Search

Dialeurodes citri is a major pest in citrus producing areas, and large-scale outbreaks have occurred increasingly often in recent years. Lecanicillium attenuatum is an important entomopathogenic fungus that can parasitize and kill D. citri. We separated the fungus from corpses of D. citri larvae. However, the sound immune defense system of pests makes infection by an entomopathogenic fungus difficult. Here we used RNA sequencing technology (RNA-Seq) to build a transcriptome database for D. citri and performed digital gene expression profiling to screen genes that act in the immune defense of D. citri larvae infected with a pathogenic fungus. De novo assembly generated 84,733 unigenes with mean length of 772 nt. All unigenes were searched against GO, Nr, Swiss-Prot, COG, and KEGG databases and a total of 28,190 (33.3%) unigenes were annotated. We identified 129 immunity-related unigenes in transcriptome database that were related to pattern recognition receptors, information transduction factors and response factors. From the digital gene expression profile, we identified 441 unigenes that were differentially expressed in D. citri infected with L. attenuatum. Through calculated Log2Ratio values, we identified genes for which fold changes in expression were obvious, including cuticle protein, vitellogenin, cathepsin, prophenoloxidase, clip-domain serine protease, lysozyme, and others. Subsequent quantitative real-time polymerase chain reaction analysis verified the results. The identified genes may serve as target genes for microbial control of D. citri.

Several fenpropathrin-resistant predatory mites have been reported. However, the molecular mechanism of the resistance remains unknown. In the present study, the Neoseiulus barkeri (N. barkeri) transcriptome was generated using the Illumina sequencing platform, 34,211 unigenes were obtained, and 15,987 were manually annotated. After manual annotation, attentions were attracted to resistance-related genes, such as voltage-gated sodium channel (VGSC), cytochrome P450s (P450s), and glutathione S-transferases (GSTs). A polymorphism analysis detected two point mutations (E1233G and S1282G) in the linker region between VGSC domain II and III. In addition, 43 putative P450 genes and 10 putative GST genes were identified from the transcriptome. Among them, two P450 genes, NbCYP4EV2 and NbCYP4EZ1, and four GST genes, NbGSTd01, NbGSTd02, NbGSTd03 and NbGSTm03, were remarkably overexpressed 3.64-46.69-fold in the fenpropathrin resistant strain compared to that in the susceptible strain. These results suggest that fenpropathrin resistance in N. barkeri is a complex biological process involving many genetic changes and provide new insight into the N. barkeri resistance mechanism. [ABSTRACT FROM AUTHOR]

Panonychus citri McGregor (Trombidiformes: Tetranychidae), the widely distributed citrus red mite, has developed resistance to most registered acaricides. Adaptation of arthropods to extreme environmental conditions has been related to increased expression of their heat shock proteins (HSPs). The objectives of this study were to explore the relationship between HSPs and resistance of Panonychus citri to the acaricide abamectin and the adaptation of Panonychus citri to high temperatures. The full-length cDNA of the HSP90 gene was cloned from an abamectin-sensitive strain of Panonychus citri. This gene consisted of 2,495 nucleotides with a complete open reading frame (ORF) of 2,169 nucleotides. This gene encoded a polypeptide of 721 amino acids with a predicted molecular weight of 83.44 kDa, a theoretical isoelectric point of 5.06, a 3' untranslated region (UTR) of 228 bp, and a 5' UTR of 98 bp. The results of real-time PCR analyses indicated that the expression of the HSP90 gene in P. citri was markedly affected by the concentration of abamectin, the duration of exposure to it and the temperature, suggesting that the up-regulation of the HSP90 gene may play an important role in abamectin resistance and adaptation to high temperatures in Panonychus citri. The results of RNA interference experiments indicated that the HSP90 gene from adult female Panonychus citri was sensitive to down-regulation by double-stranded RNA (0.1-0.2 μg/μL). This study provides a molecular basis for further analysis of the relationships between the HSP90 gene and the resistance of Panonychus citri to abamectin and to high temperatures. [ABSTRACT FROM AUTHOR]