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To gain a deeper understanding of the mechanisms behind biomass accumulation, it is important to study plant growth behavior. Manually phenotyping large sets of plants requires important human resources and expertise and is typically not feasible for detection of weak growth phenotypes. Here, we established an automated growth phenotyping pipeline for Arabidopsis thaliana to aid researchers in comparing growth behaviors of different genotypes.
The analysis pipeline includes automated image analysis of two-dimensional digital plant images and evaluation of manually annotated information of growth stages. It employs linear mixed-effects models to quantify genotype effects on total rosette area and relative leaf growth rate (RLGR) and ANOVAs to quantify effects on developmental times.
Using the system, a single researcher can phenotype up to 7000 plants d(-1). Technical variance is very low (typically < 2%). We show quantitative results for the growth-impaired starch-excessmutant sex4-3 and the growth-enhancedmutant grf9.
We show that recordings of environmental and developmental variables reduce noise levels in the phenotyping datasets significantly and that careful examination of predictor variables (such as d after sowing or germination) is crucial to avoid exaggerations of recorded phenotypes and thus biased conclusions.
Objective
Leaders differ in their personalities from non-leaders. However, when do these differences emerge? Are leaders "born to be leaders" or does their personality change in preparation for a leadership role and due to increasing leadership experience?
Method
Using data from the German Socio-Economic Panel Study, we examined personality differences between leaders (N = 2683 leaders, women: n = 967; 36.04%) and non-leaders (N = 33,663) as well as personality changes before and after becoming a leader.
Results
Already in the years before starting a leadership position, leaders-to-be were more extraverted, open, emotionally stable, conscientious, and willing to take risks, felt to have greater control, and trusted others more than non-leaders. Moreover, personality changed in emergent leaders: While approaching a leadership position, leaders-to-be (especially men) became gradually more extraverted, open, and willing to take risks and felt to have more control over their life. After becoming a leader, they became less extraverted, less willing to take risks, and less conscientious but gained self-esteem.
Conclusions
Our findings suggest that people are not simply "born to be leaders" but that their personalities change considerably in preparation for a leadership role and due to leadership experience. Some changes are transient, but others last for a long time.
Individuals differ in their sensitivity toward injustice. Justice-sensitive persons perceive injustice more frequently and show stronger responses to it. Justice sensitivity has been studied predominantly in adults; little is known about its development in childhood and adolescence and its connection to prosocial behavior and emotional and behavioral problems. This study evaluates a version of the justice sensitivity inventory for children and adolescents (JSI-CA5) in 1472 9- to 17-year olds. Items and scales showed good psychometric properties and correlations with prosocial behavior and conduct problems similar to findings in adults, supporting the reliability and validity of the scale. We found individual differences in justice sensitivity as a function of age and gender. Furthermore, justice sensitivity predicted emotional and behavioral problems in children and adolescents over a 1- to 2-year period. Justice sensitivity perspectives can therefore be considered as risk and/or protective factors for mental health in childhood and adolescence.
Peer groups are critical socialization agents for the development of social behavior in adolescence, but studies examining peer-group effects on individuals' prosocial behavior are scarce. Using a two-wave, multilevel data set (N = 16,893, 8481 male; 8412 female; mean age at Time 1: 14.0 years) from 1308 classes in 252 secondary schools in Germany, main effects of the classroom level of prosocial behavior, cross-level interactions between the classroom and the individual levels of prosocial behavior at Time 1, and the moderating role of gender were examined. The results showed that adolescents in classrooms with high collective levels of prosocial behavior at Time 1 reported more prosocial behavior at Time 2, about two years later, reflecting a class-level main effect. A significant cross-level interaction indicated that a high classroom level of prosocial behavior particularly affected individuals with lower levels of prosocial behavior at Time 1. The influence of same-gender peers was larger compared with opposite-gender peers. The findings are discussed with respect to social learning mechanisms in the development of prosocial behavior and their implications for interventions to promote prosocial behavior.
Leaves are the main photosynthetic organs of vascular plants, and leaf development is dependent on a proper control of gene expression. Transcription factors (TFs) are global regulators of gene expression that play essential roles in almost all biological processes among eukaryotes. This PhD project focused on the characterization of the sink-to-source transition of Arabidopsis leaves and on the analysis of TFs that play a role in early leaf development. The sink-to-source transition occurs when the young emerging leaves (net carbon importers) acquire a positive photosynthetic balance and start exporting photoassimilates. We have established molecular and physiological markers (i.e., CAB1 and CAB2 expression levels, AtSUC2 and AtCHoR expression patterns, chlorophyll and starch levels, and photosynthetic electron transport rates) to identify the starting point of the transition, especially because the sink-to-source is not accompanied by a visual phenotype in contrast to other developmental transitions, such as the mature-to-senescent transition of leaves. The sink-to-source transition can be divided into two different processes: one light dependent, related to photosynthesis and light responses; and one light independent or impaired, related to the changes in the vascular tissue that occur when leaves change from an import to an export mode. Furthermore, starch, but not sucrose, has been identified as one of the potential signalling molecules for this transition. The expression level of 1880 TFs during early leaf development was assessed by qRTPCR, and 153 TFs were found to exhibit differential expression levels of at least 5-fold. GRF, MYB and SRS are TF families, which are overrepresented among the differentially expressed TFs. Additionally, processes like cell identity acquisition, formation of the epidermis and leaf development are overrepresented among the differentially expressed TFs, which helps to validate the results obtained. Two of these TFs were further characterized. bZIP21 is a gene up-regulated during the sink-to-source and mature-to-senescent transitions. Its expression pattern in leaves overlaps with the one observed for AtCHoR, therefore it constitutes a good marker for the sink-to-source transition. Homozygous null mutants of bZIP21 could not be obtained, indicating that the total absence of bZIP21 function may be lethal to the plant. Phylogenetic analyses indicate that bZIP21 is an orthologue of Liguleless2 from maize. In these analyses, we identified that the whole set of bZIPs in plants originated from four founder genes, and that all bZIPs from angiosperms can be classified into 13 groups of homologues and 34 Possible Groups of Orthologues (PoGOs). bHLH64 is a gene highly expressed in early sink leaves, its expression is downregulated during the mature-to-senescent transition. Null mutants of bHLH64 are characterized by delayed bolting when compared to the wild-type; this indicates a possible delay in the sink-to-source transition or the retention of a juvenile identity. A third TF, Dof4, was also characterized. Dof4 is neither differentially expressed during the sink-to-source nor during the senescent-to-mature transition, but a null mutant of Dof4 develops bigger leaves than the wild-type and forms a greater number of siliques. The Dof4 null mutant has proven to be a good background for biomass accumulation analysis. Though not overrepresented during the sink-to-source transition, NAC transcription factors seem to contribute significantly to the mature-to-senescent transition. Twenty two NACs from Arabidopsis and 44 from rice are differentially expressed during late stages of leaf development. Phylogenetic analyses revealed that most of these NACs cluster into three big groups of homologues, indicating functional conservation between eudicots and monocots. To prove functional conservation of orthologues, the expression of ten NAC genes of barley was analysed. Eight of the ten NAC genes were found to be differentially expressed during senescence. The use of evolutionary approaches combined with functional studies is thus expected to support the transfer of current knowledge of gene control gained in model species to crops.
Postpartale Depressionen sind häufige und schwerwiegende psychische Erkrankungen mit ungünstigem Einfluss auf die kindliche Entwicklung. Als Haupttransmissionsweg gilt die frühe Mutter-Kind-Interaktion. Über die langfristigen Auswirkungen auf die Kinder im Erwachsenenalter und die Rolle der Interaktion liegen kaum Ergebnisse vor. Im Rahmen der Mannheimer Risikokinderstudie wurden postpartale Depressionen bis zwei Jahre nach der Geburt erfasst. Die kindliche Entwicklung wurde fortlaufend und die Mutter-Kind-Interaktion im Alter von 3 Monaten standardisiert erhoben. 28 Kinder postpartal depressiver und 107 Kinder gesunder Mütter konnten mit 25 Jahren untersucht werden. Beeinträchtigungen der kognitiven und psychischen Entwicklung bei Kindern postpartal depressiver Mütter waren bis ins Erwachsenenalter nachweisbar. Responsives bzw. sensitives mütterliches Verhalten wirkte der negativen Entwicklung entgegen. Dies betont die Bedeutung einer hohen Qualität der Mutter-Kind-Interaktion für die Entwicklung von Risikokindern.
Postpartale Depressionen sind häufige und schwerwiegende psychische Erkrankungen mit ungünstigem Einfluss auf die kindliche Entwicklung. Als Haupttransmissionsweg gilt die frühe Mutter-Kind-Interaktion. Über die langfristigen Auswirkungen auf die Kinder im Erwachsenenalter und die Rolle der Interaktion liegen kaum Ergebnisse vor. Im Rahmen der Mannheimer Risikokinderstudie wurden postpartale Depressionen bis zwei Jahre nach der Geburt erfasst. Die kindliche Entwicklung wurde fortlaufend und die Mutter-Kind-Interaktion im Alter von 3 Monaten standardisiert erhoben. 28 Kinder postpartal depressiver und 107 Kinder gesunder Mütter konnten mit 25 Jahren untersucht werden. Beeinträchtigungen der kognitiven und psychischen Entwicklung bei Kindern postpartal depressiver Mütter waren bis ins Erwachsenenalter nachweisbar. Responsives bzw. sensitives mütterliches Verhalten wirkte der negativen Entwicklung entgegen. Dies betont die Bedeutung einer hohen Qualität der Mutter-Kind-Interaktion für die Entwicklung von Risikokindern.
Background
The forelimb-specific gene tbx5 is highly conserved and essential for the development of forelimbs in zebrafish, mice, and humans. Amongst birds, a single order, Dinornithiformes, comprising the extinct wingless moa of New Zealand, are unique in having no skeletal evidence of forelimb-like structures.
Results
To determine the sequence of tbx5 in moa, we used a range of PCR-based techniques on ancient DNA to retrieve all nine tbx5 exons and splice sites from the giant moa, Dinornis. Moa Tbx5 is identical to chicken Tbx5 in being able to activate the downstream promotors of fgf10 and ANF. In addition we show that missexpression of moa tbx5 in the hindlimb of chicken embryos results in the formation of forelimb features, suggesting that Tbx5 was fully functional in wingless moa. An alternatively spliced exon 1 for tbx5 that is expressed specifically in the forelimb region was shown to be almost identical between moa and ostrich, suggesting that, as well as being fully functional, tbx5 is likely to have been expressed normally in moa since divergence from their flighted ancestors, approximately 60 mya.
Conclusions
The results suggests that, as in mice, moa tbx5 is necessary for the induction of forelimbs, but is not sufficient for their outgrowth. Moa Tbx5 may have played an important role in the development of moa’s remnant forelimb girdle, and may be required for the formation of this structure. Our results further show that genetic changes affecting genes other than tbx5 must be responsible for the complete loss of forelimbs in moa.
Many human infants grow up learning more than one language simultaneously but only recently has research started to study early language acquisition in this population more systematically. The paper gives an overview on findings on early language acquisition in bilingual infants during the first two years of life and compares these findings to current knowledge on early language acquisition in monolingual infants. Given the state of the research, the overview focuses on research on phonological and early lexical development in the first two years of life. We will show that the developmental trajectory of early language acquisition in these areas is very similar in mono- and bilingual infants suggesting that these early steps into language are guided by mechanisms that are rather robust against the differences in the conditions of language exposure that mono- and bilingual infants typically experience.
Background: Aggression is a severe behavioral problem that interferes with many developmental challenges individuals face in middle childhood and adolescence. Particularly in the peer and in the academic domain, aggression inhibits the individual from making important learning experiences that are predictive for a healthy transition into adulthood. Furthermore, the resulting developmental deficits have the propensity to feedback and to promote aggression at later developmental stages. The aim of the present PhD thesis was to investigate pathways and processes involved in the etiology of aggression by examining the interrelation between multiple developmental problems in the peer and in the academic domain. More specifically, the relevance of affiliation with deviant peers as a driving mechanism for the development of aggression, factors promoting the affiliation with deviant peers (social rejection; academic failure), and mechanisms by which affiliation with deviant peers leads to aggression (external locus of control) were investigated.
Method: The research questions were addressed by three studies. Three data waves were available for the first study, the second and third study were based on two data waves. The first study specified pathways to antisocial behavior by investigating the temporal interrelation between social rejection, academic failure, and affiliation with deviant peers in a sample of 1,657 male and female children and adolescents aged between 6 and 15 years. The second study examined the role of external control beliefs as a potential mediator in the link between affiliation with deviant peers and aggression in a sample of 1,466 children and adolescents in the age of 9 to 19 years, employing a half-longitudinal design. The third study aimed to expand the findings of Study 1 and Study 2 by examining the differential predictivity of combinations of developmental risks for different functions of aggression, using a sample of 1,479 participants in the age between 9 and 19 years. First, profiles of social rejection, academic failure, and affiliation with deviant peers were identified, using latent profile analysis. Second, prospective pathways between risk-profiles and reactive and proactive aggression were investigated, using latent path analysis.
Results: The first study revealed that antisocial behavior at T1 was associated with social rejection and academic failure at T2. Both mechanisms promoted affiliation with deviant peers at the same data wave, which predicted deviancy at T3. Furthermore, both an indirect pathway via social rejection and affiliation with deviant peers and an indirect pathway via academic failure and affiliation with deviant peers significantly mediated the link between antisocial behavior at the first and the third data wave. Additionally, the proposed pathways generalized across genders and different age groups. The second study yielded that external control beliefs significantly mediated the link between affiliation with deviant peers and aggression, with affiliation with deviant peers at T1 predicting external control beliefs at T2 and external control beliefs at T1 predicting aggressive behavior at T2. Again, the analyses provided no evidence for gender and age specific variations in the proposed pathways. In the third study, three distinct risk groups were identified, made up of a large non-risk group, with low scores on all risk measures, a group characterized by high scores on social rejection (SR group), and a group with the highest scores on measures of affiliation with deviant peers and academic failure (APAF group). Importantly, risk group membership was differentially associated with reactive and proactive aggression. Only membership in the SR group at T1 was associated with the development of reactive aggression at T2 and only membership in the APAF group at T1 predicted proactive aggression at T2. Additionally, proactive aggression at T1 predicted membership in the APAF group at T2, indicating a reciprocal relationship between both constructs.
Conclusion: The results demonstrated that aggression causes severe behavioral deficits in social and academic domains which promote future aggression by increasing individuals’ tendency to affiliate with deviant peers. The stimulation of external control beliefs provides an explanation for deviant peers’ effect on the progression and intensification of aggression. Finally, multiple developmental risks were shown to co-occur within individuals and to be differentially predictive of reactive and proactive aggression. The findings of this doctoral dissertation have possible implications for the conceptualization of prevention and intervention programs aimed to reduce aggression in middle childhood and adolescence.