scholarly journals Plant root development: is the classical theory for auxin-regulated root growth false?

PROTOPLASMA ◽  
2021 ◽  
Author(s):  
Hans G. Edelmann
Keyword(s):  
Root Growth ◽  
Root Development ◽  
Cell Elongation ◽  
Growth Regulation ◽  
Plant Root ◽  
Inhibitory Effect ◽  
Elongation Growth ◽  
Root Cells ◽  
Role Taking ◽  
Regulation Model

AbstractOne of the longest standing theories and, therein-based, regulation-model of plant root development, posits the inhibitory action of auxin (IAA, indolylacetic acid) on elongation growth of root cells. This effect, as induced by exogenously supplied IAA, served as the foundation stone for root growth regulation. For decades, auxin ruled the day and only allowed hormonal side players to be somehow involved, or in some way affected. However, this copiously reiterated, apparent cardinal role of auxin only applies in roots immersed in solutions; it vanishes as soon as IAA-supplied roots are not surrounded by liquid. When roots grow in humid air, exogenous IAA has no inhibitory effect on elongation growth of maize roots, regardless of whether it is applied basipetally from the top of the root or to the entire residual seedling immersed in IAA solution. Nevertheless, such treatment leads to pronounced root-borne ethylene emission and lateral rooting, illustrating and confirming thereby induced auxin presence and its effect on the root — yet, not on root cell elongation. Based on these findings, a new root growth regulatory model is proposed. In this model, it is not IAA, but IAA-triggered ethylene which plays the cardinal regulatory role — taking effect, or not — depending on the external circumstances. In this model, in water- or solution-incubated roots, IAA-dependent ethylene acts due to its accumulation within the root proper by inhibited/restrained diffusion into the liquid phase. In roots exposed to moist air or gas, there is no effect on cell elongation, since IAA-triggered ethylene diffuses out of the root without an impact on growth.

scholarly journals Auxin Controlled by Ethylene Steers Root Development

2018 ◽  
Vol 19 (11) ◽  
pp. 3656 ◽  
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.

scholarly journals A mechanism coordinating root elongation, endodermal differentiation, redox homeostasis and response

2019 ◽  
Author(s):  
Jing Fu ◽  
Jiaming Liu ◽  
Xudong Gao ◽  
Xinglin Zhang ◽  
Juan Bai ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
Stress Response ◽  
Root Growth ◽  
Cell Elongation ◽  
Growth Regulation ◽  
Redox Homeostasis ◽  
Oxidative Stress Response ◽  
Radial Patterning ◽  
Endodermal Differentiation

AbstractRoot growth relies on both cell division and elongation, which occur in the meristem and elongation zones respectively. SCARECROW (SCR) is a GRAS family gene essential for root growth and radial patterning in the Arabidopsis root. Previous studies showed that SCR promotes root growth by suppressing cytokinin response in the meristem, but there is also evidence that SCR expressed beyond the meristem is required as well for root growth. Here we report that SCR promotes root growth by promoting cell elongation through suppression of oxidative stress response and maintenance of redox homeostasis in the elongation zone. In the scr root, a higher level of hydrogen peroxide was detected, which can be attributed to down-regulation of peroxidase gene 3. When stress response was blocked or redox status was ameliorated by the aba2 or upb1 mutation, the scr mutant produced a significantly longer root with longer cells and a larger and mitotically more active meristem, even though the stem cell and radial patterning defects still persisted. We showed that WRKY15, an oxidative responsive gene, was a direct target of SCR down-regulated in the scr mutant, which suggests that SCR has an active role in suppressing oxidative stress response. Since hydrogen peroxide and peroxidases are essential for endodermal differentiation, these results suggest that SCR plays a central role in coordinating cell elongation, endodermal differentiation, redox homeostasis, and oxidative stress response in plant root.One sentence summaryThis study reveals a novel mechanism of root growth regulation, which involves a previously unrecognized role of SCR in regulating cell elongation, endodermal differentiation, and redox homeostasis.

scholarly journals Visible light-triggered NO generation from Naphthalimide-based probe for photoreceptor-mediated plant root growth regulation

2019 ◽  
Author(s):  
Suprakash Biswas ◽  
Neha Upadhyay ◽  
Debojyoti Kar ◽  
Sourav Datta ◽  
Apurba Lal Koner
Keyword(s):  
Nitric Oxide ◽  
Root Growth ◽  
Visible Light ◽  
Growth Regulation ◽  
Plant Root ◽  
Spectroscopic Techniques ◽  
Fluorescent Molecule

ABSTRACTAn efficient visible light-triggered nitric oxide (NO) releasing fluorescent molecule is designed and synthesized by coupling 2,6-dimethyl nitrobenzene moiety at the peri-position of 1, 8-naphthalimide through an alkene bond. The NO-releasing ability is investigated in details using various spectroscopic techniques, and the photoproduct was also characterized. Further, the photo-generated NO has been employed to examine the effect of photoreceptor-mediated NO uptake on plant root growth regulation.

scholarly journals Graphene promotes plant root growth by enhancing root respiration

2021 ◽  
Author(s):  
Zhiwen Chen ◽  
Jianguo Zhao ◽  
Jun Qiao ◽  
Weijia Li ◽  
Sai Ge ◽  
...  
Keyword(s):  
Root Growth ◽  
Plant Species ◽  
Root Length ◽  
Plant Root ◽  
Plant Roots ◽  
Pathway Enrichment Analysis ◽  
Total Root Length ◽  
Root Cells ◽  
Growth Effects ◽  
Effect Ratio

Abstract To explore the effects of graphene on plant root growth and development, 25 mg/L graphene were used to treat the seedling roots of 48 plant species. These results showed that the total root length of the plants was decreased when cultured by hydroponics method. Whereas the total root length of plant species cultured by soil showed different growth effects, among which the ratio of promotion effect was 69.77%, the ratio of inhibition effect was 11.63% and the no-effect ratio was 18.60%. To gain insights into the molecular mechanisms by which graphene presents different growth effects on the root length, we performed RNA-seq for 32 plant roots treated with 25 mg/L graphene. We totally identified 90,259 DEGs in 32 plant species, among which 55,537 were graphene-induced and 34,722 were graphene-repressed. KEGG pathway enrichment analysis indicated that 43 pathways were assigned to these enriched differentially expressed genes in response to the graphene treatment. Top enriched pathways include starch and sucrose metabolism, glycolysis/gluconeogenesis, pyruvate metabolism, the citrate cycle (TCA cycle), phenylpropanoid biosynthesis, glutathione metabolism, endocytosis, peroxisome etc. The gene expressions of these pathway were induced or repressive in plant roots showing promotion or inhibitory effects, respectively. Accumulation of antioxidant enzyme as well as enhanced respiration might lead to the increasing plant root length. In addition, transcriptome and TEM data showed that graphene enters plant root cells by endocytosis. These results uncovered molecular level influences of graphene on plant roots development.

scholarly journals The piperazine compound ASP activates an auxin response in Arabidopsis thaliana

BMC Genomics ◽  
2020 ◽  
Vol 21 (1) ◽  
Author(s):  
Fengyang Xu ◽  
Shuqi Xue ◽  
Limeng Deng ◽  
Sufen Zhang ◽  
Yaxuan Li ◽  
...  
Keyword(s):  
Root Growth ◽  
Root Development ◽  
Gene Knockout ◽  
Primary Root ◽  
Inhibitory Effect ◽  
Root Tip ◽  
Ethylene Response Factor ◽  
Auxin Response ◽  
Root Tips ◽  
Chemical Library

Abstract Background Auxins play key roles in the phytohormone network. Early auxin response genes in the AUX/IAA, SAUR, and GH3 families show functional redundancy, which makes it very difficult to study the functions of individual genes based on gene knockout analysis or transgenic technology. As an alternative, chemical genetics provides a powerful approach that can be used to address questions relating to plant hormones. Results By screening a small-molecule chemical library of compounds that can induce abnormal seedling and vein development, we identified and characterized a piperazine compound 1-[(4-bromophenoxy) acetyl]-4-[(4-fluorophenyl) sulfonyl] piperazine (ASP). The Arabidopsis DR5::GFP line was used to assess if the effects mentioned were correlated with the auxin response, and we accordingly verified that ASP altered the auxin-related pathway. Subsequently, we examined the regulatory roles of ASP in hypocotyl and root development, auxin distribution, and changes in gene expression. Following ASP treatment, we detected hypocotyl elongation concomitant with enhanced cell elongation. Furthermore, seedlings showed retarded primary root growth, reduced gravitropism and increased root hair development. These phenotypes were associated with an increased induction of DR5::GUS expression in the root/stem transition zone and root tips. Auxin-related mutants including tir1–1, aux1–7 and axr2–1 showed phenotypes with different root-development pattern from that of the wild type (Col-0), and were insensitive to ASP. Confocal images of propidium iodide (PI)-stained root tip cells showed no detectable damage by ASP. Furthermore, RT-qPCR analyses of two other genes, namely, Ethylene Response Factor (ERF115) and Mediator 18 (MED18), which are related to cell regeneration and damage, indicated that the ASP inhibitory effect on root growth was not attributable to toxicity. RT-qPCR analysis provided further evidence that ASP induced the expression of early auxin-response-related genes. Conclusions ASP altered the auxin response pathway and regulated Arabidopsis growth and development. These results provide a basis for dissecting specific molecular components involved in auxin-regulated developmental processes and offer new opportunities to discover novel molecular players involved in the auxin response.

Visible light-controlled NO generation for photoreceptor-mediated plant root growth regulation

Nitric Oxide ◽  
2019 ◽  
Vol 92 ◽  
pp. 34-40
Author(s):  
Suprakash Biswas ◽  
Neha Upadhyay ◽  
Debojyoti Kar ◽  
Sourav Datta ◽  
Apurba Lal Koner
Keyword(s):  
Root Growth ◽  
Visible Light ◽  
Growth Regulation ◽  
Plant Root

scholarly journals High throughput phenotyping of root growth dynamics, lateral root formation, root architecture and root hair development enabled by PlaRoM

2009 ◽  
Vol 36 (11) ◽  
pp. 938 ◽  
Author(s):  
Nima Yazdanbakhsh ◽  
Joachim Fisahn
Keyword(s):  
Root Growth ◽  
Growth Kinetics ◽  
Lateral Root ◽  
Root Architecture ◽  
Imaging Techniques ◽  
Plant Root ◽  
Primary Root ◽  
Growth Media ◽  
Root Extension ◽  
Lateral Root Development

Plant organ phenotyping by non-invasive video imaging techniques provides a powerful tool to assess physiological traits and biomass production. We describe here a range of applications of a recently developed plant root monitoring platform (PlaRoM). PlaRoM consists of an imaging platform and a root extension profiling software application. This platform has been developed for multi parallel recordings of root growth phenotypes of up to 50 individual seedlings over several days, with high spatial and temporal resolution. PlaRoM can investigate root extension profiles of different genotypes in various growth conditions (e.g. light protocol, temperature, growth media). In particular, we present primary root growth kinetics that was collected over several days. Furthermore, addition of 0.01% sucrose to the growth medium provided sufficient carbohydrates to maintain reduced growth rates in extended nights. Further analysis of records obtained from the imaging platform revealed that lateral root development exhibits similar growth kinetics to the primary root, but that root hairs develop in a faster rate. The compatibility of PlaRoM with currently accessible software packages for studying root architecture will be discussed. We are aiming for a global application of our collected root images to analytical tools provided in remote locations.

scholarly journals A novel putative microtubule-associated protein is involved in arbuscule development during arbuscular mycorrhiza formation

2021 ◽  
Author(s):  
Tania Ho-Plágaro ◽  
Raúl Huertas ◽  
María I Tamayo-Navarrete ◽  
Elison Blancaflor ◽  
Nuria Gavara ◽  
...  
Keyword(s):  
Plant Root ◽  
Arbuscular Mycorrhizal ◽  
Host Cells ◽  
Root Cells ◽  
Filament Dynamics ◽  
Fungal Structure ◽  
Genes Encoding ◽  
Associated Proteins ◽  
Mycorrhizal Development

Abstract The formation of arbuscular mycorrhizal (AM) symbiosis requires plant root host cells to undergo major structural and functional reprogramming in order to house the highly branched AM fungal structure for the reciprocal exchange of nutrients. These morphological modifications are associated with cytoskeleton remodelling. However, molecular bases and the role of microtubules (MTs) and actin filament dynamics during AM formation are largely unknown. In this study, the tomato tsb gene, belonging to a Solanaceae group of genes encoding MT-associated proteins for pollen development, was found to be highly expressed in root cells containing arbuscules. At earlier stages of mycorrhizal development, tsb overexpression enhanced the formation of highly developed and transcriptionally active arbuscules, while tsb silencing hampers the formation of mature arbuscules and represses arbuscule functionality. However, at later stages of mycorrhizal colonization, tsb OE roots accumulate fully developed transcriptionally inactive arbuscules, suggesting that the collapse and turnover of arbuscules might be impaired by TSB accumulation. Imaging analysis of the MT cytoskeleton in cortex root cells overexpressing tsb revealed that TSB is involved in MT-bundling. Taken together, our results provide unprecedented insights into the role of novel MT-associated protein in MT rearrangements throughout the different stages of the arbuscule life cycle.

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

Plant Methods ◽  
2019 ◽  
Vol 15 (1) ◽  
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.

scholarly journals The Arabidopsis Root Tip (Phospho)Proteomes at Growth-Promoting versus Growth-Repressing Conditions Reveal Novel Root Growth Regulators

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1665
Author(s):  
Natalia Nikonorova ◽  
Evan Murphy ◽  
Cassio Flavio Fonseca de Lima ◽  
Shanshuo Zhu ◽  
Brigitte van de Cotte ◽  
...  
Keyword(s):  
Cell Wall ◽  
Root Growth ◽  
Growth Regulators ◽  
Growth Regulation ◽  
Phosphorylation Site ◽  
Primary Root ◽  
Root Tip ◽  
Arabidopsis Root ◽  
Growth Promoting ◽  
The Impact

Auxin plays a dual role in growth regulation and, depending on the tissue and concentration of the hormone, it can either promote or inhibit division and expansion processes in plants. Recent studies have revealed that, beyond transcriptional reprogramming, alternative auxin-controlled mechanisms regulate root growth. Here, we explored the impact of different concentrations of the synthetic auxin NAA that establish growth-promoting and -repressing conditions on the root tip proteome and phosphoproteome, generating a unique resource. From the phosphoproteome data, we pinpointed (novel) growth regulators, such as the RALF34-THE1 module. Our results, together with previously published studies, suggest that auxin, H+-ATPases, cell wall modifications and cell wall sensing receptor-like kinases are tightly embedded in a pathway regulating cell elongation. Furthermore, our study assigned a novel role to MKK2 as a regulator of primary root growth and a (potential) regulator of auxin biosynthesis and signalling, and suggests the importance of the MKK2 Thr31 phosphorylation site for growth regulation in the Arabidopsis root tip.

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