ECOLOGICALLY-BASED MANAGEMENT OF INSECT PESTS OF CORN, WITH EMPHASIS ON CORN BORERS, ROOTWORMS, AND CUTWORMS
Location: Corn Insects and Crop Genetics Research
Title: Cloning of the heat shock protein 90 and 70 genes from the beet armyworm, Spodoptera exigua, and expression characteristics in relation to thermal stress and development
Submitted to: Cell Stress and Chaperones
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 21, 2011
Publication Date: January 1, 2012
Citation: Jiang, X., Zhai, H., Wang, L., Luo, L., Sappington, T.W., Zhang, L. 2012. Cloning of the heat shock protein 90 and 70 genes from the beet armyworm, Spodoptera exigua, and expression characteristics in relation to thermal stress and development. Cell Stress and Chaperones. 17(1):67-80.
Interpretive Summary: The beet armyworm is a major invasive pest of cotton and vegetables in much of the world, including the U.S. It overwinters in southern latitudes and migrates long distances northward each year to infest summer crops in the north. Its long-range movements and predicting the areas where it can cause damage are controlled in part by heat and cold tolerance. When an insect is stressed by extreme temperature, heat shock proteins are produced to help keep cells alive, therefore helping the insect survive long enough for temperatures to moderate. In this study, two heat shock proteins were identified and their amino acid sequences determined. Levels of their production were measured at different growth stages and under different temperatures. The threshold temperatures were determined, indicating that the species has higher than usual tolerance for heat, but that it does not tolerate temperatures much below freezing. Both proteins are produced during immature stages even in the absence of temperature stress, suggesting that they may play a role in development. This information will be used by university, government, and industry scientists who study beet armyworm, and all researchers who study heat shock proteins or their gene regulation in any insect.
Two full-length complementary DNAs (cDNAs) of heat shock protein (HSP) genes (Se-hsp90 and Se-hsp70) were cloned from the beet armyworm, Spodoptera exigua, and their expression was investigated in relation to cold shock, heat shock, and development. The open reading frames of Se-hsp90 and Sehsp70 are 2,154 and 2,004 base pairs (bp) in length, encoding polypeptides of 717 and 667 amino acids with a molecular mass of 82.6 and 72.5 kDa, respectively. Both genes showed high similarity to their counterparts in other species. Transcriptional expression profiles revealed that both genes were significantly up-regulated under thermal stress. However, the temperature at which expression level became significantly higher than that of controls varied between genes. Intensity of response to temperature was more intense for Se-hsp70 than for Se-hsp90, regardless of temperature or developmental stage. However, intensities of response to temperature of either Se-hsp90 or Se-hsp70 varied with developmental stage. The basal expression of both genes was highest in young larvae and decreased with age. Translational expression of Se-Hsp70 was observed by using Western blot. The expression profiles of Se-Hsp70 protein were in high agreement with those of Se-hsp70 RNA under heat or cold stress in larvae and pupae. However, it does not completely accord with that of Sehsp70 RNA expression during development without thermal stress. These results indicated that, in addition to heat shock responses, both Se-hsp90 and Se-hsp70 might be involved in development.