Iron-responsive transcription factor SreA regulates calcium homeostasis independently of calcineurin–Crz1 pathway in Fusarium graminearum

Calcium is an abundant intracellular ion that is intricately involved in various cellular processes. The precise regulation of calcium homeostasis is critical for fungal physiology. In fungi, calcium signaling is primarily mediated by the calmodulin–calcineurin pathway, with the transcription factor Crz1 acting as a key downstream regulator of calcium homeostasis. However, other transcription factors that contribute to calcium homeostasis in Fusarium graminearum are yet to be systematically identified. Here, we screened 675 transcription factor deletion mutants of F. graminearum under calcium stress and identified eight mutants, including crz1 and sreA . We found that SreA, a known iron homeostasis regulator, is required for calcium stress tolerance, separate from its role in iron homeostasis. Furthermore, SreA functions independently of the calcineurin–Crz1 pathway, and deletion of SREA alters cytosolic Ca ²⁺ dynamics following calcium stimulation. Our findings highlight a previously unrecognized role of SreA in fungal calcium homeostasis and suggest that SreA contributes to calcium stress response by maintaining appropriate cytosolic Ca ²⁺ signaling in F. graminearum .