ABA Regulation of Plant Response to Biotic Stresses - Abscisic Acid: Metabolism, Transport and Signaling - page 406

synchronously restore the necrotrophic mode of resistance by enhancing JA bio-
synthesis (Mazumder et al. 2013 ). Thus, ABA can function in plant disease resist-
ance by enhancing one defense pathway but inhibiting another defense pathway.
Besides of the above-mentioned regulation of ABA during plant patho-
gen defense, such as stomatal innate immunity, callose deposition, ROS, and
cross talk with SA/JA/ET, ABA can affect plant defense responses by modulat-
ing the cell wall composition (Sánchez-Vallet et al. 2012 ) and also functions in
induced systemic resistance (ISR) that is elicited by below-ground rhizobacteria in
Arabidopsis (Van der Ent et al. 2009 ; Kumar et al. 2012 ).
20.11 Roles of ABA in Plant-Herbivore Interaction
In order to efficiently counteract the attack by herbivorous insects, plants have
evolved surveillance systems aimed to recognize attacking harmful insects and
respond with proper defense mechanisms, including the “early warning” response,
wound-induced resistance (WIR), and herbivore-associated molecular pattern
(HAMP)-induced immunity (HTI) (Erb et al. 2012 ). Following the recognition
of an herbivorous insect, plants use an complex signaling cascades to reprogram
their phenotype. Although the recognition of pathogens or herbivores can be very
specific, plants may use a “common downstream signaling machinery” to acti-
vate defense responses (Katagiri et al. 2010 ). Similar to their important roles in
plant response to pathogen infection, phytohormones are also involved in herbi-
vore defense, with the JA pathway playing a dominant role in host resistance. In
addition to this core hormonal signal, other plant hormones, including ABA, are
also been shown to participate in herbivore defense, and more and more evidence
demonstrated that different multiple hormone signaling pathways can cross-talk
or interact to translate initial perception events into appropriate responses that
increase survival and/or reproduction of plants under herbivore attack (Erb et al.
2012 ). Below, we will focus on the role of ABA in herbivore defense.
Several studies have showed that herbivore attack or treatment with herbivo-
rous oral secretions (OS) increases the ABA level in the host plant (Erb et al. 2009 ;
Sch￤fer et al. 2011 ; Erb et al. 2011 ; Tooker and De Moraes 2011 ). Analysis using
of mutants with altered ABA biosynthesis or signaling also supports participation
of ABA in herbivore defense. In most cases, ABA-deficient mutants were reported
to be more susceptible to herbivory (Thaler and Bostock 2004 ; Bodenhausen and
Reymond 2007 ). Transcription profiling analysis also revealed a modulating influ-
ence of ABA on herbivore-induced gene expression (Bodenhausen and Reymond
2007 ). Interestingly, recent studies have shown that ABI4 may integrate redox
signaling pathway to promote resistance to aphid feeding, while the aba2 and
abi1 mutant plants showed opposite aphid resistance to those of abi4 (Kerchev
et al. 2013 ), suggesting that the ABI4-mediated redox regulation may have a
greater effect than ABA on aphid resistance in Arabidopsis . Another study showed
that mutation in aba2 gene compromised Pieris rapae -induced resistance and