Publication of the month January 2011
Date: January 2011
Location: Of PAMPs and Effectors: The Blurred PTI-ETI Dichotomy
Typically, pathogen-associated molecular patterns (PAMPs) are
considered to be conserved throughout classes of microbes and to
contribute to general microbial fitness, whereas effectors are
species, race, or strain specific and contribute to pathogen
virulence. Both types of molecule can trigger plant immunity,
designated PAMP-triggered and effector-triggered immunity (PTI and
ETI, respectively). However, not all microbial defense activators
conform to the common distinction between PAMPs and effectors. For
example, some effectors display wide distribution, while some PAMPs
are rather narrowly conserved or contribute to pathogen virulence.
As effectors may elicit defense responses and PAMPs may be required
for virulence, single components cannot exclusively be referred to
by one of the two terms.
Therefore, we put forward that the distinction between PAMPs and
effectors, between PAMP receptors and resistance proteins, and,
therefore, also between PTI and ETI, cannot strictly be maintained.
Rather, as illustrated by examples provided here, there is a
continuum between PTI and ETI. We argue that plant resistance is
determined by immune receptors that recognize appropriate ligands
to activate defense, the amplitude of which is likely determined by
the level required for effective immunity.
