Caracterização do ciclo de multiplicação do orpheovírus e análise comparativa do transcriptoma de Nucleocytoviricota

Abstract

The discovery of the first giant virus, the Acanthamoeba polyphaga mimivirus, promoted debates about virus classification and its evolutionary process. Several new giant viruses havebeen isolated in recent years using different isolation platforms, as orpheovírus in V.vermiformis. This group, generically called nucleocytoplasmic large DNA viruses (NCLDVs) has unique characteristics never seen before in other viruses, such as the size of its viral particles, as well as the complexity of the genomes. In addition, they have the ability to temporarily regulate the expression of their genes. As new isolates have been discovered, studies have been conducted with the aim of increasing knowledge about their biology andinteraction with the host. This is possible through more in-depth investigations related to the multiplication cycle of these microorganisms. Thus, in this study it was observed that infectionby the orpheovirus is capable of morphologically changing the host cell and causing increased cell motility. Our data also demonstrated, that in the early stages of the orpheovirus multiplication cycle, phagocytosis is exploited as entry mechanism, and after entry, electronlucent viral factories are formed. It was observed an intense recruitment of mitochondria and membranes that are important in the process of morphogenesis, that begins with the formation of crescents that extend until the formation of the mature particle. It was also observed by counting particles, that they would be released from the host cell by exocytosis. In addition,when performing a comparative analysis of the transcriptome of different NCLDV, a temporal profile of expression of their genes throughout the multiplication cycle was observed as acommon characteristic of this group, which apparently remains throughout the evolution of this group of viruses. Furthermore, we observed that genes involved in viral morphogenesis are preferentially expressed at later times, while genes involved in DNA transcription and replication are mostly expressed at earlier times. Of the genes expressed by Marseillevirus,17% were classified as early, 48% as intermediate and 33% as late expression genes. The main functions observed for early genes are related to DNA replication and recombination,transcription and signal transduction. For intermediate genes are related to DNA replication and in late stages structural genes. A similar functional profile of early andintermediate genes was observed for both mimiviruses and vaccinia virus (VACV) and Frog virus 3 (FV-3). However,for FV-3 and VACV genes related to morphogenesis and structure were also observed to be expressed at intermediate and early times. Thus, although a common pattern of temporalgene expression ofthe analyzed viruses was observed, being a feature possibly inherited from the last common ancestor of Nucleocytoviricota, it is more likely that each viral group had adifferent history of gene gain and loss, possibly due to the interaction with different hosts.Understanding how the genes of a particular pathogen are expressed provides data that help to understand both its biology and interaction with its hosts. Understanding how the genes of a particular pathogen are expressed provides data that help in understanding its biology andinteraction with its hosts.