RESUMO
Rice tungro disease is caused by a complex of two viruses, Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV). To examine the RNAi-based defence response in rice during tungro disease, we characterized the virus-derived small RNAs and miRNAs by Deep Sequencing. We found that, while 21 nt/22 nt (nucleotide) siRNAs are predominantly produced in a continuous, overlapping and asymmetrical manner from RTBV, siRNA accumulation from RTSV were negligible. Additionally, 54 previously known miRNAs from rice, predicted to be regulating genes involved in plant defence, hormone signaling and developmental pathways were differentially expressed in the infected samples, compared to the healthy ones. This is the first study of sRNA profile of tungro virus complex from infected rice plants. The biased response of the host antiviral machinery against the two viruses and the differentially-expressed miRNAs are novel observations, which entail further studies.
Assuntos
Regulação da Expressão Gênica de Plantas/imunologia , Regulação Viral da Expressão Gênica , Oryza/genética , RNA Interferente Pequeno/genética , Tungrovirus/genética , Waikavirus/genética , Perfilação da Expressão Gênica , Sequenciamento de Nucleotídeos em Larga Escala , Interações Hospedeiro-Patógeno , MicroRNAs/antagonistas & inibidores , MicroRNAs/genética , MicroRNAs/metabolismo , Oryza/imunologia , Oryza/virologia , Doenças das Plantas/genética , Doenças das Plantas/imunologia , Doenças das Plantas/virologia , Imunidade Vegetal/genética , Proteínas de Plantas/genética , Proteínas de Plantas/imunologia , RNA Interferente Pequeno/metabolismo , RNA Viral/antagonistas & inibidores , RNA Viral/genética , RNA Viral/metabolismo , Tungrovirus/metabolismo , Waikavirus/metabolismoRESUMO
Rice tungro disease (RTD) is a significant yield constraint in rice-growing areas of South and Southeast Asia. Disease symptoms are caused largely by infection by the rice tungro bacilliform virus (RTBV). Two host transcription factors, RF2a and RF2b, regulate expression of the RTBV promoter and are important for plant development. Expression of a dominant negative mutant of these factors in transgenic rice resulted in phenotypes that mimic the symptoms of RTD, whereas overexpression of RF2a and RF2b had essentially no impact on plant development. Conversely, lines with elevated expression of RF2a or RF2b showed weak or no symptoms of infection after Agrobacterium inoculation of RTBV, whereas control plants showed severe stunting and leaf discoloration. Furthermore, transgenic plants exhibited reduced accumulation of RTBV RNA and viral DNA compared with nontransgenic plants. Similar results were obtained in studies after virus inoculation by green leafhoppers. Gaining disease resistance by elevating the expression of host regulators provides another strategy against RTD and may have implications for other pararetrovirus infections.
