Root Cell Walls Research Articles

Boron supplying alters cadmium retention in root cell walls and glutathione content in Capsicum annuum

Large areas of farmland in southern China are facing environmental problems such as cadmium (Cd) contamination and boron (B) deficiency. The aim of this study was to investigate the biochemical and molecular mechanisms underlying the reduction in Cd accumulation in hot pepper (Capsicum annuum) by B application. A hydroponic experiment was conducted to compare the subcellular distribution of Cd, transcriptome profile, degree of pectin methylation, and glutathione (GSH) synthesis in the roots of hot pepper under different B and Cd conditions. Boron supply promoted root cell wall biosynthesis and pectin demethylation by upregulating related genes and increasing cell wall Cd concentration by 28%. In addition, with the application of B, the proportion of Cd in root cell walls increased from 27% to 37%. Boron supplementation upregulated sulfur metabolism-related genes but decreased cysteine and GSH contents in the roots. As a result, shoot Cd concentration decreased by 27% due to the decrease in GSH, a critical long-distance transport carrier of Cd. Consequently, B supply could reduce the uptake, translocation, and accumulation of Cd in hot pepper by retaining Cd in the root cell walls and decreasing GSH content.

Nitric oxide amplifies cadmium binding in root cell wall of a high cadmium-accumulating rice (Oryza sativa L.) line by promoting hemicellulose synthesis and pectin demethylesterification

Nitric oxide (NO) is tightly associated with plant response against cadmium (Cd) stress in rice since NO impacts Cd accumulation via modulating cell wall components. In the present study, we investigated that whether and how NO regulates Cd accumulation in root in two rice lines with different Cd accumulation ability. The variation of polysaccharides in root cell wall (RCW) of a high Cd-accumulating rice line Lu527–8 and a normal rice line Lu527–4 in response to Cd stress when exogenous NO supplied by sodium nitroprusside (SNP, a NO donor) was studied. Appreciable amounts of Cd distributed in RCW, in which most Cd ions were bound to pectin for the two rice lines when exposed to Cd. Exogenous NO upregulated the expression of OsPME11 and OsPME12 that were involved in pectin demethylesterification, resulting in more low methyl-esterified pectin and therefore stronger pectin-Cd binding. Exogenous NO also enhanced the concentration of hemicellulose and the amount of Cd ions in it. These results demonstrate that NO-induced more Cd binding in RCW in the two rice lines through promoting pectin demethylesterification and increasing hemicellulose accumulation. Higher OsPMEs expression and more hemicellulose synthesis contributed to more Cd immobilization in RCW of the high Cd-accumulating rice line Lu527–8. The main findings of this study reveal the regulation of NO on cell wall polysaccharides modification under Cd stress and help to elucidate the physiological and molecular mechanism of NO participating in Cd responses of rice.

The aluminum distribution and translocation in two citrus species differing in aluminum tolerance

BackgroundMany citrus orchards of south China suffer from soil acidification, which induces aluminum (Al) toxicity. The Al-immobilization in vivo is crucial for Al detoxification. However, the distribution and translocation of excess Al in citrus species are not well understood.ResultsThe seedlings of ‘Xuegan’ [Citrus sinensis (L.) Osbeck] and ‘Shatianyou’ [Citrus grandis (L.) Osbeck], that differ in Al tolerance, were hydroponically treated with a nutrient solution (Control) or supplemented by 1.0 mM Al3+ (Al toxicity) for 21 days after three months of pre-culture. The Al distribution at the tissue level of citrus species followed the order: lateral roots > primary roots > leaves > stems. The concentration of Al extracted from the cell wall (CW) of lateral roots was found to be about 8 to 10 times higher than in the lateral roots under Al toxicity, suggesting that the CW was the primary Al-binding site at the subcellular level. Furthermore, the Al distribution in CW components of the lateral roots showed that pectin had the highest affinity for binding Al. The relative expression level of genes directly relevant to Al transport indicated a dominant role of Cs6g03670.1 and Cg1g021320.1 in the Al distribution of two citrus species. Compared to C. grandis, C. sinensis had a significantly higher Al concentration on the CW of lateral roots, whereas remarkably lower Al levels in the leaves and stems. Furthermore, Al translocation revealed by the absorption kinetics of the CW demonstrated that C. sinensis had a higher Al retention and stronger Al affinity on the root CW than C. grandis. According to the FTIR (Fourier transform infrared spectroscopy) analysis, the Al distribution and translocation might be affected by a modification in the structure and components of the citrus lateral root CW.ConclusionsA higher Al-retention, mainly attributable to pectin of the root CW, and a lower Al translocation efficiency from roots to shoots contributed to a higher Al tolerance of C. sinensis than C. grandis. The aluminum distribution and translocation of two citrus species differing in aluminum tolerance were associated with the transcriptional regulation of genes related to Al transport and the structural modification of root CW.

Pectin Methylesterases Enhance Root Cell Wall Phosphorus Remobilization in Rice

Pectin contributes greatly to cell wall phosphorus (P) remobilization. However, it is currently unclear whether the methylesterification degree of the pectin, which is related to the activity of pectin methylesterases (PMEs), is also involved in this process. Here, we demonstrated that elevated PME activity can facilitate the remobilization of P deposited in the cell wall. P-deficient conditions resulted in the reduction of root cell wall P content. This reduction was more pronounced in Nipponbare than in Kasalath, in company with a significant increment of the PME activity, indicating a possible relationship between elevated PME activity and cell wall P remobilization. This hypothesis was supported by in vitro experiments, as pectin with lower methylesterification degree had higher ability to release inorganic P (Pi) from insoluble FePO4. Furthermore, among the 35 OsPME members in rice, only the expression of OsPME14 showed a relationship with PME activity. In addition, transgenic rice lines overexpressing OsPME14 had increased PME activity, released more P from the root cell wall, and more resistant to P deficiency. In conclusion, PMEs enhance P remobilization in P-starved rice by increasing PME activity in Nipponbare, which in turn helps to remobilize P from the cell wall, and thus makes more available P.

Plant elicitor peptide 1 fortifies root cell walls and triggers a systemic root-to-shoot immune signaling in Arabidopsis

ABSTRACT Plant immunity is initiated by cell surface-localized receptors upon perception of pathogen-derived microbe or pathogen-associated molecular patterns (MAMPs/PAMPs), damage/danger-associated molecular patterns (DAMPs), and phytocytokines. Different patterns activate highly overlapping immune signaling at the early stage but divergent physiological responses at the late stage. Here, we indicate that plant elicitor peptide 1 (Pep1), a well-known DAMP, induces lignin and callose depositions, two types of late immune responses for strengthening the plant cell wall. Pep1-induced lignin and callose depositions in Arabidopsis root rely on early signaling components for Pep1 perception and signaling propagation. The phytohormone jasmonic acid and ethylene differently regulate the Pep1-regulated cell wall consolidation. Pep1 application in root also triggers a systemic immune signaling in shoot, and reactive oxygen species (ROS) is essential for the signaling communication between root and shoot. Collectively, the study reveals that Pep1 strengthens cell walls in root and triggers a systemic immune signaling from root to shoot.

Assessing implications of nanoplastics exposure to plants with advanced nanometrology techniques

Despite the increasing attention given to the impacts of nanoplastics in terrestrial environments, there is limited data about the effects on plants, and the quantitative information on uptake. In the present study, wheat plants grown in hydroponics were exposed to Pd-doped nanoplastics. This allowed us to quantify nanoplastics uptake and translocation to the shoots. Visualization of nanoplastics in roots was performed with synchrotron micro X-ray fluorescence (µXRF). Nanoplastics accumulated on the root epidermis, especially at the root tip and in root maturation zones. A close relationship between plant roots, rhizodeposits and nanoplastics behaviour was shown. Reinforcement of the cell wall in roots was evidenced using Fourier transform infrared spectroscopy (FTIR) and synchrotron-computed microtomography (µCT). Synchrotron-computed nanotomography (nanoCT) evidenced the presence of globular structures but they could not be identified as nanoplastics since they were observed both in the control and treated roots. By utilizing the inorganic tracer in the doped-nanoplastics, this study paves the road for elucidating interactions in more complex systems by using an integrative approach combining classical phytotoxicity markers with advanced nanometrology techniques.

Jasmonic acid is involved in root cell wall phosphorus remobilization through the nitric oxide dependent pathway in rice.

Jasmonic acid (JA) is involved in phosphorus (P) stress in plants, but its underlying molecular mechanisms are still elusive. In this study, we found root endogenous JA content in rice increased under P deficiency (-P), suggesting that JA might participate in P homeostasis in plants. This hypothesis was further confirmed through the addition of exogenous JA (+JA), as this could increase both the root and shoot soluble P content through regulating root cell wall P reutilization. In addition, -P+JA treatment significantly induced the expression of P transporter gene OsPT2, together with increased xylem P content, implying that JA is also important for P translocation from the root to the shoot in P-deficient rice. Furthermore, the accumulation of the molecular signal nitric oxide (NO) was enhanced under -P+JA treatment when compared with -P treatment alone, while the addition of c-PTIO, a scavenger of NO, could reverse the P-deficient phenotype alleviated by JA. Taken together, our results reveal a JA-NO-cell wall P reutilization pathway under P deficiency in rice.

Building Blocks of the Protective Suberin Plant Polymer Self-Assemble into Lamellar Structures with Antibacterial Potential.

The protection of terrestrial plants from desiccation, mechanical injury, and pathogenic invasion is achieved by waxes and cutin polyesters on leaf and fruit surfaces as well as suberin polymers that are embedded in the cell walls of roots, but the physicochemical principles governing the organization of these biological composites remain incompletely understood. Despite the well-established enzymatic mediation of suberin formation in the skins of potato tubers, cork oak trees, and internal plant tissues, the additional possibility of self-assembly in this system was suggested by our serendipitous finding that solvent extracts from potato phellem tissues form suspended fibers and needles in the absence of such catalysts over a period of several weeks. In the current study, we investigated self-assembly for three-component model chemical mixtures comprised of a hydroxyfatty acid, glycerol, and either of two hydroxycinnamic acids that together typify the building blocks of potato suberin biopolymers. We demonstrate that these mixtures spontaneously form lamellar structures that are reminiscent of suberized plant tissues, incorporate all constituents into self-assemblies, can form covalently bound ester structures, and display antibacterial activity. These findings provide new perspectives on the self-association and reactivity of these classes of organic compounds, insights into agriculturally important suberin formation in food crops, and a starting point for engineering sustainable materials with antimicrobial capabilities.

Accumulation Mechanism and Risk Assessment of Artemisia selengensis Seedling In Vitro with the Hydroponic Culture under Cadmium Pressure.

Artemisia selengensis is a perennial herb of the Compositae with therapeutic and economic value in China. The cadmium (Cd) accumulation mechanism and healthy risk evaluation of A. selengensis were investigated in this study. Tissue culture seedlings were obtained by plant tissue culture in vitro, and the effect of Cd stress (Cd concentration of 0.5, 1, 5, 10, 25, 50 and 100 μM) on A. selengensis was studied under hydroponic conditions. The results showed that low-Cd (0.5–1 μM) stress caused a rare effect on the growth of A. selengensis seedlings, which regularly grew below the 10 μM Cd treatment concentration. The biomass growth rate of the 0.5, 1, and 5 μM treatment groups reached 105.8%, 96.6%, and 84.8% after 40 days of cultivation, respectively. In addition, when the concentration of Cd was greater than 10 μM, the plant growth was obviously inhibited, i.e., chlorosis of leaves, blackening roots, destroyed cell ultrastructure, and increased malondialdehyde (MDA) content. The root could be the main location of metal uptake, 57.8–70.8% of the Cd was concentrated in the root after 40 days of cultivation. Furthermore, the root cell wall was involved in the fixation of 49–71% Cd by subcellular extraction, and the involvement of the participating functional groups of the cell wall, such as -COOH, -OH, and -NH2, in metal uptake was assessed by FTIR analysis. Target hazard quotient (THQ) was used to assess the health risk of A. selengensis, and it was found that the edible part had no health risk only under low-Cd stress (0.5 to 1 μM) and short-term treatment (less than 20 days).

Mechanisms of Stress Alleviation after Lime and Biochar Applications for Brassica napus L. in Cadmium-Contaminated Soil

Lime and biochar amendments are widely used to immobilize cadmium (Cd) in agricultural soils and to ensure food security. However, the effects of these two soil amendments on the mechanisms of Cd stress alleviation in crops are unclear. Therefore, the effects of lime and biochar applications on Cd uptake, transport, subcellular distribution, antioxidant system, N metabolism, and related factors were examined in a soil- Brassica napus L. ( B. napus) system. We found that lime application significantly increased the root Cd content by 41.5% but decreased Cd TF and shoot Cd by 81.0% and 74.3%, respectively, whereas biochar amendment decreased root and shoot Cd contents by 67.6% and 34.3%, respectively, but increased Cd TF by 104.1%. Lime treatment immobilized Cd in the cell wall of the root to reduce Cd transport, but biochar treatment increased the soluble fraction of Cd in root cells to improve the migration capacity of Cd. The significant negative relationship between the soil exchangeable Cd and Ca and the positive relationships between Cd and Ca both in shoot and root indicated that the Ca mediated Cd transport from soil to B. napus after lime and biochar applications. Additionally, lime amendment increased Cd proportion in the root cell walls to immobilize Cd, but biochar amendment increased Cd proportion in the soluble fraction to enhance Cd migration. Furthermore, biochar application significantly increased SOD, CAT, and POD by 17.5%, 95.4%, and 26.6%, whereas lime amendment only significantly enhanced CAT by 51.0%. Besides, both of biochar and lime applications increased shoot N content and GDH activity, but only the shoot NO3 - content and nitrate reductase under biochar treatment were significantly altered. Overall, these findings suggested that lime is more efficient in reducing the transport of Cd from underground to aboveground and in improving Cd tolerance, whereas biochar tends to improve the antioxidant capacity and facilitate N metabolism. These results will provide significant strategies for selecting appropriate amendments to ensure the crops safety.

Benzodifuran-based fluorescent brighteners: A novel platform for plant cell wall imaging

Herein we designed three novel fluorescent brightening agents based on a benzodifuran skeleton. The compounds are colorless fluorophores emitting in the blue region with an improved water solubility and ability to interact with living cells. A complete understanding of the emission mechanisms was achieved by Density Functional Theory study based on X-ray crystallographic analysis. The fluorescence quantum yields were measured in different solvents and at different pH values. The ability of the different fluorophores to stain cell compartments of plant root samples was tested in water- and glycerol-based solutions. Through fluorescence microscopy technique two probes with a different functionalized branching chain proved to be efficient stains for plant root cell wall. The cationic probe has no harmful effect on plant tissues and is suitable for in vivo fluorescent visualization of plant root cell boundaries. This study sheds light on the potential use of brighteners containing a central benzodifuran core as tools for imaging of fixed and alive plant tissues.

Putrescine is involved in root cell wall phosphorus remobilization in a nitric oxide dependent manner

Phosphorus (P) deficiency is a key limited factor to affect the crop production in rice (Oryza sativa). Recently, accumulating evidences have shown that root cell wall P reutilization could be released to the cytoplasm to alleviate the P starvation and a set of plant hormone and signal molecules have been identified to be involved in it. However, the role of putrescine (Put) in this process is still unknown. In this study, we found that Put with a concentration of 0.001 mM, 0.01 mM and 0.1 mM increased the root and shoot biomass in Nipponbare (Nip) and Kasalath (Kas) under P deficiency, although only 0.1 mM Put could significantly elevated the root and shoot soluble P concentration in Nip. Exogenous 0.1 mM Put treatment reduced the root cell wall P content through increasing the pectin content and pectin methylesterase (PME) activity, indicating that Put can be involved in the root cell wall P reutilization under P starvation. In addition, Put treatment also stimulated the root-to-shoot translocation of P through upregulating the expression of PHOSPHORUS TRANSPORTER 2 (OsPT2) and OsPT8 that responsible for the long-distance transport. Put under P-deficient condition significantly enhanced the Nitric Oxide (NO) accumulation in root and the application of NO inhibitor carboxy-PTIO (cPTIO) could reverse the Put-alleviated P-deficient phenotype, suggesting this process is mediated by NO. In conclusion, our results demonstrated that Put acts upstream of NO to activate the root cell wall P remobilization in rice.

Autotoxin Rg1 Induces Degradation of Root Cell Walls and Aggravates Root Rot by Modifying the Rhizospheric Microbiome.

ABSTRACTManagement of crop root rot disease is one of the key factors in ensuring sustainable development in agricultural production. The accumulation of autotoxins and pathogens in soil has been reported as a primary driver of root rot diseases; however, less is known about the correlation of plants, their associated pathogens and microbiome mediated by autotoxins as well as the contributions autotoxins make to the occurrence of root rot disease. Here, we integrated metabolomic, transcriptomic, and rhizosphere microbiome analyses to identify the root cell wall degradants cellobiose and d-galacturonic acid as being induced by the autotoxic ginsenoside Rg1 of Panax notoginseng, and we found that exogenous cellobiose and d-galacturonic acid in addition to Rg1 could aggravate root rot disease by modifying the rhizosphere microbiome. Microorganisms that correlated positively with root rot disease were enriched and those that correlated negatively were suppressed by exogenous cellobiose, d-galacturonic acid, and Rg1. In particular, they promoted the growth and infection of the soilborne pathogen Ilyonectria destructans by upregulating pathogenicity-related genes. Cellobiose showed the highest ability to modify the microbiome and enhance pathogenicity, followed by Rg1 and then d-galacturonic acid. Collectively, autotoxins damaged root systems to release a series of cell wall degradants, some of which modified the rhizosphere microbiome so that the host plant became more susceptible to root rot disease.IMPORTANCE The accumulation of autotoxins and pathogens in soil has been reported as a primary driver of root rot disease and one of the key factors limiting sustainable development in agricultural production. However, less is known about the correlation of plants, their associated pathogens, and the microbiome mediated by autotoxins, as well as the contributions autotoxins make to the occurrence of root rot disease. In our study, we found that autotoxins can damage root systems, thus releasing a series of cell wall degradants, and both autotoxins and the cell wall degradants they induce could aggravate root rot disease by reassembling the rhizosphere microbiome, resulting in the enrichment of pathogens and microorganisms positively related to the disease but the suppression of beneficial microorganisms. Deciphering this mechanism among plants, their associated pathogens, and the microbiome mediated by autotoxins will advance our fundamental knowledge of and ability to degrade autotoxins or employ microbiome to alleviate root rot disease in agricultural systems.

Effects of the Dark Septate Endophyte (DSE) Exophiala pisciphila on the Growth of Root Cell Wall Polysaccharides and the Cadmium Content of Zea mays L. under Cadmium Stress.

This paper aims to investigate the mechanism by which dark septate endophytes (DSEs) enhance cadmium (Cd) tolerance in there host plants. Maize (Zea mays L.) was inoculated with a DSE, Exophiala pisciphila, under Cd stress at different concentrations (0, 5, 10, and 20 mg·kg−1). The results show that, under 20 mg/kg Cd stress, DSE significantly increased maize biomass and plant height, indicating that DSE colonization can be utilized to increase the Cd tolerance of host plants. More Cd was retained in DSE-inoculated roots, especially that fixed in the root cell wall (RCW). The capability of DSE to induce a higher Cd holding capacity in the RCW is caused by modulation of the total sugar and uronic acid of DSE-colonized RCW, mainly the pectin and hemicellulose fractions. The fourier-transform spectroscopy analysis results show that carboxyl, hydroxyl, and acidic groups are involved in Cd retention in the DSE-inoculated RCW. The promotion of the growth of maize and improvement in its tolerance to Cd due to DSEs are related to restriction of the translocation of Cd from roots to shoots; resistance of Cd uptake Cd inside cells; and the increase in RCW-integrated Cd through modulating RCW polysaccharide components.

The role and its transcriptome mechanisms of cell wall polysaccharides in vanadium detoxication of rice

Cell wall-polysaccharides play a crucial role in heavy metals binding, and hence, contribute to heavy metal detoxication in plants. However, there is no data regarding the molecular mechanisms of vanadium (V) binding to root cell walls in plants, especially in rice (Oryza sativa L.). Taking two rice cultivars with various V tolerance as the research material, the present study investigated the effect of various V concentrations on subcellular distribution of V and revealed the regulatory mechanism of cell wall polysaccharides to V exposure. The results showed that rice roots inhibited the upward movement of V, and root cell walls accumulated 69.85–82.71% of V in roots. Furthermore, hemicellulose-1 (HC-1) in cell walls shared up to 67.72% and 66.95% of the cell-wall-bound V in tolerant and sensitive cultivars, respectively. FTIR spectroscopy demonstrated that V stress induced the remolding of cell wall polysaccharides. Under V stress, V-tolerant rice generated up to 19.3% pectin, 40.9% HC-1, and 49.34% HC-2, which were higher than V-sensitive cultivar. The genes encoding UGDH, UGE, and AXS for polysaccharide biosynthesis were higher expressed in V-tolerant rice than V-sensitive rice when exposed to V. The results could provide novel insight for phytoremediation and food security guarantees.

Ammonium has stronger Cd detoxification ability than nitrate by reducing Cd influx and increasing Cd fixation in Solanum nigrum L.

Cadmium (Cd) is a harmful heavy metal that affects the growth and development of plants. Nitrogen (N) is an essential nutrient for plants, and appropriate N management can improve Cd tolerance. The aim of our study was to explore the effects of different forms of N on the molecular and physiological responses of the hyperaccumulator Solanum nigrum to Cd toxicity. Measurement of biomass, photosynthetic parameters, and Cd2+ fluxes using non-invasive micro-test technique, Cd fluorescent dying, biochemical methods and quantitative real-time PCR analysis were performed in our study. Our results showed that ammonium (NH4+) has stronger Cd detoxification ability than nitrate (NO3-), which are likely attributed to the following three reasons: (1) NH4+ decreased the influx and accumulation of Cd2+ by regulating the transcription of Cd transport-related genes; (2) the ameliorative effects of NH4+ were accompanied by the increased retention of Cd in the cell walls of roots; and (3) NH4+ up-regulated SnExp expression.

Root dynamic growth strategies in response to salinity.

Increasing soil salinization largely impacts crop yield worldwide. To deal with salinity stress, plants exhibit an array of responses, including root system architecture remodelling. Here, we review recent progress in physiological, developmental and cellular mechanisms of root growth responses to salinity. Most recent research in modulation of root branching, root tropisms, as well as in root cell wall modifications under salinity stress, is discussed in the context of the contribution of these responses to overall plant performance. We highlight the power of natural variation approaches revealing novel potential pathways responsible for differences in root salt stress responses. Together, these new findings promote our understanding of how salt shapes the root phenotype, which may provide potential avenues for engineering crops with better yield and survival in saline soils.

Phytotoxicity mechanism of the natural radionuclide thorium in Vicia faba

Elucidation of the phytotoxic mechanisms of thorium (Th) is important for controlling Th accumulation in crops and improving the efficiency of phytoremediation. Here, we analyzed the subcellular distribution of Th in Vicia faba seedlings and the toxic reaction of seedlings to Th (5–40 μmol·L−1) at the subcellular and cellular levels. Increasing the phosphate level in the culture medium from 0.01 to 0.1 mmol·L−1 decreased the Th accumulation by the roots by 47–57%. Th was mainly distributed in the root cell walls (94–96%) and existed mainly in the form of residue (92–94%). Th accumulation in the root was similar to the changes observed for P, Ni, Cu, and Fe. High concentrations of Th (40 μmol·L−1) induced abnormal root growth and leaf photosynthetic metabolism. At the cellular level, Th (40 μmol·L−1) induced root edge cell death and inhibited root respiration and cell mitosis. SOD, POD and CAT activities were involved in the regulation of reactive oxygen species accumulation in the roots. Untargeted metabolomics identified 580 and 262 differentially expressed metabolites in roots and leaves. At the metabolic level, its toxicological mechanism involved a severe inhibition of the expression of nucleotides in roots and leaves.

Calmodulin-like protein CML24 interacts with CAMTA2 and WRKY46 to regulate ALMT1-dependent Al resistance in Arabidopsis thaliana.

ALUMINUM-ACTIVATED MALATE TRANSPORTER1 (ALMT1)-mediated malate exudation from roots is critical for aluminium (Al) resistance in Arabidopsis. Its upstream molecular signalling regulation is not yet well understood. The role of CALMODULIN-LIKE24 (CML24) in Al-inhibited root growth and downstream molecular regulation of ALMT1-meditaed Al resistance was investigated. CML24 confers Al resistance demonstrated by an increased root-growth inhibition of the cml24 loss-of-function mutant under Al stress. This occurs mainly through the regulation of the ALMT1-mediated malate exudation from roots. The mutation and overexpression of CML24 leads to an elevated and reduced Al accumulation in the cell wall of roots, respectively. Al stress induced both transcript and protein abundance of CML24 in root tips, especially in the transition zone. CML24 interacts with CALMODULIN BINDING TRANSCRIPTION ACTIVATOR2 (CAMTA2) and promotes its transcriptional activity in the regulation of ALMT1 expression. This results in an enhanced malate exudation from roots and less root-growth inhibition under Al stress. Both CML24 and CAMTA2 interacted with WRKY46 suppressing the transcriptional repression of ALMT1 by WRKY46. The study provides novel insights into understanding of the upstream molecular signalling of the ALMT1-depdendent Al resistance.

The Effect of Polymetallic Pollution on Ion-Exchange Properties of Barley Root and Shoot Cell Walls.

For the first time we determined the ion-exchange properties of the cell walls (CWs) isolated from roots and shoots of barley plants grown in the conditions of polymetallic pollution. The content of all the types of cation-exchange groups in the CWs was found to be considerably higher in the shoots than in the roots, which resulted in higher metal-binding capacity of the shoot CWs and higher swelling capacity of CW polymers. It was shown for the first time that the heavy metal excess causes an increase in the content of demethylated pectins in the shoot CWs.