5.2 Hormone signaling
Significant work has been done to investigate plant hormone signaling
crosstalk between biotic and abiotic stresses (for review see Shigenaga
et al., 2017; Ku et al., 2018). This work has found ABA is a key
regulator of abiotic stress and biotic stress responses. ABA is
considered “the” abiotic stress hormone (Shigenaga et al., 2017), and
through its antagonistic relationships with SA and JA/ET signaling
pathways, it allows for crosstalk at multiple levels in biotic stress
responses for both necrotrophic and biotrophic pathogens (Atkinson &
Urwin, 2012; Kissoudis et al., 2014). Future research efforts should
focus on ABA signaling pathways, along with their interaction with SA,
JA/ET, to increase plant resilience to climate change. Other growth
hormones have been implicated in biotic and abiotic stress responses,
including gibberellin, cytokinin, auxin, and brassinosteroids (Kissoudis
et al., 2014). Additionally, it has been recently demonstrated through
genetic analysis that modification of epistatic interactions between the
hormone jasmonate and the photoreceptor phyB uncoupled the plant growth
and defense trade-off in Arabidopsis (Campos et al., 2016). This
indicates that future breeding efforts involving hormone signaling may
overcome growth-defense tradeoffs associated with combined
biotic-abiotic stress responses.