High-purity and wide-angle reflective structural colors based on an all-dielectric Fabry-Pérot cavity structure.

High-purity structural colors with low fabrication cost are in demand for their commercial applications. Here, we demonstrate an all-dielectric Fabry-Pérot cavity structure consisting of four-layer lossy and lossless dielectric films alternately stacked for producing high-purity and angle-invariant reflective colors. Multiple cavity resonances function together to significantly suppress the undesired reflection with the enhanced optical absorption, leading to a distinct and saturated color with a high efficiency of ∼70%. Besides, due to the high refractive indices of constituent materials, the color appearance of the designed structure can be maintained well at ±50° incident angle for two polarization states. The excellent color performance of the proposed device together with cost-effective manufacturing convenience opens up new avenues for their large-area applications in various areas.

Field Manipulations in On-Chip Micro/Nanoscale Lasers Based on Colloid Nanocrystals.

Owning to merits such as bandgap tunability, solution processability, large absorption coefficients, and high photoluminescence quantum yields, colloidal quantum dots (CQDs) emerged as a promising gain material to make on-chip micro/nanoscale lasers with high silicon compatibility. In this paper, we review the recent progress in CQD on-chip micro/nanoscale lasers, with a special focus on the physical properties achieved through field manipulation schemes in different types of cavities. Key aspects include manipulating and engineering wavelength, polarization, and direction as well as coupling and light extraction. Finally, we give our prospects for future research directions toward the integration of robust CQD nano/microscale lasers with photonic integrated circuits.

Angle-Insensitive Ultrathin Broadband Visible Absorber Based on Dielectric-Semiconductor-Lossy Metal Film Stacks.

Ultrathin broadband absorbers with high efficiency, wide angular tolerance, and low fabrication cost are in demand for various applications. Here, we present an angle-insensitive ultrathin (<150 nm) broadband absorber with an average 96.88% (experiment) absorptivity in the whole visible range by utilizing a simple dielectric-semiconductor-lossy metal triple-layer film structure. The excellent broadband absorption performance of the device results from the combined action of the enhanced absorptions in the semiconductor and lossy metal layers exploiting strong interference effects and can be maintained over a wide viewing angle up to ±60°. Benefiting from the lossy metal providing additional absorption, our design reduces the requirement for the semiconductor's material dispersion and has great flexibility in the material selection of the metal layer. Additionally, the lithography-free nature of the proposed broadband visible absorber provides a high-throughput fabrication convenience, thus holding great potential for its large-area applications in various fields.

Comparative Analysis of Salt Responsive MicroRNAs in Two Sweetpotato [Ipomoea batatas (L.) Lam.] Cultivars With Different Salt Stress Resistance.

Sweetpotato [Ipomoea batatas (L.) Lam.] is an important food, vegetable and economic crop, but its productivity is remarkably affected by soil salinity. MiRNAs are a class of endogenous non-coding small RNAs that play an important role in plant resistance to salt stress. However, the function of miRNAs still remains largely unknown in sweetpotato under salt stress. Previously, we identified salt-responsive miRNAs in one salt-sensitive sweetpotato cultivar "Xushu 32." In this study, we identified miRNAs in another salt-tolerant cultivar "Xushu 22" by high-throughput deep sequencing and compared the salt-responsive miRNAs between these two cultivars with different salt sensitivity. We identified 687 miRNAs in "Xushu 22," including 514 known miRNAs and 173 novel miRNAs. Among the 759 miRNAs from the two cultivars, 72 and 109 miRNAs were specifically expressed in "Xushu 32" and "Xushu 22," respectively, and 578 miRNAs were co-expressed. The comparison of "Xushu 32" and "Xushu 22" genotypes showed a total of 235 miRNAs with obvious differential expression and 177 salt-responsive miRNAs that were obviously differently expressed between "Xushu 32" and "Xushu 22" under salt stress. The target genes of the miRNAs were predicted and identified using the Target Finder tool and degradome sequencing. The results showed that most of the targets were transcription factors and proteins related to metabolism and stress response. Gene Ontology analysis revealed that these target genes are involved in key pathways related to salt stress response and secondary redox metabolism. The comparative analysis of salt-responsive miRNAs in sweetpotato cultivars with different salt sensitivity is helpful for understanding the regulatory pattern of miRNA in different sweetpotato genotypes and improving the agronomic traits of sweetpotato by miRNA manipulation in the future.

Identification and Functional Characterization of Plant MiRNA Under Salt Stress Shed Light on Salinity Resistance Improvement Through MiRNA Manipulation in Crops.

Salinity, as a major environmental stressor, limits plant growth, development, and crop yield remarkably. However, plants evolve their own defense systems in response to salt stress. Recently, microRNA (miRNA) has been broadly studied and considered to be an important regulator of the plant salt-stress response at the post-transcription level. In this review, we have summarized the recent research progress on the identification, functional characterization, and regulatory mechanism of miRNA involved in salt stress, have discussed the emerging manipulation of miRNA to improve crop salt resistance, and have provided future direction for plant miRNA study under salt stress, suggesting that the salinity resistance of crops could be improved by the manipulation of microRNA.

Intraband hot-electron photoluminescence of a silver nanowire-coupled gold film via high-order gap plasmons.

We report a strong one-photon photoluminescence (PL) behavior of a silver nanowire directly coupled gold film. The PL peak position of the silver nanowire-coupled gold film deviates from the intrinsic interband transition of gold materials and is not sensitive to the diameter change of the silver nanowire. We attribute this strong PL behavior to the intraband transition of hot electrons dominated by high-order gap plasmons, which are excited in the ultra-small gap formed by an ultra-thin polyvinyl pyrrolidone (PVP) layer coated on the silver nanowire. The results show that the energy required for the strong PL of the heterogeneous system mainly comes from the gold film, acting as an incident energy absorber enhanced by the high-order gap plasmons, while the silver nanowire acts an efficient incident energy focusing antenna. In situ Raman scattering spectra and time-resolved PL intensity integral curves were used to record the carbonization and disappearance process of PVP. The understanding of the PL behavior of the silver nanowire directly coupled gold film proves the universality of plasmon-modulated PL theory and is also of great significance to improve the generation and utilization efficiency of hot electrons with high-order gap plasmons in the fields of catalysis and incident energy capture.

Periodic planar Fabry-Perot nanocavities with tunable interference colors based on filling density effects.

Structural colors of high performance and economically feasible fabrication are desired in various applications. Herein, we demonstrate that reflective full-color filters based on the interference effect can be realized in periodic Fabry-Perot (F-P) nanocavity arrays of the same thickness. Enabled by simply adjusting the nanocavity size and array period, the resonant wavelengths can be successively tuned in the whole visible light range, which is mainly attributed to the varied effective refractive index introduced by the different filling density of the F-P nanocavity. Compared to the plasmonic colors utilizing the similar nanostructures, the proposed interference colors offer unique advantages of higher color contrast, wider gamut, and lower fabrication requirements. Besides, these color filters do not involve modulating the vertical dimensions of the F-P nanocavities, which is conducive to the monolithic integration of multicolor optical cavities and their large-area applications in consumable products combined with replica patterning techniques, such as nanoimprinting and soft lithography.

Recent advances in focused ion beam nanofabrication for nanostructures and devices: fundamentals and applications.

The past few decades have witnessed growing research interest in developing powerful nanofabrication technologies for three-dimensional (3D) structures and devices to achieve nano-scale and nano-precision manufacturing. Among the various fabrication techniques, focused ion beam (FIB) nanofabrication has been established as a well-suited and promising technique in nearly all fields of nanotechnology for the fabrication of 3D nanostructures and devices because of increasing demands from industry and research. In this article, a series of FIB nanofabrication factors related to the fabrication of 3D nanostructures and devices, including mechanisms, instruments, processes, and typical applications of FIB nanofabrication, are systematically summarized and analyzed in detail. Additionally, current challenges and future development trends of FIB nanofabrication in this field are also given. This work intends to provide guidance for practitioners, researchers, or engineers who wish to learn more about the FIB nanofabrication technology that is driving the revolution in 3D nanostructures and devices.

High-throughput deep sequencing reveals the important role that microRNAs play in the salt response in sweet potato (Ipomoea batatas L.).

BACKGROUND: MicroRNAs (miRNAs), a class of small regulatory RNAs, have been proven to play important roles in plant growth, development and stress responses. Sweet potato (Ipomoea batatas L.) is an important food and industrial crop that ranks seventh in staple food production. However, the regulatory mechanism of miRNA-mediated abiotic stress response in sweet potato remains unclear. RESULTS: In this study, we employed deep sequencing to identify both conserved and novel miRNAs from salinity-exposed sweet potato cultivars and its untreated control. Twelve small non-coding RNA libraries from NaCl-free (CK) and NaCl-treated (Na150) sweet potato leaves and roots were constructed for salt-responsive miRNA identification in sweet potatoes. A total of 475 known miRNAs (belonging to 66 miRNA families) and 175 novel miRNAs were identified. Among them, 51 (22 known miRNAs and 29 novel miRNAs) were significantly up-regulated and 76 (61 known miRNAs and 15 novel miRNAs) were significantly down-regulated by salinity stress in sweet potato leaves; 13 (12 known miRNAs and 1 novel miRNAs) were significantly up-regulated and 9 (7 known miRNAs and 2 novel miRNAs) were significantly down-regulated in sweet potato roots. Furthermore, 636 target genes of 314 miRNAs were validated by degradome sequencing. Deep sequencing results confirmed by qRT-PCR experiments indicated that the expression of most miRNAs exhibit a negative correlation with the expression of their targets under salt stress. CONCLUSIONS: This study provides insights into the regulatory mechanism of miRNA-mediated salt response and molecular breeding of sweet potatoes though miRNA manipulation.

Genome-wide identification, characterisation and expression profile analysis of DEAD-box family genes in sweet potato wild ancestor Ipomoea trifida under abiotic stresses.

BACKGROUND: DEAD-box protein family is the largest subfamily of RNA helicases and plays an important role in RNA metabolism and plant growth, development, and stress responses. Although DEAD-box genes have been characterized in various major crop plants, their identification and characterization in Convolvulaceae is still in infancy. Sweet potato (Ipomoea batatas, in Convolvulaceae) is the seventh most important crop in the world. Ipomoea trifida is one of the ancestors of sweet potato and is an effective resource for sweet potato cross-breeding. OBJECTIVE: Identification and characterisation of DEAD-box transcription factors in sweet potato wild ancestor I. trifida genome. METHOD: A systematic genome-wide analysis was conducted to identify the DEAD-box transcription factors in the I. trifida genome. RESULTS: We identified 17 ItfDEAD-box genes which distributed unevenly on the nine chromosomes of I. trifida and encoded 29 DEAD transcripts. The phylogenetic analysis classified the DEAD-box proteins into nine groups named I-IX. Homology model prediction of ItfDEAD-box proteins obtained 14 models which lay a preliminary foundation for the further functional exploration of the ItfDEAD-box proteins. The tissue-specific and abiotic stress-responsive expression profiles of ItfDEAD-box genes were analyzed in different tissues and under abiotic stress responses by RNA-seq data and confirmed by quantitative PCR analysis. Some genes were significantly up- or down-regulated by different abiotic stress, suggesting that ItfDEAD-box plays a crucial role in stress responses in I. trifida. CONCLUSION: The identification and gene expression of the ItfDEAD-box gene family might shed light on the function exploration of DEAD-box gene in I. trifida and promote the molecular breeding of sweet potato.

Genome-wide identification, structural and gene expression analysis of the bZIP transcription factor family in sweet potato wild relative Ipomoea trifida.

BACKGROUND: The basic leucine zipper (bZIP) transcription factor is one of the most abundant and conserved transcription factor families. In addition to being involved in growth and development, bZIP transcription factors also play an important role in plant adaption to abiotic stresses. RESULTS: A total of 41 bZIP genes that encode 66 proteins were identified in Ipomoea trifida. They were distributed on 14 chromosomes of Ipomoea trifida. Segmental and tandem duplication analysis showed that segmental duplication played an important role in the ItfbZIP gene amplification. ItfbZIPs were divided into ten groups (A, B, C, D, E, F, G, H, I and S groups) according to their phylogenetic relationships with Solanum lycopersicum and Arabidopsis thaliana. The regularity of the exon/intron numbers and distributions is consistent with the group classification in evolutionary tree. Prediction of the cis-acting elements found that promoter regions of ItfbZIPs harbored several stress responsive cis-acting elements. Protein three-dimensional structural analysis indicated that ItfbZIP proteins mainly consisted of α-helices and random coils. The gene expression pattern from transcriptome data and qRT-PCR analysis showed that ItfbZIP genes expressed with a tissue-specific manner and differently expressed under various abiotic stresses, suggesting that the ItfbZIPs were involved in stress response and adaption in Ipomoea trifida. CONCLUSIONS: Genome-wide identification, gene structure, phylogeny and expression analysis of bZIP gene in Ipomoea trifida supplied a solid theoretical foundation for the functional study of bZIP gene family and further facilitated the molecular breeding of sweet potato.

Genome-wide identification and expression analysis of glycine-rich RNA-binding protein family in sweet potato wild relative Ipomoea trifida.

Glycine-rich RNA-binding proteins (GRPs) contain RNA recognition motif (RRM) and glycine-rich domains at the N- or C-terminus, respectively, and they participate in varied physiological and biochemical processes, as well as environmental stresses. Sweet potato from the genus Ipomoea is one of the most important crops. However, the role of the GRP gene family in Ipomoea plant species has not been reported yet. At the same time, the genome of sweet potato remains to be elucidated, but the genome of I. trifida which is most probably the progenitor of the sweet potato was released recently. In this regard, we carried out genome-wide analysis of GRP family members in I. trifida. Here, we identified nine GRP genes in I. trifida and investigated their motif distribution, promoters and gene structure. Subsequently, we performed phylogenetic analysis with the GRP genes from I. trifida, Arabidopsis thaliana, Zea mays L. and Oryza sativa to investigate their phylogenetic relationship. Moreover, we studied the expression patterns of ItGRPs in the roots, stems, young and mature leaves and flowers and found that ItGRP genes were tissue-specific. Meanwhile, the expression profiles under four abiotic stress conditions, including heat, cold, salt and drought stress treatments, revealed that some genes were markedly up-regulated or down-regulated. Taken together, our findings will provide reference to studies on the function of GRP genes in the development and stress response of I. trifida.

Stepwise-Nanocavity-Assisted Transmissive Color Filter Array Microprints.

Visible-light color filters using patterned nanostructures have attracted much interest due to their various advantages such as compactness, enhanced stability, and environmental friendliness compared with traditional pigment or dye-based optical filters. While most existing studies are based on planar nanostructures with lateral variation in size, shape, and arrangement, the vertical dimension of structures is a long-ignored degree of freedom for the structural colors. Herein, we demonstrate a synthetic platform for transmissive color filter array by coordinated manipulations between height-varying nanocavities and their lateral filling fractions. The thickness variation of those nanocavities has been fully deployed as an alternative degree of freedom, yielding vivid colors with wide gamut and excellent saturation. Experimental results show that the color-rendering capability of the pixelated nanocavities can be still retained as pixels are miniaturized to 500 nm. Crosstalk between closely spaced pixels of a Bayer color filter arrangement was calculated, showing minimal crosstalk for 1 µm2 square subpixels. Our work provides an approach to designing and fabricating ultracompact color filter arrays for various potential applications including stained-glass microprints, microspectrometers, and high-resolution image sensing systems.

PRR11 is a novel gene implicated in cell cycle progression and lung cancer.

Identification and functional analysis of novel potential cancer-associated genes is of great importance for developing diagnostic, preventive and therapeutic strategies for cancer treatment and management. In the present study, we isolated and identified a novel gene, proline-rich protein 11 (PRR11), implicated in both cell cycle progression and lung cancer. Our results showed that PRR11 was periodically expressed in a cell cycle-dependent manner, and RNAi-mediated silencing of PRR11 caused significant S phase arrest as well as growth retardation in HeLa cells. Moreover, PRR11 was overexpressed at both mRNA and protein levels in lung cancer tissues as compared with normal lung tissues. Large scale in silico analysis of clinical microarray datasets also indicated that high expression of PRR11 was significantly associated with poor prognosis in lung cancer patients. RNAi-mediated silencing of PRR11 caused S phase arrest, suppressed cellular proliferation, colony formation ability in lung cancer cells and inhibited tumorigenic potential in nude mice. Knockdown of PRR11 also inhibited cell migration and invasion ability in lung cancer cells. Furthermore, microarray analysis revealed that PRR11 knockdown caused the dysregulation of multiple critical pathways and various important genes involved in cell cycle, tumorigenesis and metastasis (e.g. CCNA1, RRM1, MAP4K4 and EPB41L3). Taken together, our results strongly demonstrated that this newly identified gene, PRR11, had a critical role in both cell cycle progression and tumorigenesis, and might serve as a novel potential target in the diagnosis and/or treatment of human lung cancer.

NFBD1/MDC1 is a protein of oncogenic potential in human cervical cancer.

A large nuclear protein of 2089 amino acids, NFBD1/MDC1 has recently been implicated in tumorigenesis and tumor growth. In this study, we investigated its expression in cervical cancers and explored its function using gene knockdown approaches. We report here that NFBD1 expression is substantial increased in 24 of 39 cases (61.5%) of cervical cancer tissues at the mRNA level and in 35 of 60 cases (58.3%) at the protein level compared with the case matched normal tissues. Tumors with higher grade of malignancy tend to have higher levels of NFBD1 expression. By infecting cells with retroviruses expressing NFBD1 shRNA, we successfully knocked down NFBD1 expression in cervical cancer cell lines HeLa, SiHa, and CaSki. NFBD1 knockdown cells display significant growth inhibition, cell cycle arrest, higher apoptotic rate, and enhanced sensitivity to adriamycin. Furthermore, NFBD1 knockdown also inhibits the growth of HeLa cells in nude mice. Western blot analyses further revealed that NFBD1 knockdown induced Bax, Puma, and Noxa while down-regulating Bcl-2; it also up-regulated cytochrome C and activated caspases 3 and 9. Therefore, the function of NFBD1 may be involved in the CDC25C-CyclinB1/CDC2 pathway at the G2/M checkpoint, and the cytochrome C/caspase 3 apoptotic pathway. Since expression of NFBD1 seems to be related to the oncogenic potential of cervical cancer, and suppression of its expression can inhibit cancer cell growth both in vitro and in vivo, NFBD1 may be a potential therapeutic target in human cervical cancer.

Rapid functional screening of effective siRNAs against Plk1 and its growth inhibitory effects in laryngeal carcinoma cells.

Plk 1 is overexpressed in many human malignancies including laryngeal carcinoma. However, its therapeutic potential has been never examined in laryngeal carcinoma. In the present study, a simple cellular morphology-based strategy was firstly proposed for rapidly screening the effective siRNAs against Plk1. Furthermore, we investigated the effects of Plk1 depletion via a novel identified effective siRNA against Plk1, Plk1 siRNA-607, on human laryngeal carcinoma Hep-2 cells. The results indicated that Plk1 siRNA-607 transfection resulted in a significant inhibition in Plk1 expression in cells, and subsequently caused a dramatic mitotic cell cycle arrest followed by massive apoptotic cell death, and eventually resulted in a significant decrease in growth and viability of the laryngeal carcinoma cells. Taken together, our present study not only suggests a simple strategy for rapidly screening effective siRNAs against Plk1 but also implicates that Plk1 may serve as a potential therapeutic target in human laryngeal carcinoma.

Growth inhibition, morphology change, and cell cycle alterations in NFBD1-depleted human esophageal cancer cells.

NFBD1/MDC1 is a large nuclear protein mainly participating in DNA damage response, indicating its therapeutic potential as a radio-/chemosensitizer target in cancer field. Esophageal cancer ranks among one of the most frequent cause of cancer death in the world. In this study, we used three representative esophageal cancer cell lines to investigate the effects of NFBD1 silencing on cell proliferation, cell morphology, and cell cycle distribution. Synthetic small interfering RNA (siRNA) duplexes against NFBD1 were introduced into three esophageal cancer cell lines, which subsequently resulted in a significant inhibition in NFBD1 expression in the cells. Our results have shown that a targeted siRNA depletion of NFBD1 resulted in a significant growth inhibition, morphology change, and cell cycle alterations in esophageal cancer cells. Furthermore, NFBD1 depletion also sensitized all the three esophageal cancer cell lines to chemotherapeutic agents including adriamycin and cisplatin. Taken together, our study strongly suggested that NFBD1 may serve as a potential therapeutic target in human esophageal cancer.

Silencing of polo-like kinase (Plk) 1 via siRNA causes inhibition of growth and induction of apoptosis in human esophageal cancer cells.

Esophageal cancer ranks among one of the most frequent causes of cancer death in the world. Polo-like kinase 1 (Plk1) is overexpressed in human tumors and has prognostic value in many cancers including esophageal cancer, indicating its potential as a therapeutic target. In this study, we investigated the therapeutic potential of Plk1 in esophageal cancer using the technique of RNA silencing via small interfering RNA (siRNA). Synthetic siRNA duplexes against Plk1 were introduced into 4 esophageal cancer cell lines, which subsequently resulted in a significant inhibition in Plk1 expression in the cells. We found that the targeted depletion of Plk1 caused a dramatic mitotic catastrophe (mitotic cell cycle arrest as well as defects in several mitotic events such as incomplete separation of sister chromatids and failure of cytokinesis) followed by massive apoptotic cell death, and eventually resulted in a significant decrease in growth and viability of all 4 esophageal cancer cell lines studied. In addition, our results also indicated that the mitotic arrest induced by Plk1 depletion is mediated by the inactivation of the cdc2/cyclin B1 complex. Taken together, our study strongly suggests that Plk1 may serve as a potential therapeutic target in human esophageal cancer.