ABA Regulation of Plant Response to Biotic Stresses - Abscisic Acid: Metabolism, Transport and Signaling - page 399

(Grant and Jones 2009 ; Robert-Seilaniantz et al. 2011 ). The SA signaling pathway
is mainly linked to resistance to biotrophic pathogens that feed on living host tissues
and often associated with hypersensitive response (HR; Durrant and Dong 2004 ;
Vlot et al. 2009 ), while the JA and ET signaling pathways are predominantly associ-
ated with resistance to necrotrophic pathogens that promote host cell death at early
stages of infection (Glazebrook 2004 ). It is well known that there has an mutual
antagonism between SA-mediated and JA/ET-mediated defense signaling pathways
(Kunkel and Brooks 2002 ). More recently, other plant hormones, including the stress
hormone ABA and the developmental hormones, such as cytokinins (CKs), auxin,
brassinosteroids (BRs), and gibberellins (GAs), have also been demonstrated to be
important regulators during plant-microbe interactions (Mauch-Mani and Mauch
2005 ; Robert-Seilaniantz et al. 2007 ; Grant and Jones 2009 ). Interestingly, numer-
ous studies have suggested that these hormones participated in disease responses by
interaction antagonistically or synergistically with the SA-JA-ET backbone of the
plant immune signaling network (Verhage et al. 2010 ; Pieterse et al. 2012 ; Robert-
Seilaniantz et al. 2007 ). Thus, it is interesting to reveal how pathogens disturb and
evade plant defense responses by manipulation of hormone signaling and how hosts
counteract this manipulation (Grant and Jones 2009 ). In this chapter, we focus on
recent literature dealing with the roles of ABA in plant immunity.
20.3 Roles of ABA in Plant-Pathogen Interaction
Beside of its prominent roles in plant response to abiotic stress, the plant hormone
ABA has also been demonstrated to function as a crucial regulator in plant biotic
defense responses. Accumulated studies have shown that ABA can exert a posi-
tive or negative influence on the host defense against almost all types of attack-
ers, such as bacterial, fungal, and oomycete pathogens, as well as herbivore and
virus, and its efficacy is dependent on the specific plant-attacker combination (Ton
et al. 2009 ; Cao et al. 2011 ). Further more, studies have demonstrated that ABA
has variable roles throughout different phases of plant defense (Ton et al. 2009 ).
Below, we will first talk about the role of ABA in defense against bacterial, fungal,
and oomycete pathogens.
20.4 Expression Pattern of ABA Pathway Core
Components Under Pathogen Challenge
The public availability of micro-array datasets allows researchers to obtain some
clues as to certain gene's function toward particular stress conditions. Recently,
Chan summarized the transcriptional profiling of Arabidopsis ABA pathway core
components under different pathogen infection based on both publicly available
micro-array data and their qRT-PCR results. Their results showed that most ABA