Jun-Zhong Wang

Artificial nanocluster crystal: Lattice of identical Al clusters

A two-dimensional artificial crystal, which is made up of artificial atoms—identical Al clusters with nanometer size and spacing, was fabricated by taking advantage of surface-mediated clustering on a growth template. In situ scanning tunneling microscopy analysis and first-principles total energy calculations were used to determine the atomic structure of the Al nanoclusters. The Al clusters exhibit more remarkable thermal stability than the In clusters we reported previously. Based on our systematic observations and calculations, the formation mechanism and the high stability of these magic clusters are discussed.

Spontaneous assembly of perfectly ordered identical-size nanocluster arrays

Perfectly ordered arrays of identical Al and Ga clusters of nanometre size and spacing were spontaneously obtained using a novel technique, in which surface-mediated magic clustering is used to achieve the identical cluster size while the Si(111)-7 × 7 surface is used as a template for positioning the clusters in order. The atomic structures, formation mechanism and stability of the nanoclusters were studied with in situ scanning tunnelling microscopy combined with first-principles total energy calculations. The very high stability of these nanocluster arrays provides unprecedented opportunities for exploring new physical phenomena and great potential in technological applications.

Transcriptome profiling of the testis reveals genes involved in spermatogenesis and marker discovery in the oriental fruit fly, Bactrocera dorsalis

The testis is a highly specialized tissue that plays a vital role in ensuring fertility by producing spermatozoa, which are transferred to the female during mating. Spermatogenesis is a complex process, resulting in the production of mature sperm, and involves significant structural and biochemical changes in the seminiferous epithelium of the adult testis. The identification of genes involved in spermatogenesis of Bactrocera dorsalis (Hendel) is critical for a better understanding of its reproductive development. In this study, we constructed a cDNA library of testes from male B.u2009dorsalis adults at different ages, and performed de novo transcriptome sequencing to produce a comprehensive transcript data set, using Illumina sequencing technology. The analysis yielded 52u2009016u2009732 clean reads, including a total of 4.65u2009Gb of nucleotides. These reads were assembled into 47u2009677 contigs (average 443u2009bp) and then clustered into 30u2009516 unigenes (average 756u2009bp). Based on BLAST hits with known proteins in different databases, 20u2009921 unigenes were annotated with a cut‐off E‐value of 10−5. The transcriptome sequences were further annotated using the Clusters of Orthologous Groups, Gene Orthology and the Kyoto Encyclopedia of Genes and Genomes databases. Functional genes involved in spermatogenesis were analysed, including cell cycle proteins, metalloproteins, actin, and ubiquitin and antihyperthermia proteins. Several testis‐specific genes were also identified. The transcripts database will help us to understand the molecular mechanisms underlying spermatogenesis in B.u2009dorsalis. Furthermore, 2913 simple sequence repeats and 151u2009431 single nucleotide polymorphisms were identified, which will be useful for investigating the genetic diversity of B.u2009dorsalis in the future.

Detoxification activity and energy cost is attenuated in whiteflies feeding on Tomato yellow leaf curl China virus‐infected tobacco plants

The begomovirus Tomato yellow leaf curl China virus (TYLCCNV) can benefit its vector, the whitefly Bemisia tabaci, through suppressing the defences of their shared host plants. However, the mechanisms of this vector−virus mutualism remain largely unknown on the insect side of the interaction. Here, we compared the transcriptional profiles of female adult whiteflies of B.u2009tabaciu2005Middle East‐Asia Minor 1 feeding on TYLCCNV‐free and TYLCCNV‐infected tobacco plants using the next‐generation sequencing technique and quantitative real‐time PCR. Interestingly, the genes involved in the oxidative phosphorylation (OXPHOS) pathway and detoxification enzyme were down‐regulated in whiteflies feeding on virus‐infected plants. Decreased detoxification activity costs less energy, which may reduce OXPHOS activity. Moreover, the genes involved in redox activity were also down‐regulated, which may indicate that the reduced OXPHOS activity decreased reactive oxygen species production. Reduced detoxification activity is likely to attenuate energy costs, thereby enhancing the performance of whiteflies on virus‐infected plants. These results provide further insight into the mechanisms of the plant‐mediated whitefly−virus mutualism. Moreover, our study suggests that investigating the transcriptional profiles on the insect side of the interaction can advance our understanding of the tripartite interactions.

De novo characterization of the Dialeurodes citri transcriptome: mining genes involved in stress resistance and simple sequence repeats (SSRs) discovery

The citrus whitefly, Dialeurodes citri (Ashmead), is one of the three economically important whitefly species that infest citrus plants around the world; however, limited genetic research has been focused on D. citri, partly because of lack of genomic resources. In this study, we performed de novo assembly of a transcriptome using Illumina paired‐end sequencing technology (Illumina Inc., San Diego, CA, USA). In total, 36u2009766 unigenes with a mean length of 497 bp were identified. Of these unigenes, we identified 17u2009788 matched known proteins in the National Center for Biotechnology Information database, as determined by Blast search, with 5731, 4850 and 14u2009441 unigenes assigned to clusters of orthologous groups (COG), gene ontology (GO), and SwissProt, respectively. In total, 7507 unigenes were assigned to 308 known pathways. In‐depth analysis of the data showed that 117 unigenes were identified as potentially involved in the detoxification of xenobiotics and 67 heat shock protein (Hsp) genes were associated with environmental stress. In addition, these enzymes were searched against the GO and COG database, and the results showed that the three major detoxification enzymes and Hsps were classified into 18 and 3, 6, and 8 annotations, respectively. In addition, 149 simple sequence repeats were detected. The results facilitate the investigation of molecular resistance mechanisms to insecticides and environmental stress, and contribute to molecular marker development. The findings greatly improve our genetic understanding of D. citri, and lay the foundation for future functional genomics studies on this species.

Chiral Pinwheel Clusters Lacking Local Point Chirality

The supramolecular pinwheel cluster is a unique chiral structure with evident handedness. Previous studies reveal that the chiral pinwheels are composed of chiral or achiral molecules with polar groups, which result in strong intermolecular interactions such as hydrogen-bonding or dipole interactions. Herein, it is shown that the simple linear aromatic molecule, pentacene, can be self-assembled into large chiral pinwheel clusters on the semimetal Bi(111) surface, due to enhanced intermolecular interactions. The pentacene pinwheels reveal two levels of organizational chirality: the chiral hexamers resulting from asymmetric shifting along the long molecular axis, and chiral arrangement of six hexamers with a rotor motif. Furthermore, a new relation between the local point chirality and organizational chirality is identified from the pinwheels: the former is not essential for the latter in 2D pinwheel clusters of the pentacene molecule.

Identification, characterization and functional analysis of a chitin synthase gene in the brown citrus aphid, Toxoptera citricida (Hemiptera, Aphididae)

Chitin synthase (CHS) is a crucial enzyme involved in the final step of the insect chitin biosynthetic pathway. In this study, we cloned the full‐length cDNA sequence of a chitin synthase gene (TCiCHS) from the brown citrus aphid, Toxoptera citricida, an important citrus pest and the main vector of citrus tristeza virus worldwide. TCiCHS was expressed during the entire lifecycle and in all insect tissues examined. Expression was highest in first–second‐instar nymphs, nymph–adult transitions and in the abdomen (6.7‐fold higher than head). Embryos had a higher expression level than the integument. Fourth‐instar nymphs were exposed to 5 and 500 mg/l concentrations of the chitin synthesis inhibitor diflubenzuron (DFB) for 48 h and had the highest mortality at the 500 mg/l concentration. The mRNA expression levels of TCiCHS were significantly enhanced upon the exposure of nymphs to both low and high DFB concentrations. Silencing of TCiCHS occurred through plant‐mediated double‐stranded RNA (dsRNA) feeding. Most dsRNA‐fed nymphs were unable to moult to the next stage, and the expression of TCiCHS decreased 48% compared with controls. These results demonstrate that TCiCHS plays an important role in nymph to adult development, is possibly help identify molecular targets for To. citricida control.

An analysis of the small RNA transcriptome of four developmental stages of the citrus red mite (Panonychus citri).

The citrus red mite (Panonychus citri) can feed on more than 112 plant species around the world. Endogenous small RNAs (sRNAs) have proved to be important components of gene regulation in many eukaryotes. Recently, many sRNAs have been shown to be involved in various biological processes, such as development in many animals, including insects; however, to date, no sRNAs have been reported in the citrus red mite. Using Illumina sequencing, several categories of sRNAs were identified, including 594 known microRNAs (miRNAs) grouped into 206 families and 31 novel miRNAs in the four developmental stages of citrus red mite. In addition, according to bioinformatics analysis and S‐Poly(T) miRNA assays, the expression level of many miRNAs varied among the developmental stages. Furthermore, the prediction of miRNAs target genes and their functional annotation indicated that miRNAs are involved in the regulation of multiple pathways in the citrus red mite. As the first report of the sRNA world in citrus red mite, the present study furthers our understanding of the roles played by sRNAs in the development of citrus red mite and the data may help to develop methods of controlling the pests in the field.

Structural transitions in different monolayers of cobalt phthalocyanine film grown on Bi(1 1 1)

The structural evolution of cobalt phthalocyanine (CoPc) thin films grown on a Bi(1 1 1) surface from the sub-monolayer to the third layer has been investigated with low-temperature scanning tunneling microscopy (STM). Two crucial transitions have been identified during the film epitaxial growth: one is the structural transition from zigzag chains to linear dimerized chains in the monolayer regime; the other is the molecular orientational transition from a flat-lying to a standing-up configuration in the multilayer regime. These results are helpful in understanding the growth mechanism of transition-metal phthalocyanine films on semi-metallic surfaces.

Absolute configuration and chiral self-assembly of rubrene on Bi(111)

We investigated the chiral self-assembly of rubrene molecules on a semi-metallic Bi(111) surface using low-temperature scanning tunneling microscopy. The absolute configuration of isolated rubrene enantiomers was identified from high-resolution images. Two types of homochiral domains of rubrene monomers and hexamers were observed, respectively. For rubrene monomers, chiral separation was spontaneous with each chiral monomer appearing in their respective domain. For rubrene hexamers, two levels of organization chirality were recorded: one is six heterochiral rubrene molecules arranged alternatively in a rubrene hexamer; and the other is a homochiral arrangement of individual hexamers. After annealing at 350 K, a large area of supramolecular self-assembled L- and R-type triangular heterochiral hexamers was obtained at the narrow terrace of Bi(111). Moreover, a molecular chiral inversion from the L-(R-) type to the R-(L-) type occurs during the formation of the hexamer domain structure and can be attributed to the enhanced intermolecular interactions governed by the intensive intermolecular extrusion at the narrow terrace.