30 research outputs found
The COP9 SIGNALOSOME is required for postembryonic meristem maintenance in Arabidopsis thaliana
Cullin-RING E3 ligases (CRLs) regulate different aspects of plant development, and are activated by modification of their cullin subunit with the ubiquitin-like protein NEDD8 (NEural precursor cell expressed Developmentally Down-regulated 8) (neddylation) and deactivated by NEDD8 removal (deneddylation). The CONSTITUTIVELY PHOTOMORPHOGENIC9 (COP9) signalosome (CSN) acts as a molecular switch of CRLs activity by reverting their neddylation status, but its contribution to embryonic and early seedling development remains poorly characterized. Here, we analyzed the phenotypic defects of csn mutants and monitored the cullin deneddylation/neddylation ratio during embryonic and early seedling development. We show that while csn mutants can complete embryogenesis (albeit at a slower pace than wild type) and are able to germinate (albeit at a reduced rate), they progressively loose meristem activity upon germination, until they become unable to sustain growth. We also show that the majority of cullin proteins is progressively neddylated during the late stages of seed maturation and becomes deneddylated upon seed germination. This developmentally regulated shift in the cullin neddylation status is absent in csn mutants. We conclude that the CSN and its cullin deneddylation activity are required to sustain postembryonic meristem function in Arabidopsis
GRMA: Generalized Range Move Algorithms for the efficient optimization of MRFs
Markov Random Fields (MRF) have become an
important tool for many vision applications, and the optimization
of MRFs is a problem of fundamental importance.
Recently, Veksler and Kumar et al. proposed the range move
algorithms, which are some of the most successful optimizers.
Instead of considering only two labels as in previous
move-making algorithms, they explore a large search space
over a range of labels in each iteration, and significantly
outperform previous move-making algorithms. However, two
problems have greatly limited the applicability of range
move algorithms: 1) They are limited in the energy functions
they can handle (i.e., only truncated convex functions); 2)
They tend to be very slow compared to other move-making
algorithms (e.g., �-expansion and ��-swap). In this paper,
we propose two generalized range move algorithms (GRMA)
for the efficient optimization of MRFs. To address the
first problem, we extend the GRMAs to more general energy
functions by restricting the chosen labels in each move so
that the energy function is submodular on the chosen subset.
Furthermore, we provide a feasible sufficient condition for
choosing these subsets of labels. To address the second
problem, we dynamically obtain the iterative moves by solving
set cover problems. This greatly reduces the number of
moves during the optimization.We also propose a fast graph
construction method for the GRMAs. Experiments show
that the GRMAs offer a great speedup over previous range
move algorithms, while yielding competitive solutions
Chalcogenide Glass-on-Graphene Photonics
Two-dimensional (2-D) materials are of tremendous interest to integrated
photonics given their singular optical characteristics spanning light emission,
modulation, saturable absorption, and nonlinear optics. To harness their
optical properties, these atomically thin materials are usually attached onto
prefabricated devices via a transfer process. In this paper, we present a new
route for 2-D material integration with planar photonics. Central to this
approach is the use of chalcogenide glass, a multifunctional material which can
be directly deposited and patterned on a wide variety of 2-D materials and can
simultaneously function as the light guiding medium, a gate dielectric, and a
passivation layer for 2-D materials. Besides claiming improved fabrication
yield and throughput compared to the traditional transfer process, our
technique also enables unconventional multilayer device geometries optimally
designed for enhancing light-matter interactions in the 2-D layers.
Capitalizing on this facile integration method, we demonstrate a series of
high-performance glass-on-graphene devices including ultra-broadband on-chip
polarizers, energy-efficient thermo-optic switches, as well as graphene-based
mid-infrared (mid-IR) waveguide-integrated photodetectors and modulators
The complete mitochondrial genome of Aconurella prolixa (Lethierry 1885) (Hemiptera: Cicadellidae: Deltocephalinae: Chiasmini)
The complete mitochondrial genome of the widespread leafhopper species Aconurella prolixa (Hemiptera: Cicadellidae: Deltocephalinae: Chiasmini) was obtained via next-generation sequencing. This mitochondrial genome is 14,832 bp in length with the 37 classical eukaryotic mitochondrial genes and a control region. All 13 protein-coding genes (PCGs) are initiated with ATN, except ND5 uses TTG as the start codon, and terminate with TAA or TAG with the exception of COX2 and ND4 which use a single T residue as the stop codon. Twenty-one of the 22 transfer RNA (tRNAs) genes have the typical clover-leaf structure except for trnS1. Unlike some other species of deltocephalinae, no tRNA rearrangements were detected. The monophyly of Cicadellidae and Deltocephalinae, as well as the monophyly of Chiasmini, with a sister relationship between A. prolixa and (Exitianus indicus + Nephotettix cincticeps) is supported by Bayesian inference phylogenetic analyses based on 13 PCGs
Mitogenomic Analysis and Phylogenetic Implications for the Deltocephaline Tribe Chiasmini (Hemiptera: Cicadellidae: Deltocephalinae)
The grassland leafhopper tribe Chiasmini (Cicadellidae: Deltocephalinae) presently comprises 324 described species worldwide, with the highest species diversity occurring in the Nearctic region but a greater diversity of genera occurring in the Old World. In China, this tribe comprises 39 described species in 11 genera, but the fauna remains understudied. The complete mitogenomes of three species of this tribe have been sequenced previously. In order to better understand the phylogenetic position of Chiasmini within the subfamily Deltocephalinae and to investigate relationships among Chiasmini genera and species, we sequenced and analyzed the complete mitogenomes of 13 species belonging to seven genera from China. Comparison of the newly sequenced mitogenomes reveals a closed circular double-stranded structure containing 37 genes with a total length of 14,805 to 16,269 bp and a variable number of non-coding A + T-rich regions. The gene size, gene order, gene arrangement, base composition, codon usage, and secondary structure of tRNAs of the newly sequenced mitogenomes of these 13 species are highly conserved in Chiasmini. The ATN codon is commonly used as the start codon in protein-coding genes (PCGs), except for ND5 in Doratura sp. and ATP6 in Nephotettix nigropictus, which use the rare GTG start codon. Most protein-coding genes have TAA or TAG as the stop codon, but some genes have an incomplete T stop codon. Except for the tRNA for serine (trnS1(AGN)), the secondary structure of the other 21 tRNAs is a typical cloverleaf structure. In addition to the primary type of G–U mismatch, five other types of tRNA mismatches were observed: A–A, A–C, A–G, U–C, and U–U. Chiasmini mitochondrial genomes exhibit gene overlaps with three relatively stable regions: the overlapping sequence between trnW and trnC is AAGTCTTA, the overlapping sequence between ATP8 and ATP6 is generally ATGATTA, and the overlapping sequence between ND4 and ND4L is generally TTATCAT. The largest non-coding region is the control region, which exhibits significant length and compositional variation among species. Some Chiasmini have tandem repeat structures within their control regions. Unlike some other deltocephaline leafhoppers, the sequenced Chiasmini lack mitochondrial gene rearrangements. Phylogenetic analyses of different combinations of protein-coding and ribosomal genes using maximum likelihood and Bayesian methods under different models, using either amino acid or nucleotide sequences, are generally consistent and also agree with results of prior analyses of nuclear and partial mitochondrial gene sequence data, indicating that complete mitochondrial genomes are phylogenetically informative at different levels of divergence within Chiasmini and among leafhoppers in general. Apart from Athysanini and Opsiini, most of the deltocephaline tribes are recovered as monophyletic. The results of ML and BI analyses show that Chiasmini is a monophyletic group with seven monophyletic genera arranged as follows: ((Zahniserius + (Gurawa + (Doratura + Aconurella))) + (Leofa + (Exitianus + Nephotettix)))
Quantifying the Dzyaloshinskii-Moriya Interaction Induced by the Bulk Magnetic Asymmetry
A broken interfacial inversion symmetry in ultrathin ferromagnet/heavy metal
(FM/HM) bilayers is generally believed to be a prerequisite for accommodating
the Dzyaloshinskii-Moriya interaction (DMI) and for stabilizing chiral spin
textures. In these bilayers, the strength of the DMI decays as the thickness of
the FM layer increases and vanishes around a few nanometers. In the present
study, through synthesizing relatively thick films of compositions CoPt or
FePt, CoCu or FeCu, FeGd and FeNi, contributions to DMI from the composition
gradient induced bulk magnetic asymmetry (BMA) and spin-orbit coupling (SOC)
are systematically examined. Using Brillouin light scattering spectroscopy,
both the sign and amplitude of DMI in films with controllable direction and
strength of BMA, in the presence and absence of SOC are experimentally studied.
In particular, we show that a sizable amplitude of DMI (0.15 mJ/m^2) can be
realized in CoPt or FePt films with BMA and strong SOC, whereas negligible DMI
strengths are observed in other thick films with BMA but without significant
SOC. The pivotal roles of BMA and SOC are further examined based on the
three-site Fert-Levy model and first-principles calculations. It is expected
that our findings may help to further understand the origin of chiral magnetism
and to design novel non-collinear spin textures.Comment: Physical Review Letters, in pres