Identification and characterisation of ten glutathione S-transferase genes from oriental migratory locust, Locusta migratoria manilensis (Meyen).

BACKGROUND

Synthetic pyrethroids are the primary insecticides that are widely used for controlling Locusta migratoria manilensis (Meyen), a major pest in eastern and southern Asia and the Pacific region. In this paper, ten cDNAs encoding glutathione S-transferases (GSTs) were sequenced and characterised in L. migratoria manilensis. The effects of deltamethrin on the ten GST gene expressions were studied.

RESULTS

Phylogenetic analysis revealed nine GSTs in three different classes, including seven in sigma, one in delta and one in theta. The remaining GST (LmGSTu1) was unclassified. RT-PCR analysis showed that most GST genes were expressed in all tissues examined, including the foregut, midgut, gastric caecum, hindgut, Malpighian tubules, fat bodies, muscles, spermaries and ovaries, except that LmGSTs2, LmGSTs4, LmGSTs7 and LmGSTu1 were expressed in several tissues. LmGSTu1 appeared to be the only gene whose expressions could not be detected in eggs. Real-time quantitative PCR showed that deltamethrin at 0.08 and/or 0.12 µg mL⁻¹ increased almost all ten GST gene expressions in third-instar nymph locusts. However, deltamethrin at 0.16 and/or 0.2 µg mL⁻¹ decreased the expressions of LmGSTd1, LmGSTs1, LmGSTs5 and LmGSTs6.

CONCLUSION

The increases in GST gene expressions after deltamethrin exposure in L. migratoria manilensis might result in its elevating tolerance to other insecticides and xenobiotics.