| Abstract | dc.description.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. | en_US |
