关键词: 黑尾叶蝉, 卵黄原蛋白受体, 基因克隆, 序列分析, 表达模式

Abstract: 【Aim】 Vitellogenin receptor (VgR), which belongs to low-density lipoprotein receptor (LDLR) superfamily, mediates vitellogenin/yolk protein absorption by developing oocytes for embryonic development and plays a critical role in insect reproduction. In order to define the physiological functions of VgR and its roles in reproduction of the green rice leafhopper, Nephotettix cincticeps, we cloned and characterized the VgR gene (NcVgR), and monitored its expression profiles. 【Methods】  NcVgR was cloned using RT-PCR according to previous transcriptomic data of N. cincticeps and analyzed by bioinformatic tools, and the mRNA levels of NcVgR  in different developmental stages and adult tissues were detected via real-time PCR. 【Results】 The complete cDNA of  NcVgR is 6 676 bp in length with a 5 568 bp of open reading frame, encoding a 206 kD protein with 1 855 amino acids including a putative 17-amino-acid signal peptide at the N-terminus. NcVgR has 5 typical conserved domains of LDLR family, including ligand-binding domain (LBD), EGF-precursor homology domain (EGFP), O-linked sugar domain (OLSD), transmembrane domain (TMD) and cytoplasmic domain. Phylogenetic tree analysis indicated that NcVgR was most closely related to N. lugens VgR. Real-time PCR results showed that the expression of NcVgR started at the 5th instar nymphal stage, increased rapidly after adult eclosion, reached the peak at 8 d post adult eclosion, and decreased subsequently. Interestingly, the transcriptional level of NcVgR increased again and reached the peak at 16 d post adult eclosion when N. cincticeps female adults started to lay eggs. The mRNA level of  NcVgR was very specially high in ovary, but only trace level was measured in fat body and gut of female adults. NcVgR was not expressed in both brains of female and male adults. 【Conclusion】 We cloned the NcVgR gene, and demonstrated that it is specifically expressed in ovaries of female adults and displays a higher expression after adult eclosion. Our results provide the molecular information for further studying the regulation mechanisms of reproduction of female N. cincticeps.

Key words: Nephotettix cincticeps, vitellogenin receptor (VgR), gene cloning, sequence analysis, expression profile