Mechanisms behind basal immunity to plant viruses
Organisms detect microbes by recognising pathogen-associated molecular patterns (PAMPs) through pattern recognition receptors (PRRs). The interaction between PAMPs and PRRs activates a range of rapid, efficient defence responses resulting in PAMP-triggered immunity (PTI). However, some pathogens can overcome these defences by using effector proteins to interfere with PTI. The EU-funded project IBIS (Identification of basal immunity mechanisms against plant pathogenic viruses) investigated how plants perceive viruses and signal immunity to achieve plant resistance. Researchers set out to identify basal immunity against plant viruses using transcriptomic analyses to investigate how the plum pox virus (PPV) interacts with the model organism Arabidopsis thaliana. Basal immunity is the first line of preformed defences that protect plants against entire groups of pathogens. Plant biologists identified the cellular components involved in basal immunity against PPV and conducted a functional characterisation of PPV effectors that suppress plant basal immunity. They also evaluated the overlap between the basal immunity pathways triggered by plant pathogens. Reverse genetic analysis was conducted on Arabidopsis to determine if proteins already adopted in plant basal immunity against non-viral pathogens could also play a role in plant resistance to viruses. The results revealed the role of the PTI machinery in Arabidopsis, supporting the hypothesis that plants defend themselves against viruses through basal immunity. They also supported the hypothesis that basal immunity pathways against viral pathogens are at least partially shared with basal immunity pathways against non-viral pathogens. Furthermore, researcher found that one PPV protein can negatively regulate PAMP-triggered responses, showing for the first time that the genome of plant viruses can encode PTI suppressing-pathogenic effectors. Viruses can evolve very quickly to overcome the genetic resistance employed by plant breeders to control viral epidemics. Therefore, translating fresh knowledge from IBIS concerning antiviral PTI mechanisms into crop improvement programmes will be a major step forward in the fight to control viral epidemics in the field.
Keywords
Basal immunity, pathogenic viruses, pathogen-associated molecular patterns, pattern recognition receptors
