Plant-virus interactions during the infective process

Abstract

Viruses that infect plants are generally single-stranded (ss) positive-sense RNA viruses. The accumulation of the virus progeny inside the plant cells involves translation, replication, cell–to-cell and long-distance movement of viral sequences. Over the past 30 years high progress has been made in understanding the interactions between the virus and the host plant during these processes. Reports of host factors implicated in promoting viral cycle and the characterization of plant virus receptors (R) and their resistance mechanisms in Solanaceae, Cucurbitaceae, Leguminoseae and in Arabidopsis thaliana have contributed extensively to understanding this complex interaction. Almost all of the R genes cloned share structural similarity, harbouring LRR, NBS, TIR and LZ domains, suggesting a convergence in the signal transduction machinery in plant defence. Plant viruses evolve very rapidly. This is possible because of their very short replication cycles, large numbers of genomes within each cell and across many cells per host, and many hosts infected. Therefore, viruses readily produce new avirulence factors and resistance-breaking viral genotypes. To overcome the appearance of new viral races, plants generate R gene variants through recombination processes and develop specialized defence mechanisms such as post-transcriptional gene silencing. However, viruses such as Potyvirus X can overcome this type of plant resistance. Recent insights into virus-host interactions have been compiled in this review, focusing on the interaction between Tobacco mosaic virus and the N receptor in Nicotiana tabacum, to describe the possible transduction mechanisms that trigger a cascade of downstream events leading to viral defence in plants.