier findings.