Description
The mechanisms by which plants coordinate intracellular calcium (Ca²⁺) signaling with extracellular Ca²⁺ availability, ion homeostasis, and nutrient compartmentalization remain an open question. In Arabidopsis, ACA8 and ACA10 are two major plasma membrane-localized autoinhibited Ca²⁺-ATPases that mediate Ca²⁺ efflux from the cytosol and altered ACA8 and ACA10 activities leads to changes in intracellular Ca²⁺ levels. Here, we investigate whether these cytosolic Ca²⁺ level changes caused by knockout mutations or overexpression of ACA8 and ACA10 affect extracellular Ca²⁺ reservoirs and the balance of other micronutrient ions. Using synchrotron X-ray fluorescence microscopy (SXRF) and inductively coupled plasma mass spectrometry (ICP-MS), we mapped spatial ion distribution and quantified elemental abundance across leaf tissues. We found increased Ca²⁺ abundance in both aca8 aca10 and ACA8-overexpression, as well as opposite changes in iron abundance between the two genetic backgrounds. These observations suggest that perturbed Ca²⁺ homeostasis may be accompanied by broader changes in the balance of micronutrients including iron, which is closely linked to plant stress and immune responses. Together, this study provides preliminary insight into the role of intracellular Ca²⁺ status in modulating extracellular ion homeostasis and stress adaptation.