Edinburgh, Scotland, United Kingdom - TAIR

Networking by small-molecule hormones in
plant immunity
Plants live in complex environments in which they interact with a broad range of
pathogens and insects. Various genomics approaches expanded our understanding
of the molecular mechanisms by which plants tailor their defense
response to harmful attackers. Diverse small-molecule hormones such as
salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) play pivotal roles in the
regulation of the defense signaling network. 1 Their signaling pathways crosscommunicate,
providing the plant with a powerful capacity to finely tailor its
immune response to the attacker encountered. 2 Our research is focused on the
antagonism between SA and JA signaling. Using a pharmacological approach to
dissect the kinetics and mechanisms underlying SA-JA crosstalk, we
demonstrated that SA-JA antagonism is conserved among Arabidopsis
accessions, highlighting the importance of this mechanism for plant survival. The
kinetics of SA and JA signaling appears to play an important role in the outcome
(antagonistic, synergistic) of the SA-JA interaction. The antagonistic effect of SA
on JA-responsive gene transcription appears to be linked to SA-induced changes
in the cellular redox potential, suggesting that SA-JA cross-talk is redox
regulated. Several key regulatory proteins involved in pathway cross-talk have
been identified, including the redox-sensitive protein NPR1. ET appears to act
as an important modulator of NPR1 function in SA-JA crosstalk. Furthermore we
showed that SA-mediated suppression of JA signaling acts downstream of SCF-
COI1-JAZ components of the JA signaling pathways and is directly targeted at
GCC-box containing promoters of JA-responsive genes. Molecular mechanisms
of SA-JA crosstalk will be discussed.
1 Pieterse, Leon-Reyes, Van der Ent, Van Wees (2009). Networking by smallmolecule
hormones in plant immunity. Nature Chem. Biol., in press.
2 Koornneef and Pieterse (2008). Cross-talk in defense signaling. Plant Physiol.
146:839-844.
35
L10
Thursday 11:00 - 11:30
Plant Defence
Corné Pieterse
Antonio Leon-Reyes
Dieuwertje Van der Does
Adriaan Verhag,
Annemart Koornneef
Saskia Van Wees
Utrecht University
Utrecht
The Netherlands