Comparative analysis of RNA interference and pattern-triggered immunity induced by dsRNA reveals different efficiencies in the antiviral response to potato virus X.

Antiviral responses induced by double-stranded RNA (dsRNA) include RNA interference (RNAi) and pattern-triggered immunity (PTI), but their relative contributions to antiviral defence are not well understood. We aimed at testing the impact of exogenous applied dsRNA on both layers of defence against potato virus X expressing GFP (PVX-GFP) in Nicotiana benthamiana. Co-inoculation of PVX-GFP with either sequence-specific (RNAi) or nonspecific dsRNA (PTI) showed that nonspecific dsRNA reduced virus accumulation in both inoculated and systemic leaves.

Adaptive substitutions at two amino acids of HCPro modify its functional properties to separately increase the virulence of a potyviral chimera.

We had previously reported that a plum pox virus (PPV)-based chimera that had its P1-HCPro bi-cistron replaced by a modified one from potato virus Y (PVY) increased its virulence in some Nicotiana benthamiana plants, after mechanical passages. This correlated with the natural acquisition of amino acid substitutions in several proteins, including in HCPro at either position 352 (Ile→Thr) or 454 (Leu→Arg), or of mutations in non-coding regions. Thr in position 352 is not found among natural potyviruses, while Arg in 454 is a reversion to the native PVY HCPro amino acid.

Transgenerational Tolerance to Salt and Osmotic Stresses Induced by Plant Virus Infection.

Following pathogen infection, plants have developed diverse mechanisms that direct their immune systems towards more robust induction of defense responses against recurrent environmental stresses. The induced resistances could be inherited by the progenies, rendering them more tolerant to stressful events. Although within-generational induction of tolerance to abiotic stress is a well-documented phenomenon in virus-infected plants, the transgenerational inheritance of tolerance to abiotic stresses in their progenies has not been explored.

Adaptation of a Potyvirus Chimera Increases Its Virulence in a Compatible Host through Changes in HCPro.

A viral chimera in which the bi-cistron of a plum pox virus construct (PPV-GFP) was replaced by that of potato virus Y (PVY) spread slowly systemically in plants and accumulated to levels that were 5-10% those of parental PPV-GFP. We tested whether consecutive mechanical passages could increase its virulence, and found that after several passages, chimera titers rose and symptoms increased. We sequenced over half the genome of passaged chimera lineages infecting two plants.

Water Deficit Improves Reproductive Fitness in Plants Infected by .

Plants are concurrently exposed to biotic and abiotic stresses, including infection by viruses and drought. Combined stresses result in plant responses that are different from those observed for each individual stress. We investigated compensatory effects induced by virus infection on the fitness of hosts grown under water deficit, and the hypothesis that water deficit improves tolerance, estimated as reproductive fitness, to virus infection.