Agradecimentos: We thank the Laboratório de Vírus of Universidade Federal de Minas Gerais for all the support provided and the Microscopy Center of UFMG, in particular the technicians Denilson Cunha, Rodrigo Ferreira, Altair Mendes, Thalita Arantes, Marilene Oliveira, and Breno Moreira, who collaborated from the preparation to the session for observation of the samples. We would also like to thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), and Pró-Reitorias de Pesquisa e Pós-Graduação da UFMG (PRPG-UFMG) for the financial support, and LNNano/CNPEM for access to the EM facility via project 20230751. J.S.A., J.P.A.J., and F.R.S. are CNPq researchers Ver menos

Abstract: Giant viruses are noteworthy not only due to their enormous particles but also because of their gigantic genomes. In this context, a fundamental question has persisted: how did these genomes evolve? Here we present the discovery of cedratvirus pambiensis, featuring the largest genome ever described for a cedratvirus. Our data suggest that the larger size of the genome can be attributed to an unprecedented number of duplicated genes. Further investigation of this phenomenon in other viruses has illuminated gene duplication as a key evolutionary mechanism driving genome expansion in diverse giant viruses. Although gene duplication has been described as a recurrent event in cellular organisms, our data highlights its potential as a pivotal event in the evolution of gigantic viral genomes Ver menos