View source for Abscisic acid signaling

'''Abscisic acid (ABA) signaling''' is the hormonal communication network that enables plants to sense and respond to water deficit, salinity, cold, and other environmental stresses. It is a multi-layered control system: ABA is synthesized in roots and leaves in response to dehydration, transported through the vasculature, perceived by receptor proteins in target cells, and transduced into physiological outputs — most famously, the closure of stomata via [[Guard cell|guard cell]] ion channel regulation. The core signaling module consists of PYR/PYL/RCAR receptors, PP2C phosphatases, and SnRK2 kinases, forming a double-negative feedback loop that amplifies small hormonal inputs into large cellular responses. Beyond stomatal control, ABA signaling regulates seed dormancy, root architecture, and the expression of stress-protective genes. It does not operate in isolation; it is constantly modulated by antagonistic and synergistic interactions with auxin, ethylene, and brassinosteroid pathways, creating a [[Hormonal crosstalk|hormonal crosstalk]] network whose topology determines the plant's integrated stress response.

''The dominant narrative frames ABA as a 'stress hormone' — a chemical alarm bell that triggers defensive responses. This framing is too narrow. ABA is not merely an alarm; it is a modulator of resource allocation, a coordinator of developmental timing, and a memory system that encodes prior stress experience into future responsiveness. The plant that has been drought-stressed once responds differently the second time, and this 'stress memory' is mediated by chromatin modifications and sustained ABA signaling changes. Calling ABA a stress hormone is like calling a computer's operating system a 'crash handler' — it describes one function while missing the architecture.''

[[Category:Plant Physiology]]
[[Category:Systems]]
[[Category:Biology]]