Abstract
The hormone abscisic acid (ABA) orchestrates the plant stress response and regulates sophisticated metabolic and physiological mechanisms essential for survival in a changing environment. Plant ABA receptors were described more than 10 years ago, and a considerable amount of information is available for the model plant Arabidopsis thaliana. Unfortunately, this knowledge is still very limited in crops that hold the key to feeding a growing population. In this review, we summarize genomic, genetic and structural data obtained in crop ABA receptors. We also provide an update on ABA perception in major food crops, highlighting specific and common features of crop ABA receptors.
Highlights
Abscisic acid (ABA) is a phytohormone involved in the regulation of many aspects of plant development and adaptation to external cues
The binding of ABA induces a conformational rearrangement, which results in the dissociation of the pyrabactin resistance (PYR)/PYL dimer allowing for the interaction with the phosphatases 2 C (PP2C)
We have focused on soybean, tomato (Solanum lycopersicum, Sl) and citrus (Citrus sinensis, Cs), as they are the highest producing eudicot plant crop species from which data on PYR/PYL receptors have been reported
Summary
Abscisic acid (ABA) is a phytohormone involved in the regulation of many aspects of plant development and adaptation to external cues. ZcPYL8, the only PYR/PYL protein encoded in the Z. circumcarinatum genome, cannot bind ABA, but is able to interact with and inhibit PP2Cs in a PYL concentration-dependent manner [33] This suggests that PYR/PYL proteins have an ABA-independent ancestral role and do not require ABA for their function. In Bryophytes like Marchantia polymorfa or Physcomitrella patens, PYR/PYL proteins have evolved and can bind ABA with KD values similar to those of PYR/PYL receptors of higher plants [33] They still retain the ability to inhibit PP2Cs independently of ABA binding. The binding of ABA induces a conformational rearrangement, which results in the dissociation of the PYR/PYL dimer allowing for the interaction with the PP2C This molecular strategy limits the inhibition of PP2Cs to ABA-bound PYR/PYLs exclusively, repurposing the original ligand-independent regulatory role of ancestral PYLs into a ligand-binding dependent process [34]. We discuss recent developments in crop ABA receptors, with a special focus on staple food crops
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