Functional characterization of four Hsp70 genes involved in high-temperature tolerance in Aphis aurantii (Hemiptera: Aphididae).

The tea aphid, Aphis aurantii (Boyer de Fonscolombe), is a serious pest that can infest many economically important plants. Tea aphids damage plants by directly sucking phloem sap, transmitting viruses, and secreting honeydew to cause sooty mold. At present, tea aphids has become one of the most important pests in tropical and subtropical tea plants. The heat shock protein 70 (Hsp70) is a key protein involved in heat stress tolerance. In this study, we cloned four Hsp70 genes that are highly expressed in tea aphids after heat shock. Bioinformatic analysis of the deduced amino acid sequences showed that these four AaHsp70s had a close genetic relationship to Hsp70 in Hemiptera insects and shared a conserved ATPase domain. After incubation at low (14 °C) or high (36 °C) temperature, the expression of four AaHsp70s was significantly up-regulated compared to the control (25 °C); however, the up-regulation of the AaHsp70s in the low-temperature treatment was far less than that of the high-temperature treatment. The ATPase activity of the four purified recombinant AaHsp70 proteins after high-temperature treatment was significantly increased compared to the control. In addition, these proteins effectively improved the heat tolerance of Escherichia coli in vivo. Our data indicate that AaHsp701, AaHsp702, AaHsp703, AaHsp704 play important roles in response to the high-temperature tolerance in tea aphids. [ABSTRACT FROM AUTHOR]