Evolution of Abscisic Acid Synthesis and Signaling Mechanisms

Abstract

The plant hormone abscisic acid (ABA) mediates seed dormancy, controls seedling development and triggers tolerance to abiotic stresses, including drought. Core ABA signaling components consist of a recently identified group of ABA receptor proteins of the PYRABACTIN RESISTANCE (PYR)/REGULATORY COMPONENT OF ABA RECEPTOR (RCAR) family that act as negative regulators of members of the PROTEIN PHOSPHATASE 2C (PP2C) family. Inhibition of PP2C activity enables activation of SNF1-RELATED KINASE 2 (SnRK2) protein kinases, which target downstream components, including transcription factors, ion channels and NADPH oxidases. These and other components form a complex ABA signaling network. Here, an in depth analysis of the evolution of components in this ABA signaling network shows that (i) PYR/RCAR ABA receptor and ABF-type transcription factor families arose during land colonization of plants and are not found in algae and other species, (ii) ABA biosynthesis enzymes have evolved to plant- and fungal-specific forms, leading to different ABA synthesis pathways, (iii) existing stress signaling components, including PP2C phosphatases and SnRK kinases, were adapted for novel roles in this plant-specific network to respond to water limitation. In addition, evolutionarily conserved secondary structures in the PYR/RCAR ABA receptor family are visualized.

Chitin and chitin-related compounds in plant–fungal interactions

“…ethylene (ET) (Ton et al 2002), salicylic acid (SA) (Janda and Ruelland 2014), JA (Wasternack 2007; Van Der Ent et al 2009) and ABA (Hauser et al 2011) have been associated with plant defence signalling against biotic stress. SA signalling induces protection against biotrophic pathogens, whereas JA against necrotrophic pathogens (Glazebrook 2005).…”

Mechanisms and ecological implications of plant‐mediated interactions between belowground and aboveground insect herbivores

“…For example, ABA levels were increased systemically after BG herbivory in maize plants . It is known that ABA plays a role in plant responses to both wounding and abiotic stresses including drought (Christmann et al 2006;Hauser et al 2011;Nguyen et al 2016). Since herbivory by BG or AG chewing insects is accompanied by wounding and water loss (Aldea et al 2005;Erb et al 2009a;Consales et al 2011), it seems likely that root herbivore-mediated abiotic stress may result in systemic induction of AG ABA levels, which may affect AG induced defenses .…”

Evolution of the Stomatal Regulation of Plant Water Content

“…Whether these alternative SnRK2-independent ABA signaling pathways play an adaptively relevant role in stomatal function is yet to be determined. The core SnRK2-centric ABA signaling pathway is highly conserved across land plants with all lineages, including those species without stomata, such as liverworts, displaying functional physiological responses to ABA (Ghosh et al, 2016), RCAR/PYR/PYL ABA receptors present in genomes (Hauser et al, 2011), and functional PP2Cs (Tougane et al, 2010). This highly conserved ABA signaling pathway is known to regulate desiccation tolerance mechanisms (Tougane et al, 2010), spore dormancy, and sex determination in nonseed plants , among other processes.…”