Characterization of Vitellogenin and Vitellogenin Receptor of Conopomorpha sinensis Bradley and Their Responses to Sublethal Concentrations of Insecticide

Abstract

Conopomorpha sinensis Bradley is the dominant borer pest of Litchi chinesis and Euphoria longan. Current management of C. sinensis relies upon insecticide application to adult moths. In addition to the direct mortality induced by insecticides, a sublethal dose of insecticides also affects growth, survival, and reproduction in the exposed insects. Vitellogenin (Vg) and vitellogenin receptor (VgR) are normally identified as essential reproduction-related proteins in insects. In this study, we characterized these two genes from C. sinensis, and investigated their differential responses to sublethal concentrations of insecticide. Cloned CsVg and CsVgR consist of 5391 and 5424-bp open reading frames, which encode proteins of 1796 and 1807 amino acid residues, respectively. The CsVg protein contains the typical vitellogenin, DUF1943 and VWFD domains as other reported lepidopteran Vgs. The CsVgR was characterized as a typical low density lipoprotein receptor with two highly conserved LBD and EGF precursor domains, one hydrophobic transmembrane domain, one cytoplasmic domain, and 13 putative N-glycosylation sites. We next assessed the sublethal effect of four major insecticides on egg-laying in C. sinensis. The toxicity against C. sinensis varied among the insecticides tested, with LC50 values ranging from 0.23 ppm for chlorpyrifos to 20.00 ppm for β-cypermethrin, among which emamectin benzoate (EB) showed a significant negative impact on egg-laying, survival rate, ovarian development, and mating rate of C. sinensis at LC30 doses. Further investigation showed that the transcriptional level of CsVg and CsVgR were impaired in different way at 24, 48, and 72 h after EB exposure, and this result was in agreement with the diminished egg-laying of C. sinensis in the sublethal concentration EB-treated group. A repressed transcription level of CsVgR was observed at 48 h after treatment, suggesting that EB elicits a delayed response in the abundance of CsVgR. These results established different roles of CsVg and CsVgR in response to the sublethal effect of insecticides. CsVg might be a better parameter than CsVgR for assessing the effect of sublethal insecticides on reproduction in C. sinensis.

Molecular Characterization of Vitellogenin and Its Receptor in Sogatella furcifera, and Their Function in Oocyte Maturation

“…We cloned and identified the ORF sequences of SfVg and SfVgR from S. furcifera and analyzed the molecular characteristics of these genes. As expected, the amino acid sequence of SfVg contains the LPD_N, VWD and DUF1943 domains, all of which are highly conserved in most insects (Tufail et al, 2010;Wu et al, 2018;Yao et al, 2018). The motifs GL/ICG, DGXR and K/RXXR/K are also regarded as conserved domains in insect Vg proteins (Sappington and Raikhel, 1998;Upadhyay et al, 2016) and we found a GLCG motif at the C-terminal of SfVg.…”

“…VgR belongs to the low-density lipoprotein receptor (LDLR) family (Tufail and Takeda, 2009;Zhao et al, 2018). The amino acid sequences of VgR include five highly conserved and functionally different amino acids domains; a ligand binding domain (LBD), an epidermal growth factorprecursor domain (EGF), an O-linked sugar domain, low-density lipoprotein-receptor Tyr-Trp-Thr-Asp (YWTD) repeats and a transmembrane domain (Sappington and Raikhel, 1998;Tufail and Takeda, 2009;Shang et al, 2018;Yao et al, 2018).…”

Effects of Sublethal Concentrations of Insecticides on the Fecundity of Sogatella furcifera (Hemiptera: Delphacidae) via the Regulation of Vitellogenin and Its Receptor

“…In Chilo suppressalis , the sublethal concentration of chlorantraniliprole significantly inhibited CsVg expression ( Huang et al 2016 ). In Conopomorpha sinensis , the sublethal concentration of emamectin benzoate significantly inhibited Vg expression ( Yao et al 2018 ). Overall, these results indicate that insecticides affect insect reproduction via stimulation or inhibition by regulating Vg gene expression and synthesis and its transfer to the ovary.…”

Molecular Features and Expression Patterns of Vitellogenin Receptor in Calliptamus italicus (Orthoptera: Acrididae)

“…Reproduction is one of the most important physiological behaviors of insects, which is also the basis for the population growth. Further investigations on the processes of reproduction and underlying mechanisms of the injurious insects could reveal potential molecular targets for the prevention of the insects, which are current research hotspots across the world (Roy et al 2018; Shang et al 2018; Yao et al 2018; Zhao et al 2018; Liu et al 2019).…”

“…Vitellogenin receptor is the exclusive receptor for endocytosis of vitellogenesis, which has a critical role in the uptake of vitellogenesis (Tufail and Takeda 2009). Previous studies have shown that when the expression of VgR gene is abnormal, the deposition of vitellin in oocytes is disrupted, which in turn delays the development of ovary and can even lead to female sterility (Lu et al 2015; Upadhyay et al 2016; Shang et al 2018; Yao et al 2018).…”