ABA and Stomatal Biology: From Transcriptional and Biosynthesis to Multicellular Coordination Across Cell Types

Abscisic acid (ABA) was first identified in plants over six decades ago and is now recognized as one of the central phytohormones in plants, regulating growth, development, and physiological adaptation to environmental changes. In this Centennial Update, we use two influential ABA-related articles published in Plant Physiology in the early 2000s and discuss complementary advances in stress-responsive transcription and ABA biosynthetic regulation. We extend the Update from ABA-relevant gene discovery to recent advances in multicellular coordination of stomatal control. Growing evidence supports the view that ABA-regulated stomatal movement and gas exchange are coordinated across multiple cell types, including guard cells, mesophyll cells, bundle sheath cells, and vascular tissues in roots and leaves. We also highlight emerging tools to dissect this ABA-mediated multicellular network by using emerging technologies in single-cell and spatial omics, plant optogenetics, and artificial intelligence (AI). These advances will shape ABA research from single cell models toward multicellular collaborative networks for understanding plant-environment interactions. Together, this article links the history of ABA research with emerging single-cell resolution datasets and AI-assisted computational approaches, proposing a framework for moving ABA biology from well-established guard-cell signaling models toward a broader understanding of multicellular ABA coordination.