Zinc Stress Alters Sugar Content in Rice Plants and the Reproduction and Trehalose Metabolism in Nilaparvata lugens

Excessive zinc (Zn) is toxic to plants, but the effect of zinc-stressed plants on herbivorous insects is still unclear. Hence, we assessed the effect of zinc-stressed rice plants on its feeding pest, Nilaparvata lugens. The soil–rice–N. lugens system was treated with Zn2+ solution. Sugar content in rice was measured, and the reproduction and trehalose metabolism in N. lugens were assessed. The trehalase activity in rice significantly decreased at 100 mg·kg−1 Zn2+, and the trehalose content increased. The glucose and starch content increased at higher Zn2+ concentrations. The fecundity and trehalose content of N. lugens decreased after feeding on zinc-stressed rice, and the glucose content in the high Zn2+ group was significantly higher than that in the low Zn2+ group. In addition, the soluble trehalase activity of N. lugens significantly decreased under the 125 mg·kg−1 treatment, while the activity of membrane-bound trehalase significantly increased under the 150 mg·kg−1 treatment. Quantitative RT-PCR indicated significantly lower expressions of NlTre1-1, NlTre2, and NITps after Zn treatment. In conclusion, Zn2+ treatment significantly altered the sugar content in rice plants; it also decreased the fecundity of N. lugens, which may be mediated by alterations in trehalose metabolism.