Gate-Tunable Berry Curvature Dipole Polarizability in Dirac Semimetal Cd_{3}As_{2}.

We reveal the gate-tunable Berry curvature dipole polarizability in Dirac semimetal Cd_{3}As_{2} nanoplates through measurements of the third-order nonlinear Hall effect. Under an applied electric field, the Berry curvature exhibits an asymmetric distribution, forming a field-induced Berry curvature dipole, resulting in a measurable third-order Hall voltage with a cubic relationship to the longitudinal electric field. Notably, the magnitude and polarity of this third-order nonlinear Hall effect can be effectively modulated by gate voltages. Furthermore, our scaling relation analysis demonstrates that the sign of the Berry curvature dipole polarizability changes when tuning the Fermi level across the Dirac point, in agreement with theoretical calculations. The results highlight the gate control of nonlinear quantum transport in Dirac semimetals, paving the way for promising advancements in topological electronics.

Room-temperature orbit-transfer torque enabling van der Waals magnetoresistive memories.

The non-volatile magnetoresistive random access memory (MRAM) is believed to facilitate emerging applications, such as in-memory computing, neuromorphic computing and stochastic computing. Two-dimensional (2D) materials and their van der Waals heterostructures promote the development of MRAM technology, due to their atomically smooth interfaces and tunable physical properties. Here we report the all-2D magnetoresistive memories featuring all-electrical data reading and writing at room temperature based on WTe2/Fe3GaTe2/BN/Fe3GaTe2 heterostructures. The data reading process relies on the tunnel magnetoresistance of Fe3GaTe2/BN/Fe3GaTe2. The data writing is achieved through current induced polarization of orbital magnetic moments in WTe2, which exert torques on Fe3GaTe2, known as the orbit-transfer torque (OTT) effect. In contrast to the conventional reliance on spin moments in spin-transfer torque and spin-orbit torque, the OTT effect leverages the natural out-of-plane orbital moments, facilitating field-free perpendicular magnetization switching through interface currents. Our results indicate that the emerging OTT-MRAM is promising for low-power, high-performance memory applications.

Control over Berry Curvature Dipole with Electric Field in WTe_{2}.

Berry curvature dipole plays an important role in various nonlinear quantum phenomena. However, the maximum symmetry allowed for nonzero Berry curvature dipole in the transport plane is a single mirror line, which strongly limits its effects in materials. Here, via probing the nonlinear Hall effect, we demonstrate the generation of Berry curvature dipole by applied dc electric field in WTe_{2}, which is used to break the symmetry constraint. A linear dependence between the dipole moment of Berry curvature and the dc electric field is observed. The polarization direction of the Berry curvature is controlled by the relative orientation of the electric field and crystal axis, which can be further reversed by changing the polarity of the dc field. Our Letter provides a route to generate and control Berry curvature dipole in broad material systems and to facilitate the development of nonlinear quantum devices.

Surface Engineering of Antisymmetric Linear Magnetoresistance and Spin-Polarized Surface State Transport in Dirac Semimetals.

Topological materials that possess spin-momentum locked surface states provide an ideal platform to manipulate the quantum spin states by electrical means. However, an antisymmetric magnetoresistance (MR) superimposed on the spin-polarized transport signals is usually observed in the spin potentiometric measurements of topological materials, rendering more power loss and reduced signal-to-noise ratio. Here we reveal the mechanism of surface-bulk interaction for the observed antisymmetric linear MR in the spin transport of Dirac semimetal Cd3As2 nanoplates. The antisymmetric linear MR can be eliminated through sample surface modifications. As a consequence, clean signals of charge current induced spin-polarized transport are observed, robust up to room temperature. The purification of spin signals can be attributed to the isolation of surface and bulk transport channels via forming a charge depletion layer with surface modifications. This surface engineering strategy should be valuable for high-performance spintronic devices on topological materials.

Development and innovation of haploid induction technologies in plants.

Haploid induction is one of the main techniques for breeding new varieties of major crops, and its key steps are improving the haploid induction rate and simplifying the induction procedure. With the development and innovation of plant haploid induction technologies, haploid breeding has been widely used in varietal improvement of important crops, showing the advantages of rapid homozygosity of heterozygous genes, shortening breeding period, and improving breeding efficiency. The combination of haploid breeding with crossing breeding, mutation breeding, reverse breeding, and molecular marker-assisted selection will greatly improve the effectiveness of crop breeding. Haploids and doubled haploids have demonstrated their usefulness in production of genetic populations, characterization of gene functions, and transgenic and cytological studies in plants. In this review, we summarize the progress of haploid induction technologies in view of various haploid induction techniques and applications of haploids and double haploids. In particular, the advances on the haploid induction in several major crops by genome editing were briefly described. Finally, we discuss current issues and future perspectives in this field, so as to promote the application of the haploid induction techniques, especially the techniques of creating haploid inducer lines by genome editing in crop breeding.

Topological Semimetal Nanostructures: From Properties to Topotronics.

Characterized by bulk Dirac or Weyl cones and surface Fermi-arc states, topological semimetals have sparked enormous research interest in recent years. The nanostructures, with large surface-to-volume ratio and easy field-effect gating, provide ideal platforms to detect and manipulate the topological quantum states. Exotic physical properties originating from these topological states endow topological semimetals attractive for future topological electronics (topotronics). For example, the linear energy dispersion relation is promising for broadband infrared photodetectors, the spin-momentum locking nature of topological surface states is valuable for spintronics, and the topological superconductivity is highly desirable for fault-tolerant qubits. For real-life applications, topological semimetals in the form of nanostructures are necessary in terms of convenient fabrication and integration. Here, we review the recent progresses in topological semimetal nanostructures and start with the quantum transport properties. Then topological semimetal-based electronic devices are introduced. Finally, we discuss several important aspects that should receive great effort in the future, including controllable synthesis, manipulation of quantum states, topological field effect transistors, spintronic applications, and topological quantum computation.

Improved drought tolerance in wheat plants overexpressing a synthetic bacterial cold shock protein gene SeCspA.

Cold shock proteins (CSPs) enhance acclimatization of bacteria to adverse environmental circumstances. The Escherichia coli CSP genes CspA and CspB were modified to plant-preferred codon sequences and named as SeCspA and SeCspB. Overexpression of exogenous SeCspA and SeCspB in transgenic Arabidopsis lines increased germination rates, survival rates, and increased primary root length compared to control plants under drought and salt stress. Investigation of several stress-related parameters in SeCspA and SeCspB transgenic wheat lines indicated that these lines possessed stress tolerance characteristics, including lower malondialdehyde (MDA) content, lower water loss rates, lower relative Na+ content, and higher chlorophyll content and proline content than the control wheat plants under drought and salt stresses. RNA-seq and qRT-PCR expression analysis showed that overexpression of SeCsp could enhance the expression of stress-responsive genes. The field experiments showed that the SeCspA transgenic wheat lines had great increases in the 1000-grain weight and grain yield compared to the control genotype under drought stress conditions. Significant differences in the stress indices revealed that the SeCspA transgenic wheat lines possessed significant and stable improvements in drought tolerance over the control plants. No such improvement was observed for the SeCspB transgenic lines under field conditions. Our results indicated that SeCspA conferred drought tolerance and improved physiological traits in wheat plants.

The tae-miR408-Mediated Control of TaTOC1 Genes Transcription Is Required for the Regulation of Heading Time in Wheat.

Timing of flowering is not only an interesting topic in developmental biology, but it also plays a significant role in agriculture for its effects on the maturation time of seed. The hexaploid wheat (Triticum aestivum) is one of the most important crop species whose flowering time, i.e. heading time, greatly influences yield. However, it remains unclear whether and how microRNAs regulate heading time in it. In our current study, we identified the tae-miR408 in wheat and its targets in vivo, including Triticum aestivum TIMING OF CAB EXPRESSION-A1 (TaTOC-A1), TaTOC-B1, and TaTOC-D1. The tae-miR408 levels were reciprocal to those of TaTOC1s under long-day and short-day conditions. Wheat plants with a knockdown of TaTOC1s via RNA interference and overexpression of tae-miR408 showed early-heading phenotype. Furthermore, TaTOC1s expression was down-regulated by the tae-miR408 in the hexaploid wheat. In addition, other important agronomic traits in wheat, such as plant height and flag leaf angle, were regulated by both tae-miR408 and TaTOC1s. Thus, our results suggested that the tae-miR408 functions in the wheat heading time by mediating TaTOC1s expression, and the study provides important new information on the mechanism underlying heading time regulation in wheat.

Production and identification of haploid dwarf male sterile wheat plants induced by corn inducer.

BACKGROUND: Using the cross of wheat and maize is a very useful way to produce wheat haploid plants by chromosome elimination. Dwarf male sterile wheat (DMSW) and corn inducer are potential important germplasm for wheat breeding by recurrent selection and doubled haploid strategies. There is no report yet to achieve the haploid plants from DMSW induced by maize inbred line and especially the corn inducer. RESULTS: Haploid plants of DMSW were successfully obtained in this study induced by both maize pollens of inducer line and normal inbred line. The efficiencies for wheat embryos formation and plantlets production induced by the two corn lines had no significant difference. All the eleven haploid wheat plants derived from the male sterile material were identified by botanic appearance, cytology, cytogenetics, and molecular markers. They were all haploid based on their guard cell length of 42.78-42.90 µm compared with the diploid control of 71.52 µm, and their chromosome number of 21 compared with the diploid control of 42. In addition, according to anthers, plant height, and molecular markers, the haploid plants were divided into two types. Eight of them showed dwarf, having no anthers, and the special band of Rht10, and the other three plants displayed normal plant height, having anthers, and not containing the special band of Rht10, indicating that they were originated from the MS2/Rht10 and ms2/rht10 female gametes, respectively. CONCLUSIONS: MS2/Rht10 haploid plants were successfully obtained in this study by using corn inducer and inbred line, and will be employed as candidate materials for the potential cloning of MS2 dominant male gene.

[Description and evaluation of transformation approaches used in wheat].

Genetic transformation is a valuable tool for direct crop improvement and functional genomics study. Unfortunately, wheat is considered as a recalcitrant plant to genetic transformation due to its low efficiency and genotype dependency. To overcome these problems, various transformation methods such as biolistic bombardment, Agrobacterium tumefaciens, pollen-tube pathway, ion implantation, laser microbeams puncture, treatment with polyethylene glycol and ultrasonic wave, and electroporation have been reported in wheat using various types of explants including immature embryos, mature embryos, anthers derived calluses, inflorescences, apical meristems, and other floral organs. In this review, several major transformation approaches and their applications in wheat are reviewed, and potential strategies for the development of safe transgenic wheat plants are discussed. The objective of this review is to provide an update on current status of wheat trans-formation, and to stimulate further research for improving transformation efficiency in wheat.

[Obtaining marker-free transgenic soybean plants with optimal frequency by constructing three T-DNAs binary vector].

Obtaining marker-free plants with high efficiency will benefit the environmental release of transgenic crops. To achieve this point, a binary vector pNB35SVIP1 with three T-DNAs was constructed by using several mediate plasmids, in which one copy of bar gene expression cassette and two copies of VIP1 gene expression cassette were included. EHA101 Agrobacterium strain harboring the final construct was applied to transform soybean (Glycine max) cotyledon nodes. Through 2 - 3 months regeneration and selection on 3 - 5mg/L glufosinate containing medium, transgenic soybean plants were confirmed to be obtained at 0.83% - 3.16%, and co-transformation efficiency of both gene in the same individual reached up to 86.4%, based on southern blot test. By the analysis of PCR, southern blot and northern blot combining with leaf painting of herbicide in T1 progenies, 41 plants were confirmed to be eliminated of bar gene with the frequency of 7.6% . Among the T1 populations tested, the loss of the alien genes happened in 22.7% lines, the silence of bar gene took place in 27.3% lines, and VIP1 gene silence existed in 37.1% marker-free plants. The result also suggested that the plasmid with three T-DNAs might be an ideal vector to generate maker-free genetic modified organism.

GmDREB2, a soybean DRE-binding transcription factor, conferred drought and high-salt tolerance in transgenic plants.

A novel DREB (dehydration responsive element binding protein) homologous gene, GmDREB2, was isolated from soybean. Based on its similarity with AP2 domains, GmDREB2 was classified into A-5 subgroup in DREB subfamily in AP2/EREBP family. Expression of GmDREB2 gene was induced by drought, high salt, and low temperature stresses and abscisic acid treatment. The GmDREB2 bound specifically to DRE element in vitro. Furthermore, the overexpression of GmDREB2 activated expression of downstream genes in transgenic Arabidopsis, resulting in enhanced tolerance to drought and high-salt stresses and did not cause growth retardation. Analysis of free proline contents in transgenic tobacco indicated that the overexpression of GmDREB2 accumulated higher level of free proline compared to the wild type plants under drought condition. The results from this study indicate that this novel soybean GmDREB2 gene functions as an important transcriptional activator and may be useful in improving of plant tolerance to abiotic stresses in plants.

RNA silencing of Waxy gene results in low levels of amylose in the seeds of transgenic wheat (Triticum aestivum L.).

In this study, the level of amylose was reduced in wheat seeds by RNAi strategy. Because the synthesis of amylose is catalyzed by the granule-bound starch synthase I (GBSSI or WAXY protein), the Waxy gene of wheat was isolated from wheat seeds by using RT-PCR. Southern analysis confirmed that there were three Waxy genes in wheat genome. Northern hybridization showed that Waxy mRNA accumulated in seeds following pollination. By RNAi strategy,the 683 bp sense and antisense fragments in reverse orientation separated by a 150 bp intron were cloned into pCAMBIA 3300 just downstream of the maize ub/1 promoter. By Agrobacteriurn-mediated wheat transformation method, four transgenic plants (Cultivar Yangmai 10) were identified by PCR, RT-PCR and leaf painting assay. The level of amylose in the endosperm were significantly reduced in transgenic seeds as checked by iodine staining and analysis of amylose content. The results indicated that RNA silencing of Waxy gene resulted in low level of amylose in the seeds of transgenic wheat.