Touch signaling and thigmomorphogenesis are regulated by complementary CAMTA3- and JA-dependent pathways

Plants respond to mechanical stimuli to direct their growth and counteract environmental threats. Mechanical stimulation triggers rapid gene expression changes and affects plant appearance (thigmomorphogenesis) and flowering. Previous studies reported the importance of jasmonic acid (JA) in touch signaling. Here, we used reverse genetics to further characterize the molecular mechanisms underlying touch signaling. We show that Piezo mechanosensitive ion channels have no major role in touch-induced gene expression and thigmomorphogenesis. In contrast, the receptor-like kinase Feronia acts as a strong negative regulator of the JA-dependent branch of touch signaling. Last, we show that calmodulin-binding transcriptional activators CAMTA1/2/3 are key regulators of JA-independent touch signaling. CAMTA1/2/3 cooperate to directly bind the promoters and activate gene expression of JA-independent touch marker genes like TCH2 and TCH4. In agreement, camta3 mutants show a near complete loss of thigmomorphogenesis and touch-induced delay of flowering. In conclusion, we have now identified key regulators of two independent touch-signaling pathways

A multi-mediation model on the relations of bullying, victimization, identity, and family with adolescent depressive symptoms

This study investigated a multi-mediation model of the relationship between bullying behavior, peer victimization, personal identity, and family characteristics to adolescent depressive symptoms in 194 high school students, 12-18 years of age. In the first model, peer victimization mediated the relation between bullying behavior and depressive symptoms. In the second model, personal identity mediated the relation between peer victimization and depressive symptoms. In the final model, the two mediation models were combined. The relative influence of family characteristics on all variables in the two mediation models was studied using structural equation modeling. The results supported both mediation models and confirmed the influence of family characteristics on all variables in the mediation models. This study indicates that victimization by one's peers has consequences for adolescents' psychological health when their personal identity is affected. In addition, the study was able to model several processes in which family characteristics were related to adolescent depressive symptoms. Moreover, the final combined model (in which the two mediation models and the influence of family characteristics on all variables were confirmed) explained half of the variance in adolescent depressive symptoms

Peer and self-reported victimization: Do non-victimized students give victimization nominations to classmates who are self-reported victims?

Using data from 2413 Dutch first-year secondary school students (M age. = 13.27, SD age. = 0.51, 49.0% boys), this study investigated as to what extent students who according to their self-reports had not been victimized (referred to as reporters) gave victimization nominations to classmates who according to their self-reports had been victimized (referred to as receivers). Using a dyadic approach, characteristics of the reporter-receiver dyad (i.e., gender similarity) and of the reporter (i.e., reporters' behavior during bullying episodes) that were possibly associated with reporter-receiver agreement were investigated. Descriptive analyses suggested that numerous students who were self-reported victims were not perceived as victimized by their non-victimized classmates. Three-level logistic regression models (reporter-receiver dyads nested in reporters within classrooms) demonstrated greater reporter-receiver agreement in same-gender dyads, especially when the reporter and the receiver were boys. Furthermore, reporters who behaved as outsiders during bullying episodes (i.e., reporters who actively shied away from the bullying) were less likely to agree on the receiver's self-reported victimization, and in contrast, reporters who behaved as defenders (i.e., reporters who helped and supported victims) were more likely to agree on the victimization. Moreover, the results demonstrated that reporters gave fewer victimization nominations to receivers who reported they had been victimized sometimes than to receivers who reported they had been victimized often/very often. Finally, this study suggested that reporter-receiver agreement may not only depend on characteristics of the reporter-receiver dyad and of the reporter, but on classroom characteristics as well (e.g., the number of students in the classroom)

The Mitochondrial DNA (mtDNA)-Associated Protein SWIB5 Influences mtDNA Architecture and Homologous Recombination

In addition to the nucleus, mitochondria and chloroplasts in plant cells also contain genomes. Efficient DNA repair pathways are crucial in these organelles to fix damage resulting from endogenous and exogenous factors. Plant organellar genomes are complex compared to their animal counterparts and although several plant-specific mediators of organelle DNA repair have been reported, many regulators remain to be identified. Here, we show that a mitochondrial SWI/SNF (nucleosome remodeling) complex B protein, SWIB5, is capable of associating with mitochondrial DNA (mtDNA) in Arabidopsis thaliana. Gain- and loss-of-function mutants provided evidence for a role of SWIB5 in influencing mtDNA architecture and homologous recombination at specific intermediate-sized repeats both under normal and genotoxic conditions. SWIB5 interacts with other mitochondrial SWIB proteins. Gene expression and mutant phenotypic analysis of SWIB5 and SWIB family members suggests a link between organellar genome maintenance and cell proliferation. Taken together, our work presents a protein family that influences mtDNA architecture and homologous recombination in plants and suggests a link between organelle functioning and plant development