Banca de DEFESA: Marcos Silva de Queiroz Ferreira

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Marcos Silva de Queiroz Ferreira
DATE: 28/02/2023
TIME: 14:00
LOCAL: Meio virtual
TITLE:

Diversity of Sida micrantha mosaic virus isolates and characterization of new begomoviruses in Malvaceae in Brazil

KEY WORDS:
PAGES: 60
BIG AREA: Ciências Biológicas
AREA: Biologia Geral
SUMMARY:

Begomovirus (family Geminiviridae) corresponds to the largest genus of plant viruses, encompassing viral species that have one or two single-stranded circular DNA molecules, separately encapsidated in 18-30 nanometer particles. Isolates with a bipartite genome (with DNA–A and DNA–B components) predominate in tomato in the New World. Begomoviruses are transmitted with great efficiency by the Bemisia tabaci Middle East Asian Minor 1 (MEAM-1 = biotype B) vector, which is widely distributed, with a polyphagous feeding habit and high adaptability to different environmental conditions. The introduction of B. tabaci MEAM 1 in the early 1990s was the triggering factor for begomovirus epidemics in tomato in Brazil, with a subsequent increase in the number of new viral species. Furthermore, distinct patterns of diversity and dynamics of viral subpopulations were observed in different environments. In this scenario, weeds play an important role as they function as natural reservoirs of begomovirus. New viral species have been reported in weeds, including areas in and around commercial tomato fields. Some weed begomoviruses have been identified and biologically characterized, however it is believed that these studies have not been extensive enough to estimate the actual diversity of new species in weeds. In the country, four begomoviruses were reported concomitantly infecting tomato and weeds. Globally, more than 40 begomoviruses have been described in Malvaceae species, and some of these have been detected originally infecting Solanaceae species. The small and bipartite genome, together with the transmission efficiency and polyphagy of the vector, provide favorable conditions for the occurrence of mixed infections and recombination and pseudo-recombination events between begomoviruses, thus contributing to the frequent alteration of the genetic structure of viral populations in our conditions. Different strategies have been employed to analyze the evolutionary processes capable of shaping the genetic-molecular structure of begomoviruses. The main strategy is to obtain the complete viral genome (DNA–A and DNA–B) for further analysis using different programs and evolutionary models. The metagenomics combined with High Throughput Sequencing (HTS) has allowed to determine a great viral diversity present in Brazil. A high frequency of mixed infections has been detected with many of them involving potential new species capable of inducing severe symptoms in plants. In the present work, four contigs obtained from HTS of Malvaceae leaf samples were selected for study and characterization, in according to the methodology carried out by the LVV-Fito team and summarized below. Initially foliar samples of weeds showing typical symptoms of begomovirus (generalized chlorosis, mosaics, and golden spots) were collected in tomato production areas and/or areas close to tomato cultivation, in the five regions of the country. Samplings were carried out from 2001 to 2020, with a total of 78 leaf samples from plants of the Malvaceae family analyzed (selected using the year/place of collection as criteria). Total DNA was extracted via CTAB and organic solvents and stored at -20 °C. The initial confirmation of the presence of begomovirus infection in the samples was made through PCR (polymerase chain reaction) assays using degenerate primers ‘PAR1c496’ and ‘PAL1v1978’. Viral circular DNAs were enriched in positive samples via rolling circle amplification (RCA). High-throughput sequencing (HTS) was performed on an Illumina HiSeq2500 platform. 5 The viral contigs were annotated and the reads were mapped back to the annotated genome using the ‘Map to reference’ tool available in the Geneious 11.1.5 program. About 7,391,728 million readings were obtained from the pool of 78 samples. After assembly, using the CLC Genomics Workbench 11 program, 10,679 contigs were obtained. Four contigs were selected. Three of these contigs corresponded to complete DNA–A and exhibited identity levels below 91%, consistent with the current taxonomic criteria for defining new species within the genus Begomovirus. The DNA component– Potential new species #1 showed 79% identity with Sidastrum golden leaf spot virus (HM357458), new species #2 showed 81% identity with Oxalis yellow vein virus (KM887907), while new #3 showed 78% identity with Sida yellow mosaic Alagoas virus (JX871383), confirming the occurrence of three new species of begomovirus in weeds. Sequences of DNA – B components were obtained and analyzes performed, including confirmation of cognates species. The fourth contig showed 98,24% identity with Sida micranta mosaic virus (SiMMV) (KC706535). After using specific primers, already available, a result of 41 positive samples for SiMMV was obtained. The characterization of these three species, as well as the occurrence and distribution of Sida micranta mosaic virus in five Brazilian regions will be presented in this dissertation.

BANKING MEMBERS:
Externo ao Programa - 1701961 - CLEBER FURLANETTO
Externo ao Programa - 1703888 - HELSON MARIO MARTINS DO VALE
Externa à Instituição - MIRTES FREITAS LIMA - EMBRAPA
Presidente - 1723060 - RITA DE CASSIA PEREIRA CARVALHO