Abstract
The values of physiological indices and the enzymes activities involved in the overwintering stage were studied in D. armandi larvae in each month from October 2014 to March 2015. The sorbitol, trehalose and glycerol values initially tended to increase as the ambient temperature decreased, before declining until the end of the winter. The activities of four enzymes (SOD, CAT, LDH and AchE) decreased, whereas POD, PK and MDH showed opposite trends in activity. Other enzyme activities (those of TPS, SDH and GLK) were low during the overwintering period and later increased and stabilized during spring. In this study, a polymerase chain reaction (PCR) genes of SDH, TPS and GLK was utilized to identify DarmSDH, DarmTPS and DarmGLK in D. armandi. They were found to be abundantly expressed during the overwintering stage by quantitative real-time PCR (qRT-PCR) analyses; by contrast, these three genes showed higher expression levels in December 2014 than in May 2015. The qRT-PCR results demonstrated that the reduction of mRNA expression levels was significant in DarmSDH-, DarmTPS- and DarmGLK-dsRNA-treated D. armandi compared with water-injected and non-injected controls. The mortality responses at low temperature were also increased in the dsRNA-treated D. armandi compared with the controls.
Highlights
The values of physiological indices and the enzymes activities involved in the overwintering stage were studied in D. armandi larvae in each month from October 2014 to March 2015
We examined the responses of double-stranded RNA (dsRNA)-injected, water-injected, and non-injected D. armandi larvae to low temperature by mortality analysis. (The larvae were collected in December 2014 for dsRNAi-SDH and dsRNAi-trehalose-6-phosphate synthase (TPS), and in November 2014 for dsRNAi-glycerol kinase (GLK))
We examined the mortality of dsRNA-injected, water-injected, and non-injected D. armandi larvae exposed to low temperatures (Fig. 8)
Summary
The values of physiological indices and the enzymes activities involved in the overwintering stage were studied in D. armandi larvae in each month from October 2014 to March 2015. Cold tolerance is often closely related to time in overwintering insects, whereas survival primarily depends on physiological and biochemical changes that take place in response to low ambient temperatures[8]. Their metabolic activity rate is generally low, and there is no change in their state, organ development or tissue differentiation[12] Their physiological metabolic processes continue, such as endocrine regulation, energy metabolism, lipid metabolism and sugar metabolism, among others[13,14]. The metabolic adjustment of these compounds can guarantee efficient resource utilization, maintain the dynamic balance of nutrition, and heighten the level of cold hardiness of overwintering insects, increasing the chances of winter survival[2]. The antioxidant defence system, which prevents oxidative injuries from developing during normal metabolic activity, may be significantly altered by cold stress, due to changes characteristic of cold-hardiness mechanisms
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