Identification of glucose‐regulated protein 78 (grp78) cDNA from Aphis gossypii and its expression during development, heat shock and nutritional ingestion
2016
Cha, Sangmok | Shim, Jae‐Kyoung | Lee, Kyeong‐Yeoll
Glucose‐regulated protein 78 (GRP78) is a heat shock protein 70 (HSP70) specific to the endoplasmic reticulum (ER). It acts as a chaperone and a signalling regulator that responds to ER stresses in vertebrates. However, its role in invertebrates, including in insects, is uncertain. The present study determines the full grp78 cDNA sequence and expression patterns of grp78 in Aphis gossypii Glover, which is a major pest of numerous crop plants worldwide. The A. gossypii grp78 cDNA contains highly conserved motifs of the HSP70 family, as well as the C‐terminal KDEL motif that is characteristic of ER‐specific HSPs. The amino acid sequence also exhibits 97–98% identity with HSP70 of other aphid species. Quantitative real‐time reverse transcriptase‐polymerase chain reaction analysis shows that the grp78 level is higher in fourth‐instar nymphs than in the younger instar‐nymphs and adults. Its level is not significantly affected by exposure to 0–40 °C for 1 h. The grp78 level gradually increases after ingestion of sucrose solutions that range in concentration from 0% to 30% (w/v) using Parafilm feeding chambers. In addition, the grp78 levels vary among aphids that are fed on the leaves of 13 different plant species for 24 h. More specifically, grp78 levels are higher in aphids that fed on eggplant and pepper than any other host plants examined in the present study. Thus, the results demonstrate that grp78 expression is highly associated with the nutritional uptake of aphids and provide important insights for understanding the molecular aspects of relationships between insects and their host plants.
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