Arabidopsis thaliana BOLA proteins, new actors in plant growth and iron homeostasis

SUMMARY

The universal iron–sulfur (Fe‐S) clusters embedded in proteins support numerous fundamental biological processes. However, many proteins involved in Fe‐S assembly machineries remain poorly characterized in plants. Here, we revealed that BOLA1 and BOLA4, two members of the BOLA family previously described as Fe‐S assembly factors in various organisms, are critical growth regulators that play a role in Fe homeostasis in Arabidopsis thaliana . Expression analyses showed that BOLA1 and BOLA4 are ubiquitously expressed across most Arabidopsis tissues. Using protoplast transfection assays, we also demonstrated that both BOLA‐GFP fusion proteins localize to chloroplasts and mitochondria. Mutant analyses revealed that while single bola1 or bola4 knock‐out mutants are phenotypically indistinguishable from the wild type, double bola1 bola4 mutants display severe growth defects, including early growth arrest of the primary root. Notably, this phenotype was rescued by grafting a wild‐type root system onto the bola1 bola4 aerial part. Fe quantification, Perls staining, and RT‐qPCR analyses further demonstrated that bola1 bola4 double mutants exhibit altered Fe distribution and Fe‐homeostasis‐related gene expression. Overall, our findings show that BOLA1 and BOLA4 act redundantly to maintain primary root growth and rosette development and are essential players in Fe signaling and partitioning in Arabidopsis.