Everything, Everywhere, not at Once: How Abscisic Acid Shapes Root Responses to Salt Stress

Abscisic acid (ABA) is a central hormone in plants to regulate salinity response, which is an increasing threat to plant growth and crop productivity. This review focuses on the role of ABA in salinity response in roots - an essential organ for plant nutrition acquisition and anchorage. It provides an overview of how ABA responses in roots vary across time, tissues, and salt intensity, and why these dynamics are essential for understanding root salt response. We present ABA-related gene transcriptomic profiles based on public transcriptomic datasets generated from salt-treated seedlings, including genes involved in biosynthesis, catabolism, (de)conjugation, transport and signalling of ABA. We discuss how genes and interaction networks governing each of these steps are coordinated in spatial-temporal, and salt-dose dependent manners. Finally, we highlight how ABA can potentially act as secondary signalling wave to regulate root salt responses, including the salt-avoidance response-halotropism.