The Amino Acid-Mediated TOR Pathway Regulates Reproductive Potential and Population Growth in Cyrtorhinus lividipennis Reuter (Hemiptera: Miridae).

Haowen Zhu,Jinming Xu,Sui Zheng,Qisheng Song,Qing Wu,Linquan Ge

doi:10.3389/fphys.2020.617237

Haowen Zhu, Jinming Xu + Show 4 more

Open Access

https://doi.org/10.3389/fphys.2020.617237

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Abstract

The predatory mirid bug, Cyrtorhinus lividipennis Reuter, feeds on brown planthopper (BPH) eggs that are deposited on rice and gramineous plants surrounding rice fields. The development and reproduction of C. lividipennis are inhibited by feeding on BPH eggs from gramineous species, and the underlining regulatory mechanism for this phenomenon is unclear. In the present study, HPLC-MS/MS analysis revealed that the concentrations of six amino acids (AAs:Ala, Arg, Ser, Lys, Thr, and Pro) were significantly higher in rice than in five gramineous species. When C. lividipennis fed on gramineous plants with BPH eggs, expression of several genes in the target of rapamycin (TOR) pathway (Rheb, TOR, and S6K) were significantly lower than that in the insects fed on rice plants with BPH eggs. Treatment of C. lividipennis females with rapamycin, dsRheb, dsTOR, or dsS6K caused a decrease in Rheb, TOR, and S6K expression, and these effects were partially rescued by the juvenile hormone (JH) analog, methoprene. Dietary dsTOR treatment significantly influenced a number of physiological parameters and resulted in impaired predatory capacity, fecundity, and population growth. This study indicates that these six AAs play an important role in the mediated-TOR pathway, which in turn regulates vitellogenin (Vg) synthesis, reproduction, and population growth in C. lividipennis.

Highlights

The mirid bug Cyrtorhinus lividipennis (Reuter; Hemiptera: Miridae) is a natural predator of rice planthoppers
When compared to C. lividipennis feeding on brown planthopper (BPH) eggs from rice, the expression of several target of rapamycin (TOR) pathway genes was decreased when diets consisted of gramineous plants with BPH eggs, rice plants alone, or no food
There was no significant difference in the expression of TOR pathway genes in C. lividipennis females feeding on C. cephalonica eggs and BPH eggs inhabiting rice at 2 days after emergence (DAE)

Summary

Introduction

The mirid bug Cyrtorhinus lividipennis (Reuter; Hemiptera: Miridae) is a natural predator of rice planthoppers. When C. lividipennis consumed a diet of planthoppers that inhabited gramineous species such as Echinochloa glabrescens, Leptochloa chinesis, Digitaria ciliaris, Cyodon dactylon, and Eleusine indica growing on the bunds surrounding rice fields, their development and reproduction were reduced in comparison to those consuming planthoppers (such as BPH eggs) on rice plants (Pomari-Fernandes et al, 2015), indicating that nutrition from rice plant is beneficial to the predator. Telenomus remus (Hymenoptera:Platygastridae) showed normal development when fed on C. cephalonica eggs, suggesting that C. cephalonica is a promising factitious host (Matteson, 2000). These results indicate that C. cephalonica eggs or planthopper eggs/nymphs from rice plants provide adequate nutrients for successfully rearing predatory insects

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