1Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad-500046
2Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843, USA.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
RNA has important regulatory roles in cellular metabolism, development, innate defense mechanisms, and in establishing systemic infection by viruses. The multipartite viruses with separately encapsidated genomes could have their genomes/virions introduced into different cells, or leaves of a plant, thus necessitating the trafficking of one or more of the viral RNAs for the successful completion of the infection cycle. To test this idea, individual or combinations of the plant-infecting brome mosaic virus (BMV) RNAs were transiently expressed in different leaves of Nicotiana benthamiana plants by agroinfiltration. BMV RNA3 was found to traffic from the initial site of expression to the other parts of the plant as detected by Northern blot analyses and also by the expression of an endoplasmic reticulum-targeted green fluorescent protein (ER-GFP) from chimeric RNA3 molecules. The trafficked RNA3 could restore viral RNA replication, subgenomic RNA4 transcription and virion production. Surprisingly, BMV RNA3 trafficking could take place in the absence of either of its movement or capsid proteins. However, coexpression of the movement protein increased the trafficking of BMV RNAs. All three BMV RNAs trafficked to sink leaves near the apical meristem as well as to the source leaves at the bottom of the stem, suggesting bidirectional trafficking through the phloem. Transient expression of two yeast RNA-binding proteins that specifically recognize BMV RNAs were found to debilitate BMV RNA3 trafficking.
