**Author details**

Maria R. Albiach-Marti

Address all correspondence to: maria@valgenetics.com

Molecular Phytopathology Unit, ValGenetics, The University of Valencia Science Park, C/ Catedrático Agustín Escardino, Paterna, Valencia, Spain

#### **References**


[3] Albiach-marti, M. R. Molecular Virology and Pathogenicity Determinants of Citrus Tristeza Virus. In Garcia ML. Romanowski V (ed). Viral Genomes. Rijeka: InTech; (2012). Available from www.intechopen.com, 275-302.

**9. Conclusions**

**Acknowledgements**

**Author details**

**References**

Maria R. Albiach-Marti

This book chapter was financed by ValGenetics.

Address all correspondence to: maria@valgenetics.com

Catedrático Agustín Escardino, Paterna, Valencia, Spain

*Virology*, , 208, 511-520.

*Citrus tristeza virus* research continues pushing the molecular virology technology to further limits. Molecular tools have been developed to study CTV gene expression, replication, assembly, systemic infection, viral movement, and plant-host interactions. The scientific results reveal a virus with a complex genetics that has become a model for molecular virology studies and viral biotechnology development. However, in spite of the CTV complicated genetics, further efforts need to be applied to engineer viral-based vectors, or additional biotechnological approaches, with the aim of understanding the mechanisms of viral move‐ ment, pathogenesis, resistance and aphid transmission, and the role of the D-RNAs in the CTV infection or the pathogenesis process. This valuable information will be applied to implement

The author thanks W.O. Dawson, S. Gowda, B. Belliure-Ferrer and B. Sabater for critically reviewing this manuscript. Likewise, the author is grateful to Drs A. Urbaneja, A. Hermoso de Mendoza and S. Foliminova for kindly provide the pictures included in Figures 1 and 7.

Molecular Phytopathology Unit, ValGenetics, The University of Valencia Science Park, C/

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**Chapter 2**

**RNA 5′-end Maturation: A Crucial Step in the Replication**

Viruses are a vastly diverse group of infectious particles with many different structures, mechanisms of function and ingenious strategies of invading host organisms for their own proliferation. One of the key features that ties viruses together as an inclusive group, is the reliance on living cells for replication and propagation. On their own, viruses lack the cellular machinery necessary for many life-sustaining functions including protein translation and metabolism. Regardless of the organization of a viral genome or the type of nucleic acid, infection of a host cell and viral propagation is dependent on the transcription of viral mRNA and, in turn, the translation of viral proteins as well as genome replication. Because viruses are dependent on host cell machinery for most of these processes, they have driven an outstanding virus-host co-evolution. Viruses that rely on the replication machinery of the host cell become cell-cycle dependent in their own replication. Furthermore, just as viruses have evolved ways to hijack necessary cellular proteins, cells have evolved complex mechanisms for fighting infection by detection and degradation of foreign mRNA. In order for viral mRNA to utilize host cell machinery, begin translation and remain both stable and undetected in the cytoplasm, it must contain the post-translational modifications of a host cell mRNA including, but not limited to, a 5' cap structure. By disguising viral mRNA with the same structural elements found in host mRNA, the cellular defense mechanism can be evaded and protein translation may occur. The significance of the cap structure can be seen through the diversity of cap-synthesis pathways across vastly different viral families that all lead to the formation

> © 2013 Picard-Jean et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Frédéric Picard-Jean, Maude Tremblay-Létourneau, Elizabeth Serra, Christina Dimech, Helene Schulz,

Mathilde Anselin, Vincent Dutilly and

Additional information is available at the end of the chapter

**of Viral Genomes**

Martin Bisaillon

**1. Introduction**

http://dx.doi.org/10.5772/56166
