Oral Presentation International Plant Molecular Biology Conference 2024

Uncovering BTSL1-IMA1-bHLH protein interaction module for induction of iron deficiency signalling (#394)

Dibin Baby 1 , Daniela M. Lichtblau 1 , Birte Schwarz 1 , Petra Bauer 1 2
  1. Heinrich Heine University Duesseldorf, Düsseldorf, NORDRHEIN-WESTFALEN, Germany
  2. Cluster of Excellence on Plant Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Nordrhein-Westfalen, Germany

In plants, the iron (Fe) uptake machinery is a complex regulatory cascade. Mechanistic details of Fe sensing and regulation of signalling pathways are not completely clear. We exploited Fe deficiency-induced co-expressed gene clusters to list down a set of genes for an extensive Yeast-two hybrid (Y2H) screening and uncovered several novel protein-protein interactions. Three main protein groups emerged out of this interaction map: (1) BRUTUS (BTS) and BTS-LIKE1/2 (BTSL1/BTSL2), (2) basic helix-loop-helix (bHLH) transcription factors (TFs), (3) IRONMAN1 (IMA1/FEP3). In our Y2H screening BTSL1 interacted with bHLH subgroup IVc proteins, PYE and IMA1, a possible scenario for a tripartite interaction. Hence, we designed a quantitative yeast three-hybrid assay and tested the effect of IMA1 on BTSL1-bHLH interaction strength. When IMA1 was present, some BTSL1-bHLH interactions were significantly weakened, and IMA1 expression did not affect all BTSL1-bHLH interactions equally. We pinpointed the protein interaction sites by Y2H deletion mapping and identified a conserved motif in bHLHIVc proteins that is vital for their interaction with BTS(L)s (Lichtblau et al., 2022). In further unpublished work, we can show that expression of a mutated bHLHIVc TF, having a deletion of the interaction motif, resulted in hyperaccumulation of Fe in leaves of Arabidopsis thaliana transgenic lines, which was similar to the phenotype of bts btsl1 btsl2 loss-of-function mutants. In conclusion, this study elucidated a novel protein interaction network involved in the complex regulatory system controlling iron uptake in plants, advancing our mechanistic understanding of how plants sense and respond to iron deficiency.

 

 

  1. Lichtblau DM, Schwarz B, Baby D, Endres C, Sieberg C and Bauer P (2022) The Iron Deficiency-Regulated Small Protein Effector FEP3/IRON MAN1 Modulates Interaction of BRUTUS-LIKE1 With bHLH Subgroup IVc and POPEYE Transcription Factors. Front. Plant Sci. 13:930049. doi: 10.3389/fpls.2022.930049