Cell kinetics of auxin transport and activity in Arabidopsis root growth and skewing

AbstractAuxin is a key regulator of plant growth and development. Local auxin biosynthesis and intercellular transport generates regional gradients in the root that are instructive for processes such as specification of developmental zones that maintain root growth and tropic responses. Here we present a toolbox to study auxin-mediated root development that features: (i) the ability to control auxin synthesis with high spatio-temporal resolution and (ii) single-cell nucleus tracking and morphokinetic analysis infrastructure. Integration of these two features enables cutting-edge analysis of root development at single-cell resolution based on morphokinetic parameters under normal growth conditions and during cell-type-specific induction of auxin biosynthesis. We show directional auxin flow in the root and refine the contributions of key players in this process. In addition, we determine the quantitative kinetics of Arabidopsis root meristem skewing, which depends on local auxin gradients but does not require PIN2 and AUX1 auxin transporter activities. Beyond the mechanistic insights into root development, the tools developed here will enable biologists to study kinetics and morphology of various critical processes at the single cell-level in whole organisms.

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Effects of Light Intensity on Root Development in a D-Root Growth System

Frontiers in Plant Science ◽

10.3389/fpls.2021.778382 ◽

2021 ◽

Vol 12 ◽

Author(s):

Yohanna Evelyn Miotto ◽

Cibele Tesser da Costa ◽

Remko Offringa ◽

Jürgen Kleine-Vehn ◽

Felipe dos Santos Maraschin

Keyword(s):

Light Intensity ◽

Root Growth ◽

Root Development ◽

Light Exposure ◽

Light Condition ◽

Light Response ◽

Shoot Elongation ◽

Growth Conditions ◽

Auxin Signaling ◽

Loss Of Function

Plant development is highly affected by light quality, direction, and intensity. Under natural growth conditions, shoots are directly exposed to light whereas roots develop underground shielded from direct illumination. The photomorphogenic development strongly represses shoot elongation whereas promotes root growth. Over the years, several studies helped the elucidation of signaling elements that coordinate light perception and underlying developmental outputs. Light exposure of the shoots has diverse effects on main root growth and lateral root (LR) formation. In this study, we evaluated the phenotypic root responses of wild-type Arabidopsis plants, as well as several mutants, grown in a D-Root system. We observed that sucrose and light act synergistically to promote root growth and that sucrose alone cannot overcome the light requirement for root growth. We also have shown that roots respond to the light intensity applied to the shoot by changes in primary and LR development. Loss-of-function mutants for several root light-response genes display varying phenotypes according to the light intensity to which shoots are exposed. Low light intensity strongly impaired LR development for most genotypes. Only vid-27 and pils4 mutants showed higher LR density at 40 μmol m–2 s–1 than at 80 μmol m–2 s–1 whereas yuc3 and shy2-2 presented no LR development in any light condition, reinforcing the importance of auxin signaling in light-dependent root development. Our results support the use of D-Root systems to avoid the effects of direct root illumination that might lead to artifacts and unnatural phenotypic outputs.

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Auxin Controlled by Ethylene Steers Root Development

International Journal of Molecular Sciences ◽

10.3390/ijms19113656 ◽

2018 ◽

Vol 19 (11) ◽

pp. 3656 ◽

Cited By ~ 14

Author(s):

Hua Qin ◽

Rongfeng Huang

Keyword(s):

Root Growth ◽

Root Development ◽

Growth And Development ◽

Plant Root ◽

Primary Root ◽

Control Plant ◽

Auxin Biosynthesis ◽

Root Hair Growth ◽

Fine Tune ◽

Root Growth And Development

Roots are important plant ground organs, which absorb water and nutrients to control plant growth and development. Phytohormones have been known to play a crucial role in the regulation of root growth, such as auxin and ethylene, which are central regulators of this process. Recent findings have revealed that root development and elongation regulated by ethylene are auxin dependent through alterations of auxin biosynthesis, transport and signaling. In this review, we focus on the recent advances in the study of auxin and auxin–ethylene crosstalk in plant root development, demonstrating that auxin and ethylene act synergistically to control primary root and root hair growth, but function antagonistically in lateral root formation. Moreover, ethylene modulates auxin biosynthesis, transport and signaling to fine-tune root growth and development. Thus, this review steps up the understanding of the regulation of auxin and ethylene in root growth.

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COE2 Is Required for the Root Foraging Response to Nitrogen Limitation

International Journal of Molecular Sciences ◽

10.3390/ijms23020861 ◽

2022 ◽

Vol 23 (2) ◽

pp. 861

Author(s):

Rui Wu ◽

Zhixin Liu ◽

Jiajing Wang ◽

Chenxi Guo ◽

Yaping Zhou ◽

...

Keyword(s):

Nitric Oxide ◽

Root Development ◽

Nitrogen Limitation ◽

Lateral Roots ◽

Root Hairs ◽

Normal Growth ◽

Growth Conditions ◽

Lateral Root Development ◽

New Findings ◽

Wide Range

There are numerous exchanges of signals and materials between leaves and roots, including nitrogen, which is one of the essential nutrients for plant growth and development. In this study we identified and characterized the Chlorophyll A/B-Binding Protein (CAB) (named coe2 for CAB overexpression 2) mutant, which is defective in the development of chloroplasts and roots under normal growth conditions. The phenotype of coe2 is caused by a mutation in the Nitric Oxide Associated (NOA1) gene that is implicated in a wide range of chloroplast functions including the regulation of metabolism and signaling of nitric oxide (NO). A transcriptome analysis reveals that expression of genes involved in metabolism and lateral root development are strongly altered in coe2 seedlings compared with WT. COE2 is expressed in hypocotyls, roots, root hairs, and root caps. Both the accumulation of NO and the growth of lateral roots are enhanced in WT but not in coe2 under nitrogen limitation. These new findings suggest that COE2-dependent signaling not only coordinates gene expression but also promotes chloroplast development and function by modulating root development and absorption of nitrogen compounds.

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Root development under fluctuating soil physical stress – plastic and elastic responses

10.5194/egusphere-egu2020-19056 ◽

2020 ◽

Author(s):

Tino Colombi ◽

Hanna Sjulgård ◽

Daniel Iseskog ◽

Thomas Keller

Keyword(s):

Growth Rate ◽

Root Growth ◽

Root Development ◽

Optimal Growth ◽

Penetration Resistance ◽

Growth Conditions ◽

Physical Stress ◽

Soil Air ◽

Physical Conditions ◽

Root Growth Rate

<p>Physical properties of soil such as penetration resistance and oxygen concentration of soil air strongly influence root system development in plants. Soils typically exhibit considerable spatial and temporal fluctuations in penetration resistance and oxygen concentration of soil air due to wetting-drying cycles, small-scale differences in soil compactness or hotspots of biological activity. Hence, roots of a single plant are exposed to different physical environments and thus physical stresses during their growth through the soil profile. Plants are known to adjust their root development to these spatiotemporal fluctuations in soil physical conditions. Such phenotypic adjustments include changes of root growth rate as well as alterations of root morphology and anatomy. However, these adjustments reduce accessibility of water and nutrients and may increase the carbon demand for soil exploration, which limits aboveground plant development. Until now, it is unclear whether such adjustments in root development are plastic (i.e. the phenotype is irreversibly changed even when roots re-enter zones with optimal growth conditions) or elastic (i.e. the phenotype is only temporarily changed and recovers again when roots re-enter zones with optimal growth conditions).</p><p>To investigate the plasticity and elasticity of root development, we designed customized microrhizotrons in which soil penetration resistance and the concentration of oxygen in soil air can be varied. Near-infrared (&#955;=830 nm) time-lapse imaging was applied to quantify root growth rates, and combined with measurements of root morphology and anatomy. A series of experiments was conducted using different crop species with contrasting root system properties (fibrous vs. taproot system, thin vs. thick roots). After an establishment period of three days under optimal growth conditions, roots were exposed for 24 hours to increased penetration resistance, hypoxia and the combination of both stresses. Following this, the stress was released, and plants continued to grow for 24 hours at optimal conditions, before a second stress was applied for another 24 hours. Generally, root development responded to changes in soil physical conditions across all species. However, depending on the species, the adjustments in root development were found to be constant or temporary, i.e. plastic or elastic. This difference between species was particularly pronounced for root growth rate. Root growth rate in pea recovered after soil physical stress was released, while root growth rate in wheat remained low after stress release. The obtained findings will be discussed with respect to the tolerance of different plants to soil physical stress as well as the effects of root growth on soil structure dynamics.</p>

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Integrating N signals and root growth: the role of nitrate transceptor NRT1.1 in auxin-mediated lateral root development

Journal of Experimental Botany ◽

10.1093/jxb/eraa243 ◽

2020 ◽

Vol 71 (15) ◽

pp. 4365-4368

Author(s):

Katerina S Lay-Pruitt ◽

Hideki Takahashi

Keyword(s):

Root Growth ◽

Root Development ◽

Lateral Root ◽

Auxin Biosynthesis ◽

Root Branching ◽

Lateral Root Development ◽

Experimental Botany

This article comments on: Maghiaoui A, Bouguyon E, Cuesta C, Perrine-Walker F, Alcon C, Krouk G, Benková E, Nacry P, Gojon A and Bach L. 2020. The Arabidopsis NRT1.1 transceptor coordinately controls auxin biosynthesis and transport to regulate root branching in response to nitrate. Journal of Experimental Botany 71, 4480–4494.

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Versatile Physiological Functions of Plant GSK3-Like Kinases

Genes ◽

10.3390/genes12050697 ◽

2021 ◽

Vol 12 (5) ◽

pp. 697

Author(s):

Juan Mao ◽

Wenxin Li ◽

Jing Liu ◽

Jianming Li

Keyword(s):

Stress Responses ◽

Glycogen Synthase ◽

Plant Stress ◽

Normal Growth ◽

Growth Conditions ◽

Genetic Studies ◽

Physiological Functions ◽

Environmental Signals ◽

Plant Stress Responses ◽

Diverse Plant

The plant glycogen synthase kinase 3 (GSK3)-like kinases are highly conserved protein serine/threonine kinases that are grouped into four subfamilies. Similar to their mammalian homologs, these kinases are constitutively active under normal growth conditions but become inactivated in response to diverse developmental and environmental signals. Since their initial discoveries in the early 1990s, many biochemical and genetic studies were performed to investigate their physiological functions in various plant species. These studies have demonstrated that the plant GSK3-like kinases are multifunctional kinases involved not only in a wide variety of plant growth and developmental processes but also in diverse plant stress responses. Here we summarize our current understanding of the versatile physiological functions of the plant GSK3-like kinases along with their confirmed and potential substrates.

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A low-cost aeroponic phenotyping system for storage root development: unravelling the below-ground secrets of cassava (Manihot esculenta)

Plant Methods ◽

10.1186/s13007-019-0517-6 ◽

2019 ◽

Vol 15 (1) ◽

Cited By ~ 4

Author(s):

Michael Gomez Selvaraj ◽

Maria Elker Montoya-P ◽

John Atanbori ◽

Andrew P. French ◽

Tony Pridmore

Keyword(s):

Root Growth ◽

Root Development ◽

Low Cost ◽

Root Traits ◽

Suitable Model ◽

Root Initiation ◽

Storage Root ◽

Economic Traits ◽

Storage Roots ◽

Storage Root Development

Abstract Background Root and tuber crops are becoming more important for their high source of carbohydrates, next to cereals. Despite their commercial impact, there are significant knowledge gaps about the environmental and inherent regulation of storage root (SR) differentiation, due in part to the innate problems of studying storage roots and the lack of a suitable model system for monitoring storage root growth. The research presented here aimed to develop a reliable, low-cost effective system that enables the study of the factors influencing cassava storage root initiation and development. Results We explored simple, low-cost systems for the study of storage root biology. An aeroponics system described here is ideal for real-time monitoring of storage root development (SRD), and this was further validated using hormone studies. Our aeroponics-based auxin studies revealed that storage root initiation and development are adaptive responses, which are significantly enhanced by the exogenous auxin supply. Field and histological experiments were also conducted to confirm the auxin effect found in the aeroponics system. We also developed a simple digital imaging platform to quantify storage root growth and development traits. Correlation analysis confirmed that image-based estimation can be a surrogate for manual root phenotyping for several key traits. Conclusions The aeroponic system developed from this study is an effective tool for examining the root architecture of cassava during early SRD. The aeroponic system also provided novel insights into storage root formation by activating the auxin-dependent proliferation of secondary xylem parenchyma cells to induce the initial root thickening and bulking. The developed system can be of direct benefit to molecular biologists, breeders, and physiologists, allowing them to screen germplasm for root traits that correlate with improved economic traits.

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Carbon dots inhibit root growth by disrupting auxin biosynthesis and transport in Arabidopsis

Ecotoxicology and Environmental Safety ◽

10.1016/j.ecoenv.2021.112168 ◽

2021 ◽

Vol 216 ◽

pp. 112168

Author(s):

Xiaoyan Yan ◽

Qiang Xu ◽

Dongxia Li ◽

Jianhua Wang ◽

Rong Han

Keyword(s):

Root Growth ◽

Carbon Dots ◽

Auxin Biosynthesis ◽

Inhibit Root Growth

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Sequence and regulation of a gene encoding a human 89-kilodalton heat shock protein.

Molecular and Cellular Biology ◽

10.1128/mcb.9.6.2615 ◽

1989 ◽

Vol 9 (6) ◽

pp. 2615-2626 ◽

Cited By ~ 172

Author(s):

E Hickey ◽

S E Brandon ◽

G Smale ◽

D Lloyd ◽

L A Weber

Keyword(s):

Heat Shock ◽

Heat Shock Protein ◽

Normal Growth ◽

Gene Families ◽

Growth Conditions ◽

Complete Sequence ◽

Start Codon ◽

Hybridization Probe ◽

Reading Frame ◽

Alpha Gene

Vertebrate cells synthesize two forms of the 82- to 90-kilodalton heat shock protein that are encoded by distinct gene families. In HeLa cells, both proteins (hsp89 alpha and hsp89 beta) are abundant under normal growth conditions and are synthesized at increased rates in response to heat stress. Only the larger form, hsp89 alpha, is induced by the adenovirus E1A gene product (M. C. Simon, K. Kitchener, H. T. Kao, E. Hickey, L. Weber, R. Voellmy, N. Heintz, and J. R. Nevins, Mol. Cell. Biol. 7:2884-2890, 1987). We have isolated a human hsp89 alpha gene that shows complete sequence identity with heat- and E1A-inducible cDNA used as a hybridization probe. The 5'-flanking region contained overlapping and inverted consensus heat shock control elements that can confer heat-inducible expression on a beta-globin reporter gene. The gene contained 10 intervening sequences. The first intron was located adjacent to the translation start codon, an arrangement also found in the Drosophila hsp82 gene. The spliced mRNA sequence contained a single open reading frame encoding an 84,564-dalton polypeptide showing high homology with the hsp82 to hsp90 proteins of other organisms. The deduced hsp89 alpha protein sequence differed from the human hsp89 beta sequence reported elsewhere (N. F. Rebbe, J. Ware, R. M. Bertina, P. Modrich, and D. W. Stafford (Gene 53:235-245, 1987) in at least 99 out of the 732 amino acids. Transcription of the hsp89 alpha gene was induced by serum during normal cell growth, but expression did not appear to be restricted to a particular stage of the cell cycle. hsp89 alpha mRNA was considerably more stable than the mRNA encoding hsp70, which can account for the higher constitutive rate of hsp89 synthesis in unstressed cells.

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The positive regulatory function of the 5'-proximal open reading frames in GCN4 mRNA can be mimicked by heterologous, short coding sequences

Molecular and Cellular Biology ◽

10.1128/mcb.8.9.3827-3836.1988 ◽

1988 ◽

Vol 8 (9) ◽

pp. 3827-3836

Author(s):

N P Williams ◽

P P Mueller ◽

A G Hinnebusch

Keyword(s):

Translational Control ◽

Normal Growth ◽

Regulatory Elements ◽

Growth Conditions ◽

Open Reading Frames ◽

Regulatory Function ◽

Yeast Saccharomyces Cerevisiae ◽

Reading Frame ◽

Yeast Genes ◽

Reading Frames

Translational control of GCN4 expression in the yeast Saccharomyces cerevisiae is mediated by multiple AUG codons present in the leader of GCN4 mRNA, each of which initiates a short open reading frame of only two or three codons. Upstream AUG codons 3 and 4 are required to repress GCN4 expression in normal growth conditions; AUG codons 1 and 2 are needed to overcome this repression in amino acid starvation conditions. We show that the regulatory function of AUG codons 1 and 2 can be qualitatively mimicked by the AUG codons of two heterologous upstream open reading frames (URFs) containing the initiation regions of the yeast genes PGK and TRP1. These AUG codons inhibit GCN4 expression when present singly in the mRNA leader; however, they stimulate GCN4 expression in derepressing conditions when inserted upstream from AUG codons 3 and 4. This finding supports the idea that AUG codons 1 and 2 function in the control mechanism as translation initiation sites and further suggests that suppression of the inhibitory effects of AUG codons 3 and 4 is a general consequence of the translation of URF 1 and 2 sequences upstream. Several observations suggest that AUG codons 3 and 4 are efficient initiation sites; however, these sequences do not act as positive regulatory elements when placed upstream from URF 1. This result suggests that efficient translation is only one of the important properties of the 5' proximal URFs in GCN4 mRNA. We propose that a second property is the ability to permit reinitiation following termination of translation and that URF 1 is optimized for this regulatory function.

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