Study published in the international journal “Frontiers in Physiology”, through the Horizon 2020 research and innovation program.
“Frontiers in Physiology” is a leading journal in its field, publishing rigorously peer-reviewed research on the physiology of living systems, from the subcellular and molecular domains to the intact organism, and its interaction with the environment.
The study of the effect of the circadian clock in lepidoptera will also allow practical effects on silkworms rearing
First of all, the circadian clock is a sort of biological clock with a period of 24 hours, owned by almost all living organisms that serves to synchronize vital activities with the external environment, and characterized by 24-hour rhythms (those of the day, with the alternation between dark and light). This biological clock is extensively studied in all living beings (so much so that the genetic mechanism that regulates the circadian rhythm was the protagonist of the Nobel Prize for Medicine in 2017). The importance of studying it in Lepidoptera (butterflies and moths) derives from the fact that this order of insects is one of the richest in species, some of which with very important functions such as pollinators or nourishment of other animal species, others because, like silkworm, important producers of silk, textile fiber with multiple applications. Furthermore, many Lepidoptera are parasites of important plant species of agricultural interest (we recall as an example the corn borer or the grapevine moth).
From the article published on 11/17/2021 “The Circadian Clock in Lepidoptera”:
[…] This review presents an updated overview of the molecular and anatomical organization of the circadian clock in Lepidoptera. We report different behavioral circadian rhythms currently identified, focusing on the importance of the circadian clock in controlling developmental, mating and migration phenotypes. We then describe the ecological importance of circadian clocks detailing the complex interplay between the feeding behavior of these organisms and plants.Finally, we discuss how the characterization of these features could be useful in both pest control, and in optimizing the rearing of beneficial Lepidoptera such as silkworms.
Introduction
The daily rotation of the Earth causes predictable 24-h environmental cycles that have resulted in the evolution of circadian clocks, endogenously (therefore thanks to internal factors of the organism, Ed.) maintained timing mechanisms in almost all organisms, including bacteria, fungi, plants, and metazoan. These internal clocks are synchronized (entrained) by environmental stimuli, such as daylight or temperature, enabling organisms to adapt to environmental changes in phase with the 24-h day. Moreover, they regulate molecular, cellular, physiological, and behavioral rhythms, which show a periodicity of 24h in the absence of any external cue (free-running condition).
In insects, circadian clocks control the rhythmicity of several behaviors and physiological features, including egg-hatching, pupation, adult eclosion, locomotion, mating, feeding, and metabolism. The first circadian clock gene (period) was identified in 1971 in Drosophila melanogaster (fruit fly, Ed.); since then, the species has been the dominant model to elucidate the molecular genetic mechanisms underlying circadian rhythms in insects. However, studies have also been conducted in other insect species, many including Lepidoptera, an order of insects to which butterflies and moths also belong, including those of the silkworm.
The overwhelming majority of Lepidoptera (>99%) are herbivores with over 90% having a host plant range of three or fewer species; they are found in almost all terrestrial ecosystems and have fundamental ecosystem roles as pollinators and prey. They also have a significant impact on the human economy, as many species represent serious food crop pests, while others such as the domesticated silkworm Bombyx mori and Antheraea pernyi (Chinese tasar moth, Ed.) produce silk that is utilized by the textile industry. Moreover, silk is employed in innovative applications of both the biomedical and cosmetics sectors.
Conclusion
To date, the circadian clock has been examined in a relatively small number of species compared to the multitude of existent Lepidoptera. Nevertheless, the studies performed so far indicate the ecological relevance of the lepidopteran circadian system, as it influences the fitness of a single organism and in turn impacts the biodiversity of an ecosystem. It is easy to predict that the technological advances in Next Generation Omic technologies*, as well as genome editing methodologies will facilitate the study and manipulation of model and non-model species.
When applied to lepidopteran chronobiology, these methodologies will expand our current knowledge on the role of the circadian clocks in these organisms when considered in their natural habitat. Similar approaches will also be useful for the systematic study of species with economic importance such as Bombyx mori, to understand whether manipulating the circadian clock can improve both rearing conditions and/or silk production efficiency. It is worthy to mention that Bmper KD lines exhibited a reduction in developmental time which did not affect silk productivity parameters (Sandrelli et al., 2007). Thus, the employment of genome editing techniques which generated Bmper and Bmtim KO B. mori mutants (Ikeda et al., 2019; Nartey et al., 2020) for producing a battery of silkworm lines carrying mutations in different clock genes might permit an efficient evaluation of these aspects in Bombyx mori.
*Omics Sciences are defined as those disciplines that use analysis technologies that allow the production of information (data), in a very large number and in the same time interval, useful for the description and interpretation of the biological system studied.
Authors
(2) Council for Agricultural Research and Economics, Research Centre for Agriculture and Environment (CREA-AA) – Sericulture Laboratory of Padua, Italy
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 765937 (CINCHRON – Comparative Insect Chronobiology).