PVA interferes with the host methionine cycle
The methionine cycle (MTC), also known as activated methionine cycle, is among those primary metabolic pathways affected by plant virus infection. We found that PVA protein helper component-proteinase (HCPro) interacts with the enzymes of the host methionine cycle, S-adenosyl-L-methionine synthase and S-adenosyl-L-homocysteine hydrolase, to suppress RNA silencing and promote infection [2] and that HCPro is up-regulating via its interactions with MTC enzymes the high potato virus X titers and great symptom severity during mixed PVA-PVX infection [3]
PVA infection and host RNA metabolism
Virus infection begins by the production of viral replication proteins and establishment of the replication complex for multiplication of progeny genomes.
Newly synthesized vRNAs released from the replication complexes fight against the host’s defense pathways. Therefore, for a robust and productive infection, the viral RNA molecules need to be able to suppress gene silencing and cope also with the other cellular RNA metabolic pathways and degradation machineries.
Multifunctional potyviral protein called helper component-proteinase (HCPro) is a suppressor of RNA silencing. We found that it induces RNA granules (PGs), which are required to overcome active RNA silencing, achieve optimal viral gene expression and support virus accumulation. We proposed that PGs are the sites for active RNA silencing suppression. Many of the PG-associated host factors are important susceptibility factors of PVA infection.