Daily expression of two circadian clock genes in compound eyes of Helicoverpa armigera: evidence for peripheral tissue circadian timing

Abstract

Circadian clock genes in peripheral tissues usually play an important role in regulating the circadian rhythms. Light is the most important environmental signal for synchronizing endogenous rhythms with the daily light-dark cycle, and compound eyes are known as the principal circadian photoreceptor for photic entrainment in most moths. However, there is little evidence for circadian timing in compound eyes. In the current study, we isolated the timeless gene, designated Ha-tim (GenBank accession number: KM233162), from the cotton bollworm Helicoverpa armigera. Ha-tim and period (Ha-per) showed low messenger RNA levels in the compound eyes compared to the other tested adult organs. Ha-tim and Ha-per transcript levels were dependent on an endogenous rhythm that fluctuated over a daily cycle in the compound eyes and heads. The cycles of Ha-tim and Ha-per transcript levels followed similar time courses, and identical expression patterns of the two genes were observed in the compound eyes and heads. Ha-tim and Ha-per were down-regulated in the compound eyes after light exposure, copulation and starvation. These results indicated that Ha-tim and Ha-per transcript levels were regulated by endogenous and exogenous factors. Our study helped to improve our understanding of the circadian clock machinery in compound eyes and other peripheral tissues.

The Circadian Clock in Lepidoptera

“…The presence of circadian clocks outside the brain has been demonstrated in adults of different lepidopteran species, including A. pernyi , M. sexta , B. mori , S. littoralis , D. plexippus , E. kuehniella , and H. armigera ( Sauman and Reppert, 1996 ; Wise et al, 2002 ; Syrova et al, 2003 ; Iwai et al, 2006 ; Schuckel et al, 2007 ; Kotwica et al, 2009 ; Merlin et al, 2009 ; Kobelková et al, 2015 ; Yan et al, 2019 ). In insects, these circadian clocks appear to be important for the daily regulation of the physiological activities typical of peripheral tissues or organs ( Tomioka et al, 2012 ).…”

“…Some of these peripheral clocks depend on the clock located in the brain, others are self-sustained oscillators, autonomously ticking with respect to the master clock, as nicely demonstrated in the dipteran D. melanogaster ( Plautz et al, 1997 ). Throughout expression studies and/or physiological analyses, peripheral clocks have been detected in different adult structures, such as eyes, antennae, thorax, abdomen, flight muscles, midgut, testis, and legs ( Sauman and Reppert, 1996 ; Wise et al, 2002 ; Iwai et al, 2006 ; Schuckel et al, 2007 ; Merlin et al, 2009 ; Yan et al, 2014 , 2019 ; Kobelková et al, 2015 ; Figure 3B ). Here, we will focus on peripheral clocks located in the eye, antenna, and testis, for which most of the data are available.…”

“…The molecular mechanism connecting opsin daily expression and circadian clocks is still unknown. However, cycling mRNA levels of different core clock genes (Ha per , Ha tim , Ha cry1 , and Ha cry2 ) have been detected in H. armigera eyes, suggesting the presence of a peripheral clock ( Yan et al, 2014 , 2019 ).…”

Bioprospecting of endophytes in medicinal plants of Thar Desert: An attractive resource for biopharmaceuticals

“…Horizontal transmission produce highly localized infections within the leaf, petiole, bark, or stem of the host plant that has been got infected through endophyte inoculums [ 19 , 20 , 21 , 22 ]. Endophytes possibly may produce sexually or asexually [ 191 ]. Unlike the vertical mode of transmission, the horizontal mode of transmission is independent of host plant parts such as host seeds or vegetative parts for the dissemination of inoculums of endophytes [ 19 , 23 ].…”

Circadian Rhythms of Locomotor Activity Mediated by Cryptochrome 2 and Period 1 Genes in the Termites Reticulitermes chinensis and Odontotermes formosanus

“…In insects and mammals, it is well recognized that Cry, Per and Tim play a vital role in the endogenous circadian clock pathway [15][16][17]. In the cockroach Blattella germanica, the knockdown of Cry2 severely disrupted the circadian rhythms of locomotor activity even in constant darkness (DD) [18].…”