Abstract
Multilevel interactions among nutrients occur in the soil-plant system. Among them, Fe and Zn homeostasis in plants are of great relevance because of their importance for plant and human nutrition. However, the mechanisms underlying the interplay between Fe and Zn in plants are still poorly understood. In order to elucidate how Zn interacts with Fe homeostasis, it is crucial to assess Zn distribution either in the plant tissues or within the cells. In this study, we investigated the subcellular Zn distribution in Fe-deficient leaf cells of cucumber plants by using two different approaches: cellular fractionation coupled with inductively coupled plasma mass spectrometry (ICP/MS) and nanoscopic synchrotron X-ray fluorescence imaging. Fe-deficient leaves showed a strong accumulation of Zn as well as a strong alteration of the organelles’ ultrastructure at the cellular level. The cellular fractionation-ICP/MS approach revealed that Zn accumulates in both chloroplasts and mitochondria of Fe deficient leaves. Nano-XRF imaging revealed Zn accumulation in chloroplast and mitochondrial compartments, with a higher concentration in chloroplasts. Such results show that (i) both approaches are suitable to investigate Zn distribution at the subcellular level and (ii) cellular Fe and Zn interactions take place mainly in the organelles, especially in the chloroplasts.
Highlights
Among nutrients, iron (Fe) represents an essential element for the life cycle of plants, because it is a key cation to ensure electron flow in photosynthetic and respiratory pathways
We provide evidence about the localization and homeostasis of Zn at sub-cellular level in Fe-deficient cucumber leaves by mapping for the first time a plant cell with X-ray fluorescence (XRF) at nanometers resolution, and by comparing XRF data with data from cell fractionation coupled to inductively coupled plasma mass spectrometry (ICP/MS) analysis
We compared the results from two different analytical approaches in order to assess Zn distribution at sub-cellular level under Fe deficiency: ion determination by ICP/MS technique on different cellular fractions separated by ultracentrifugation, and nanoscopic XRF imaging method
Summary
Iron (Fe) represents an essential element for the life cycle of plants, because it is a key cation to ensure electron flow in photosynthetic and respiratory pathways. For this reason, Fe can be a limiting factor for biomass production as well as for the quality of plant products. The chlorosis observed in younger leaves represents the most typical visual symptom of Fe deficiency in plants. Fe deficiency impairs chlorophyll synthesis, leading to interveinal chlorosis in developing leaves (Rodriguez-Celma et al, 2013) and decreased photosynthesis rates (Terry, 1980). The excess of several heavy metals can induce such chlorosis as well (Vert et al, 2002; Leskova et al, 2017), probably because Fe shares a number of similarities (i.e., electronic configuration, availability in the soil, or uptake mechanisms by plant) with other transition metals
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