Effects of the parasitoid Microplitis pallidipes on the menanization and phenoloxidase activity of the hemolymph of Spodoptera frugiperda larvae
Author of the article:HUANG Lan-Lan;JIANG Jie-Xian;WANG Jin-Yan;ZHANG Hao
Author's Workplace:1. College of Life Science and Fishery, Shanghai Ocean University, Shanghai 201306, China; Eco-environmental Protection Research Institute, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China
Key Words:Microplitis pallidipes; Spodoptera frugiperda; menanization; phenoloxidase; biological control
Abstract:
[Objectives]
To
investigate the effects of Microplitis
pallidipes on the menanization, prophenoloxidase
(PPO) gene expression and phenoloxidase
(PO) activity, of the hemolymph of Spodoptera
frugiperda larvae, and thereby provide a foundation for the more effective use of this
endoparasitoid to control this pest. [Methods] The S. frugiperda larval instar most
susceptible to parasitism by M.
pallidipes was determined experimentally and RT-qPCR was then used to
analyze the temporal and spatial expression profiles of two S. frugiperda PPO genes. The menanization rate of larvae was counted using the film method, and the PO activity of
larvae was measured using the
absorbance method. The expression of SfPPO1 and SfPPO2 in the hemolymph of S. frugiperda was determined with RT-qPCR. [Results] 3rd instar S. frugiperda larvae were found to be
the most susceptible to being parasitized by M. pallidipes. The relative expression of the two SfPPO genes in eggs and 4th instar larvae was relatively high, and
both genes were mainly expressed in the hemolymph.
Hemolymph menanization rates of parasitized larvae were significantly
lower than those of the non-parasitized larvae after 12, 24, 48 and 72 hours
(P<0.05). PPO expression and PO activity of parasitized larvae were also
lower than those of non-parasitized larvae. There was a strong, positive linear
correlation between the expression
of PPO1 and PPO2 (R2=0.912
4), and there were also positive
correlations among PO activity, PPO expression and the menanization
rate. [Conclusion]
Parasitism of M. pallidipes inhibited the menanization of S.
frugiperda larvae and down-regulated the expression of two PPO genes and PO activity.
PO activity, PPO gene expression and
menanization rate were all positively correlated.