Regulation of the iron deficiency-induced transcription factor FIT by CBL-CIPK-mediated phosphorylation and stress signaling in root epidermis cells

• Applicant: Professorin Dr. Petra Bauer
• Subject Area: Plant Physiology ; Plant Genetics and Genomics
• Term: since 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 218662525

The iron (Fe)-deficiency-induced transcription factor and basic helix-loop-helix protein FIT is essential for Fe acquisition in Arabidopsis roots. FIT acts as a regulatory hub in root cells and cross-connects stress and hormonal signaling pathways with iron uptake regulation. Key regulators from different pathways interact directly with FIT and modulate its activity through protein-protein interactions. FIT is then able to steer Fe acquisition in response to developmental and environmental cues. FIT is phosphorylated and activated through calcium (Ca2+)-induced protein kinase CIPK11 in response to Fe deficiency. Calcineurin B-Like (CBL)-interacting protein kinases (CIPKs) form a family of more than 25 members that are activated by CBL-type Ca2+-sensors upon stress. With this proposal we will explore Fe deficiency signaling by the CIPK-CBL network focusing on two further CIPKs in addition to CIPK11. This project proposal builds on the working hypothesis that CIPK-CBL modules steer joint responses to abiotic stress, Fe nutrition and oxidative stress in the root epidermis to achieve a coordinated plant response. We will test the idea that all three CIPKs interact with, phosphorylate and activate FIT to enhance Fe uptake into the root. Because of their different regulatory behavior in response to Fe, we hypothesize that the three CIPKs act in different contexts to regulate Fe uptake. We will examine whether ABA and heat stress activate the three CIPKs which then affect FIT activity and Fe acquisition responses in root epidermis cells.In summary, we will combine protein phosphorylation, protein localization and protein interaction studies with physiological analysis in plants to obtain proofs for the role of three CIPKs in different Fe nutrition and abiotic stress situations on FIT regulation in roots.

• DFG Programme: Research Grants