A CYBDOM protein impacts iron homeostasis and primary root growth under phosphate deficiency in Arabidopsis

Arabidopsis primary root growth response to phosphate (Pi) deficiency is mainly controlled by changes in apoplastic iron (Fe). Upon Pi deficiency, apoplastic Fe deposition in the root apical meristem activates pathways leading to the arrest of meristem maintenance and inhibition of cell elongation. Here, we report that a member of the uncharacterized cytochrome b561 and DOMON domain (CYBDOM) protein family, named CRR, promotes iron reduction in an ascorbate-dependent manner and controls apoplastic iron deposition. Under low Pi, the crr mutant shows an enhanced reduction of primary root growth associated with increased apoplastic Fe in the root meristem and a reduction in meristematic cell division. Conversely, CRR overexpression abolishes apoplastic Fe deposition rendering primary root growth insensitive to low Pi. The crr single mutant and crr hyp1 double mutant, harboring a null allele in another member of the CYDOM family, shows increased tolerance to high-Fe stress upon germination and seedling growth. Conversely, CRR overexpression is associated with increased uptake and translocation of Fe to the shoot and results in plants highly sensitive to Fe excess. Our results identify a ferric reductase implicated in Fe homeostasis and developmental responses to abiotic stress, and reveal a biological role for CYBDOM proteins in plants.

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Data associated with all figures and tables is provided in the Source Data file as well as Supplementary Data files.The RNA seq datasets for crr-1 and CRR OE have been deposited at the Gene Expression Omnibus (https://www.ncbi.nlm.nih.gov/geo/)(GSE235511 and GSE215755), while the proteomic data from this work has been deposited at ProteomeXchange Consortium via the PRIDE partner repository (http://www.ebi.ac.uk/pride) with the dataset identifier PXD040981.Plant lines will be made available upon request to the corresponding author.

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No sample-size calculation was performed No data was excluded from analysis All controls and samples in a single experiment were handled in parallel at the same time and conditions.In general, three or more biological replicates were performed in all experiments Samples from wild-type, mutants and transgenic plants were randomly collected for analysis.Petri dishes or pots where plants were grown, were randomly allocated in the growth chambers.