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Genome sequencing and the role of juvenile hormone on the queen phenotype in the genus Melipona


Dr. Natália de Souza Araujo's project is specifically directed towards a long-standing question in stingless bee biology, the genetics underlying the determination of the queen and worker castes in the genus Melipona. While in practically all social bee species, caste fate in the female sex is determined by nutritional factors, i.e., the quantity and/or quality of the larval food that the nurse bees provide to the larvae, the genus Melipona is an exception. All brood cells are of the same size and so is the quantity of the larval food. Yet, about 20-25% of the females in Melipona colonies develop as queens. This observation led Prof. Dr. Warwick E. Kerr to propose a Mendelian genetic caste determination mechanism for this genus. He assumed that queens should be heterozygous at two loci, each comprising two alleles, while workers should be homozygous in one or both loci, resulting in a 1:3 segregation of queens to workers. Subsequent attempts to test the hypothesis via topical treatment of the larvae with juvenile hormone (JH) were only partially successful. These larvae did develop a queen phenotype, but they did not found colonies and, hence, the caste proportions in the offspring could not be determined. The advances in the genomics field now offer the tools to address this question through direct sequencing of the genomes of queens and workers. For this, Dr. Natália de Souza Araujo will collect pupae of two Melipona species kept in our meliponary. At the pupal stage the respective caste fate is clearly visible, allowing to assess genomic, epigenomic, and transcriptomic differences between the queens and the workers, and whether such differences are evolutionarily shared among Melipona species. A second part of the project addresses the role of JH in the determination of the caste phenotype. For this, synthetic JH-III will be topically applied to larvae, to assess JH-dependent transcriptomics changes during the critical temporal window for the determination of the caste phenotype during development. The sampling of the queens and workers for the genomic and epigenomic analyses and the JH-application experiments will be done during Dr. Araujo's stay in Ribeirão Preto. The sequencing of the respective genomes and transcriptomes will be done in the genomics facility of the University of Brussel, funded by Dr. Araujo FNRS project. This genome information on two Melipona species will represent a major synergism with the genomics resources for stingless bees to be generated in our own FAPESP-funded project. Dr. Natália de Souza Araujo is currently a post-doctoral fellow of the Belgian Research Foundation (FNRS) at the Université Libre de Bruxelles, Belgium. Her Doctoral work done at IB-USP and defended in 2016, was on the expression of genes related to social behavior in bees of different levels of sociality. After her PhD she accepted a post-doctoral position at the Université de Liége, Belgium, where she worked from 2017-2019 on applied genomics and bioinformatics of mammals. In 2019, she moved to the Université Libre de Bruxelles, where she now has her own FNRS funded project on genetic and epigenetic factors involved in queen determination in the stingless bee genus Melipona. This current research project is developed in collaboration with my laboratory, and its results will make a direct major contribution to our current FAPESP-funded project (2020/13296-9) on comparative genomics and gene expression related to the life histories of the Neotropical stingless bees. Her extensive experience in the generation and analysis of genomic and transcriptomic data of bees will generate a considerable amount of synergy between her project and our current FAPESP-funded project. (AU)

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