Exogenous Calcium Suppresses the Oviposition Choices of Frankliniella occidentalis (Thysanoptera: Thripidae) and Promotes the Attraction of Orius similis (Hemiptera: Anthocoridae) by Altering Volatile Blend Emissions in Kidney Bean Plants.

Frankliniella occidentalis is a destructive pest of horticultural plants, while Orius similis is a natural enemy of thrips. It has been demonstrated that exogenous calcium could induce plant defenses against herbivore attack. We examined whether CaCl2 supplementation altered the volatile emissions of kidney bean plants, which influence the oviposition preference of F. occidentalis. We also assessed the influence of volatile cues on O. similis. Using Y-tube olfactometer tests, we found that exogenous CaCl2 treatment inhibited the selectivity of F. occidentalis but attracted O. similis. In addition, CaCl2 treatment reduced the oviposition preference of F. occidentalis. Gas chromatography-mass spectrometry analyses revealed that CaCl2 treatment altered the number and relative abundance of the volatile compounds in kidney bean plants and that (E)-2-hexen-1-ol, 1-octen-3-ol, ß-lonone, and (E,E)-2,4-hexadienal might be potential olfactory cues. Furthermore, the results of the six-arm olfactometer test indicated that 1-octen-3-ol (10-2 µL/µL), ß-lonone (10-2 µL/µL), and (E,E)-2,4-hexadienal (10-3 µL/µL) repelled F. occidentalis but attracted O. similis. Overall, our results suggested that exogenous CaCl2 treatment induced defense responses in kidney bean plants, suggesting that CaCl2 supplementation may be a promising strategy to enhance the biological control of F. occidentalis.

FoxO Transcription Factor Regulate Hormone Mediated Signaling on Nymphal Diapause.

Diapause is a complex physiological adaptation phenotype, and the transcription factor Forkhead-box O (FoxO) is a prime candidate for activating many of its diverse regulatory signaling pathways. Hormone signaling regulates nymphal diapause in Laodelphax striatellus. Here, the function of the FoxO gene isolated from L. striatellus was investigated. After knocking-down LsFoxO in diapausal nymphs using RNA interference, the titers of juvenile hormone III and some cold-tolerance substances decreased significantly, and the duration of the nymphal developmental period was severely shorted to 25.5 days at 20°C under short day-length (10 L:14 D). To determine how LsFoxO affects nymphal diapause, analyses of RNA-sequencing transcriptome data after treatment with LsFoxO-RNA interference was performed. The differentially expressed genes affected carbohydrate, amino acid and fatty acid metabolism, and phosphatidylinositol 3-kinase/protein kinase B signaling pathway. Thus, LsFoxO acts on L. striatellus nymphal diapause and is, therefore, a potential target gene for pest control. This study may lead to new information on the regulation of nymphal diapause in this important pest.