Time-Series Elemental Imaging Reveals CAX-Dependent Redistribution Patterns for Anoxia Recovery

Flooding-induced oxygen deprivation (anoxia) is a challenge to plant survival, necessitating adaptive mechanisms for recovery. This study investigates elemental redistribution during anoxia recovery using time-series elemental imaging to show changes in nutrient distribution. Focusing on the role of Cation/H⁺ Exchangers (CAXs) in Arabidopsis thaliana, we show how mutants deficient in specific CAX transporters (cax1 and the cax1-4 quadruple mutant; qKO) respond to anoxia and metal stress. Mutants had reduced lipid peroxidation and increased expression of flood-tolerance proteins during recovery. X-ray Fluorescence Microscopy (XFM) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) were used to show elemental redistribution over time. In wild-type plants (Col-0), post-anoxia elemental distribution resembled the elemental distribution of CAX mutants under normoxic conditions, suggesting CAX-mediated elemental distribution before anoxia enables faster recovery post-anoxia, rather than affecting remobilization post-anoxia. While CAX mutants had altered tolerance to excess manganese and copper, leaf metal distribution during anoxia was not altered. These findings introduce the potential utility of time-series elemental imaging to show stress response phenotypes and the importance of elemental distribution to anoxia recovery. The novelty of this work lies in resolving spatial distribution patterns in a non-static system to gain insight into mechanisms of stress resilience in plants.