AUTHOR=Ge Linquan , Jiang Lu , Zheng Sui , Zhou Yongkai , Wu Qing , Liu Fang 

TITLE=Frizzled 2 Functions in the Regulation of TOR-Mediated Embryonic Development and Fecundity in Cyrtorhinus lividipennis Reuter

JOURNAL=Frontiers in Physiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.579233

DOI=10.3389/fphys.2020.579233

ISSN=1664-042X

ABSTRACT=<p>The mirid bug, <italic>Cyrtorhinus lividipennis</italic> Reuter, is an important predator of rice planthoppers in Asia. In a previous study, <italic>C. lividipennis</italic> fed on gramineous weeds with brown planthopper (BPH) eggs had reduced development compared to those fed on rice with BPH eggs. In the current study, the concentrations of selected amino acids (AAs) were higher in rice than five gramineous species, which might explain the enhanced growth of <italic>C. lividipennis</italic> on rice. When <italic>C. lividipennis</italic> was fed on AA-deprived artificial diets, the Wnt/β-catenin pathway was inhibited. Furthermore, <italic>C. lividipennis</italic> females silenced for expression of <italic>Frizzled 2</italic> (<italic>Fz2</italic>) showed a significant reduction in the Wnt/β-catenin and target of rapamycin (TOR) pathways. Silencing <italic>Fz2</italic> led to decreased expression of the vitellogenin gene (<italic>Vg</italic>), lower Vg accumulation in oocytes, reduced soluble protein in ovaries and fat bodies, reduced titers of juvenile hormone, prolonged preoviposition periods, and lower predation capacity, body weight, and egg numbers as controlled to controls. <italic>Fz2</italic> silencing resulted in undeveloped ovaries and the inhibition of oocyte growth in the ovarioles, resulting in decreased numbers of offspring and reduced hatching rates. The silencing of <italic>Fz2</italic> also resulted in aberrant embryos with undeveloped eyespots and organs, suggesting that <italic>Fz2</italic> is an essential gene for embryonic development, oogenesis, and egg maturation. In summary, this study established a potential link between Wnt and TOR pathways, which interact synergistically to regulate <italic>C. lividipennis</italic> reproduction in response to AA signals. These results provide valuable new information that can be applied to large-scale rearing of <italic>C. lividipennis</italic> predators, which is important for reducing planthopper damage in rice fields.</p>