Newswise – A grasshopper hatched in a crowded environment may look and behave differently than a grasshopper hatched in isolation – even though they have the same genes. The mechanism for this density-dependent phenomenon, called polyphenism, is well documented in aphids and locusts, but how genes regulate these traits has remained obscure until now. Researchers from the University of Hiroshima analyzed data sets collected in previous studies to better understand how genes can influence each other to change their expression based on environmental conditions.
They published their results on September 23 in Insects.
“Aphids exhibit several types of wings and locusts exhibit different body colors and behaviors,” said the corresponding author. Hidemasa Bonoprofessor at Hiroshima University Graduate School of Integrated Life Sciences. “These well-known agricultural pests are representative of insects that exhibit density-dependent plasticity. To reveal the molecules common to all or several species that exhibit this same type of plasticity, we collected and reanalyzed publicly available RNA sequencing data from aphids and locusts.
RNA sequencing data, called transcriptome, is a collection of various expressed genes. It can also help identify new genes involved in producing specific traits. By performing a meta-analysis, researchers combine transcriptome results from multiple studies to see what the data says. In this study, researchers analyzed 66 public transcriptome datasets of seven species of aphids and locusts.
“Meta-analysis is believed to be effective in providing additional information about density-dependent polyphenism because it can uncover new information that would not be found with conventional hypothesis-based research methods,” said the first author Kouhei Toga, researcher at Hiroshima University. integrated sciences for life. “This study is the first meta-analysis conducted on datasets from two evolutionarily distant lineages, and it identified many density-responsive genes, which have barely been the subject of research aimed at elucidating the molecular mechanisms of density-dependent plasticity.
Specifically, the researchers found that DNA replication, DNA metabolic processes, and the mitotic cell cycle were all enriched in response to crowded conditions. According to Toga, their findings underscore the importance of these processes—which have rarely been investigated in this area—as regulatory mechanisms in research on density-dependent polyphenism.
They also found discrepancies with some studies, including one that found that a gene linked to pigmentation in more gregarious locusts was more highly expressed under isolated conditions. Compared to data from other studies, the researchers found that the gene fell into a category of other genes that upregulated their expression under oxidative stress. According to Bono, oxidative stress is a more likely explanation for the high gene expression in solitary locusts than under crowded conditions.
“We also found that changes in the neurological system can play an important role in inducing density-dependent phenotypic changes in two lineages,” Bono said, explaining that several genes functioning in the nervous system, which would lead to density-dependent behavioral changes increased under isolated conditions. conditions.
The findings can be broadly applied to other species that exhibit density-dependent polyphenism due to the amount of data from so many studies, which serves as a cross-check of previous hypotheses and results, according to Toga.
“With the increase in public RNA sequencing data, a meta-analysis that combines data from multiple studies has successfully provided new insights into targeted biological processes,” Toga said. “We hope that the functional analysis of the genes identified in this study will lead to the development of methods to control the growth of aphids and locusts. We also hope to clarify how organisms respond and adapt to density by applying meta-analysis to various species.
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The Innovation Center for Biodigital Transformation and the Japan Science and Technology Agency supported this research. The calculations for this work were performed on computers at Hiroshima University’s Genome Editing Innovation Center.
About Hiroshima University
Since its founding in 1949, Hiroshima University has strived to become one of Japan’s most important and comprehensive universities for the promotion and development of scholarship and education. Consisting of 12 undergraduate schools and 4 graduate schools, ranging from natural sciences to humanities and social sciences, the university has become one of the most distinguished comprehensive research universities in Japan.
Website in English: https://www.hiroshima-u.ac.jp/en