How Plant Viruses Cause Disease

Tobacco plants affected by the cucumber mosaic virus (left) and resistant to it (right). Credit: Carl Davies CSIRO

Researchers have discovered how plant viruses cause disease in certain plants. While studying a common plant virus, the cucumber mosaic virus (CMV), it was discovered that the expression of symptoms of the CMV disease are dependent upon the presence of a unique viral particle called a satellite. According to researcher Dr. Ming-Bo Wang, "What we found was that CMV, accompanied by a special type of viral particle called a 'satellite', causes its distinctive yellowing symptoms in plants by slicing a gene that makes chlorophyll, the green pigment in leaves. By preventing the production of chlorophyll, the virus causes the leaves to become partially or entirely yellowed which dramatically affects growth and productivity." The gene affected by the virus was identified as CHL1.

The researchers point out that in order to cause disease, the satellite's genes must match the host's genes. This is why plant viruses only affect a limited number of hosts. The matching viral genes attach to the plant genes and splice or cut the genes leading to the production of different proteins. In this case, the genes that produce green chlorophyll pigment are altered, preventing chlorophyll production. The researchers were also successful in blocking the CMV disease by genetically modifying the chlorophyll-producing gene in plants so that it no longer matched the viral gene.

Learn more about this study:

• Major Breakthrough On How Viruses Infect Plants Science Daily