Circadian trehalose and trehalase rhythms were studied in the digestive system of Bombyx mori under 12 hr light-dark cycle (LD), continuous light (LL) and continuous dark (DD). The rhythmic changes were interpreted as synthetic cycles in gut wall and release cycles in gut lumen. The trehalose rhythm of gut wall comprised 8 trehalose synthetic cycles (TS cycles) under LD and LL and 7 under DD. The 24 hr trehalose rhythm of LD and LL was clock shifted to 27.2 hr under DD. The trehalose rhythm included 4 TR cycles under LD, 5 under LL and DD in the gut lumen and the 24 hr rhythm of LD was clock shifted to 19.2 hr under LL and DD. In the gut wall trehalase rhythm maintained 8 trehalase enzyme synthetic cycles (TES cycles) under LD, 10 LL and 7 under DD and the 24 hr rhythm of LD was clock shifted to 19.2 hr under LL and 27.2 hr under DD. In the gut lumen it included 4 TER cycles under LD and DD, 5 under LL and its 24-hr rhythm was advanced to 19.2 hr. Further analysis of data showed that LD favours trehalose synthesis, while LL and DD favour trehalase synthesis.

Abstract:The impact of photoperiod on circadian sucrose and sucrase rhythms were analyzed in the digestive system of Bombyx mori under 12 hr light-dark cycle (LD), continuous light (LL) and continuous dark (DD). The rhythmic changes were interpreted as synthetic cycles in gut wall and release or uptake cycles in gut lumen. The gut wall comprised 6 sucrose synthetic cycles (SS cycles) under LD, LL and 5 under DD. The 24 hr rhythm of LD and LL was clock shifted to 28.8 hr under DD. In gut content, the sucrose rhythm showed 7 sucrose uptake cycles (SU cycles) under LD, 6 under LL and 5 under DD and the 24 hr rhythm of LD was clock shifted to 28.0 hr under LL and 34 hr under DD. In the gut wall sucrase rhythm maintained 7 SES cycles under LD and DD and 9 cycles under LL and its 24-hr rhythm is advanced to 18.2 hr. In the gut lumen 5 SER cycles under LD, 8 under LL and 6 under DD and its rhythm is advanced to 15 hr under LL and 20 hr under DD. Further analysis of data showed that LD favoured both synthesis and uptake of sucrose while LL, favoured the sucrase synthesis and its release.

Transdeamination seems to be an important alternative energy-intensive gluconeogenesis mechanism that generates glucose from non-carbohydrate sources during pupaladult metamorphosis in Bombyx mori. Studies on four transdeamination parameters, viz., free amino acids (FAA), aspartate aminotransferase (AAT), alanine aminotransferase (AlAT) and glutamate dehydrogenase (GDH) in the fat body and haemolymph of silkworm have indicated that transdeamination shows stage-specific, region-specific and sex -specific variations during metamorphosis. Region-specific growth trends indicate that the transamination reaction, mediated by AAT and AlAT is faster in the abdominal fat body (AFB) and relatively slower in the thoracic fat body (TFB) with concomitant lower FAA levels in the former and higher levels in the latter. Stage-specific growth trends reflect that the energy mobilization through transdeamination assumes greater significance in the early pupal, late pupal and adult stages rather than the mid-pupal stage. Sex-wise trends in FAA levels indicate that the rate of amino acid utilization is significantly faster in females compared to that in males. Further, the growth trends in the levels of GDH vis-à-vis aminotransferases signify that the energy demands of male sex expressions are met largely through enhanced levels of GDH and that the alpha ketoglutarate generated in transamination reaction is used as a substrate for sperm production, sperm motility and successful mating that stimulates fecundity and productivity of in the mulberry silkworm.The study clearly demonstrates that gluconeogenesis through transdeamination supplements the energy requirements of silkworm metamorphosis and that it is facilitated by disintegrating tissues predominantly from the pupal abdominal segments.