ABA Regulation of Plant Response to Biotic Stresses - Abscisic Acid: Metabolism, Transport and Signaling - page 409

20.13 ABA-Mediated Cross Talk Between
Biotic and Abiotic Stress
In nature, plants always simultaneously suffered from biotic and abiotic stresses that
cross-talk with each other. In order to successfully adapt to such complex environ-
ments, plants have developed diverse signaling pathways for combating and tol-
erating them. Numerous evidences have accumulated supporting the notion that
different signaling pathways are interconnected to constitute the complicated net-
works that lead to various plant responses (López-P￩rez et al. 2009 ; Knight and
Knight 2001 ; Chen and Zhu 2004 ). Among them, the ABA signaling pathway is well
known for its role in abiotic stresses, especially in drought, and has also emerged
as an important regulator in plant immunity. Thus, ABA may play important roles
in mediating the cross talk between biotic and abiotic stresses. Expression profile
analysis demonstrated that both abiotic and biotic stress treatments can affect the
expression levels of ABA signaling pathway core components, indicating that abiotic
and biotic stress responses shared ABA signal pathway in Arabidopsis (Chan 2012 ).
Indeed, numerous studies demonstrated that mutations in ABA signaling pathway
core components cause altered responses to both abiotic and biotic stresses. Further
studies demonstrated that ABA participated in this process possibly by antagonisti-
cally or synergistically interacting with the prominent defense phytohormones SA,
JA, and ET, implying that pre-treatment with abiotic stresses may affect the plant's
response to subsequent pathogen or herbivore attack and vice versa (Mauch-Mani
and Mauch 2005 ; Robert-Seilaniantz et al. 2007 ; Yasuda et al. 2008 ; Anderson et al.
2004 ). Increasing evidences have showed that abiotic stresses, such as high tempera-
ture and humidity as well as drought and salinity stress, can enhance the suscepti-
bility of plant to biotic stresses (Mohr and Cahill 2003 ; Koga et al. 2004 ; Moeder
and Yoshioka 2009 ). For example, drought stresses have been shown to enhance
the susceptibility of host plants to various pathogens, such as Arabidipsis to avir-
ulent Pst 1065 , bean plants ( Phaseolus vulgaris ) to the charcoal rot causal fungus
Macrophomina phaseolina , as well as vine ( Parthenocissus quinquefolia ) to the
xylem-limited bacteria Xylella fastidiosa (Mohr and Cahill 2003 ; Mayek-Perez et al.
2002 ; McElrone et al. 2001 ). Although abiotic stress responses generally decreased
the disease resistance, in some cases, pre-exposure to abiotic stress can also enhance
the resistance to certain pathogens. Examples includes the enhanced resistance of
tomato against B.cinerea (necrotroph) and Oidium neolycopersici (biotroph) after
pre-exposure to drought stress and Arabidopsis against virulent bacterial pathogen
Pst DC3000 after pre-treatment with submergence (Achuo et al. 2006 ; Hsu et al.
2013 ). Thus, abiotic stresses can both positively or negatively affect the resistance
of host plant to pathogen or herbivore attack. Abiotic stresses, such as drought and
submergence, can affect the ABA metabolism, signal transduction, and catabolism
(Saika et al. 2007 ; Xiong et al. 2002 ; Chan et al. 2012 ), indicating that the altered
responses of host plants to pathogen or herbivore attack after pre-exposure with cer-
tain abiotic stress are at least partially dependent on the ABA signaling pathway.
Based on the above observations, the role of ABA in plant biotic stresses should not