RNA silencing against geminivirus: complementary action of posttranscriptional gene silencing and transcriptional gene silencing in host recovery.
RNA silencing in plants is a natural defense system mechanism against invading nucleic acids such as viruses. Geminiviruses, a family of plant viruses characterized by a circular, single-stranded DNA genome, are thought to be both inducers and targets of RNA silencing. Some natural geminivirus-host interactions lead to symptom remission or host recovery, a process commonly associated with RNA silencing-mediated defense. Pepper golden mosaic virus (PepGMV)-infected pepper plants show a recovery phenotype, which has been associated with the presence of virus-derived small RNAs. The results presented here suggest that PepGMV is targeted by both posttranscriptional and transcriptional gene silencing mechanisms. Two types of virus-related small interfering RNAs (siRNAs) were detected: siRNAs of 21 to 22 nucleotides (nt) in size that are related to the coding regions (Rep, TrAP, REn, and movement protein genes) and a 24-nt population primarily associated to the intergenic regions. Methylation levels of the PepGMV A intergenic and coat protein (CP) coding region were measured by a bisulfite sequencing approach. An inverse correlation was observed between the methylation status of the intergenic region and the concentration of viral DNA and symptom severity. The intergenic region also showed a methylation profile conserved in all times analyzed. The CP region, on the other hand, did not show a defined profile, and its methylation density was significantly lower than the one found on the intergenic region. The participation of both PTGS and TGS mechanisms in host recovery is discussed.
Rodríguez-Negrete
Edgar A
EA
Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del IPN-U. Irapuato, Km 9.6 Libramiento Norte, Irapuato, Gto. 36821 Mexico.
Carrillo-Tripp
Jimena
J
Rivera-Bustamante
Rafael F
RF
D001483:Base Sequence; D015152:Blotting, Northern; D002212:Capsicum / Q000821:virology; D019175:DNA Methylation; D017931:DNA Primers; D017791:Geminiviridae / Q000235:genetics*; D020868:Gene Silencing; D008970:Molecular Weight; D016133:Polymerase Chain Reaction; D012323:RNA Processing, Post-Transcriptional; D034741:RNA, Small Interfering; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D014158:Transcription, Genetic
D017931:DNA Primers; D034741:RNA, Small Interfering; D012367:RNA, Viral