title: Geminivirus Rep protein interferes with the plant DNA methylation machinery and suppresses transcriptional gene silencing.
abstract: Cytosine methylation is an epigenetic mark that promotes gene silencing and plays an important role in genome defence against transposons and invading DNA viruses. Previous data showed that the largest family of single-stranded DNA viruses, Geminiviridae, prevents methylation-mediated transcriptional gene silencing (TGS) by interfering with the proper functioning of the plant methylation cycle. Here, we describe a novel counter-defence strategy used by geminiviruses, which reduces the expression of the plant maintenance DNA methyltransferases, METHYLTRANSFERASE 1 (MET1) and CHROMOMETHYLASE 3 (CMT3), in both locally and systemically infected tissues. We demonstrated that the virus-mediated repression of these two maintenance DNA methyltransferases is widespread among geminivirus species. Additionally, we identified Rep (Replication associated protein) as the geminiviral protein responsible for the repression of MET1 and CMT3, and another viral protein, C4, as an ancillary player in MET1 down-regulation. The presence of Rep suppressed TGS of an Arabidopsis thaliana transgene and of host loci whose expression was strongly controlled by CG methylation. Bisulfite sequencing analyses showed that the expression of Rep caused a substantial reduction in the levels of DNA methylation at CG sites. Our findings suggest that Rep, the only viral protein essential for replication, displays TGS suppressor activity through a mechanism distinct from that thus far described for geminiviruses.
authors.affiliation: Area de Genética, Instituto de Hortofruticultura Subtropical y Mediterránea 'La Mayora', Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Campus Teatinos, 29071, Málaga, Spain.
authors.forename: Edgar
authors.initials: E
authors.lastname: Rodríguez-Negrete
authors.affiliation: Area de Genética, Instituto de Hortofruticultura Subtropical y Mediterránea 'La Mayora', Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Campus Teatinos, 29071, Málaga, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Lozano-Durán
authors.affiliation: Area de Genética, Instituto de Hortofruticultura Subtropical y Mediterránea 'La Mayora', Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Campus Teatinos, 29071, Málaga, Spain.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Piedra-Aguilera
authors.affiliation: Area de Genética, Instituto de Hortofruticultura Subtropical y Mediterránea 'La Mayora', Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Campus Teatinos, 29071, Málaga, Spain.
authors.forename: Lucia
authors.initials: L
authors.lastname: Cruzado
authors.affiliation: Area de Genética, Instituto de Hortofruticultura Subtropical y Mediterránea 'La Mayora', Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Campus Teatinos, 29071, Málaga, Spain.
authors.forename: Eduardo R
authors.initials: ER
authors.lastname: Bejarano
authors.affiliation: Area de Genética, Instituto de Hortofruticultura Subtropical y Mediterránea 'La Mayora', Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Campus Teatinos, 29071, Málaga, Spain.
authors.forename: Araceli G
authors.initials: AG
authors.lastname: Castillo
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000821:virology*; D003596:Cytosine / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics* / Q000378:metabolism; D015257:DNA-Cytosine Methylases / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D044127:Epigenesis, Genetic; D017791:Geminiviridae / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013489:Suppression, Genetic; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D018744:DNA, Plant; D012333:RNA, Messenger; D014764:Viral Proteins; D003596:Cytosine; D015257:DNA-Cytosine Methylases