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The homeobox family is a large and diverse superclass of genes, many of which act as transcription factors that play important roles in tissue differentiation and embryogenesis in animals. The brown planthopper (BPH), Nilaparvata lugens, is the most destructive pest of rice in Asia, and high fecundity contributes significantly to its ecological success in natural and agricultural habits. Here, we identified 94 homeobox genes in BPH, which could be divided into 75 gene families and 9 classes. This number is comparable to the number of homeobox genes found in the honeybee Apis mellifera, but is slightly less than in Drosophila or the red flour beetle Tribolium castaneum. A spatio-temporal analysis indicated that most BPH homeobox genes were expressed in a development and tissue-specific manner, of which 21 genes were highly expressed in ovaries. RNA interference (RNAi)-mediated functional assay showed that 22 homeobox genes were important for nymph development and the nymph to adult transition, whereas 67 genes were dispensable during this process. Fecundity assay showed that knockdown of 13 ovary-biased genes (zfh1, schlank, abd-A, Lim3_2, Lmxb, Prop, ap_1, Not, lab, Hmx, vis, Pknox, and C15) led to the reproductive defect. This is the first comprehensive investigation into homeobox genes in a hemipteran insect and thus helps us to understand the functional significance of homeobox genes in insect reproduction.

The brown planthopper Nilaparvata lugens is one of the most destructive insect pests in Asia, demonstrating high fertility and causing huge crop losses by sucking sap of rice as well as transmitting viruses. However, functional genomic studies on N. lugens are seriously constrained by lack of genetic tools. Here, we employed two eye pigmentation genes to generate germ-line mutations in N. lugens using the CRISPR/Cas9 (clustered regularly interspaced palindromic repeats/CRISPR-associated) system. We showed that injection of single guide RNA of the cinnabar gene of N. lugens (Nl-cn ) into pre-blastoderm eggs induced insertion and deletion (indels) in the founder generation (G 0), which were heritably transmitted to the following G1 generation, leading to bright red compound eyes and ocelli. Mutations of N. lugens white (Nl-w ) generated a high mutant rate of up to 27.3%, resulting in mosaic eyes consisting of white and lightly pigmented ommatidia in both G 0 and G1 individuals. The specificity of CRISPR/Cas9-mediated mutagenesis was further bolstered by PCR and RNA interference-based knockdown analysis. These results show that CRISPR/Cas9-mediated gene editing is achievable in a hemipteran insect, offering a valuable tool for the study of functional genomics and pest management in this planthopper species.

The homeotic complex (Hox) gene Ultrabithorax (Ubx) plays pivotal roles in modifying specific morphological differences among the second (T2), the third thoracic (T3), and the first abdomen (A1) segment in several insects. Whether Ubx regulates wing dimorphism and other morphological traits in the delphacid family (order Hemiptera) remains elusive. In this study, we cloned a full-length Ubx ortholog (NlUbx) from the wing-dimorphic planthopper Nilaparvata lugens, and identified two NlUbx isoforms. RNA-interference (RNAi)-mediated silencing of NlUbx in short-winged BPH nymphs significantly induced the development of wing-like appendages from T3 wingbuds, and this effect is likely mediated by the insulin/insulin-like signaling pathway. RNAi knockdown of NlUbx in long-winged BPH nymphs led to a transformation from hindwings to forewings. Additionally, silencing of NlUbx not only dramatically changed the T3 morphology, but also led to jumping defect of T3 legs. First-instar nymphs derived from parental RNAi had an additional leg-like appendages on A1. These results suggest that Ubx plays a role in determining some morphological traits in delphacid planthoppers, and thus help in understanding evolution of morphological characteristics in arthropods.

Valve orifice is the common place that the cavitation easily occurs in the hydraulic systems. This paper introduces a criteria to estimate the inception of the cavitation of the V-type valve orifice with the stress state. Based on this criteria, a cavitation model which considers the dynamics of the cavity and incompressible gas is proposed to analyze the pressure, stress and the cavitation distribution of the phase in the V-type orifice. The distributions of the cavitation along the axis and the cross section are analyzed. The simulation results show that the cavitation is easily occurred in the downstream just after the orifice and the bubbles are mostly gathered in the top of the cross section which is vertical to the axis of the flow field. The simulation results is reasonable according to the facts. Accordingly, the cavitation of the V-type orifice is predicted reasonably. The research and results of this paper are useful for the design of the hydraulic valves.

Histone acetylation is a specific type of chromatin modification that serves as a key regulatory mechanism for many cellular processes in mammals. However, little is known about its biological function in invertebrates. Here, we identified 12 members of histone deacetylases (NlHDACs) in the brown planthopper (BPH), Nilaparvata lugens. RNAi-mediated silencing assay showed that NlHdac1, NlHdac3 and NlHdac4 played critical roles in female fertility via regulating ovary maturation or ovipositor development. Silencing of NlHdac1 substantially increased acetylation level of histones H3 and H4 in ovaries, indicating NlHDAC1 is the main histone deacetylase in ovaries of BPH. RNA sequencing (RNA-seq) analysis showed that knockdown of NlHdac1 impaired ovary development via multiple signalling pathways including the TOR pathway. Acoustic recording showed that males with NlHdac1 knockdown failed to make courtship songs, and thus were unacceptable to wild-type females, resulting in unfertilized eggs. Competition mating assay showed that wild-type females overwhelmingly preferred to mate with control males over NlHdac1-knockdown males. These findings improve our understanding of reproductive strategies controlled by HDACs in insects and provide a potential target for pest control.

Intrinsic DNA methylation pattern is an integral component of the epigenetic network in many eukaryotes. DNA methylation plays an important role in regulating gene expression in eukaryotes. Biological stress in plant provides an inherent epigenetic driving force of evolution. Study of DNA methylation patterns arising from biological stress will help us fully understand the epigenetic regulation of gene expression and DNA methylation of biological functions. The wheat near-isogenic lines TcLr19 and TcLr41 were resistant to races THTT and TKTJ, respectively, and Thatcher is compatible in the interaction with Puccinia triticina THTT and TKTJ, respectively. By means of methylation-sensitive amplified polymorphism (MSAP) analysis, the patterns of cytosine methylation in TcLr19, TcLr41, and Thatcher inoculated with P. triticina THTT and TKTJ were compared with those of the untreated samples. All the DNA fragments, each representing a recognition site cleaved by each or both of isoschizomers, were amplified using 60 pairs of selective primers. The results indicated that there was no significant difference between the challenged and unchallenged plants at DNA methylation level. However, epigenetic difference between the near-isogenic line for wheat leaf rust resistance gene Lr41 and Thatcher was present.

Intrinsic DNA methylation pattern is an integral component of the epigenetic network in many eukaryotes. DNA methylation plays an important role in regulating gene expression in eukaryotes. Biological stress in plant provides an inherent epigenetic driving force of evolution. Study of DNA methylation patterns arising from biological stress will help us fully understand the epigenetic regulation of gene expression and DNA methylation of biological functions. The wheat near-isogenic lines TcLr19 and TcLr41 were resistant to races THTT and TKTJ, respectively, and Thatcher is compatible in the interaction with Puccinia triticina THTT and TKTJ, respectively. By means of methylation-sensitive amplified polymorphism (MSAP) analysis, the patterns of cytosine methylation in TcLr19, TcLr41, and Thatcher inoculated with P. triticina THTT and TKTJ were compared with those of the untreated samples. All the DNA fragments, each representing a recognition site cleaved by each or both of isoschizomers, were amplified using 60 pairs of selective primers. The results indicated that there was no significant difference between the challenged and unchallenged plants at DNA methylation level. However, epigenetic difference between the near-isogenic line for wheat leaf rust resistance gene Lr41 and Thatcher was present.