RESUMO
Plant viruses depend on a number of host factors for successful infection. Deficiency of critical host factors confers recessively inherited viral resistance in plants. For example, loss of Essential for poteXvirus Accumulation 1 (EXA1) in Arabidopsis thaliana confers resistance to potexviruses. However, the molecular mechanism of how EXA1 assists potexvirus infection remains largely unknown. Previous studies reported that the salicylic acid (SA) pathway is upregulated in exa1 mutants, and EXA1 modulates hypersensitive response-related cell death during EDS1-dependent effector-triggered immunity. Here, we show that exa1-mediated viral resistance is mostly independent of SA and EDS1 pathways. We demonstrate that Arabidopsis EXA1 interacts with three members of the eukaryotic translation initiation factor 4E (eIF4E) family, eIF4E1, eIFiso4E, and novel cap-binding protein (nCBP), through the eIF4E-binding motif (4EBM). Expression of EXA1 in exa1 mutants restored infection by the potexvirus Plantago asiatica mosaic virus (PlAMV), but EXA1 with mutations in 4EBM only partially restored infection. In virus inoculation experiments using Arabidopsis knockout mutants, EXA1 promoted PlAMV infection in concert with nCBP, but the functions of eIFiso4E and nCBP in promoting PlAMV infection were redundant. By contrast, the promotion of PlAMV infection by eIF4E1 was, at least partially, EXA1 independent. Taken together, our results imply that the interaction of EXA1-eIF4E family members is essential for efficient PlAMV multiplication, although specific roles of three eIF4E family members in PlAMV infection differ. IMPORTANCE The genus Potexvirus comprises a group of plant RNA viruses, including viruses that cause serious damage to agricultural crops. We previously showed that loss of Essential for poteXvirus Accumulation 1 (EXA1) in Arabidopsis thaliana confers resistance to potexviruses. EXA1 may thus play a critical role in the success of potexvirus infection; hence, elucidation of its mechanism of action is crucial for understanding the infection process of potexviruses and for effective viral control. Previous studies reported that loss of EXA1 enhances plant immune responses, but our results indicate that this is not the primary mechanism of exa1-mediated viral resistance. Here, we show that Arabidopsis EXA1 assists infection by the potexvirus Plantago asiatica mosaic virus (PlAMV) by interacting with the eukaryotic translation initiation factor 4E family. Our results imply that EXA1 contributes to PlAMV multiplication by regulating translation.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Fator de Iniciação 4E em Eucariotos , Doenças das Plantas , Potexvirus , Arabidopsis/metabolismo , Arabidopsis/virologia , Fator de Iniciação 4E em Eucariotos/genética , Fator de Iniciação 4E em Eucariotos/metabolismo , Doenças das Plantas/genética , Potexvirus/fisiologia , Proteínas de Arabidopsis/metabolismo , Resistência à Doença/genética , Ligação Proteica , Motivos de Aminoácidos , Deleção de Genes , Células Vegetais/virologia , Biossíntese de Proteínas/genéticaRESUMO
Pleioblastus mosaic virus (PleMV) is a tentative member of the genus Potyvirus in the family Potyviridae and was discovered in bamboo with mosaic symptoms in Tokyo, Japan. Since no information on the genome sequence of PleMV has been reported, its taxonomic position has long been uncertain. Here, we report the first complete genome sequences of two distinct PleMV isolates. Excluding the 3'-terminal poly(A) tail, their genomic RNA sequences consist of 9,634 and 9,643 nucleotides (nt); both contain a large open reading frame (ORF) encoding a polyprotein and a small ORF termed PIPO. The large ORFs of the two isolates share 79.2% and 87.6% sequence identity at the nucleotide (nt) and amino acid (aa) level, respectively, and were found to have the highest nt and aa sequence identity (69.0% and 69.9%) to the potyvirus johnsongrass mosaic virus (JGMV). Phylogenetic analysis showed that PleMV is most closely related to JGMV but forms its own clade. These results suggest that PleMV is a distinct member of the genus Potyvirus.
Assuntos
Genoma Viral/genética , Potyvirus/genética , Sequência de Aminoácidos , Sequência de Bases , Genômica/métodos , Japão , Fases de Leitura Aberta/genética , Filogenia , Poliproteínas/genética , RNA Viral/genética , Análise de Sequência de DNA/métodos , Sequenciamento Completo do Genoma/métodosRESUMO
The complete genome sequence of an iris severe mosaic virus isolate (ISMV) from Iris tectorum in Japan was determined for the first time. According to sequence identity analyses, our specimen is closely related to isolates reported from China.
