scholarly journals Bacterial-type plant ferroxidases tune local phosphate sensing in root development

2021 ◽  
Author(s):  
Christin Naumann ◽  
Marcus Heisters ◽  
Wolfgang Brandt ◽  
Philipp Janitza ◽  
Carolin Alfs ◽  
...  
Keyword(s):  
Root Growth ◽  
Bacterial Colonization ◽  
Root System Architecture ◽  
Root Tip ◽  
Root Growth Inhibition ◽  
Root Tips ◽  
Metal Interactions ◽  
Ferroxidase Activity ◽  
Fe Homeostasis ◽  
Pi Deficiency

Fluctuating bioavailability of inorganic phosphate (Pi), often caused by complex Pi-metal interactions, guide root tip growth and root system architecture for maximizing the foraged soil volume. Two interacting genes in Arabidopsis thaliana, PDR2 (P5-type ATPase) and LPR1 (multicopper oxidase), are central to external Pi monitoring by root tips, which is modified by iron (Fe) co-occurrence. Upon Pi deficiency, the PDR2-LPR1 module facilitates cell type-specific Fe accumulation and cell wall modifications in root meristems, inhibiting intercellular communication and thus root growth. LPR1 executes local Pi sensing, whereas PDR2 restricts LPR1 function. We show that native LPR1 displays specific ferroxidase activity and requires a conserved acidic triad motif for high-affinity Fe2+ binding and root growth inhibition under limiting Pi. Our data indicate that substrate availability tunes LPR1 function and implicate PDR2 in maintaining Fe homeostasis. LPR1 represents the prototype of an ancient ferroxidase family, which evolved very early upon bacterial colonization of land. During plant terrestrialization, horizontal gene transfer transmitted LPR1-type ferroxidase from soil bacteria to the common ancestor of Zygnematophyceae algae and embryophytes, a hypothesis supported by homology modeling, phylogenomics, and activity assays of bacterial LPR1-type multicopper oxidases.

scholarly journals Transcription Factor WRKY33 Mediates the Phosphate Deficiency-Induced Remodeling of Root Architecture by Modulating Iron Homeostasis in Arabidopsis Roots

2021 ◽  
Vol 22 (17) ◽  
pp. 9275
Author(s):  
Nuo Shen ◽  
Sifan Hou ◽  
Guoqing Tu ◽  
Wenzhi Lan ◽  
Yanping Jing
Keyword(s):  
Transcription Factor ◽  
Transcription Factors ◽  
Root Growth ◽  
Root Architecture ◽  
Iron Homeostasis ◽  
Primary Root ◽  
Negative Regulator ◽  
Phosphate Deficiency ◽  
Root Tips ◽  
Pi Deficiency

The remodeling of root architecture is regarded as a major development to improve the plant’s adaptivity to phosphate (Pi)-deficient conditions. The WRKY transcription factors family has been reported to regulate the Pi-deficiency-induced systemic responses by affecting Pi absorption or transportation. Whether these transcription factors act as a regulator to mediate the Pi-deficiency-induced remodeling of root architecture, a typical local response, is still unclear. Here, we identified an Arabidopsis transcription factor, WRKY33, that acted as a negative regulator to mediate the Pi-deficiency-induced remodeling of root architecture. The disruption of WRKY33 in wrky33-2 mutant increased the plant’s low Pi sensitivity by further inhibiting the primary root growth and promoting the formation of root hair. Furthermore, we revealed that WRKY33 negatively regulated the remodeling of root architecture by controlling the transcriptional expression of ALMT1 under Pi-deficient conditions, which further mediated the Fe3+ accumulation in root tips to inhibit the root growth. In conclusion, this study demonstrates a previously unrecognized signaling crosstalk between WRKY33 and the ALMT1-mediated malate transport system to regulate the Pi deficiency responses.

scholarly journals Pro-metaphase arrest, polyploidy, micronuclei, and mitotic abnormality inducing agents’ isolation from leaf aqueous extract of Clerodendrum viscosum Vent

2020 ◽  
Author(s):  
Sujit Roy ◽  
Lalit Mohan Kundu ◽  
Gobinda Chandra Roy ◽  
Manabendu Barman ◽  
Sanjib Ray
Keyword(s):  
Root Growth ◽  
Petroleum Ether ◽  
Aqueous Extract ◽  
Root Tip ◽  
Root Growth Inhibition ◽  
Leaf Aqueous Extract ◽  
Clerodane Diterpenoids ◽  
Clerodendrum Viscosum ◽  
Tip Cells ◽  
Root Tip Cells

AbstractClerodendrum viscosum is a traditionally used medicinal plant and the earlier reports indicate its leaf aqueous extract (LAECV) contains metaphase arresting, cell cycle delay, and mitotic abnormality inducing active principles. The present study aimed to isolate pro-metaphase arresting, polyploidy, micronuclei, and mitotic abnormality inducing active principles of LAECV. The LAECV was successively fractionated as petroleum ether (PEF), chloroform (CHF), and ethyl acetate (EAF) fractions. All the extract fractions were tested for Allium cepa and Triticum aestivum root swelling and root growth inhibition analyses. The petroleum ether fraction was selected for further cytotoxicity analysis on A. cepa root tip cells and was processed for detection of the active principles through HPLC, LC-MS, GC-MS, and IR analyses. The comparative seedlings’ root growth and swelling patterns indicate the bioactive principles are effectively fractionated in PEF and GC-MS analysis revealed the presence of Clerodin (m/z 434.3), 15-hydroxy-14, 15-dihydroclerodin (m/z 452), 15-methoxy-14, 15-dihydroclerodin (m/z 466), and 14, 15-dihydroclerodin (m/z 436) with a retention time of 14.038, 14.103, 14.480 and 14.655 respectively. Thus the present study explores clerodane diterpenoids of LAECV as pro-metaphase arresting, polyploidy, micronuclei, and mitotic abnormality inducing active principles.

Nitrate and glutamate sensing by plant roots

2005 ◽  
Vol 33 (1) ◽  
pp. 283-286 ◽  
Author(s):  
S. Filleur ◽  
P. Walch-Liu ◽  
Y. Gan ◽  
B.G. Forde
Keyword(s):  
Root Growth ◽  
Lateral Root ◽  
Lateral Roots ◽  
Primary Root ◽  
Root Tip ◽  
Root Tips ◽  
Environmental Signals ◽  
Specific Effects ◽  
Large Numbers ◽  
Low Concentrations

The architecture of a root system plays a major role in determining how efficiently a plant can capture water and nutrients from the soil. Growth occurs at the root tips and the process of exploring the soil volume depends on the behaviour of large numbers of individual root tips at different orders of branching. Each root tip is equipped with a battery of sensory mechanisms that enable it to respond to a range of environmental signals, including nutrients, water potential, light, gravity and touch. We have previously identified a MADS (MCM1, agamous, deficiens and SRF) box gene (ANR1) in Arabidopsis thaliana that is involved in modulating the rate of lateral root growth in response to changes in the external NO3− supply. Transgenic plants have been generated in which a constitutively expressed ANR1 protein can be post-translationally activated by treatment with dexamethasone (DEX). When roots of these lines are treated with DEX, lateral root growth is markedly stimulated but there is no effect on primary root growth, suggesting that one or more components of the regulatory pathway that operate in conjunction with ANR1 in lateral roots may be absent in the primary root tip. We have recently observed some very specific effects of low concentrations of glutamate on root growth, resulting in significant changes in root architecture. Experimental evidence suggests that this response involves the sensing of extracellular glutamate by root tip cells. We are currently investigating the possible role of plant ionotropic glutamate receptors in this sensory mechanism.

scholarly journals Impact of cadmium and hydrogen peroxide on ascorbate-glutathione recycling enzymes in barley root

2013 ◽  
Vol 59 (No. 2) ◽  
pp. 62-67 ◽  
Author(s):  
V. Zelinová ◽  
B. Bočová ◽  
J. Huttová ◽  
I. Mistrík ◽  
L. Tamás
Keyword(s):  
Root Growth ◽  
Growth Inhibition ◽  
Reductase Activity ◽  
Barley Root ◽  
Dehydroascorbate Reductase ◽  
Monodehydroascorbate Reductase ◽  
Root Tip ◽  
Root Growth Inhibition ◽  
Short Term ◽  
Short Term Exposure

We analyse the effect of Cd and H<sub>2</sub>O<sub>2</sub> short-term treatments on the activity of ascorbate-glutathione recycling enzymes in barley root tip. Even a short transient exposure of barley roots to low 15 &micro;mol Cd concentration caused a marked approximately 70% root growth inhibition. Higher Cd concentrations caused root growth cessation during the first 6 h after short-term Cd treatment. Similarly, a marked root growth inhibition was also detected after the short-term exposure of barley seedlings to H<sub>2</sub>O<sub>2</sub>. Our results indicate that root ascorbate pool is more sensitive to Cd treatment than glutathione pool. Rapid activation of dehydroascorbate reductase and monodehydroascorbate reductase is the important component of stress response to the Cd-induced alterations in barley root tips. H<sub>2</sub>O<sub>2</sub> is probably involved in the Cd-induced activation of monodehydroascorbate reductase, but it is not involved in the Cd-induced increase of dehydroascorbate reductase activity.

scholarly journals Heavy metals analysis and toxicity evaluation of some textile and dyeing effluents in Kano, Nigeria using Allium cepa bioassay

2020 ◽  
Vol 12 (1) ◽  
pp. 344-351
Author(s):  
U.A. Abdullahi ◽  
S. Ibrahim
Keyword(s):  
Heavy Metals ◽  
Root Growth ◽  
Mitotic Index ◽  
Allium Cepa ◽  
Statistical Difference ◽  
Root Growth Inhibition ◽  
Root Tips ◽  
Textile Processing ◽  
Significant Difference ◽  
Dividing Cells

Insufficiencies in dyeing and textile processing coupled with incomplete sewage treatment system lead to indiscriminate discharge of large amount of dyestuff into water bodies mostly used for irrigation and fishing. These wastes are potentially mutagenic and some are even carcinogenic. In this research, cytotoxicity of three industrial effluents viz; African Textile Manufacturer (ATM), Kofar Naisa and Kofar Mata dyeing centres were evaluated using Allium cepa bioassay. The concentrations of some heavy metals (Cr, Cd, Zn, Fe, Cu, Co, Pb, Mn and Ni) were also determined. Three sets of small onion bulbs were cultivated in 25%, 50% 75% and 100% effluent concentrations (v/v) and a control for each site. Root tips from each bulb were harvested and processed for cytological studies using squashing technique. After 48hrs of exposure, cytotoxic effects of the effluents on root tips (compared to control) showed root growth retardation which was more apparent at higher concentrations. This indicated that, the root growth inhibition was concentration dependent. Number of dividing cells observed and the Mitotic Index (MI) were also concentration dependent. There were decrease in number of dividing cells and MI with increase in concentration of the treatment. The effective concentrations that caused 50% effect (EC50) was 95% for ATM and K/Naisa dyeing points while it was 100% in K/mata dyeing point. Diverse structural aberrations and abnormalities were observed ranging from chromosomal bridge, which was apparent even at low concentrations of the treatment to cytokinesis failure, Micronucleus (MN) and nuclear buds or vacuolated nuclei. Analysis of Variance (ANOVA) showed no significant difference (P>0.05) in mean concentrations of Cr, Fe, Cu and Mn for K/Naisa and K/Mata dyeing centres, but there was statistical difference (P<0.05) for these parameters in ATM. Likewise, there was significant difference (P<0.05) in the root growth of A. cepa exposed to different concentrations of the effluent in ATM and K/Naisa sites but no statistical difference existed in root growth of A. cepa exposed to K/Mata effluents. Keywords: Allium cepa, Bioassay, Effluents, Cytotoxicity, Mitotic Index

Primary root growth: a biophysical model of auxin-related control

2005 ◽  
Vol 32 (9) ◽  
pp. 849 ◽  
Author(s):  
Andrés Chavarría-Krauser ◽  
Willi Jäger ◽  
Ulrich Schurr
Keyword(s):  
Growth Rate ◽  
Root Growth ◽  
Relative Growth Rate ◽  
Primary Root ◽  
Biophysical Model ◽  
Root Tip ◽  
Growth Equation ◽  
Root Tips ◽  
Relative Growth ◽  
Wall Extensibility

Plant hormones control many aspects of plant development and play an important role in root growth. Many plant reactions, such as gravitropism and hydrotropism, rely on growth as a driving motor and hormones as signals. Thus, modelling the effects of hormones on expanding root tips is an essential step in understanding plant roots. Here we achieve a connection between root growth and hormone distribution by extending a model of root tip growth, which describes the tip as a string of dividing and expanding cells. In contrast to a former model, a biophysical growth equation relates the cell wall extensibility, the osmotic potential and the yield threshold to the relative growth rate. This equation is used in combination with a refined hormone model including active auxin transport. The model assumes that the wall extensibility is determined by the concentration of a wall enzyme, whose production and degradation are assumed to be controlled by auxin and cytokinin. Investigation of the effects of auxin on the relative growth rate distribution thus becomes possible. Solving the equations numerically allows us to test the reaction of the model to changes in auxin production. Results are validated with measurements found in literature.

Allelopathic root inhibition and its mechanisms

2021 ◽  
Vol 52 (2) ◽  
pp. 181-198
Author(s):  
K. Šoln ◽  
J. Dolenc Koce
Keyword(s):  
Root Growth ◽  
Auxin Transport ◽  
Root Tip ◽  
Root Growth Inhibition ◽  
Plant Interactions ◽  
Invasive Alien Plants ◽  
Direct Production ◽  
Physiological Processes ◽  
Root Gravitropism ◽  
Root Inhibition

Allelopathy represents a valuable biochemical strategy in plant-plant interactions among different plants, e.g. among crops and weeds. It is an important strategy in the colonization of many invasive alien plants. Allelopathic plants affect the growth of other plants in the vicinity through the release of secondary metabolites (allelochemicals) into the soil. In particular, many allelochemicals suppress the root growth of target plants, but little is known about the mechanism involved in root growth inhibition. In this review, we will highlight the mechanism of root suppression involving: (i) Alterations in auxin homeostasis affecting polar auxin transport and root gravitropism, (ii) Biochemical and physiological processes in inhibited roots associated with oxidative stress due to direct production and accumulation of reactive oxygen species or suppression of antioxidative response and (iii) The ultrastructural modifications in root tip exposed to allelochemicals that drastically suppress the cell division and eventually lead to shorter roots of target plants.

Bioassay and Anatomical Study of Bas 517 Using Etiolated Crop Seedlings

Weed Science ◽  
1993 ◽  
Vol 41 (3) ◽  
pp. 490-496
Author(s):  
Hwei-Yiing Li ◽  
Chester L. Foy
Keyword(s):  
Root Growth ◽  
Growth Inhibition ◽  
Incubation Time ◽  
Inhibitory Activity ◽  
Laboratory Experiments ◽  
Anatomical Study ◽  
High Sensitivity ◽  
Root Tip ◽  
Root Tips ◽  
Soybean Seedlings

Laboratory experiments were conducted to determine the selectivity and inhibitory activity of BAS 517 using whole seedlings or root tips of corn and soybean. Effects of BAS 517 on the morphology of corn root tips were examined as well. Etiolated corn seedlings showed high sensitivity to BAS 517; soybean seedlings were not affected. Growth inhibition of corn varied with concentrations of BAS 517 and incubation time. Radicles of corn were more sensitive than mesocotyls and coleoptiles. Root meristems were the first to show symptoms (reddening tissue followed by cessation of root growth). Results using root tips were similar to those using whole seedlings. However, root tips appeared to be more sensitive than whole seedlings. Concentrations of 0.1 and 10 μM of BAS 517 caused severe vacuolization of cells in the 0.2-cm root tip of corn. A pattern of decreasing injury from epidermal cells toward the centers of roots was observed.

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