Abstract
Magnesium (Mg2+) is a necessary nutrient element for plants. Excess Mg2+ is toxic to plants; however, the molecular mechanisms underlying plant response to high-Mg stress remain largely unknown. Here, we report that transcription factor AINTEGUMENTA (ANT) modulates high-Mg stress response in Arabidopsis roots. Expression of ANT was detected in roots and suppressed by high Mg2+ levels. The ant mutant was less inhibited in root elongation upon high Mg2+ compared with wild type, exhibiting increased cortical cell length and meristem size. These growth phenotypes were fully restored by genetic complementation of ant. Whereas the high-Mg tolerance in root growth of ant was abolished by K+ supplementation. Further analyses showed that the expression of K+ transporter gene HAK5 was suppressed in ant under high Mg2+ conditions, implying compromised K+ homeostasis. Collectively, our results identify ANT as a critical factor in plant adaptation to high-Mg stress and uncover a novel role of ANT in nutrient response.