An AP2/ERF transcription factor ERF139 coordinates xylem cell expansion and secondary cell wall deposition

Abstract Differentiation of xylem elements involves cell expansion, secondary cell wall deposition and programmed cell death. Transitions between these phases require strict spatiotemporal control. The function of Populus ERF139 (Potri.013G101100) in xylem differentiation was characterized in transgenic overexpression and dominant repressor lines of ERF139 in hybrid aspen (Populus tremula x tremuloides). Xylem properties, secondary cell wall (SCW) chemistry and downstream targets were analyzed in both types of transgenic trees using microscopy techniques, FT-IR, pyrolysis-GC/MS, wet chemistry methods and RNA sequencing. Opposite phenotypes were observed in the secondary xylem vessel sizes and SCW chemistry in the two different types of transgenic trees, supporting the function of ERF139 in suppressing the radial expansion of vessel elements and stimulating accumulation of guaiacyl-type lignin and possibly also xylan. Comparative transcriptomics identified genes related to SCW biosynthesis (LAC5, LBD15, MYB86) and salt and drought stress responsive genes (ANAC002, ABA1) as potential direct targets of ERF139. The phenotypes of the transgenic trees and the stem expression profiles of ERF139 potential target genes support the role of ERF139 as a transcriptional regulator of xylem cell expansion and SCW formation, possibly in response to osmotic changes of the cells. This article is protected by copyright. All rights reserved.Peer reviewe

Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron

The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of $\sqrt s =1.96$ TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is $A_{\mathrm{FB}}^{t\bar{t}} = 0.128 \pm 0.025$. The combined inclusive and differential asymmetries are consistent with recent standard model predictions

Visual stimulation with blue wavelength light drives V1 effectively eliminating stray light contamination during two-photon calcium imaging

Background: Brain visual circuits are often studied in vivo by imaging Ca2+ indicators with green-shifted emission spectra. Polychromatic white visual stimuli have a spectrum that partially overlaps indicators´ emission spectra, resulting in significant contamination of calcium signals. New method: To overcome light contamination problems we choose blue visual stimuli, having a spectral composition not overlapping with Ca2+ indicator´s emission spectrum. To compare visual responsiveness to blue and white stimuli we used electrophysiology (visual evoked potentials –VEPs) and 3D acousto-optic two-photon (2P) population Ca2+ imaging in mouse primary visual cortex (V1). Results: VEPs in response to blue and white stimuli had comparable peak amplitudes and latencies. Ca2+ imaging in a Thy1 GP4.3 line revealed that the populations of neurons responding to blue and white stimuli were largely overlapping, that their responses had similar amplitudes, and that functional response properties such as orientation and direction selectivities were also comparable. Comparison with existing methods: Masking or shielding the microscope are often used to minimize the contamination of Ca2+ signal by white light, but they are time consuming, bulky and thus can limit experimental design, particularly in the more and more frequently used awake set-up. Blue stimuli not interfering with imaging allow to omit shielding. Conclusions: Together, our results show that the selected blue light stimuli evoke responses comparable to those evoked by white stimuli in mouse V1. This will make complex designs of imaging experiments in behavioral set-ups easier, and facilitate the combination of Ca2+ imaging with electrophysiology and optogenetics

In vivo spontaneous activity and coital-evoked inhibition of mouse accessory olfactory bulb output neurons

Little is known about estrous effects on brain microcircuits. We examined the accessory olfactory bulb (AOB) in vivo, in anesthetized naturally cycling females, as model microcircuit receiving coital somatosensory information. Whole-cell recordings demonstrate that output neurons are relatively hyperpolarized in estrus and unexpectedly fire high frequency bursts of action potentials. To mimic coitus, a calibrated artificial vagino-cervical stimulation (aVCS) protocol was devised. aVCS evoked stimulus-locked local field responses in the interneuron layer independent of estrous stage. The response is sensitive to α1-adrenergic receptor blockade, as expected since aVCS increases norepinephrine release in AOB. Intriguingly, only in estrus does aVCS inhibit AOB spike output. Estrus-specific output reduction coincides with prolonged aVCS activation of inhibitory interneurons. Accordingly, in estrus the AOB microcircuit sets the stage for coital stimulation to inhibit the output neurons, possibly via high frequency bursting-dependent enhancement of reciprocal synapse efficacy between inter- and output neurons

CellMAPtracer: A User-Friendly Tracking Tool for Long-Term Migratory and Proliferating Cells Associated with FUCCI Systems

Cell migration is a fundamental biological process of key importance in health and disease. Advances in imaging techniques have paved the way to monitor cell motility. An ever-growing collection of computational tools to track cells has improved our ability to analyze moving cells. One renowned goal in the field is to provide tools that track cell movement as comprehensively and automatically as possible. However, fully automated tracking over long intervals of time is challenged by dividing cells, thus calling for a combination of automated and supervised tracking. Furthermore, after the emergence of various experimental tools to monitor cell-cycle phases, it is of relevance to integrate the monitoring of cell-cycle phases and motility. We developed CellMAPtracer, a multiplatform tracking system that achieves that goal. It can be operated as a conventional, automated tracking tool of single cells in numerous imaging applications. However, CellMAPtracer also allows adjusting tracked cells in a semiautomated supervised fashion, thereby improving the accuracy and facilitating the long-term tracking of migratory and dividing cells. CellMAPtracer is available with a user-friendly graphical interface and does not require any coding or programming skills. CellMAPtracer is compatible with two- and three-color fluorescent ubiquitination-based cell-cycle indicator (FUCCI) systems and allows the user to accurately monitor various migration parameters throughout the cell cycle, thus having great potential to facilitate new discoveries in cell biology

Ethylene Signaling Is Required for Fully Functional Tension Wood in Hybrid Aspen

Tension wood (TW) in hybrid aspen trees forms on the upper side of displaced stems to generate a strain that leads to uplifting of the stem. TW is characterized by increased cambial growth, reduced vessel frequency and diameter, and the presence of gelatinous, cellulose-rich (G-)fibers with its microfibrils oriented parallel to the fiber cell axis. Knowledge remains limited about the molecular regulators required for the development of this special xylem tissue with its characteristic morphological, anatomical, and chemical features. In this study, we use transgenic, ethylene-insensitive (ETI) hybrid aspen trees together with time-lapse imaging to show that functional ethylene signaling is required for full uplifting of inclined stems. X-ray diffraction and Raman microspectroscopy of TW in ETI trees indicate that, although G-fibers form, the cellulose microfibril angle in the G-fiber S-layer is decreased, and the chemical composition of S- and G-layers is altered than in wild-type TW. The characteristic asymmetric growth and reduction of vessel density is suppressed during TW formation in ETI trees. A genome-wide transcriptome profiling reveals ethylene-dependent genes in TW, related to cell division, cell wall composition, vessel differentiation, microtubule orientation, and hormone crosstalk. Our results demonstrate that ethylene regulates transcriptional responses related to the amount of G-fiber formation and their properties (chemistry and cellulose microfibril angle) during TW formation. The quantitative and qualitative changes in G-fibers are likely to contribute to uplifting of stems that are displaced from their original position.Bio4Energ