# What Is Similar, What Is Different? Characterization of Mitoferrin-like Proteins from Arabidopsis thaliana and Cucumis sativus

## TL;DR

This paper investigates the role of mitoferrin-like proteins in iron transport to chloroplasts in Arabidopsis and cucumber plants.

## Contribution

The study characterizes AtMFL1 and CsMFL1 as potential chloroplast iron transporters in two plant species.

## Key findings

- AtMFL1 and CsMFL1 are localized in chloroplasts via an N-terminal transit peptide.
- MFL1 knockout and overexpression affect chloroplast iron homeostasis and plant growth.
- MFL1 expression varies with iron availability in Arabidopsis and cucumber.

## Abstract

Chloroplasts, as the organelles primarily responsible for photosynthesis, require a substantial supply of iron ions. Conversely, due to Fe toxicity, the homeostasis of these ions is subject to tight regulation. Permease in chloroplast 1 (PIC1) has been identified as the primary iron importer into chloroplasts. However, previous studies suggested the existence of a distinct pathway for Fe transfer to chloroplasts, likely involving mitoferrin-like 1 (MFL1) protein. In this work, Arabidopsis MFL1 (AtMFL1) and its cucumber homolog (CsMFL1) were characterized using, among others, Arabidopsis protoplasts as well as both yeast and Arabidopsis mutants. Localization of both proteins in chloroplasts has been shown to be mediated via an N-terminal transit peptide. At the gene level, MFL1 expression profiles differed between the model plant and the crop plant under varying Fe availability. The expression of other genes involved in chloroplast Fe homeostasis, including iron acquisition, trafficking, and storage, was affected to some extent in both AtMFL1 knockout and overexpressing plants. Moreover, root growth and photosynthetic parameters changed unfavorably in the mutant lines. The obtained results imply that AtMFL1 and CsMFL1, as putative chloroplast iron transporters, play a role in both iron management and the proper functioning of the plant.