Abstract
The mirid bug, Cyrtorhinus lividipennis Reuter, is an important predator of rice planthoppers in Asia. In a previous study, C. lividipennis 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 C. lividipennis on rice. When C. lividipennis was fed on AA-deprived artificial diets, the Wnt/β-catenin pathway was inhibited. Furthermore, C. lividipennis females silenced for expression of Frizzled 2 (Fz2) showed a significant reduction in the Wnt/β-catenin and target of rapamycin (TOR) pathways. Silencing Fz2 led to decreased expression of the vitellogenin gene (Vg), 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. Fz2 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 Fz2 also resulted in aberrant embryos with undeveloped eyespots and organs, suggesting that Fz2 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 C. lividipennis reproduction in response to AA signals. These results provide valuable new information that can be applied to large-scale rearing of C. lividipennis predators, which is important for reducing planthopper damage in rice fields.
Highlights
The mirid bug, Cyrtorhinus lividipennis Reuter (Hemiptera: Miridae), is prevalent in rice fields and is an important predator of leafhoppers and planthoppers, including the brown planthopper (BPH), Nilaparvata lugens Stål (Hemiptera: Delphacidae)
With respect to developmental stages, Frizzled 2 (Fz2) expression increased in fifth instar nymphs and adult C. lividipennis (F = 213.8; df = 7, 23; P = 0.0001) and was 49∼132% higher than that in egg (Figure 1A)
C. lividipennis treated with dsFz2 showed a significant reduction in the expression of Fz2 (Figure 3B; ↓82%: F = 595.1; df = 1, 5; P = 0.0001), Dvl (Figure 3C; ↓59%: F = 42.0; df = 1, 5; P = 0.0029), β-catenin (Figure 3E; ↓37%: F = 18.7; df = 1, 5; P = 0.0001), and TCF (Figure 3F; ↓32%: F = 15.6; df = 1, 5; P = 0.0167) relative to dsGFP treatments at 2 days after emergence (DAE)
Summary
The mirid bug, Cyrtorhinus lividipennis Reuter (Hemiptera: Miridae), is prevalent in rice fields and is an important predator of leafhoppers and planthoppers, including the brown planthopper (BPH), Nilaparvata lugens Stål (Hemiptera: Delphacidae). C. lividipennis feeds on planthopper eggs and nymphs in irrigated rice fields (Katti et al, 2007; Sigsgaard, 2007). C. lividipennis was shown to feed on BPH eggs inhabiting different gramineous species growing in the perimeter of rice fields; longevity, development, and reproduction were reduced on gramineous species when compared to rice plants (Yu et al, 1996). The AAdependent TOR signaling pathway was shown to mediate the phosphorylation of S6K kinase (Hansen et al, 2005), which is a critical regulator of Vg expression (Attardo et al, 2003; Park et al, 2006)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
