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Title: Differential heat shock tolerance and expression of heat shock inducible proteins in two stored-product psocids

item Guedes, Raul
item Zhu, Kun Yan
item Opit, George
item Throne, James - Jim

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2008
Publication Date: 12/1/2008
Citation: Guedes, R.N., Zhu, K., Opit, G.P., Throne, J.E. 2008. Differential Heat Shock Tolerance and Expression of Heat-Inducible Proteins in Two Stored-Product Psocids. Journal of Economic Entomology 101: 1974-1982.

Interpretive Summary: Psocids, or booklice, are emerging pests of stored products, such as in grain storages and flour mills. Heat treatments are increasingly used to control insects in flour mills, and there is no information on efficacy of heat for controlling psocids. We tested susceptibility of two species of psocids, Liposcelis entomophila and Lepinotus reticulatus, to heat, and we determined whether heat shock proteins, which are proteins which protect other proteins in the bodies of animals during stress, play a role in tolerance to heat in these two species. Liposcelis entomophila was over 2-fold more heat tolerant than L. reticulatus. We found heat shock proteins only in Liposcelis entomophila, which might explain its greater tolerance to heat treatment and its more common occurrence in warmer parts of the world. Our results indicate that heat treatments should be efficacious for control of both of these psocid species.

Technical Abstract: The recent recognition of psocid infestations as a major concern in stored products, where their management with fumigants and conventional insecticides has proven difficult, and also the recent reemergence of heat treatment as a potential tactic for control of stored-product insects led to the present investigation. The objectives of this study were to determine if there are differences in heat shock tolerance of two species of stored-product psocids – Lepinotus reticulatus Enderlein (Trogiidae) and Liposcelis entomophila (Enderlein) (Liposcelididae), and to determine whether heat shock proteins (HSPs) underlay such tolerance. Time-response bioassays were therefore carried out at increasing temperatures (37.5, 40.0, 42.5, 45.0, and 47.5°C) for both psocids. The LT50 and LT95 (lethal times for 50 and 95% mortalities) estimates were subsequently correlated with the expression of heat shock proteins after exposure at the same range of temperatures for 30 min. The expression of HSP was determined through western blot analyses using HSP 70 antibody. Liposcelis entomophila was over 2-fold more heat shock tolerant than L. reticulatus for nearly all of the range of temperatures (greater than or equal to 40.0°C) with LT50s ranging from 14.99 to 1.25 hours and 7.10 to 0.44 hours with increasing temperature for both species, respectively. Expression of HSP 70 was not observed for either of the psocid species, but the expression of two low-molecular-mass heat shock proteins (23 and 27 kDa) was observed in L. entomophila. The expression of these small heat shock proteins was induced by exposure to higher temperatures, and the trend was particularly strong for the HSP 27. In contrast, no expression of small heat shock proteins was detected in L. reticulatus, reflecting its higher susceptibility to heat treatments. The relatively high heat tolerance of L. entomophila might help explain its more common occurrence in grain stored in warmer regions of the world. Our data show that heat treatments should be efficacious for control of both of these psocid species.