Chitin synthase is a critical enzyme that catalyzes N-acetylglucosamine to form chitin, which plays an important role in the growth and development of insects. In this study, we identified a chitin synthase gene (CHS) with a complete open reading frame (ORF) of 3180 bp from the genome database of Diaphorina citri, encoding a protein of 1059 amino acid residues with the appropriate signature motifs (EDR and QRRRW). Reverse transcription-quantitative PCR (RT-qPCR) analysis suggested that D. citri CHS (DcCHS) was expressed throughout all developmental stages and all tissues. DcCHS had the highest expression level in the integument and fifth-instar nymph stage. Furthermore, the effects of diflubenzuron (DFB) on D. citri mortality and DcCHS expression level were investigated using fifth-instar nymph through leaf dip bioassay, and the results revealed that the nymph exposed to DFB had the highest mortality compared with control group (Triton-100). Silencing of DcCHS by RNA interference resulted in malformed phenotypes and increased mortality with decreased molting rate. In addition, transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH) also revealed corresponding ultrastructural defects. Our results suggest that DcCHS might play an important role in the development of D. citri and can be used as a potential target for psyllid control.

Seven isolates of a putative cytorhabdovirus (family Rhabdoviridae, order Mononegavirales) designated as citrus-associated rhabdovirus (CiaRV) were identified in citrus, passion fruit, and paper bush from the same geographical area in China. CiaRV, bean-associated cytorhabdovirus (Brazil), and papaya virus E (Ecuador) should be taxonomically classified in the species Papaya cytorhabdovirus. Due to natural mutations, the glycoprotein (G) and P4 genes were impaired in citrus-infecting isolates of CiaRV, resulting in an atypical rhabdovirus genome organization of 3′ leader-N-P-P3-M-L-5′ trailer. The P3 protein of CiaRV shared a common origin with begomoviral movement proteins (family Geminiviridae). Secondary structure analysis and trans-complementation of movement-deficient tomato mosaic virus and potato virus X mutants by CiaRV P3 supported its function in viral cell-to-cell trafficking. The wide geographical dispersal of CiaRV and related viruses suggests an efficient transmission mechanism, as well as an underlying risk to global agriculture. Both the natural phenomenon and experimental analyses demonstrated presence of the “degraded” type of CiaRV in citrus, in parallel to “undegraded” types in other host plant species. This case study shows a plant virus losing the function of an important but nonessential gene, likely due to host shift and adaption, which deepened our understanding of course of natural viral diversification.

A multiplex reverse transcription polymerase chain reaction (multiplex RT-PCR) assay was developed to enable the simultaneous detection and differentiation of four viruses that infect passion fruit, citrus-associated rhabdovirus (CiaRV), East Asian Passiflora virus (EAPV), Passiflora latent virus (PLV), and Telosma mosaic virus (TeMV). The optimized parameters included the primer concentration, annealing temperature, extension time, and number of cycles. The established multiplex RT-PCR assay produced the corresponding products with sizes of 597 bp, 529 bp, 320 bp, and 235 bp, which were specific for CiaRV, EAPV, PLV, and TeMV, respectively. The fragments could be distinguished clearly by agarose gel electrophoresis. The detection limit of the assay was 100 pg of total RNA for CiaRV and EAPV, 10 pg of total RNA for PLV, and 1.0 ng of total RNA for TeMV. The multiplex RT-PCR assay was also tested using field samples, and the results showed that the developed assay could detect the viruses in single or multiple infections of passion fruit. The multiplex RT-PCR established here will be quite helpful for the diagnosis of passion fruit infected with various combinations of the four viruses in the field.

Papaya leaf curl China virus (PaLCuCNV), a monopartite begomovirus, belongs to genus Begomovirus, family Geminiviridae. It was originally reported on Carica papaya L. in Guangxi province of China (...