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

doi:10.1073/pnas.1907971116

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^*

^*Corresponding author for this work

Strathclyde Institute Of Pharmacy And Biomedical Sciences

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116 Citations (Scopus)

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Abstract

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 language	English
Pages (from-to)	17584-17591
Number of pages	8
Journal	Proceedings of the National Academy of Sciences of the United States of America
Volume	116
Issue number	35
Early online date	14 Aug 2019
DOIs	https://doi.org/10.1073/pnas.1907971116
Publication status	Published - 27 Aug 2019

Funding

ACKNOWLEDGMENTS. We thank Dr. Huilan Wu for help with western blot analysis of FIT and IRT1; Benjamin Planterose for assistance with cloning of the BTSL:GFP constructs; Abigail Turner and Jed de Ruiter-Swain for cloning and protein expression; and the Bioimaging platform at the John Innes Centre for sectioning and confocal microscopy. This work was funded by a Marie Sklodowska Curie fellowship form the European Union Horizon 2020 programme, Ref. 655043 (J.R.-C.); the Biotechnology and Biological Sciences Research Council, grant awards BB/N001079/1, BB/P012523/1, and BB/J004561/1 (J.R.-C., J.M.C., I.K., R.T.G., M.F., and J.B.); the John Innes Centre/ Chinese Academy of Sciences Center of Excellence for Plant and Microbial Sciences (J.R.-C., Y.C., H.-Q.L., and J.B.); grant award 2016ZX08009003-005 from the Ministry of Agriculture of China (H.-Q.L); and grants from the Academia Sinica (Y.-T.C. and K.-C.Y.).

Keywords

BHLH transcription factor
dicotyledon
iron
micronutrient
ubiquitin

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10.1073/pnas.1907971116Licence: CC BY 4.0

Rodriguez-Celma-etal-PNAS2019-Arabidopsis-BRUTUS-LIKE-E3-ligases-negatively-regulate-iron-uptakeFinal published version, 1.55 MBLicence: CC BY 4.0

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Rodríguez-Celma, J., Connorton, J. M., Kruse, I., Green, R. T., Franceschetti, M., Chen, Y.-T., Cui, Y., Ling, H.-Q., Yeh, K.-C., & Balk, J. (2019). Arabidopsis BRUTUS-LIKE E3 ligases negatively regulate iron uptake by targeting transcription factor FIT for recycling. Proceedings of the National Academy of Sciences of the United States of America, 116(35), 17584-17591. https://doi.org/10.1073/pnas.1907971116

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

abstract = "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.",

keywords = "BHLH transcription factor, dicotyledon, iron, micronutrient, ubiquitin",

author = "Jorge Rodr{\'i}guez-Celma and Connorton, \{James M.\} and Inga Kruse and Green, \{Robert T.\} and Marina Franceschetti and Yi-Tze Chen and Yan Cui and Hong-Qing Ling and Kuo-Chen Yeh and Janneke Balk",

year = "2019",

month = aug,

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Rodríguez-Celma, J, Connorton, JM, Kruse, I, Green, RT, Franceschetti, M, Chen, Y-T, Cui, Y, Ling, H-Q, Yeh, K-C & Balk, J 2019, 'Arabidopsis BRUTUS-LIKE E3 ligases negatively regulate iron uptake by targeting transcription factor FIT for recycling', Proceedings of the National Academy of Sciences of the United States of America, vol. 116, no. 35, pp. 17584-17591. https://doi.org/10.1073/pnas.1907971116

Arabidopsis BRUTUS-LIKE E3 ligases negatively regulate iron uptake by targeting transcription factor FIT for recycling. / Rodríguez-Celma, Jorge; Connorton, James M.; Kruse, Inga et al.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 116, No. 35, 27.08.2019, p. 17584-17591.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Arabidopsis BRUTUS-LIKE E3 ligases negatively regulate iron uptake by targeting transcription factor FIT for recycling

AU - Rodríguez-Celma, Jorge

AU - Connorton, James M.

AU - Kruse, Inga

AU - Green, Robert T.

AU - Franceschetti, Marina

AU - Chen, Yi-Tze

AU - Cui, Yan

AU - Ling, Hong-Qing

AU - Yeh, Kuo-Chen

AU - Balk, Janneke

PY - 2019/8/27

Y1 - 2019/8/27

N2 - 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.

AB - 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.

KW - BHLH transcription factor

KW - dicotyledon

KW - iron

KW - micronutrient

KW - ubiquitin

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DO - 10.1073/pnas.1907971116

M3 - Article

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AN - SCOPUS:85071515006

SN - 0027-8424

VL - 116

SP - 17584

EP - 17591

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

IS - 35

ER -

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

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