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Picea mariana1813

This work demonstrates the dominance of a Ni(0/II/III) cycle for Ni-photoredox amide arylation, which contrasts with other Ni-photoredox C-heteroatom couplings that operate via Ni(I/III) self-sustained cycles. The kinetic data gathered when using different Ni precatalysts supports an initial Ni(0)-mediated oxidative addition into the aryl bromide. Using NiCl2 as the precatalyst resulted in an observable induction period, which was found to arise from a photochemical activation event to generate Ni(0) and to be prolonged by unproductive comproportionation between the Ni(II) precatalyst and the in-situ generated Ni(0) active species. Ligand exchange after oxidative addition yields a Ni(II) aryl amido complex, which was identified as the catalyst resting state for the reaction. Stoichiometric experiments showed that oxidation of this Ni(II) aryl amido intermediate was required to yield functionalized amide products. The kinetic data presented supports a rate-limiting photochemically-mediated Ni(II/III) oxidation to enable C-N reductive elimination. An alternative Ni(I/III) self-sustained manifold was discarded based on EPR and kinetic measurements. The mechanistic insights uncovered herein will inform the community on how subtle changes in Ni-photoredox reaction conditions may impact the reaction pathway, and have enabled us to include aryl chlorides as coupling partners and to reduce the Ni loading by 20-fold without any reactivity loss.

This paper describes a mild strategy to promote amide arylations. Photoinduced oxidation of a Ni(II) aryl amido intermediate is proposed to facilitate the challenging C-N reductive elimination step at moderate temperatures. Notably, the mildly basic conditions employed facilitate access to a broad scope including protected amino acids, heterocycles, phenols, and sterically hindered substituents. Hence, this work presents an attractive strategy to enable late-stage functionalization of pre-existing amide moieties in commercial drugs and natural products.

Research Findings: We examined whether Head Start teachers' depressive symptoms are associated with their engagement in high-quality conversations with children, and we considered the extent to which this association is consistent across classroom contexts and activities. Observations of Head Start teachers' conversations with children were conducted using a teacher-focal coding system and teachers reported on depressive symptoms. Generalized estimating equations were used to test study hypotheses. Teachers' depressive symptoms were negatively associated with the likelihood that a high-quality conversation would occur during an observation interval. The relation between teacher depressive symptoms and high-quality conversations was negative during both structured settings and free choice settings. This relation also remained negative during play (e.g. art, music) and routine (e.g. personal care, clean up) activities. However, the relation between teacher depressive symptoms and high-quality conversations was not significant during academic activities (e.g. math, books, language). Practice or Policy: Potential explanations, strengths and limitations, and implications for study results are discussed.

White spruce is a commercially important tree species in Canadaâs boreal forest, and studies are underway to determine the best conditions for planting nursery grown seedlings in the field. Here, we studied effects of low thinning (1/3 harvested), shelterwood (2/3 harvested), and clear-cut harvesting on soil chemical properties, on the growth and nutrition of white spruce seedlings, and on diffuse non-intercepted (DIFN) light levels at 75 cm above the soil surface. The study was conducted on a nutrient-rich clayey soil in the Abitibi region of Québec. DIFN light was lowest in non-harvested control plots and increased curvilinearly with basal area removal. Thus, DIFN light in clear-cut plots was more than twice the amount in shelterwood plots. At three years post-planting, significant linear relationships were found between DIFN light and seedling growth parameters, which were significantly higher in clear-cut than in other treatment plots. Harvesting treatments had no significant effects on soil chemical properties or on four indices of mineral N availability. Needle mass increased with harvesting intensity. Mg and K concentrations in current-year needles were lower in clear-cut than in other treatment plots. In previous-year needles, Ca concentration was higher and Mg concentrations lower in clear-cut plots, whereas as K concentration was higher in non-harvested control plots. Nutrient concentrations were nearly all sufficient in all harvesting treatments according to diagnostic norms established for white spruce. Relative nutrient content (mg nutrient needleâ1) of current-year late-summer needles increased, whereas relative nutrient concentration (mg nutrient mgâ1 needle) varied slightly, with increasing harvesting intensity, indicating that all nutrients were sufficient in all treatments. There were significant linear relationships between seedling growth and needle Ca, Mg and K concentrations. We conclude that light availability, rather than nutrient limitations, is the main determinant of white spruce seedling growth on these fertile soils.

Most eukaryotes harbor two distinct pre-mRNA splicing machineries: the major spliceosome, which removes >99% of introns, and the minor spliceosome, which removes rare, evolutionarily conserved introns. Although hypothesized to serve important regulatory functions, physiologic roles of the minor spliceosome are not well understood. For example, the minor spliceosome component ZRSR2 is subject to recurrent, leukemia-associated mutations, yet functional connections among minor introns, hematopoiesis and cancers are unclear. Here, we identify that impaired minor intron excision via ZRSR2 loss enhances hematopoietic stem cell self-renewal. CRISPR screens mimicking nonsense-mediated decay of minor intron-containing mRNA species converged on LZTR1, a regulator of RAS-related GTPases. LZTR1 minor intron retention was also discovered in the RASopathy Noonan syndrome, due to intronic mutations disrupting splicing and diverse solid tumors. These data uncover minor intron recognition as a regulator of hematopoiesis, noncoding mutations within minor introns as potential cancer drivers and links among ZRSR2 mutations, LZTR1 regulation and leukemias.

Many of the most highly conserved elements in the human genome are "poison exons," alternatively spliced exons that contain premature termination codons and permit post-transcriptional regulation of mRNA abundance through induction of nonsense-mediated mRNA decay (NMD). Poison exons are widely assumed to be highly conserved due to their presumed importance for organismal fitness, but this functional importance has never been tested in the context of a whole organism. Here, we report that a poison exon in Smndc1 is conserved across mammals and plants and plays a molecular autoregulatory function in both kingdoms. We generated mouse and A. thaliana models lacking this poison exon to find its loss leads to deregulation of SMNDC1 protein levels, pervasive alterations in mRNA processing, and organismal size restriction. Together, these models demonstrate the importance of poison exons for both molecular and organismal phenotypes that likely explain their extraordinary conservation. Author summary: Poison exons are highly conserved elements in the human genome and are known for their roles in regulating mRNA abundance. Despite their assumed importance for organismal fitness, their functional significance has not been tested in whole organisms. Our study focuses on a poison exon in the Smndc1 gene. We discovered that this poison exon is conserved between mammals and plants and sought to test its functional importance. We generated mouse and plant models lacking this specific poison exon. The loss of this exon led to dysregulated SMNDC1 protein levels and widespread disruptions in RNA processing. These molecular changes resulted in a noticeable reduction in organismal size, underscoring the physiological impact of poison exon loss. Our findings demonstrate that poison exons are crucial for maintaining proper protein levels and mRNA processing homeostasis, which may partially explain their remarkable evolutionary conservation. This study highlights the importance of poison exons in both molecular regulation and overall organismal health, providing insights into their conservation across diverse species. [ABSTRACT FROM AUTHOR]

Parent and child relationships continuously evolve, part of an ongoing dialectic that derives from developmental changes in both parent and child. The focus of this study is on changes in the strength of association among four types of parenting behaviors considered important for children’s development: supportive presence, respect for autonomy, stimulation, and hostility. Mother–child interaction was observed for 1229 parent–child dyads at 36 months, 54 months, 1st grade, 3rd grade, and 5th grade using similar observational paradigms. The association between respect for autonomy and supportive presence was strong at age three and continued to be strong over time. The association between respect for autonomy and stimulation was modest but also showed little change from age three to 5th grade. Respect for autonomy was negatively associated with maternal hostility, but the relation was complex. It was stronger at 54 months than 36 months but then became weaker through time. Supportive presence showed a moderate relation with stimulation at age 3 but the association became weaker over time. Supportive presence showed an expected negative association with hostility, a relation that changed little over time. The relation between hostility and stimulation also became weaker over time. In effect, there appears to be a shifting pattern of relations between maternal behaviors during early and middle childhood, one that reflects an evolving dialectic in the mother–child relationship.