The evolution of seed size may be influenced by intrinsic attributes of populations, such as mating system and extrinsic factors, such as climate. Several hypotheses propose that the evolution of ...self‐fertilization from an outcrossing progenitor will be accompanied by a reduction in seed size, but this prediction has not been rigorously tested. Many studies report that the mean seed size of populations or taxa is associated with long‐term climate conditions. Here, we examined the effects on seed size of both mating system and climate within a single genus.
In the California wildflower genus, Clarkia (Onagraceae), we sampled seeds from 58 populations representing three pairs of sister taxa; each pair included a predominantly outcrossing and a facultatively selfing taxon. We then examined the independent effects on population mean seed size of mating system, elevation, long‐term (30‐year) climate conditions, and climate anomalies (the deviation between conditions in the year of collection and the long‐term mean), focusing on maximum monthly temperature (Tmax), cumulative moisture deficit and cumulative precipitation (PPT) during Clarkia's growing season (fall, winter and spring).
In each taxon pair, the selfing taxon had smaller seeds than the outcrosser. Local, long‐term (1921–1980 and 1981–2000) mean Tmax, PPT and elevation were independently and negatively associated with seed size. Long‐term means for Tmax and PPT explain geographical variation in seed size better than climate anomalies in the year of collection.
Synthesis. We corroborated two key hypotheses concerning the drivers of geographical variation in mean seed size. Small seeds in Clarkia co‐evolve with selfing (although the mechanism remains elusive) and in response to chronically warm and wet conditions. The effect of long‐term mean precipitation on seed size differs qualitatively from the effect of precipitation anomalies; relatively large seeds are produced in populations experiencing wetter‐than‐normal years. Ongoing climate change may therefore generate conflicting selection on seed size in Clarkia: intensifying drought is likely to lead to an evolutionary increase in seed size due to its effects on seedling survivorship, while climate‐driven declines in pollinators or selection favouring more rapid reproduction may promote the evolution of self‐pollination, facilitating the evolution of smaller seeds.
We corroborated two key hypotheses concerning the drivers of geographical variation in mean seed size. Small seeds in Clarkia co‐evolve with selfing (although the mechanism remains elusive) and in response to chronically warm and wet conditions. The effect of long‐term mean precipitation on seed size differs qualitatively from the effect of precipitation anomalies; relatively large seeds are produced in populations experiencing wetter‐than‐normal years. Ongoing climate change may therefore generate conflicting selection on seed size in Clarkia: intensifying drought is likely to lead to an evolutionary increase in seed size due to its effects on seedling survivorship, while climate‐driven declines in pollinators or selection favouring more rapid reproduction may promote the evolution of self‐pollination, facilitating the evolution of smaller seeds. Image credit: Heather Schneider merits credit for the photo of Clarkia unguiculata, and Leah Dudley took the photo of Clarkia xantiana.
The whipped cream complements the tea's bitter notes and can be made ahead of time. ¾ cup oat or other plant-based milk 1 tsp apple cider vinegar 1 cup all-purpose flour 1 cup icing sugar 1/3 cup ...cornstarch 4 tsp matcha powder 1½ tsp baking powder 1 tsp baking soda ½ tsp sea salt ¼ cup vegetable oil 1 tbsp vanilla bean paste ½ cup aquafaba, whipped (see tip) Matcha Whipped Cream 1 to 2 tsp matcha powder 1 400-mL can coconut whipping cream, such as Cha's Organics, chilled ½ cup icing sugar 1 tbsp vanilla bean paste 1. Matcha Macadamia Vegan White Chocolate Cookies PREP 15 MIN; TOTAL 45 MIN MAKES 20 COOKIES These cookies have a chewy texture, which plays offthe buttery-ness of the nuts and the sweetness of the vegan white chocolate. 1 cup all-purpose flour 4 tsp matcha powder ½ tsp baking soda ½ tsp baking powder ½ tsp salt ½ cup plant-based butter ½ cup granulated sugar ¼ cup brown sugar ¼ cup oat or other plant-based milk 1 tbsp vanilla bean paste 8 tbsp vegan white chocolate chips, divided 8 tbsp chopped macadamia nuts, divided Flaked sea salt, for garnish 1. Matcha Cocoa Butter Truffles PREP 15 MIN TOTAL 1 HR 45 MIN MAKES 49 TRUFFLES These intense-green truffles are showstoppers that require minimal effort. 1 cup icing sugar 5 tsp matcha powder, divided 1 tsp sea salt 1 cup cacao butter, melted 1 cup vegan white chocolate chips, melted 1 tsp vanilla bean paste 1.
Chemical modifications of the nucleosides that comprise transfer RNAs are diverse. However, the structure, location and extent of modifications have been systematically charted in very few organisms. ...Here, we describe an approach in which rapid prediction of modified sites through reverse transcription-derived signatures in high-throughput transfer RNA-sequencing (tRNA-seq) data is coupled with identification of tRNA modifications through RNA mass spectrometry. Comparative tRNA-seq enabled prediction of several Vibrio cholerae modifications that are absent from Escherichia coli and also revealed the effects of various environmental conditions on V. cholerae tRNA modification. Through RNA mass spectrometric analyses, we showed that two of the V. cholerae-specific reverse transcription signatures reflected the presence of a new modification (acetylated acp
U (acacp
U)), while the other results from C-to-Ψ RNA editing, a process not described before. These findings demonstrate the utility of this approach for rapid surveillance of tRNA modification profiles and environmental control of tRNA modification.
The factors and mechanisms that govern tRNA stability in bacteria are not well understood. Here, we investigated the influence of posttranscriptional modification of bacterial tRNAs (tRNA ...modification) on tRNA stability. We focused on Thil-generated 4-thiouridine (s⁴U), a modification found in bacterial and archaeal tRNAs. Comprehensive quantification of Vibrio cholerae tRNAs revealed that the abundance of some tRNAs is decreased in a Δthil strain in a stationary phase-specific manner. Multiple mechanisms, including rapid degradation of a subset of hypomodified tRNAs, account for the reduced abundance of tRNAs in the absence of thil. Through transposon insertion sequencing, we identified additional tRNA modifications that promote tRNA stability and bacterial viability. Genetic analysis of suppressor mutants as well as biochemical analyses revealed that rapid degradation of hypomodified tRNA is mediated by the RNA degradosome. Elongation factor Tu seems to compete with the RNA degradosome, protecting aminoacyl tRNAs from decay. Together, our observations describe a previously unrecognized bacterial tRNA quality control system in which hypomodification sensitizes tRNAs to decay mediated by the RNA degradosome.
Luminescence imaging has gained attention as a promising bio-imaging modality in situations where fluorescence imaging cannot be applied. However, wider application to multicolour and dynamic imaging ...is limited by the lack of bright luminescent proteins with emissions across the visible spectrum. Here we report five new spectral variants of the bright luminescent protein, enhanced Nano-lantern (eNL), made by concatenation of the brightest luciferase, NanoLuc, with various colour hues of fluorescent proteins. eNLs allow five-colour live-cell imaging, as well as detection of single protein complexes and even single molecules. We also develop an eNL-based Ca
indicator with a 500% signal change, which can image spontaneous Ca
dynamics in cardiomyocyte and neural cell models. These eNL probes facilitate not only multicolour imaging in living cells but also sensitive imaging of a wide repertoire of proteins, even at very low expression levels.
Endogenous retroviruses (ERVs), retrovirus-like elements with long terminal repeats, are widely dispersed in the euchromatic compartment in mammalian cells, comprising ∼10% of the mouse genome. These ...parasitic elements are responsible for >10% of spontaneous mutations. Whereas DNA methylation has an important role in proviral silencing in somatic and germ-lineage cells, an additional DNA-methylation-independent pathway also functions in embryonal carcinoma and embryonic stem (ES) cells to inhibit transcription of the exogenous gammaretrovirus murine leukaemia virus (MLV). Notably, a recent genome-wide study revealed that ERVs are also marked by histone H3 lysine 9 trimethylation (H3K9me3) and H4K20me3 in ES cells but not in mouse embryonic fibroblasts. However, the role that these marks have in proviral silencing remains unexplored. Here we show that the H3K9 methyltransferase ESET (also called SETDB1 or KMT1E) and the Krüppel-associated box (KRAB)-associated protein 1 (KAP1, also called TRIM28) are required for H3K9me3 and silencing of endogenous and introduced retroviruses specifically in mouse ES cells. Furthermore, whereas ESET enzymatic activity is crucial for HP1 binding and efficient proviral silencing, the H4K20 methyltransferases Suv420h1 and Suv420h2 are dispensable for silencing. Notably, in DNA methyltransferase triple knockout (Dnmt1-/-Dnmt3a-/-Dnmt3b-/-) mouse ES cells, ESET and KAP1 binding and ESET-mediated H3K9me3 are maintained and ERVs are minimally derepressed. We propose that a DNA-methylation-independent pathway involving KAP1 and ESET/ESET-mediated H3K9me3 is required for proviral silencing during the period early in embryogenesis when DNA methylation is dynamically reprogrammed.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Standards for EMG and Neurography are suggested.•Electrophysiological tests in Pediatric practice are summarized.•Implementation and clinical utility of less common methods for EMG and neurography ...are presented.
This document is an update and extension of ICCN Standards published in 1999. It is the consensus of experts on the current status of EMG and Neurography methods. A panel of authors from different countries with different approach to routines in neurophysiological methods was chosen based on their particular interest and previous publications. Each member of the panel submitted a section on their particular area of interest and these submissions were circulated among the panel members for edits and comments. This process continued until a consensus was reached.
The document covers EMG topics such as conventional EMG, Macro EMG, applications of surface EMG and electrical impedance myography. Single Fiber EMG is not included, since it is the topic in a separate IFCN document. A neurography section covers topics such as motor and sensory neurography, F wave recordings, H-reflex, short segment recordings, CMAP scan and motor unit number methods. Other sections cover repetitive nerve stimulation and Pediatric electrodiagnostic testing.
Each method includes a description of methodologies, pitfalls, and the use of reference values. Clinical applications accompany some of these sections.
•Diverse chemical modifications of tRNAs (tRNA modifications) modulate protein synthesis.•tRNA sequencing and RNA mass spectrometry enable rapid identification of the structures and sites of tRNA ...modifications..•Novel modifications have been discovered in a variety of organisms.•tRNA modification frequencies are regulated by environmental conditions.
Transfer RNAs (tRNAs) are non-coding RNAs essential for protein synthesis. tRNAs are heavily decorated with a variety of post-transcriptional modifications (tRNA modifications). Recent methodological advances provide new tools for rapid profiling of tRNA modifications and have led to discoveries of novel modifications and their regulation. Here, we provide an overview of the techniques for investigating tRNA modifications and of the expanding knowledge of their chemistry and regulation.
In adults, leukocyte telomere length (LTL) is variable, familial, and longer in women and in offspring conceived by older fathers. Although short LTL is associated with atherosclerotic cardiovascular ...disease, long LTL is associated with major cancers. The prevailing notion is that LTL is a "telomeric clock," whose movement (expressed in LTL attrition) reflects the pace of aging. Accordingly, individuals with short LTL are considered to be biologically older than their peers. Recent studies suggest that LTL is largely determined before adulthood. We examined whether factors that largely characterize LTL in adults also influence LTL in newborns.
LTL was measured in blood samples from 490 newborns and their parents.
LTL (mean ± SD) was longer (9.50 ± 0.70 kb) in newborns than in their mothers (7.92 ± 0.67 kb) and fathers (7.70 ± 0.71 kb) (both P < .0001); there was no difference in the variance of LTL among the 3 groups. Newborn LTL correlated more strongly with age-adjusted LTL in mothers (r = 0.47; P < .01) than in fathers (r = 0.36; P < .01) (P for interaction = .02). Newborn LTL was longer by 0.144 kb in girls than in boys (P = .02), and LTL was longer by 0.175 kb in mothers than in fathers (P < .0001). For each 1-year increase in father's age, newborn LTL increased by 0.016 kb (95% confidence interval: 0.04 to 0.28) (P = .0086).
The large LTL variation across newborns challenges the telomeric clock model. Having inherently short or long LTL may be largely determined at birth, anteceding by decades disease manifestation in adults.
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