Intracellular levels of Mg2+ are tightly regulated, as Mg2+ deficiency or excess affects normal plant growth and development. In Arabidopsis, we determined that phospholipase Dα1 (PLDα1) is involved in the stress response to high‐magnesium conditions. The T‐DNA insertion mutant pldα1 is hypersensitive to increased concentrations of magnesium, exhibiting reduced primary root length and fresh weight. PLDα1 activity increases rapidly after high‐Mg2+ treatment, and this increase was found to be dose dependent. Two lines harbouring mutations in the HKD motif, which is essential for PLDα1 activity, displayed the same high‐Mg2+ hypersensitivity of pldα1 plants. Moreover, we show that high concentrations of Mg2+ disrupt K+ homeostasis, and that transcription of K+ homeostasis‐related genes CIPK9 and HAK5 is impaired in pldα1. Additionally, we found that the akt1, hak5 double mutant is hypersensitive to high‐Mg2+. We conclude that in Arabidopsis, the enzyme activity of PLDα1 is vital in the response to high‐Mg2+ conditions, and that PLDα1 mediates this response partially through regulation of K+ homeostasis.

Intracellular levels of Mg 2+ are tightly regulated, as Mg 2+ deficiency or excess affects normal plant growth and development. In Arabidopsis, we determined that phospholipase Dα1 (PLDα1) is involved in the stress response to high-magnesium conditions. The T-DNA insertion mutant pldα1 is hypersensitive to increased concentrations of magnesium, exhibiting reduced primary root length and fresh weight. PLDα1 activity increases rapidly after high-Mg 2+ treatment, and this increase was found to be dose-dependent. Two lines harboring mutations in the HKD motif, which is essential for PLDα1 activity, displayed the same high-Mg 2+ hypersensitivity of pldα1 plants. Moreover, we show that high concentrations of Mg 2+ disrupt K + homeostasis, and that transcription of K + homeostasis-related genes CIPK9 and HAK5 is impaired in pldα1. Additionally, we found that the akt1, hak5 double mutant is hypersensitive to high-Mg 2+. We conclude that in Arabidopsis, the enzyme activity of PLDα1 is vital in the response to high-Mg 2+ conditions, and that PLDα1 mediates this response partially through regulation of K + homeostasis.

Magnesium (Mg2+) is a macronutrient involved in essential cellular processes. Its deficiency or excess is a stress factor for plants, seriously affecting their growth and development and therefore, its accurate regulation is essential. Recently, we discovered that phospholipase Dα1 (PLDα1) activity is vital in the stress response to high-magnesium conditions in Arabidopsis roots. This study shows that PLDα1 acts as a negative regulator of high-Mg2+-induced leaf senescence in Arabidopsis. The level of phosphatidic acid produced by PLDα1 and the amount of PLDα1 in the leaves increase in plants treated with high Mg2+. A knockout mutant of PLDα1 (pldα1-1), exhibits premature leaf senescence under high-Mg2+ conditions. In pldα1-1 plants, higher accumulation of abscisic and jasmonic acid (JA) and impaired magnesium, potassium and phosphate homeostasis were observed under high-Mg2+ conditions. High Mg2+ also led to an increase of starch and proline content in Arabidopsis plants. While the starch content was higher in pldα1-1 plants, proline content was significantly lower in pldα1-1 compared with wild type plants. Our results show that PLDα1 is essential for Arabidopsis plants to cope with the pleiotropic effects of high-Mg2+ stress and delay the leaf senescence.

Magnesium is a macronutrient involved in essential cellular processes. Its deficiency or excess is a stress factor for plants, seriously affecting their growth and development and therefore, its accurate regulation is essential. Recently, we discovered that phospholipase Dα1 (PLDα1) activity is vital in the stress response to high-magnesium conditions in Arabidopsis roots. This study shows that PLDα1 acts as a negative regulator of high-Mg2+-induced leaf senescence in Arabidopsis. The level of phosphatidic acid produced by PLDα1 and the amount of PLDα1 in the leaves increase in plants treated with high Mg2+. A knockout mutant of PLDα1 (plda1-1), exhibits premature leaf senescence under high-Mg2+ conditions. In pldα1-1 plants, higher accumulation of abscisic and jasmonic acid and impaired magnesium, potassium and phosphate homeostasis were observed under high-Mg2+ conditions. High Mg2+ also led to an increase of starch and proline content in Arabidopsis plants. While the starch content was higher in plda1-1 plants, proline content was significantly lower in plda1-1 compared with WT. Our results show that PLDα1 is essential for Arabidopsis plants to cope with the pleiotropic effects of high-Mg2+ stress and delay the leaf senescence.