Function and diversity of P0 proteins among cotton leafroll dwarf virus isolates

Abstract\ud \ud Background\ud The RNA silencing pathway is an important anti-viral defense mechanism in plants. As a counter defense, some members of the viral family Luteoviridae are able to evade host immunity by encoding the P0 RNA silencing suppressor protein. Here we explored the functional diversity of P0 proteins among eight cotton leafroll dwarf virus (CLRDV) isolates, a virus associated with a worldwide cotton disease known as cotton blue disease (CBD).\ud \ud \ud Methods\ud CLRDV-infected cotton plants of different varieties were collected from five growing fields in Brazil and their P0 sequences compared to three previously obtained isolates. P0’s silencing suppression activities were scored based on transient expression experiments in Nicotiana benthamiana leaves.\ud \ud \ud Results\ud High sequence diversity was observed among CLRDV P0 proteins, indicating that some isolates found in cotton varieties formerly resistant to CLRDV should be regarded as new genotypes within the species. All tested proteins were able to suppress local and systemic silencing, but with significantly variable degrees. All P0 proteins were able to mediate the decay of ARGONAUTE proteins, a key component of the RNA silencing machinery.\ud \ud \ud Conclusions\ud The sequence diversity observed in CLRDV P0s is also reflected in their silencing suppression capabilities. However, the strength of local and systemic silencing suppression was not correlated for some proteins.Instituto Matogrossense do AlgodãoConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de\ud Janeiro (FAPERJ

Analysis of the full-length genome sequence of papaya lethal yellowing virus (PLYV), determined by deep sequencing, confirms its classification in the genus Sobemovirus

Papaya lethal yellowing virus (PLYV) causes an economically important disease in papayas in northeastern Brazil. Based on biological and molecular properties, PLYV has been tentatively assigned to the genus Sobemovirus. We report the sequence of the full-length genome of a PLYV isolate from Brazil, determined by deep sequencing. The PLYV genome is 4,145 nt long and contains four ORFs, with an arrangement identical to that of sobemoviruses. The polyprotein and CP display significant sequence identity with the corresponding proteins of other sobemoviruses. Pairwise comparisons and phylogenetic analysis based on complete nucleotide sequences confirm the classification of PLYV in the genus Sobemovirus