Sequence and coexpression analysis of iron-regulated ZIP transporter genes reveals crossing points between iron acquisition strategies in green algae and land plants

Abstract

Dicotyledonous plants, such as Arabidopsis, acquire soil iron using a reduction-based mechanism, named Strategy I, where the final step involves Fe2+ import by the ZIP-family transporter AtIRT1. The universal presence of IRT1-like genes, suggests that Strategy I represents a basic process in the green lineage. However, for some green organisms, like Chlamydomonas and rice, alternative iron-acquisition mechanisms are known. We aimed to outline potential interactions between Strategy I and alternative iron acquisition mechanisms. We investigated gene-coexpression networks in Chlamydomonas, rice and Arabidopsis, and used the sequences of the variable regions of the selected IRT proteins to identify the conservation of key amino acids. IRT genes in Chlamydomonas and rice were found to be closely coexpressed with components of alternative available iron-acquisition systems. On protein level, we could observe conservation of potential phosphorylation sites in close proximity to predicted or experimentally-demonstrated ubiquitination sites. Data suggest that the regulation of Strategy I is closely connected to alternative existing iron-acquisition strategies. Transciptional control, together with potential post-transcriptional modifications of IRT transporters, may be involved in fine-tuning iron import. This study provides a basis for experimentally analyzing the regulation of iron acquisition in an evolutionary context.