Temporal Expression Of Cucumber Mosaic Virus Genomic RNAs And Its Influence To The Expression Of Host MiRNAs And Target MRNAs

Viral infections generally destroy normal physiological activity of host plant, cause a series of disease symptoms, from chlorosis to plant developmental anomalies even necrosis of whole plant. Cucumber mosaic virus (CMV) is a prevalent plant pathogen all over the world. In addition, naturally isolates of CMV often encapsidate a satellite RNA (satRNA), which can usually attenuate disease symptoms induced by the helper virus. However, it is also found that some satRNAs have no or enhancement effects on pathogenicity of helper virus. In recent years, more and more researchs have shown that microRNAs (miRNAs) and small interfering RNAs (siRNAs) play important roles in the virus-host plants interaction process.miRNAs are an abundant subset of non-coding small RNA population, they can regulate the expression of target mRNAs in a sequence-specific manner. Similar to other environmental stress factors, disease symptoms caused by virus infection are the results of many gene expression regulation factors and signaling pathways interaction, and the mechanism of miRNAs in this process is not clear. On the one hand, this probably due to the difficulties in miRNA detection, and some miRNAs have not been realized. On the other hand, different viral pathogenic determinant would disrupt the miRNA pathway of host plants by different mechanisms.In this study, the wild type CMV-Fny, CMV-FnyΔ2b (CMV-Fny with 2b coding sequence deleted), CMV-Fny-satYn12 (CMV-Fny plus a benign satRNA), CMV-Fny-satT1 (CMV-Fny plus an aggressive satRNA), and the naturally isolate Tomato aspermy virus (TAV)-Bj were inoculated on tomato seedlings, we choose real-time RT-PCR as the monitoring method, to investigate the role of 2b and different satRNAs in perturbing miRNA pathways in the course of infections.The results shown that the accumulation of CMV RNAs were reduced in the presence of both satYn12 and satT1, with a higher reduction caused by satYn12 than that of satT1. The accumulation levels of eleven miRNAs and ten target mRNAs were enhanced by different degrees upon CMV-Fny and TAV-Bj infections. But the ability of CMV-Fny to interfere with miRNA pathway was dramatically suppressed in the addition of satYn12, whereas slightly affected by satT1. In plants harboring the infection of CMV-FnyΔ2b, the unaltered miRNAs and target mRNAs levels compared with mock inoculated plants indicated that 2b ORF was essential for perturbation of miRNA metabolism. These results indicate the complex mechanism by which satRNAs participate in CMV-tomato interaction, and suggest that the severity of disease symptoms positively correlates to some extent with the perturbation of miRNA pathway in tomato.