While plant viruses can severely damage crops, many wild plants remain remarkably tolerant to infections. What mechanisms allow them to manage viral threats without succumbing to disease?
A new review by Laura Elvira-Gonzales, Todd Blevins, and Manfred Heinlein (IBMP), published in the Journal of Experimental Botany, examines the molecular foundations of plant virus tolerance. Unlike resistance, which limits virus multiplication, tolerance mitigates the harmful effects of infection even as the virus persists.
The review builds on earlier findings by the Heinlein lab (Nature Plants, Körner et al., 2018), which showed that Arabidopsis plants infected with oilseed rape mosaic virus (ORMV) first display disease symptoms, then recover through an siRNA-mediated tolerance mechanism. This response depends on the accumulation of both virus- and host-derived small interfering RNAs (siRNAs), and the inactivation of the viral suppressor of RNA silencing (VSR).
Interestingly, symptom recovery occurs only in young, carbon-sink tissues, implying that siRNAs must be transported from mature, source tissues via plasmodesmata and the phloem. By reaching new tissues ahead of viral spread, mobile siRNAs can saturate the binding capacity of VSRs—neutralizing their interference with essential microRNA pathways.
This review highlights how mobile siRNAs, transported through the plant’s symplasmic network, act as key regulators of tolerance and developmental balance during viral infection. Understanding these pathways may help harness natural tolerance traits for crop improvement and virus-resilient agriculture.
