Factors that influence the movement of Cauliflower mosaic virus in susceptible and resistant plants
[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Since the first description of Cauliflower mosaic virus (CaMV), it has been the subject of many research papers, both as a model system for plant molecular virology and for the diseases it causes in major winter crops. CaMV has been associated with a number of ground-breaking papers. Movement through the plant is a necessary step for virus survival. For this reason, each viral protein is likely to interact with multiple host factors. Inactivation of one or more of these multiple interactions could lead to a delay in viral movement. The 40 kDa CaMV P1 movement protein (P1) is an essential protein in CaMV cell-to-cell movement. A CaMV mutant virus that contained a non-functional gene I coding sequence was not able to cause a systematic infection in plants, but the accumulation of encapsidated forms of virion DNA could still be detected, which indicated that P1 is not involved in CaMV replication. Upon transient expression in plant protoplasts, the P1 protein alone is sufficient to cause the formation of tubular extensions projecting out of the cell membrane. Furthermore, P1 is also able to induce the formation of tubules in whole leaves upon agroinfiltration into Nicotiana benthamiana leaves. ... Aphid transmission is essential for CaMV spread in nature. Previous studies have shown that the degree of aphid preference for virus-infected plants can alter the progress of virus epidemics. I tested whether infection of turnip plants (Brassica rapa L. var. rapa) with different strains of CaMV can influence turnip aphids' (Lipaphis erysimi) choice of host. Three different strains of CaMV that cause different types of symptoms on turnips were used in this study. These strains were NY8153 (severe), W260 (mild) and H12 (symptomless). I found that turnip aphids preferred W260-infected plants more than NY8153-, H12-infected or healthy plants. I concluded that aphids can recognize different strains of CaMV and will choose plants with specific strains over others; specifically aphids prefer W260-infected turnips over other choices. These results suggest that virus infection affects the aphid host choice and this in turn may have implications for the spread of different virus strains.
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