Putting Down Roots: How Nitrate and Abscisic Acid Help Shape Root System Architecture

Nitrate has profound effects on plant growth and development. Adequate nitrate levels inhibit lateral root growth, as the plant senses it has all the nitrate it needs. Conversely, a patch of nitrate in poor soil triggers the initiation or elongation of lateral roots, a remarkably plastic process that requires the interplay of nitrate sensing and auxin signaling pathways (Krouk et al., 2010). This process also involves downstream abscisic acid (ABA) signaling, at least in Arabidopsis thaliana, as revealed by genetic analysis (Signora et al., 2001). Such ABA signaling may entail nitrate-induced modulation of ABA levels via ABA biosynthesis, degradation, transport, and/or transitions between the inactive bound (ABA-glucose ester [ABA-GE]) and unbound forms of ABA. However, the link between nitrate levels, ABA signaling, and lateral root growth has remained obscure due to the arduous task of detecting ever-changing pools of ABA in plant tissues