Dermanyssus gallinae, the poultry red mite (PRM), is a highly deleterious ectoparasite with a global prevalence, predominantly affecting poultry and wild birds, particularly laying hens (Flochlay, et al., 2017). PRM infestations can cause severe adverse consequences, including anemia and malnutrition of host birds, leading to diminished egg production, compromised egg quality, increased poultry morbidity, and elevated mortality rates (Sleeckx, et al., 2019). Additionally, the PRM has been implicated as a transmission vector for dozens of poultry pathogens (Moro et al., 2009a, Moro et al., 2009b; Moro et al., 2009). The formidable reproductive capacity and superb resistance to starvation of PRMs make complete eradication of the mites unattainable. A female mite generally produces a batch of about 4 eggs with eight or more batches in its lifespan (Wood, 1919). PRMs are capable of surviving for approximately 9 months in the absence of blood meal (Nordenfors, et al., 1999). Presently, spraying chemical insecticide is the primary control mean of D. gallinae. However, pesticide resistance has been widely found in the field populations of PRMs across the world (Katsavou, et al., 2020), Moreover, insecticide contamination of the environment and animal products has drawn more and more concerning, further limiting the available drugs for PRM chemical control (Marangi, et al., 2012). A better understanding of mite biological characteristics is crucial to develop novel control strategies.

For oviparous arthropods, vitellogenesis, involving the synthesis and absorption of vitellogenin (Vg), is an essential process for egg formulation and population multiplication. As the precursor of the yolk protein vitellin (Vn), Vg is stored as Vn and releases synthesized amino acids during embryogenesis, providing nutrition and energy for the development of ovaries and embryos (Wu, et al., 2020). Arthropod Vgs are large molecules (∼200 kDa), which are mainly synthesized in the fat body of females, then are secreted into the hemolymph and finally are taken up by the developing oocytes via receptor-mediated endocytosis (Sappington, et al., 1996). Studies have shown that Vg is polygenic and some species present multiple Vg genes (Tufail, et al., 2014). For example, Nilaparvata lugens Stål has only one Vg gene (Ge, et al., 2010), while Aedes aegypti and Neoseiulus barkeri have three (Price, et al., 2011), and Culex tarsalis has four (Provost-Javier, et al., 2010). It has also been demonstrated that Vg is evolutionarily conserved with similar domains and sequences, such as the lipoprotein N-terminal domain (LPD_N), unknown functional domain (DUF1943), Von Willebrand factor D domain (VWD), cleavage site (R/KXXR), and C-terminal GL/ICG motif (Tufail and Takeda, 2008). Studies have confirmed that suppression of Vg by dsRNA-mediated knockdown could inhibit oocyte maturation and ovarian development, leading to a significant decrease in fecundity in Spodoptera frugiperda and Panonychus citri (Ali, et al., 2017; Han et al., 2022). In D. gallinae, Vg1 has been characterized and confirmed to have vaccine potential against PRMs (Bartley, et al., 2015). In addition, a recent study has identified three Vg homologues within the adult D. gallinae transcriptome (Ribeiro, et al., 2023). However, the precise gene structure and physiological functions of Vgs in D. gallinae remain inadequately understood.

The TOR (Target of Rapamycin) belongs to the phosphatidylinositol kinase-related kinase protein family, which is highly conserved and plays a pivotal role in regulating protein translation, and closely relating to organism growth, aging and disease in eukaryotic cells (Liu and Sabatini, 2020; Loewith et al., 2002). In arthropods, the TOR pathway exerts its influence by mediating the nutritional status of an organism, orchestrating the biosynthesis and secretion of juvenile hormone (JH) and ecdysone (20E). In turn, these hormonal regulators modulate vitellogenesis and stimulate Vg synthesis, facilitating egg development (Lu, et al., 2016; Zhu et al., 2020). Furthermore, TOR is instrumental in sensing nutritional signals, which trigger Vg synthesis, activating egg development, and regulating the development of the reproductive system. This holds particularly true for insects that rely on protein or amino acid nutrients to initiate Vg synthesis (Roy and Raikhel, 2011). In many insect species, the intake of proteins or amino acids serves as a pivotal trigger for the onset of vitellogenesis. This phenomenon is especially pronounced in most anautogenous arthropods (such as mosquitoes, ticks and PRMs), where egg development remains arrested until a female partakes in a blood meal (Hansen, et al., 2004). The TOR gene in PRMs was recently identified, revealing a potential post-feeding activity of the TOR pathway in adult mites (Ribeiro, et al., 2023). Despite this discovery, the specific function of TOR in PRMs has not been thoroughly explored yet.

In the present study, we conducted a comprehensive investigation of D. gallinae Vg genes (Dg-Vgs) and TOR gene (Dg-TOR), elucidating their molecular characteristics and establishing phylogenetic relationships. Additionally, the expression profiles of Dg-Vgs and Dg-TOR across various developmental stages and oviposition cycle were assessed. Finally, the function of Dg-Vgs and Dg-TOR in the vitellogenesis of D. gallinae was determined by dsRNA-mediated gene silencing. These findings contribute to clarifying the reproductive regulation mechanism of D. gallinae and offer novel potential targets for mite control.