Virus infection mechanism identified
Researchers from the Australian research organisation, the CSIRO, have identified a key gene that enables viruses to infect hosts. They studied the process by which cucumber mosaic virus (CMV) infects plant cells, and confirmed that specific satellite viral particles are needed to cause symptoms, such as leaf yellowing, in host plants. Satellite particles comprise small non-protein coding RNA sequences that silence expression of specific host genes through RNA interference (siRNA). The researchers found that CMV infections could only cause chlorotic symptoms when the satellite RNA sequence matched that of a fragment of the host magnesium chelatase subunit gene, CHL1, mRNA, which is essential for chlorophyll biosynthesis. In this case, satellite and host have a 22 nucleotide (nt) sequence in common, which is targeted for mRNA cleavage by CMV satellite siRNA.