pone-0000985-g004: Rate of cell-cell movement of TEV-GUS in inoculated leaves of B149 and C24.Leaves from plants inoculated with TEV-GUS were harvested at time points indicated and infiltrated with the colorimetric substrate X-gluc. Foci diameter were measured microscopically at time points indicated and represented as mean (±SD). Data at 24 h represent mean of 17 foci, other points represent mean of 39 foci.

Mentions: The rate of cell-to-cell movement of TEV-GUS in B149 was compared to that of C24 by measuring the diameter of infection foci microscopically (i.e., epidermal cells expressing GUS activity) at different time points. B149 had some impairment in the rate of cell-to-cell movement (foci diameter of 2.72 cells versus 3.88 cells in parental genotype) as early as day 2. While the limited foci that formed on B149 expanded slowly and stopped expanding after a few days, foci on C24 continued to expand rapidly (Figure 4 and Figure 3-Panels B and C). These two phenotypes i.e., reduction in foci initiation and expansion will be referred to as SLIM, for suppressed leaf infection and cell-to-cell movement.

Gopalan S - PLoS ONE (2007)

Bottom Line: Molecular genetic analysis and complementation analysis with three alleles of a previously published mutant lsp1 (loss of susceptibility to potyviruses) indicate a genetic interaction conferring haploinsufficiency between the B149 locus and certain alleles of lsp1 resulting in impaired host susceptibility.The pattern of restriction of TEV foci on leaves at or near the boundaries of certain cell types and leaf boundaries suggest dysregulation of a multidirectional non-cell autonomous regulatory mechanism.Understanding the nature of this multidirectional signal and the molecular genetic mechanism conferring it should potentially reveal a novel arsenal in the cellular machinery.

Affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington, United States of America. gopalans2@hotmail.com

Abstract: Viruses constitute a major class of pathogens that infect a variety of hosts. Understanding the intricacies of signaling during host-virus interactions should aid in designing disease prevention strategies and in understanding mechanistic aspects of host and pathogen signaling machinery.An Arabidopsis mutant, B149, impaired in susceptibility to Tobacco etch virus (TEV), a positive strand RNA virus of picoRNA family, was identified using a high-throughput genetic screen and a counterselection scheme. The defects include initiation of infection foci, rate of cell-to-cell movement and long distance movement.The defect in infectivity is conferred by a recessive locus. Molecular genetic analysis and complementation analysis with three alleles of a previously published mutant lsp1 (loss of susceptibility to potyviruses) indicate a genetic interaction conferring haploinsufficiency between the B149 locus and certain alleles of lsp1 resulting in impaired host susceptibility. The pattern of restriction of TEV foci on leaves at or near the boundaries of certain cell types and leaf boundaries suggest dysregulation of a multidirectional non-cell autonomous regulatory mechanism. Understanding the nature of this multidirectional signal and the molecular genetic mechanism conferring it should potentially reveal a novel arsenal in the cellular machinery.