Viral pathogens plants

One of the best understood of the many viral pathogens of plants is the tobacco mosaic virus (Fig. 7-8). Its 6.7-kb positive strand RNA encodes a replicase, coat protein, and at least one other protein.696... 

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One of fhe best understood of the many viral pathogens of plants is the tobacco mosaic virus (Fig. 

Studies in the plant disease resistance area gave further support to the presence of a mammalian-type NOS in plants. In resistance to fungal, bacterial or viral infections, plants deploy specific mechanisms. These mechanisms are largely based on the specific recognition of pathogen... 

Photosynthesis in plants can be inhibited by many conditions, such as invasion by viral pathogens. The effects of TMV on photosynthesis are quite variable (4-6), which may reflect the different effects on photosynthesis induced by the different TMV strains. One of the key issues still to be resolved with the pathology of viral infection is what viral effect causes the expression of disease symptoms. Since TMV infection can affect leaf development and pigmentation and often plant growth, it is quite likely that a primal site of TMV infection is in the chloroplast. However, it is not known if the expression of chlorotic symptoms from TMV infection is the result of the inhibition of photosynthesis (5,7,8) or if TMV inhibits some other host process which induces symptoms and this then causes the inhibition of photosynthesis. 

Members of the stilbene family which have the C6-C2-C6 structure (Table 1.1), like flavon-oids, are polyphenolic compounds. Stilbenes are phytoalexins, compounds produced by plants in response to attack by fungal, bacterial and viral pathogens. Resveratrol is the most common stilbene. It occurs as both the cts and the trans isomers and is present in plant tissues primarily as fra s-resveratrol-3-0-glucoside which is known as piceid and polydatin (Figure 1.14). A family of resveratrol polymers, viniferins, also exists. 

Several plant vims coat proteins, including those of TMV, CPMV, AlMV and Tomato bushy stunt vims (TBSV), have been used to produce and deliver antigenic determinants from a variety of viral and bacterial pathogens. These data have been summarized in numerous publications and several reviews [12,13]. The ease of virus purification coupled with enhanced peptide immunogenicity when fused to carrier molecules makes this approach very attractive for vaccine development. 

The tobacco mosaic virus (center right), a plant pathogen, has a structure similar to that of MB, but contains ssRNA instead of DNA. The poliovirus, which causes poliomyelitis, is also an RNA virus. In the influenza virus, the pathogen that causes viral flu, the nucleocapsid is additionally surrounded by a coat derived from the plasma membrane of the host cell (C). The coat carries viral proteins that are involved in the infection process. 

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