Search

Key message A 7.9 kb deletion which contains a cyclin-dependent protein kinase inhibitor leads to determinate growth and dwarf phenotype in cucumber. Abstract Plant architecture is a composite character which are mainly defined by shoot branching, internode elongation and shoot determinacy. Ideal architecture tends to increase the yield of plants, just like the case of “Green Revolution” increased by the application of semi-dwarf cereal crop varieties in 1960s. Cucumber (Cucumis sativus L.) is an important vegetable cultivated worldwide, and suitable architecture varieties were selected for different production systems. In this study, we obtained a novel dwarf mutant with strikingly shortened plant height and determinate growth habit. By bulked segregant analysis and map-based cloning, we delimited the dw2 locus to a 56.4 kb region which contain five genes. Among all the variations between WT and dw2 within the 56.4 kb region, a 7.9 kb deletion which resulted in complete deletion of CsaV3_5G035790 in dw2 was co-segregated with the dwarf phenotype. Haplotype analysis and gene expression analysis suggest that CsaV3_5G035790 encoding a cyclin-dependent protein kinase inhibitor (CsSMR1) be the candidate gene responsible for the dwarf phenotype in dw2. RNA-seq analysis shows that several kinesin-like proteins, cyclins and reported organ size regulators are expressed differentially between WT and dw2, which may account for the reduced organ size in dwarf plants. Additionally, the down-regulation of CsSTM and CsWOX9 in dw2 resulted in premature termination of shoot apical meristem development, which eventually reduces the internode number and plant height. Identification and characterization of the CsSMR1 provide a new insight into cucumber architecture modification to be applied to mechanized production system.

The flow control effects on the S809 airfoil produced by an oscillating micro-cylinder placed upstream of the airfoil suction surface were investigated using numerical simulations at Reynold number of 1 × 10 6 and high angles of attack (α) range from 20° to 24°. The oscillating mode and initial position of the micro-cylinder are two main parameters considered in this paper. The numerical results suggest that at the start of a heavy stall angle of attack (α 22°), its aerodynamic performance could only be lightly improved or even deteriorated because of the strong and large adverse separation which could not be controlled effectively by the small oscillating cylinder. It was also found that a better control effect can be obtained when the initial position of the cylinder was set adjacent to the separation point compared with that placed near the leading edge at α = 21°. Furthermore, our results also showed that higher dimensionless oscillating amplitudes and a larger frequency can obtain a higher lift-to-drag ratio when the micro-cylinder was placed at optimal initial position.

Flow separation is a common phenomenon on vertical-axis wind turbine (VAWT), delaying or restraining flow separation is very beneficial to improve the wind energy absorption efficiency of VAWT. This paper first reviews flow separation control methods of airfoil and VAWT. Then the influence of the maximum thickness position and curvature of airfoil on boundary layer suction position is studied on NACA-021 series airfoils. Results show that the effect of suction position is dominated by both the separation point and the maximum position of curvature variation downstream the maximum thickness position. With the maximum thickness position moves downstream, the optimal suction position for airfoil with the largest lift-drag ratio also moves towards to the trailing edge. Furthermore, multi-suction slots are studied on NACA0021 airfoil and also applied on VAWT, keeping the total suction momentum as constant, proper double chordwise suction slots can obtain higher power efficiency for low and high TSRs compared with single suction slots at x/c = 30%.

This paper presents an Orthogonal Time Frequency Space Direct Sequence (OTFS-DS) modulation scheme to provide a more robust link. In this scheme, the information symbols are spread in either the delay or Doppler domain by spreading codes. The proposed scheme can gain extra diversity in the delay or Doppler domain as well as full diversity in the time-frequency domain. Channel adaptive spreading codes are designed to minimize the autocorrelation after OTFS modulation at the delay taps of channel such that the interference is reduced. Simulation results show that OTFS-DS modulation with m-sequences can outperform OTFS modulation by approximately 20 dB over the doubly-selective fading channels, which is 5.1 dB more than the spreading gain of 14.9 dB.

In this paper, a new type of blade model driven by single input for vertical axis wind turbine was developed, and it could achieve synchronous active deformation for both of blade leading edge and trailing edge. Firstly, by taking the concept of ribs and by taking NACA0012 airfoil as an example, the mechanical structure and skin with adhesion mechanism of pre-tightening force was adopted based on the continuous deflection and deformation mode of the blade leading and trailing edges with constant thickness. In this way, the adaptive blade could achieve reciprocating smooth deformation with different cambers. Secondly, the experimental platform for measurement of wind tunnel force and flow visualization was built up, where the smoke wire instrument, seven-hole probe, two-component balance were applied for measuring of quasi steady force and flow visualization under different deformation quantities. Finally, the aerodynamic performance of adaptive blade under different deformation factors was revealed. It is found that within an appropriate range of deformation factor, the blade aerodynamic performance can be improved by deforming. When exceeding the critical camber, the friction resistance becomes a dominant factor effecting blade aerodynamic performance. In all, the experimental results in this paper could provide reference for subsequent unsteady experiments.

In order to achieve high spectral efficiency and low access delay, this paper introduces cyclical non-orthogonal multiple access (NOMA) into unmanned aerial vehicle (UAV)-enabled wireless network. It allows the UAV to communicate with multiple ground users in the same time–frequency resources, cyclically. The minimum throughput over all ground users is maximized by jointly optimizing multiuser communication scheduling with cyclical NOMA and UAV trajectory. It turns out that the maximization of minimum throughput is a mixed integer non-linear non-convex optimization problem. In this paper, this problem is decoupled into two blocks, i.e., the optimization of multiuser communication scheduling with cyclical NOMA and the optimization of UAV trajectory. Then, a joint optimization algorithm is proposed based on the block coordinate descent method. The simulation results demonstrate that the proposed joint optimization method can double the minimum throughput, compared with cyclical TDMA. In addition, it reduces users’ average access delay and UAV’s flying range under the same minimum throughput.

Unisexual flowers provide a useful system for studying plant sex determination. In cucumber (Cucumis sativus L.), three major Mendelian loci control unisexual flower development, Female (F), androecious [a; 1-aminocyclopropane-1-carboxylate {ACC} synthase 11, acs11], and Monoecious (M; ACS2), referred to here as the Female, Androecious, Monoecious (FAM) model, in combination with two genes, gynoecious (g, the WIP family C2H2 zinc finger transcription factor gene WIP1) and the ethylene biosynthetic gene ACC oxidase 2 (ACO2). The F locus, conferring gynoecy and the potential for increasing fruit yield, is defined by a 30.2-kb tandem duplication containing three genes. However, the gene that determines the Female phenotype, and its mechanism, remains unknown. Here, we created a set of mutants and revealed that ACS1G is responsible for gynoecy conferred by the F locus. The duplication resulted in ACS1G acquiring a new promoter and expression pattern; in plants carrying the F locus duplication, ACS1G is expressed early in floral bud development, where it functions with ACO2 to generate an ethylene burst. The resulting ethylene represses WIP1 and activates ACS2 to initiate gynoecy. This early ACS1G expression bypasses the need for ACS11 to produce ethylene, thereby establishing a dominant pathway for female floral development. Based on these findings, we propose a model for how these ethylene biosynthesis genes cooperate to control unisexual flower development in cucumber.

© 2020. Published by The Company of Biologists Ltd. The phytohormone cytokinin regulates diverse aspects of plant growth and development. Our understanding of the metabolism and perception of cytokinin has made great strides in recent years, mostly from studies of the model dicot Arabidopsis Here, we employed a CRISPR/Cas9-based approach to disrupt a subset of cytokinin histidine kinase (HK) receptors in rice (Oryza sativa) in order to explore the role of cytokinin in a monocot species. In hk5 and hk6 single mutants, the root growth, leaf width, inflorescence architecture and/or floral development were affected. The double hk5 hk6 mutant showed more substantial defects, including severely reduced root and shoot growth, a smaller shoot apical meristem, and an enlarged root cap. Flowering was delayed in the hk5 hk6 mutant and the panicle was significantly reduced in size and infertile due to multiple defects in floral development. The hk5 hk6 mutant also exhibited a severely reduced cytokinin response, consistent with the developmental phenotypes arising from a defect in cytokinin signaling. These results indicate that HK5 and HK6 act as cytokinin receptors, with overlapping functions to regulate diverse aspects of rice growth and development.

The purpose of this study was to investigate the influence of selected saccharides (glucose, sucrose, and maltodextrin) on the foam characteristic of egg white liquid. The rheological measurements suggested that increasing sugar concentrations in egg white led to an increase in both apparent viscosity and viscoelasticity. Moreover, the addition of saccharides shortened the relaxation time of hydrogen proton, indicating the presence of hydration effect between sugar and water. Samples with 3% saccharides increased the surface hydrophobicity and reduced the surface tension of the compound egg white solution, leading to the increase of foam capacity and stability. The best foam performance of compound egg white solution was achieved when the 3% maltodextrin was present in egg white, along with the smallest and most homogeneous bubbles. The classification of mixture conditions by the principal component analysis (PCA) and cluster analysis (HCA) revealed that the maltodextrin-egg white system had good scores both at 0.6% and 3% adding ratios, indicating maltodextrin is a suitable additive for the modification of egg white foam properties.

We isolated a mutant showing perturbations in the development of male and female floral organs and fruits. Analysis of the single nucleotide polymorphisms from bulked F2 pools identified the causative variant occurring in Csa4G126690. Csa4G126690 shows high homology to Arabidopsis SEPALLATA2 (SEP2) thus being designated CsSEP2. The causative variant was located on the splicing site of CsSEP2, resulting in the skipping of exon 6 and abolishment of the transcriptional activity. Our data suggest that CsSEP2 is involved in the floral organ and fruits development by conferring transcriptional activity.

Vertical axis wind turbine (VAWT) has become a research hotspot because of its structural advantages and omni-direction capability. While a further performance improvement is needed for its lower power coefficient and complex flow on blades for VAWT. Boundary layer suction (BLS) as an effective separation control method for airfoil can be a potential way to enhance the performance of VAWT. The current study first investigates boundary layer suction momentum on NACA0021 airfoil by numerical simulation. Suction momentums from 0.001 to 0.4 are investigated systematically using steady simulation with SST κ-ω turbulence model. Three zones are concluded by the corrected lift-drag ratio with suction momentum. The corrected lift-drag ratio can be increased to more than 8–14 times higher compared with the airfoil without suction within the 2°–26° angles and suction momentum within 0.02–0.2. The percentage increase in power coefficient for BLS applied on VAWT can reach to about 34.25% at the optimal tip speed ratio (TSR) for boundary layer suction VAWT at TSR = 2.33 for Cμ = 0.0075. The instantaneous power coefficient during one blade revolution and the behavior of vortex and flow structures around the suction blade are also studied to explore the physical mechanism of improving aerodynamic performance.

Structural variations (SVs) represent a major source of genetic diversity. However, the functional impact and formation mechanisms of SVs in plant genomes remain largely unexplored. Here, we report a nucleotide-resolution SV map of cucumber (Cucumis sativas) that comprises 26,788 SVs based on deep resequencing of 115 diverse accessions. The largest proportion of cucumber SVs was formed through nonhomologous end-joining rearrangements, and the occurrence of SVs is closely associated with regions of high nucleotide diversity. These SVs affect the coding regions of 1676 genes, some of which are associated with cucumber domestication. Based on the map, we discovered a copy number variation (CNV) involving four genes that defines the Female (F) locus and gives rise to gynoecious cucumber plants, which bear only female flowers and set fruit at almost every node. The CNV arose from a recent 30.2-kb duplication at a meiotically unstable region, likely via microhomology-mediated break-induced replication. The SV set provides a snapshot of structural variations in plants and will serve as an important resource for exploring genes underlying key traits and for facilitating practical breeding in cucumber.

In this work, lithium-doped tantalum oxide (lithium-Ta2O5) particles were synthesized using a low-temperature hydrothermal method. X-ray photoelectron spectroscopy (XPS) indicated that the state of lithium on the Ta2O5 surface is the Li+ form. The crystal phase of the samples was analyzed using X-ray diffraction (XRD). The analysis revealed that the lithium-Ta2O5 particles are well crystallized into an orthorhombic phase. Calculation from density functional theory (DFT) indicated that the band gap of Ta2O5 narrows when it is doped with lithium, resulting in improved conductivity and electrocatalytic activity over Ta2O5. The electrocatalytic activity of a lithium-Ta2O5 film coated electrode was investigated in a 0.1 mol dm−3 KCl solution containing ascorbic acid (AA) using cyclic voltammetry (CV). The lithium-Ta2O5 film coated electrode has excellent electrocatalytic activity toward the oxidation of AA with much reduced overpotential. The anodic peak potential of AA shifted from 0.72 V (versus Ag|AgCl) on a bare glassy carbon electrode (GCE) to 0.42 V on the lithium-Ta2O5 film coated electrode.

Sex determination in plants gives rise to unisexual flowers that facilitate outcrossing and enhance genetic diversity. In cucumber and melon, ethylene promotes carpel development and arrests stamen development. Five sex-determination genes have been identified, including four encoding 1-aminocyclopropane-1-carboxylate (ACC) synthase that catalyzes the rate-limiting step in ethylene biosynthesis, and a transcription factor gene CmWIP1 that corresponds to the Mendelian locus gynoecious in melon and is a negative regulator of femaleness. ACC oxidase (ACO) converts ACC into ethylene; however, it remains elusive which ACO gene in the cucumber genome is critical for sex determination and how CmWIP1 represses development of female flowers. In this study, we discovered that mutation in an ACO gene, CsACO2, confers androecy in cucumber that bears only male flowers. The mutation disrupts the enzymatic activity of CsACO2, resulting in 50% less ethylene emission from shoot tips. CsACO2 was expressed in the carpel primordia and its expression overlapped with that of CsACS11 in female flowers at key stages for sex determination, presumably providing sufficient ethylene required for proper CsACS2 expression. CmACO3, the ortholog of CsACO2, showed a similar expression pattern in the carpel region, suggesting a conserved function of CsACO2/CmACO3. We demonstrated that CsWIP1, the ortholog of CmWIP1, could directly bind the promoter of CsACO2 and repress its expression. Taken together, we propose a presumably conserved regulatory module consisting of WIP1 transcription factor and ACO controls unisexual flower development in cucumber and melon.

We isolated a mutant showing perturbations in the development of male and female floral organs and fruits. Analysis of the single nucleotide polymorphisms from bulked F2 pools identified the causative variant occurring in Csa4G126690. Csa4G126690 shows high homology to Arabidopsis SEPALLATA2 (SEP2) thus being designated CsSEP2. The causative variant was located on the splicing site of CsSEP2, resulting in the skipping of exon 6 and abolishment of the transcriptional activity. Our data suggest that CsSEP2 is involved in the floral organ and fruits development by conferring transcriptional activity.

Next-generation sequencing enabled a fast discovery of a major QTL controlling early flowering in cucumber, corresponding to the FT gene conditioning flowering time in Arabidopsis. Next-generation sequencing technologies are making it faster and more efficient to establish the association of agronomic traits with molecular markers or candidate genes, which is the requirement for marker-assisted selection in molecular breeding. Early flowering is an important agronomic trait in cucumber (Cucumis sativus L.), but the underlying genetic mechanism is unknown. In this study, we identified a candidate gene for early flowering QTL, Ef1.1 through QTL-seq. Segregation analysis in F2 and BC1 populations derived from a cross between two inbred lines “Muromskij” (early flowering) and “9930” (late flowering) suggested quantitative nature of flowering time in cucumber. Genome-wide comparison of SNP profiles between the early and late-flowering bulks constructed from F2 plants identified a major QTL, designated Ef1.1 on cucumber chromosome 1 for early flowering in Muromskij, which was confirmed by microsatellite marker-based classical QTL mapping in the F2 population. Joint QTL-seq and traditional QTL analysis delimited Ef1.1 to an 890 kb genomic region. A cucumber gene, Csa1G651710, was identified in this region, which is a homolog of the FLOWERING LOCUS T (FT), the main flowering switch gene in Arabidopsis. Quantitative RT-PCR study of the expression level of Csa1G651710 revealed significantly higher expression in early flowering genotypes. Data presented here provide support for Csa1G651710 as a possible candidate gene for early flowering in the cucumber line Muromskij.