Agriculture Reference
In-Depth Information
20.7 ABA and ROS
Reactive oxygen species (ROS) burst is one of the most important plant defense
responses to pathogens, whose efficacy in plant defense remains controversial
(Elad
1992
; Mehdy
1994
; Asselbergh et al.
2007
). Several studies implied that
there may exist an correlation between ABA level or signaling and ROS gen-
eration. Studies using the ABA-deficient
sitiens
tomato mutant revealed that the
timely and localized hyper-induction of hydrogen peroxide (H
2
O
2
, a major ROS)
and subsequent HR-mediated defense response in the epidermal cell wall can
effectively arrest the necrotrophic pathogens
B. cinerea
and
Erwinia chrysanthemi
(Asselbergh et al.
2007
,
2008
). Consistently, treatment with exogenous ABA can
restore the pathogen susceptibility of
sitiens
and also suppress H
2
O
2
accumula-
tion in this mutant (Asselbergh et al.
2007
). Thus, ABA deficiency in
sitiens
contributes to the generation of H
2
O
2
which may result in the epidermal ROS/
HR-mediated defense responses. Recently, Seifi et al. further showed that both
epidermal HR-mediated response and mesophyllic GS1/GABA-shunt-mediated
anti-cell death mechanism constitute the multifaceted resistance mechanism in
sitiens
against
B. cinerea
(Seifi et al.
2013
).
On the other hand, ROS are important messengers in ABA-mediated stress
responses. Studies have demonstrated that ROS play important roles in both
MAMP- and ABA-induced stomatal closure. ABA and flg22 activate the plasma
membrane-resident NADPH oxidases to trigger H
2
O
2
production (Kwak et al.
2003
; Mersmann et al.
2010
). The NADPH oxidase
RESPIRATORY BURST
OXIDASE HOMOLOGUE D
and
F
(
RBOHD
and
RBOHF
) function redundantly
in ABA-induced stomatal closure, and the
atrbohD/F
double mutations severely
impair this process (Kwak et al.
2003
). However, the MAMP-triggered ROS pro-
duction is mainly dependent on the
RBOHD
, whose mutation abolished the flg22-
and elf18-dependent stomatal closure (Mersmann et al.
2010
; Macho et al.
2012
).
In addition, the chloroplastic enzyme ASPARTATE OXIDASE (AO), which cata-
lyzes the first irreversible step in the de novo biosynthesis of NAD, is also required
for PAMP-induced RBOHD-dependent ROS burst and stomatal closure; however,
it does not impact RBOHF-mediated ABA-induced ROS burst or ABA-induced
stomatal closure (Macho et al.
2012
). Thus, the ABA and MAMP-triggered pro-
duction of ROS is achieved partially by sharing some common components.
20.8 Interplay Between ABA and SA-JA-ET During
Plant-Pathogen Interaction
Based on the above observations, impairment in ABA synthesis or signal resulted
in altered responses of host plants to various pathogen attack, indicating the
involvement of ABA in plant biotic stresses. Besides of the above-mentioned
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