OsCAX1a-Dependent Ca-Mg Balance Is Required for Optimal Growth in Rice

Magnesium (Mg) and calcium (Ca) are the most abundant divalent cations in plants. Cause their antagonistic interaction in plant cell, maintaining Ca-Mg balance is critical for optimal plant growth and development. However, the molecular mechanisms underlying the regulation of Ca-Mg balance remain poorly understood. In this study, we found that the expression of OsCAX1a was highly induced under high Ca:Mg ratio conditions in rice. Heterologous expression of OsCAX1a in yeast demonstrated that it enhances cytosolic Mg efficiency by mediating Ca efflux. Genetic knockout or overexpression of OsCAX1a in rice altered the Ca:Mg ratio and impaired growth performance. Collectively, our results indicate that OsCAX1a-mediated Ca efflux plays an important role in Mg homeostasis, providing a new insight for Ca-Mg balance in plant.