The work developed by the Institute of Integrative Systems Biology (I2SysBio), of the scientific area of the Scientific Park of the University of Valencia (PCUV), is important to understand how biological cycles are regulated, not only of aphids, but of many insects and to design strategies for their control
Together with other centers, a research group from the Institute of Integrative Systems Biology (I2SysBio, CSIC-UV), located at the University of Valencia Science Park (PCUV), has discovered that the gene for the protein Pigment-Dispersing Factor (PDF), which is part of the circadian clock of insects (responsible for daily rhythms) is also found in the pea aphid. The research has been published in the journal Open Biology, where an image of this work is the cover of the July issue.
"This research is important to understand how biological cycles are regulated, not only for aphids, but for many insects, and to design strategies or tools for their control. Ideally, if we could prevent the annual diapause (physiological state of dormancy) of an insect vector or pest, it would be unable to withstand the harsh conditions of winter. And vice versa, if we induce diapause in a benign period, the insect will be absent, thus avoiding its potential damage", say David Martínez Torres, Professor of Genetics (Universitat de València) and researcher at I2SysBio, and Gustavo L. Rezende, distinguished researcher at the joint center.
The research has discovered that the pdf gene is present in all aphid species, when, after 10 years since the publication of the first pea aphid genome, it was already taken for granted that these insects lacked this gene. In addition, "we have also located the neurons that produce this neuropeptide (small proteins that act as chemical messengers) and their connections, on the one hand, with photoreceptors, and on the other, with cells involved in the response through the insulin pathway," according to the two researchers from the I2SysBio Aphid Biological Cycles Research Group.
"This research is important to understand how biological cycles are regulated, not only of aphids, but also of many insects, and to design strategies or tools for their control," David Martínez Torres, professor of Genetics at the University of Valencia and researcher at I2SysBio, and Gustavo L. Rezende, distinguished researcher at the joint center
The work also confirms that more neuropeptide is produced on short days than on long days, which could be a signal (or part of a signal) that informs about the photoperiod (or length of the day), according to the researchers.
Animals have adaptations known as biological rhythms versus Earth's rhythms. Circadian rhythms are adaptations to daily changes, while seasonal rhythms are important in the face of changes throughout the year. Among the latter, we can highlight the migrations of birds or the hibernation of bears and the diapause in insects. But it is necessary to anticipate the arrival of bad weather, and it is not possible to make a mistake and migrate too early or too late, and for this the most reliable clue is the length of the day.
Photoperiodism is the ability of many species to detect changes in day length (photoperiod) and respond with changes in their physiology or behavior. In insects, how the photoperiodic system works is only partially understood, and in some species the involvement of PDF (which is part of the circadian clock of all insects) has been demonstrated. Aphids are photoperiodic insects par excellence, with a life cycle absolutely determined by the photoperiod.
"Our work demonstrates the presence of a very distinct form of PDF in aphids and localizes the cells in which it is produced, as well as its connections and quantity, which vary with photoperiod. This leads us to propose that PDF would be involved in the transmission of the photoperiodic message that modulates the seasonal response in these insects"
In this sense, according to Martínez Torres and Gustavo L. Rezende, "in aphids, PDF seemed to be absent. Our work demonstrates the presence of a very different form of PDF in aphids and localizes the cells in which it is produced, as well as its connections and quantity, which vary with photoperiod. This leads us to propose that PDF is involved in the transmission of the photoperiodic message that modulates the seasonal response in these insects". Following the description of photoperiodism for the first time in plants in 1920, the year 2023 marks the centenary of the description of aphids as the first photoperiodic animals.
This research, in which Francesca Sara Colizzi and Charlotte Helfrich-Förster from the Universität Würzburg in Germany and Jan A. Veenstra from the Université de Bordeaux in France also participate, has been supported by the Ministry of Science and Innovation, Ministry of Universities (Ayudas María Zambrano) and by funds from the European Union (Horizon 2020 Program).
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