The AFB1 auxin receptor controls rapid auxin signaling and root growth through membrane depolarization in Arabidopsis thaliana

AbstractThe existence of an electric gradient across membranes is essential for a cell operation. In plants, application of the growth regulator auxin (IAA) causes almost instantaneous membrane depolarization in various cell types, making membrane depolarization a hallmark of the rapid non-transcriptional responses to IAA. Auxin triggers rapid root growth inhibition; a process that underlies gravitropic bending. The growth and depolarization responses to auxin show remarkable similarities in dynamics, requirement of auxin influx and the involvement of the TIR1/AFB auxin coreceptors, but whether auxin-induced depolarization participates in root growth inhibition remains unanswered. Here, we established a toolbox to dynamically visualize membrane potential in vivo in Arabidopsis thaliana roots by combining the DISBAC2(3) fluorescent probe with microfluidics and vertical stage microscopy. This way we show that auxin-induced membrane depolarization tightly correlates with rapid root growth inhibition and that the cells of the transition zone/early elongation zone are the most responsive to auxin. Further, we demonstrate that auxin cycling in and out of the cells through AUX1 influx and PIN2 efflux is not essential for membrane depolarization and rapid root growth inhibition but acts as a facilitator of these responses. The rapid membrane depolarization by auxin instead strictly depends on the AFB1 auxin receptor, while the other TIR1/AFB paralogues contribute to this response. The lack of membrane depolarization in the afb1 mutant explains the lack of the immediate root growth inhibition. Finally, we show that AFB1 is required for the rapid depolarization and rapid growth inhibition of cells at the lower side of the gravistimulated root. These results are instrumental in understanding the physiological significance of membrane depolarization for the gravitropic response of the root and clarify the role of AFB1 as the receptor central for rapid auxin responses, adding another piece to the puzzle in understanding the biology of the phytohormone auxin.

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Jasmonate Signalling Contributes to Primary Root Inhibition Upon Oxygen Deficiency in Arabidopsis thaliana

Plants ◽

10.3390/plants9081046 ◽

2020 ◽

Vol 9 (8) ◽

pp. 1046 ◽

Cited By ~ 1

Author(s):

Vinay Shukla ◽

Lara Lombardi ◽

Ales Pencik ◽

Ondrej Novak ◽

Daan A. Weits ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Root Growth ◽

Growth Inhibition ◽

Feedback Inhibition ◽

Oxygen Sensing ◽

Oxygen Deficiency ◽

Primary Root ◽

Root Growth Inhibition ◽

Root Inhibition ◽

Active Root

Plants, including most crops, are intolerant to waterlogging, a stressful condition that limits the oxygen available for roots, thereby inhibiting their growth and functionality. Whether root growth inhibition represents a preventive measure to save energy or is rather a consequence of reduced metabolic rates has yet to be elucidated. In the present study, we gathered evidence for hypoxic repression of root meristem regulators that leads to root growth inhibition. We also explored the contribution of the hormone jasmonic acid (JA) to this process in Arabidopsis thaliana. Analysis of transcriptomic profiles, visualisation of fluorescent reporters and direct hormone quantification confirmed the activation of JA signalling under hypoxia in the roots. Further, root growth assessment in JA-related mutants in aerobic and anaerobic conditions indicated that JA signalling components contribute to active root inhibition under hypoxia. Finally, we show that the oxygen-sensing transcription factor (TF) RAP2.12 can directly induce Jasmonate Zinc-finger proteins (JAZs), repressors of JA signalling, to establish feedback inhibition. In summary, our study sheds new light on active root growth restriction under hypoxic conditions and on the involvement of the JA hormone in this process and its cross talk with the oxygen sensing machinery of higher plants.

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Faculty Opinions recommendation of The Arabidopsis cell cycle checkpoint regulators TANMEI/ALT2 and ATR mediate the active process of aluminum-dependent root growth inhibition.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.715297816.790752822 ◽

2012 ◽

Author(s):

Daniel Gallie

Keyword(s):

Cell Cycle ◽

Root Growth ◽

Growth Inhibition ◽

Cell Cycle Checkpoint ◽

Root Growth Inhibition ◽

Active Process ◽

Cycle Checkpoint

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Sound Waves Promote Arabidopsis thaliana Root Growth by Regulating Root Phytohormone Content

International Journal of Molecular Sciences ◽

10.3390/ijms22115739 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5739

Author(s):

Joo Yeol Kim ◽

Hyo-Jun Lee ◽

Jin A Kim ◽

Mi-Jeong Jeong

Keyword(s):

Arabidopsis Thaliana ◽

Cell Division ◽

Root Growth ◽

Apical Meristem ◽

Cell Number ◽

Root Apical Meristem ◽

Control Group ◽

Auxin Signaling ◽

Ethylene Signaling ◽

Sound Waves

Sound waves affect plants at the biochemical, physical, and genetic levels. However, the mechanisms by which plants respond to sound waves are largely unknown. Therefore, the aim of this study was to examine the effect of sound waves on Arabidopsis thaliana growth. The results of the study showed that Arabidopsis seeds exposed to sound waves (100 and 100 + 9k Hz) for 15 h per day for 3 day had significantly longer root growth than that in the control group. The root length and cell number in the root apical meristem were significantly affected by sound waves. Furthermore, genes involved in cell division were upregulated in seedlings exposed to sound waves. Root development was affected by the concentration and activity of some phytohormones, including cytokinin and auxin. Analysis of the expression levels of genes regulating cytokinin and auxin biosynthesis and signaling showed that cytokinin and ethylene signaling genes were downregulated, while auxin signaling and biosynthesis genes were upregulated in Arabidopsis exposed to sound waves. Additionally, the cytokinin and auxin concentrations of the roots of Arabidopsis plants increased and decreased, respectively, after exposure to sound waves. Our findings suggest that sound waves are potential agricultural tools for improving crop growth performance.

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Long-distance blue light signalling regulates phosphate deficiency-induced primary root growth inhibition

Molecular Plant ◽

10.1016/j.molp.2021.06.002 ◽

2021 ◽

Author(s):

Yi-Qun Gao ◽

Ling-Hua Bu ◽

Mei-Ling Han ◽

Ya-Ling Wang ◽

Zong-Yun Li ◽

...

Keyword(s):

Root Growth ◽

Growth Inhibition ◽

Blue Light ◽

Primary Root ◽

Phosphate Deficiency ◽

Root Growth Inhibition ◽

Long Distance ◽

Light Signalling ◽

Primary Root Growth

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Root growth inhibition and ultrastructural changes in radish root tips after treatment with aqueous extracts of Fallopia japonica and F. ×bohemica rhizomes

PROTOPLASMA ◽

10.1007/s00709-021-01668-4 ◽

2021 ◽

Author(s):

Katarina Šoln ◽

Nada Žnidaršič ◽

Jasna Dolenc Koce

Keyword(s):

Root Growth ◽

Growth Inhibition ◽

Ultrastructural Changes ◽

Root Growth Inhibition ◽

Aqueous Extracts ◽

Root Tips ◽

Fallopia Japonica ◽

Radish Root

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Phyto-toxic Influence of an Atrazine-based Selective Herbicide – Arda-force® on Onions (Allium cepa L)

Chemical Science International Journal ◽

10.9734/csji/2020/v29i330169 ◽

2020 ◽

pp. 40-46

Author(s):

Doris Fovwe Ogeleka ◽

Esther Obasi

Keyword(s):

Root Growth ◽

Growth Inhibition ◽

Allium Cepa ◽

Environmental Protection Agency ◽

Toxic Effects ◽

Root Growth Inhibition ◽

Allium Cepa L ◽

Test Concentration ◽

Maximum Root ◽

Selective Herbicide

Introduction: The constant impact on the environment occasioned by pollution, indiscriminate application of agricultural chemicals, security challenges and crisis in the Niger Delta ecological area of Nigeria has caused severe damage to plants, soil organisms and humans. Aim and Methodology: In this research, onions (Allium cepa L) was exposed to varying concentrations of an atrazine-based selective herbicide Arda-force® to estimate the phyto-toxic effects on the plant species using the Organization for Economic Co-operation and Development, (OECD) protocol #208. Results: The mean effective concentration (EC50) using root growth inhibition produced indications of phyto-toxicity to the exposed species at a concentration of 0.55 ± 0.06 mg/L. Similarly, the maximum root growth inhibition efficiency relative to the control was 65% as recorded in the highest test concentration of 1.25 mg/L. Discussion: The study indicated that constant application / indiscriminate use of the herbicide Arda-force® could cause deleterious influence on these plant and vegetable species, daily consumed by humans as a rich source of anti-oxidants. Conclusion: This study concluded that atrazine-based herbicide Arda-force® used in this assessment resulted in phyto-toxic effects to Allium cepa L. At the exposed concentrations of the herbicide to non-target specie – Allium cepa L. that are integral parts of the ecosystems, the ‘‘harmless’’ status of atrazine acclaimed by the United State Environmental Protection Agency (USEPA) is still very much in doubt.

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