Maize DLR1/NHX7 Is Required for Root Development Under Potassium Deficiency.

ABSTRACT Root System Architecture (RSA) is a crucial plant trait that governs a plant's ability to absorb water and nutrients. In this study, we describe a mutant with nutrient‐dependent defects in root development, affecting both the primary root and lateral roots (LRs). This mutant, identified through a screen for defects in LR development, has been designated <italic>dlr1‐1</italic>. The <italic>dlr1‐1</italic> mutant exhibits impaired LR emergence rather than defects in the LR primordium (LRP) formation, particularly under potassium (K+)‐deprivation conditions. This impairment likely stems from inhibited cell proliferation caused by the <italic>dlr1‐1</italic> mutation. K+ deprivation specifically leads to the accumulation of salicylic acid (SA) in the <italic>dlr1‐1</italic> mutant, consistent with the upregulation of SA biosynthesis genes. Moreover, exogenous application of SA to wild‐type plants (B73) mimics the <italic>dlr1‐1</italic> phenotype. Conversely, treatment of the <italic>dlr1‐1</italic> mutant with 2‐aminoindane‐2‐phosphonic acid, an SA biosynthesis inhibitor, partially restores LR emergence, indicating that elevated SA levels may be responsible for the mutant's developmental defects. MutMap analysis and allelism tests confirmed that the phenotypes of the <italic>dlr1‐1</italic> mutant results from the loss of the Na+/H+ antiporter, ZmNHX7. Additionally, the application of NaCl exacerbates the <italic>dlr1‐1</italic> mutant phenotype, suggesting that the root defects in <italic>dlr1‐1</italic> mutant depend on ion homoeostasis. In conclusion, our findings demonstrate that maize DLR1/NHX7 is essential for root development under potassium deprivation. [ABSTRACT FROM AUTHOR]