Phospho‐mutant activity assays provide evidence for alternative phospho‐regulation pathways of the transcription factor <scp>FER‐LIKE IRON DEFICIENCY‐INDUCED TRANSCRIPTION FACTOR</scp>

Grätz, R.; Brumbarova, Tzvetina; Ivanov, Rumen; Trofimov, Ksenia; Tünnermann, Laura; Ochoa-Fernandez, Rocio; Blomeier, Tim; Meiser, Johannes; Weidtkamp‐Peters, Stefanie; Zurbriggen, Matías D.; Bauer, Petra

doi:10.1111/nph.16168

Cited by 25 publications

(27 citation statements)

References 84 publications

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“…ubiquitin ligase recruitment and ubiquitination (Dubeaux et al 2018;Mithoe and Menke, 2018). Several kinases are involved in the phosphorylationdependent regulation of iron acquisition (Dubeaux et al 2018;Gratz et al 2020), and multiple phosphorylation residues have been identified in FREE1 by mass spectrometry (Zulawski et al 2013;Li et al 2019). It will be intriguing to dissect the potential links between the phosphorylation and ubiquitination of FREE1 in response to iron deficiency in the future.…”

Section: Discussionmentioning

confidence: 99%

SINAT E3 ligases regulate the stability of the ESCRT component FREE1 in response to iron deficiency in plants

Xiao

Yang

Liu

et al. 2020

JIPB

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The endosomal sorting complex required for transport (ESCRT) machinery is an ancient, evolutionarily conserved membrane remodeling complex that is essential for multivesicular body (MVB) biogenesis in eukaryotes. FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING 1 (FREE1), which was previously identified as a plant‐specific ESCRT component, modulates MVB‐mediated endosomal sorting and autophagic degradation. Although the basic cellular functions of FREE1 as an ESCRT component have been described, the regulators that control FREE1 turnover remain unknown. Here, we analyzed how FREE1 homeostasis is mediated by the RING‐finger E3 ubiquitin ligases, SINA of Arabidopsis thaliana (SINATs), in response to iron deficiency. Under iron‐deficient growth conditions, SINAT1‐4 were induced and ubiquitinated FREE1, thereby promoting its degradation and relieving the repressive effect of FREE1 on iron absorption. By contrast, SINAT5, another SINAT member that lacks ubiquitin ligase activity due to the absence of the RING domain, functions as a protector protein which stabilizes FREE1. Collectively, our findings uncover a hitherto unknown mechanism of homeostatic regulation of FREE1, and demonstrate a unique regulatory SINAT–FREE1 module that subtly regulates plant response to iron deficiency stress.

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Section: Discussionmentioning

confidence: 99%

SINAT E3 ligases regulate the stability of the ESCRT component FREE1 in response to iron deficiency in plants

Xiao

Yang

Liu

et al. 2020

JIPB

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“…We could recently show that FIT phosphorylation by CIPK11 at Ser272 is a major FIT‐activating process, whereby both Ser272‐phosphorylated and non‐phosphorylated FIT forms can interact with bHLH039, with the non‐phosphorylated S272AA FIT form showing a weaker interaction with bHLH039 (Gratz, Manishankar, et al, ). Additionally, phosphorylation events at Ser221, Tyr238, and Tyr278 also affect FIT activity (Gratz, Brumbarova, et al, ). Therefore, it is possible that differential FIT phosphorylation may modulate FIT activity levels and, in turn, the effect of FIT on bHLH039 nuclear accumulation.…”

Section: Discussionmentioning

confidence: 99%

Mobility and localization of the iron deficiency‐induced transcription factor bHLH039 change in the presence of FIT

et al. 2019

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Regulation of iron (Fe) acquisition and homeostasis is critical for plant survival. In Arabidopsis, Fe deficiency‐induced bHLH039 forms a complex with the master regulator FIT and activates it to upregulate Fe acquisition genes. FIT is partitioned between cytoplasm and nucleus, whereby active FIT accumulates more in the nucleus than inactive FIT. At the same time, there is so far no information on the subcellular localization of bHLH039 protein and how it is controlled. We report here that the bHLH039 localization pattern changes depending on the presence of FIT in the cell. When expressed in cells lacking FIT, bHLH039 localizes predominantly in the cytoplasm, including cytoplasmic foci in close proximity to the plasma membrane. The presence of FIT enhances the mobility of bHLH039 and redirects the protein toward primarily nuclear localization, abolishing its accumulation in cytoplasmic foci. This FIT‐dependent change in localization of bHLH039 found in transient fluorescent protein expression experiments was confirmed in both leaves and roots of Arabidopsis transgenic plants, stably expressing hemagglutinin‐tagged bHLH039 in wild‐type or fit mutant background. This posttranslational mechanism for intracellular partitioning of Fe‐responsive transcription factors suggests a signaling cascade that translates Fe sensing at the plasma membrane to nuclear accumulation of the transcriptional regulators.

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“…Interestingly, this heterodimerization capacity is affected by differential phosphorylation. Specifically, the heterodimerization is activated through Ser and deactivated through Tyr site phosphorylation (Gratz et al, 2020). Another Arabidopsis bHLH transcription factor, SPEECHLESS (SPCH), initiates the stomatal lineage (Simmons and Bergmann, 2016).…”

Section: Regulatory Mechanism Of Bhlhs Involved In Transcriptional Activationmentioning

confidence: 99%

“…The key bHLH transcription factor in iron (Fe) uptake, FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT), is critical for adjusting Fe acquisition to plant growth and environmental constraints (Gratz et al, 2020). Kool et al (1994) found that the bHLH133 transcription factor in rice can regulate the transport of Fe from roots to young leaves, revealing the important role of bHLH proteins in maintaining iron homeostasis in plant cells.…”

Section: Bhlhs Help Withstand Plant Iron and Copper Homeostasismentioning

confidence: 99%

Regulatory Mechanisms of bHLH Transcription Factors in Plant Adaptive Responses to Various Abiotic Stresses

et al. 2021

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Basic helix-loop-helix proteins (bHLHs) comprise one of the largest families of transcription factors in plants. They have been shown to be involved in responses to various abiotic stresses, such as drought, salinity, chilling, heavy metal toxicity, iron deficiency, and osmotic damages. By specifically binding to cis-elements in the promoter region of stress related genes, bHLHs can regulate their transcriptional expression, thereby regulating the plant’s adaptive responses. This review focuses on the structural characteristics of bHLHs, the regulatory mechanism of how bHLHs are involved transcriptional activation, and the mechanism of how bHLHs regulate the transcription of target genes under various stresses. Finally, as increasing research demonstrates that flavonoids are usually induced under fluctuating environments, the latest research progress and future research prospects are described on the mechanisms of how flavonoid biosynthesis is regulated by bHLHs in the regulation of the plant’s responses to abiotic stresses.

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Phospho‐mutant activity assays provide evidence for alternative phospho‐regulation pathways of the transcription factor FER‐LIKE IRON DEFICIENCY‐INDUCED TRANSCRIPTION FACTOR

Cited by 25 publications

References 84 publications

SINAT E3 ligases regulate the stability of the ESCRT component FREE1 in response to iron deficiency in plants

SINAT E3 ligases regulate the stability of the ESCRT component FREE1 in response to iron deficiency in plants

Mobility and localization of the iron deficiency‐induced transcription factor bHLH039 change in the presence of FIT

Regulatory Mechanisms of bHLH Transcription Factors in Plant Adaptive Responses to Various Abiotic Stresses

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