Arabidopsis BRUTUS-LIKE E3 ligases negatively regulate iron uptake by targeting transcription factor FIT for recycling

Jorge Rodríguez-Celma, James M. Connorton, Inga Kruse, Robert T. Green, Marina Franceschetti, Yi-Tze Chen, Yan Cui, Hong-Qing Ling, Kuo-Chen Yeh, Janneke Balk

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Organisms need to balance sufficient uptake of iron (Fe) with possible toxicity. In plant roots, a regulon of uptake genes is transcriptionally activated under Fe deficiency, but it is unknown how this response is inactivated when Fe becomes available. Here we describe the function of 2 partially redundant E3 ubiquitin ligases, BRUTUS-LIKE1 (BTSL1) and BTSL2, in Arabidopsis thaliana and provide evidence that they target the transcription factor FIT, a key regulator of Fe uptake, for degradation. The btsl double mutant failed to effectively down-regulate the transcription of genes controlled by FIT, and accumulated toxic levels of Fe in roots and leaves. The C-terminal domains of BTSL1 and BTSL2 exhibited E3 ligase activity, and interacted with FIT but not its dimeric partner bHLH39. The BTSL proteins were able to poly-ubiquitinate FIT in vitro and promote FIT degradation in vivo. Thus, posttranslational control of FIT is critical to prevent excess Fe uptake.

Original languageEnglish
Pages (from-to)17584-17591
Number of pages8
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number35
Early online date14 Aug 2019
Publication statusPublished - 27 Aug 2019

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