Rhythmic oscillations of α-amylase protein and its enzymatic activity levels in Drosophila melanogaster (Diptera: Drosophilidae)

Marcin A Ciuk,Piotr Bebas,Bronislaw Cymborowski

doi:10.14411/eje.2009.065

Abstract

In this report, we show that α-amylase activity is rhythmic in the wild-type fruit fly Drosophila melanogaster, and that this rhythm exhibits the properties of a clock output. Moreover, the rhythm of amylase activity is accompanied by fluctuations in the Amy protein level under 12L : 12D conditions. A strong sexual dimorphism is evident in the oscillations of Amy protein and enzymatic activity. Under light : dark (LD) conditions on the control diet, CantonS wild-type Drosophila melanogaster exhibit a bimodal rhythm of amylase activity, particularly of the AmyD3 (Amy3) isoform, with morning and evening peaks. Under these conditions, Amy protein levels also oscillate significantly, again more strongly for the Amy3 isoform than Amy1 (Amy1). A robust oscillation of Amy3 and Amy1 activity is also observed under DD conditions for both sexes. In constant light (LL) the rhythms dampen out, particularly in the males. A high level of dietary glucose causes an overall decrease in the amplitudes of the rhythmic oscillations of amylase activity, but the processes are nevertheless rhythmic, with peak activities at Zt8 for the females, and at Zt0 for the males in LD. In constant darkness (DD) the rhythms are maintained. Mutants lacking a functioning oscillator, per01, exhibit a slight photoperiodicity in LD, with a decrease in amylase activity in both males and females during the late night in LD, but no rhythmic oscillations in DD.

Highlights

One of the reasons that physiological processes oscillate over time is to optimize expenditures of energy, a limited resource
Because glucose is a strong repressor of D-amylase activity in D. melanogaster, in addition to the control diet (0.75% agarose, 5% each of starch, glucose and heat inactivated yeast) we examined the effect of a glucose diet (GD), which contained 5% by mass of glucose
Amy protein levels vary with in a circadian manner (Fig. 1E), the rhythm differs from the enzymatic activity

Summary

Introduction

One of the reasons that physiological processes oscillate over time is to optimize expenditures of energy, a limited resource. Their presence has been noted in the Malpighian tubules (Giebultowicz & Hege, 1997), in the rectum, fat body and gastrointestinal tract (Giebultowicz, 2001) Since most of these tissues are closely connected to foraging, feeding, digestion and metabolism, it seems very logical that peripheral oscillators participate in the regulation of these physiological functions. Our knowledge of their role(s) in insects remains minimal. The connection between metabolic mechanisms and the biological clock is documented (Sarov-Blat et al, 2000; McDonald & Rosbash, 2001; Ceriani et al, 2002) Most of these examples are enzymes of intermediary metabolism, such as malate dehydrogenase, which participates in the citric acid cycle, or several enzymes involved in glycolysis, such as hexokinase, phosphoenolopyruvate dehydrogenase and transaldolase. It was demonstrated that are the canonical mammalian molecular oscillator proteins (PER1-3, CLOCK and REV-ERB) expressed with robust circadian rhythms in the human submandibular salivary glands, but that Amylase 1 is the sole salivary glucohydrolase which cycles rhythmically in a robust fashion (Furukawa et al, 2005)

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