Cold acclimation of Trogoderma granarium Everts is tightly linked to regulation of enzyme activity, energy content and ion concentration

Abstract

In this study, cold hardiness and some physiological characteristics of T. granarium larvae were investigated under different thermal regimes, i.e. warm-acclimated (WA), cold-acclimated (CA), fluctuating-acclimated (FA) and rapid cold-hardened (RCH). In all regimes, the survival rate of the larvae decreased with a decrease in temperature and raise in exposure time. Cold acclimated larvae showed the highest cold hardiness in -15 and -20 {o}C. Control larvae had the highest glycogen content (34.4 {+/-} 2.3 {micro}g/gdw). In contrast, cold acclimation larvae had the lowest glycogen content (23.0 {+/-} 1.6 {micro}g/gdw). Change in trehalose content was reversely proportional to change in glycogen content. The greatest myo-inositol and glucose contents were detected in larvae cold acclimation treatment (10.7 {+/-} 0.4 {micro}g/gdw) and control (0.49 {+/-} 0.03 {micro}g/gdw), respectively. In control and treated larvae, the concentration of Na+ decreased, though the concentration of K+ rose, with rising the exposure time. The shape of the thermal reaction of AMP-depended protein kinase and protein phosphatase IIC followed the same norm, which is different from protein phosphatase I and protein phosphatase IIA. Protein phosphatase IIA and IIC showed a complete difference in thermal reaction norms. In did, thermal fluctuation caused the highest changes in the activity of the enzymes, whereas the RCH showed the lowest changes in the activity of the enzyme. Our results showed a significant enhancement of larval cold tolerance under CA regime that is related to the level of low molecular weight carbohydrates, protein kinase, and phosphatases activity, and hemolymph ions concentration.\n\nSUMMARY STATEMENTIn Trogoderma granarium, cold acclimation enhances the larval cold tolerance that is related to change in the level of low molecular weight carbohydrates, protein kinase, and phosphatases activity, and hemolymph ions concentration.