The sweetpotato whitelfy Bemisia tabaci distribute worldwide and infests more than 500 species of plants. To determine nutritional stress of whiteflies at molecular level, we identified a full cDNA of glucose regulated protein 78 (grp78) which is known to be respond to nutritional restriction in vertebrate species. GRP78 of B. tabaci was highly conserved motifs of the HSP70 family and the C-terminal motif of KDEL characteristic of endoplasmic reticulum-specific HSPs. Real-time RT-PCR analysis showed that the grp78 level was not changed by thermal stress treatment from 4°C to 40°C for 1 h. However, the grp78 level was proportionally increased to the ingestion of a sucrose solution ranging in concentrations from 0% to 30% in a Parafilm feeding chamber. In addition, the grp78 levels were various by the ingestion of leaves of 10 different plants for 24 h; its level was higher with eggplant and pepper but lower with rice and apple. Our study suggests that the grp78 may have a role for cellular chaperones in relation to nutritional uptake of B. tabaci.

Glucose-regulated protein 78 (GRP78) is a member of the heat shock protein 70 (HSP70) family that is specific to endoplasmic reticulum (ER). It is known as chaperones and signaling regulators that respond to ER stresses in vertebrates. However, its function in invertebrates, including insects, is uncertain. Here we determined a full cDNA sequence and the expression patterns of grp78 of Aphis gossypii, which is a major pest of numerous crop plants worldwide. Its cDNA had highly conserved motifs of the HSP70 family and the C-terminal motif of KDEL characteristic of ER-specific HSPs. It showed 98.5% identity with the GRP78 of the pea aphid Acyrthosiphon pisum. Real-time RT-PCR analysis showed that the grp78 level was higher in the fourth instar nymph than in the younger instar and adult stages. Its level was not affected by thermal stress of 10 to 40°C for 1 h. The grp78 level was proportional to the ingestion of a sucrose solution ranging in concentration from 0% to 30% in a Parafilm feeding chamber. In addition, the grp78 level varied among aphids feeding on leaves from 14 different host plants for 24 h; it was higher with eggplant and pepper but lower with pigweed and tobacco than any other plants. Our study suggests that the grp78 level is regulated by nutritional condition of A. gossypii.