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Circadian activity rhythm and molecular clock in Hemiptera D2 楊 斌

2013/06/09 16:57 に Takashi Matsuo が投稿
2013年06月10日

In response to the changing seasonality, insects have evolved circadian activity rhythm in the timing of development, reproduction and diapause state by using photoperiodic circadian clock. To receive light and synchronize with the circadian activity rhythm, insects utilize visual system composed of compound eyes and ocelli or photoreceptors such as cryptochrome [1]. 
Hemipteran insects exhibit a clear photoperiodic response for the induction of adult reproductive diapause so that they are good materials to study circadian clock [2]. Circadian system such as clock cell bodies in the brain was described in both larvae and adult stages in Rhodnius prolixus [3]. Circadian clock genes were isolated from Riptortus pedestris in which vrille (vri), and mammalian-type cryptochrome (cry-m) were first reported in hemimetabolous insects [4]. The lack of cry-m in Drosophila melanogaster indicated the difference of clockwork between these two species. Gene modification by RNAi was performed in R. pedestris revealed that period (per), cycle (cyc) and cry-m were core components of the circadian clock [5, 6]. These clock genes were upstream cascade of juvenile hormone (JH) secretion [7]. In contrast, in the linden bug, Pyrrhocoris apterus, clock genes were suggested to work at downstream of JH by observing the effect of an endocrine gland on circadian clock gene expression [8]. In addition, another studies showed organ-autonomous, yet noncircadian, involvement of clock genes and hormonal signaling in diapause regulation [9].  
These results suggest that the circadian activity rhythm was controlled by complicated factors of both circadian clock and endocrine system, but the intact mechanism was still unknown. Recent application of whole genome sequencing in the studies of circadian clock, may clarify the regulatory mechanisms of circadian activity rhythm.

References:
 [1] Claudio R. Lazzari et al. (2011) Differential control of light-dark adaptation in the ocelli and compound eyes of Triatoma infestans. Journal of Insect Physiology. 57: 1545-1552
[2] Numata H, Hidaka T (1982) Photoperiodic control of adult diapause in the bean bug, Riptortus clavatus Thunberg (Heteroptera: Coreidae). I. Reversible induction and termination of diapause. Applied Entomology and Zoology. 17, 530-538.
[3] Xanthe Vafopoulou and Colin GHS. (2012) Metamorphosis of a Clock: Remodeling of the Circadian Timing System in the Brain ofRhodnius prolixus (Hemiptera) During Larval-Adult Development. The Journal of Comparative Neurology. 520:1146-1164
[4] Ikeno T. et al. (2008) Molecular characterization of the circadian clock genes in the bean bug, Riptortus pedestris, and their expression patterns under long- and short-day conditions. Gene. 419: 56- 61
[5] Ikeno T. et al. (2011) Causal involvement of mammalian-type cryptochrome in the circadian cuticle deposition rhythm in the bean bug Riptortus pedestris. Insect Molecular Biology 20, 409-415. 
[6] Ikeno T. et al. (2011) Circadian clock genes period and cycle regulate photoperiodic diapause in the bean bug Riptortus pedestris males. Journal of Insect Physiology 57, 935-938.
[7] Ikeno T. et al. (2010) Photoperiodic diapause under the control of circadian clock genes in an insect. BMC Biology8, article 116.
[8] D. Dolezel et al. (2008) Endocrine-dependent expression of circadian clock genes in insects. Cell. Mol. Life Sci. 65: 964 - 969 
[9] Bajgar A. et al. (2013) Autonomous regulation of the insect gut by circadian genes acting downstream of juvenile hormone signaling. PNAS. 110(11): 4416-4421
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