|Zhu, Kum yan|
Submitted to: Journal of Insect Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/10/2005
Publication Date: 7/24/2005
Citation: Mahroof, R., Zhu, K., Neven, L.G., Subramanyam, B., Bai, J. 2005. Expression patterns of three heat shock protein 70 genes among developmental stages of the red flour beetle, tribolium castaneum (herbst) (coleoptera: tenebrionidae). Journal of Insect Physiology. 141:247-256. Interpretive Summary: Tribolium castaneum, commonly called the red flour beetle, is a common pest of flour and feed mills. With the loss of methyl bromide as a structural fumigant, heat treatments to disinfest mills of these pests are gaining popularity. It is important to understand the underlying mechanisms of insect heat tolerance to more accurately develop structural heat treatments to control these pests. Heat shock proteins are commonly reported to confer thermal tolerance in all living organisms and can indicate the level of tolerance to heat treatments. Scientists at the Departments of Entomology and Grain Science and Industry at Kansas State with help from scientists from the USDA-ARS, Yakima Agricultural Research Laboratory in Wapato, WA found three heat shock proteins in four different stages including young larvae, old larvae, pupae, and adults, and with and without heat shock at 40oC for 1 h. Only one gene that codes for these proteins, tchsp70 I, was found to be active in response to heat shock. The tchsp70 II gene was identified as being expressed all the time, and the tchsp70 III genewas identified as being expressed in relation to developmental stage. This work is important because it correlates the levels and expression of heat shock proteins to insect thermal tolerance in a species being targeted for heat treatments for disinfestation of flour and feed mills.
Technical Abstract: We identified three genes encoding heat shock protein 70 (hsp70) in Tribolium castaneum (Herbst) (Coleptera: Tenebrionidae) and tentatively named them as tchsp70 I, tchsc70 II, and tchsp70 III. Partial sequences of the tchsp70 I and tchsc70 II genes revealed that nucleotide sequences are 99% identical with each other. However, tchsp70 III nucleotide sequence is only 81% and 86% identical with those of tchsp70 I and tchsc70 II, respectively. Stage specific expression patterns of the tchsp70 were investigated for four different stages including, young larvae, old larvae, pupae, and adults, and with and without heat shock at 40oC for 1 h. Northern blotting and real-time qPCR were carried out to determine the levels of mRNA for three tchsp70 genes. Transcripts of all three genes have been detected by Northern blotting with the sizes of 2.4, 2.2, and 2.3 kb for tchsp70 I, tchsc70 II and tchsp70 III, respectively. Significant levels of induction (1.1- to 2.0-fold) of the expression was found in the tchsp70 I following the heat shock at 40oC in all life stages, whereas no significant changes were found in other tchsc70 II in different insect stages and temperature treatments. Significant variation in tchsp70 III levels was found among developmental stages ranging from 3.4-fold decrease to 4.3-fold increase depending on life stage. Our data suggests that tchsp70 I gene is heat-induced, and tchsc70 II gene is constitutively-expressed while tchsp70 III gene is developmentally-regulated in T. castaneum.