Root Tips Research Articles

High overlap in the richness and composition of ectomycorrhizal fungal communities associated with Corylus shrubs and co-occurring Quercus and Pinus trees

ABSTRACT Despite being present in many North American forest understories, the ectomycorrhizal (ECM) fungal communities associated with Corylus shrubs have received no prior study. To address this knowledge gap, we characterized the ECM fungal communities on roots of Corylus shrubs as well as co-occurring Quercus and Pinus trees in Minnesota, USA. ECM-colonized root tips from pairs of Corylus shrubs and four ECM tree species, Quercus macrocarpa, Quercus ellipsoidalis, Pinus strobus, and Pinus resinosa, growing in close proximity (<1 m), were sampled at the Cedar Creek Ecosystem Science Reserve. ECM fungal communities were assessed using high-throughput sequencing of the ITS2 region. ECM fungal operational taxonomic unit (OTU) richness was equivalent among the two Quercus species and their associated Corylus shrubs, but significantly higher on P. strobus–associated Corylus shrubs compared with P. strobus, P. resinosa, and P. resinosa–associated Corylus shrubs. ECM fungal community composition on Corylus shrubs largely mirrored that on each of the Quercus and Pinus species, although the two Pinus communities were significantly different from each other. Further, the same ECM fungal OTUs were commonly encountered on paired Corylus–tree host samples, suggesting a high potential for co-colonization by the same fungal individuals. Collectively, these results support the growing consensus that woody understory plants often associate with similar ECM fungal communities as co-occurring tree hosts regardless of phylogenetic relatedness.

Mitigation of aluminum toxicity in rice seedlings using biofabricated selenium nanoparticles and nitric oxide: Synergistic effects on oxidative stress tolerance and sulfur metabolism.

Biofabricated selenium nanoparticles (Se-NPs) and sodium nitroprusside-derived nitric oxide (NO) singly or in combination was evaluated to improve tolerance to aluminum (Al) stress in rice (Oryza sativa L. cv. Swarna Sub1). The major objective was to elucidate contribution of sulfur reduction processes in oxidative stress tolerance along with cellular responses. Rice seedlings were primed against Al stress (550μM) by the exogenous application of 100μM NO and 20ppm Se-NPs synthesized from a Salvinia molesta D. Mitch. extract. Green-synthesized Se-NPs (∼67nm) had a crystalline, amorphous structure, high stability with functional groups in capping agents. The seedlings reduced bioaccumulation of Al in root tissues under SNP, Se-NPs, and in combination. Bioexclusion of Al was done in endodermal tissues by callose formation and binding in a fluorescent complex in the root tips. An upregulation of sulfur metabolism, including total sulfur, cysteine, cysteine synthase, and ATP sulfurylase activity was modulated by SNP+Se-NPs combination. Oxidative stress inducing metal stress for membrane oxidation into malondialdehyde, superoxide radical, and hydrogen peroxide, were also moderated by the SNP+Se-NPs combination. The Al-induced oxidative stress was relieved by a proportionate increase in superoxide dismutase and peroxidase activity. A higher ratio of ascorbate to dehydroascorbate and reduced to oxidized glutathione induced by the SNP+Se-NPs combination was supported antioxidation. These findings may substantiate the efficiency of green-synthesized Se-NPs together with SNP (as an NO donor) for amelioration of Al hazardous in crops like rice.

Melatonin-priming ameliorates aluminum accumulation and toxicity in rice through enhancing aluminum exclusion and maintaining redox homeostasis.

Seed priming can effectively enhance the plant's ability to withstand stress during subsequent growth and development; however, the role of melatonin-priming in attenuating aluminum (Al) toxicity remain unknown. In this study, 10, 50 and 100μM melatonin were selected for rice seed priming to investigate the protective effects and potential mechanisms of melatonin against Al toxicity. Al stress inhibited seed germination by induction of abscisic acid (ABA) accumulation and reduction of α-amylase activity. However, melatonin-priming substantially rescued the Al-induced poor germination of seeds, as evidenced by less ABA content and higher α-amylase activity. Compared to no priming under Al stress, melatonin-priming significantly increased root elongation and plant fresh weight of rice seedlings by 135.1% and 39.4%, respectively. Melatonin-priming scavenged Al-induced superoxide anion (O2·-) and hydrogen peroxide (H2O2) bursts by activating the antioxidant enzymes (superoxide dismutase and catalase) and antioxidants (ascorbate and glutathione) in root tips, thereby reducing malondialdehyde (MDA) and callose levels and ultimately mitigating oxidative damage. Furthermore, melatonin-priming enhanced Al resistance by inhibiting Al uptake into the symplast through increased citric acid secretion. The decrease of Al deposition in the cell wall was attributed to melatonin-stimulated reduction of cell wall pectin and hemicellulose contents under Al stress. Collectively, these findings reveal a positive role of melatonin-priming in alleviating Al toxicity in plants.

Mowing facilitated Pb accumulation in bermudagrass by mediating root radial transport.

Moderate mowing of the shoot is an effective strategy for improving Pb-contaminated soil remediation using bermudagrass. However, the mechanisms by which mowing facilitates Pb uptake and accumulation remain insufficiently understood. Root radial transport is critical in efficient heavy metal uptake and translocation in plants and is influenced by root physiological-biochemical characteristics. Herein, radial transport in roots and its effect on root-shoot Pb transport in bermudagrass under mowing were explored. Results revealed that mowing decreased Pb in apoplasts and increased Pb in symplasts, altering Pb radial transport pathways in roots. In the apoplastic pathway, mowing pretreatment intensified the inhibitory effects of a transpiration inhibitor on Pb uptake, resulting in a reduced contribution of the apoplastic pathway. Mowing induced lateral root endodermis thickening, early suberin lamellar development and increased suberin deposition, effectively preventing Pb from entering the stele through the apoplastic pathway. Conversely, in the symplastic pathway, mowing pretreatment alleviated the inhibitory effects of a metabolic inhibitor and ion channel inhibitor on Pb uptake and significantly increased net Pb2+influx in lateral root tips, thereby promoting the symplastic pathway. Furthermore, mowing upregulated the relative expression of CdNramp5 and CdHMA2 in roots, increasing Pb translocation to the shoot via the symplastic pathway. Overall, our study provided novel evidence mowing primarily improved Pb uptake and root-to-shoot transport by increasing the efficiency of the symplastic pathway. These findings provide a theoretical foundation for the use of mowing to improve the efficacy of bermudagrass in the remediation of Pb-contaminated soils.

Effect of Exogenous IBA on Root Morphology and Endogenous Hormone Metabolic Pathways in Castor Seedlings Under Pb/Zn Stress

Ricinus communis, a plant of significant industrial value for its oil, is renowned for its robust root system and vigorous growth, qualities that render it an exemplary candidate for the ecological remediation of soils contaminated with heavy metals. The impact of heavy metal stress on root development is characterized by inhibition, a phenomenon whose underlying mechanisms are not fully elucidated. To shed light on this, a study was conducted wherein varying concentrations of the exogenous auxin, IBA, were applied to the roots of Ricinus communis to scrutinize its influence on the endogenous indole-3-acetic acid (IAA) metabolism in seedlings and to delineate the molecular underpinnings of its effects on root morphology. It was observed that IBA significantly amplified the total root surface area by a factor of 1.29 and increased the number of root tips by 40.11% under lead (Pb) stress, and by 32.29% and 91.19%, respectively, under zinc (Zn) stress. These findings underscore the efficacy of IBA in promoting the proliferation of lateral roots in seedlings subjected to stress induced by either Pb or Zn. Further analysis of auxin signaling pathways revealed that the presence of Pb or Zn impedes root growth and lateral root formation by perturbing auxin transporters and signaling molecules. Notably, IBA was found to foster the development of lateral roots by modulating the expression of specific transporters. Post-application of IBA, the endogenous levels of IAA in roots exhibited a 2.80-fold elevation under Pb stress, IBA stimulated the activity of key biosynthetic enzymes, such as RcNIT and RcTAR, culminating in elevated IAA levels. Conversely, under Zn stress, IBA was observed to diminish the levels of RcTAR, which in turn led to reduced IAA levels. These outcomes contribute to a deeper comprehension of the modulatory role of IBA in the context of heavy metal stress.

First report of Ilyonectria liriodendri causing black foot on walnut in Chile.

Walnut (Juglans regia L.) is the primary nut tree cultivated in Chile, covering 44.626 ha. In autumn 2021, walnut decline and tree mortality were observed in young and old orchards (two and 18-years-old, respectively) in the O´Higgins Region in the Chilean Central Valley. In the surveyed walnut orchards cv. Chandler (n = 2), the incidence of symptomatic plants ranged from 35 to more than 90 %. Affected trees showed poor growth, twig and branch death, early defoliation, and shoot dieback. In addition, collar base necrosis and root rot were observed in symptomatic trees, resembling the symptoms of black foot disease, with blackening of complete roots and even the entire root system. Symptomatic root tissues from 5 independent trees were cut into pieces of about 25 mm2. The samples were sterilized for three minutes in a sodium hypochlorite solution (1%), rinsed in sterile distilled water, and plated onto Potato Dextrose Agar (PDA) medium supplemented with lactic acid (10%) and 0.5 g/L of streptomycin sulfate. Mycelium grew from the samples after seven days of incubation at 24°C. The characteristics of the culture and morphology of conidiophores and conidia indicated a Cylindrocarpon-like fungus. Then, 5 single-conidial isolates were obtained and subsequently grown on a PDA medium. Genomic DNA was extracted from cultures of three representative isolates (CNCO5; CNCO6; CNSF2) and used for amplification and sequencing of the Internal Transcribed Spacer of rDNA (ITS), β-tubulin (TUB2), Histone3 (HIS3), and Translation Elongation Factor 1-alpha (TEF1-α) partial gene regions using the primers ITS1/ITS4 (White et al. 1990), T1/Bt2b (O'Donnell and Cigelnik 1997; Glass and Donaldson 1995), CYLH3F/CYLH3R (Crous et al. 2004), and EF1-728F/EF1-986R (Carbone and Kohn 1999), respectively. Isolates clustered consistently with Ilyonectria liriodendri after a multilocus molecular phylogenetic analysis. Sequences were deposited in at NCBI Genbank data base (ITS: OR871536-OR871537-OR871538, TUB2: PP780828-PP780829-PP780830, HIS3: PP780822-PP780823-PP780824, and TEF1-α: PP780825-PP780826-PP780827). A pathogenicity test was conducted by inoculating three walnut Vlach rootstocks (six months old) with one representative I. liriodendri isolate (CNCO6). Plant roots were cut 5 cm from the root tip and immersed in a 105/mL conidial suspension for 30 min; control plants were immersed in sterile distilled water. Then, the plants were transplanted to a sterile substrate. After six weeks of growing in a greenhouse, necrosis characterized by brown-black coloration of the roots was observed developing upwards from the wounded roots. Necrotic lesions were found even in secondary roots of infected plants; however, control plants remained asymptomatic. The fungus was re-isolated, completing Koch's postulates. Black foot disease caused by Ilyonectria spp. has been reported worldwide on grapevines (Ye et al., 2021) and causing root rot of other fruit trees such as olive (Úrbez-Torres et al., 2012) and kiwifruit (Erper et al., 2011). Ilyonectria liriodendri was recently identified as the cause of walnuts root rot in California (Lawrence et al. 2019). To our knowledge, this is the first detection of I. liriodendri causing black foot of walnut in Chile and worldwide. The symptoms of this disease closely resemble those of Phytophthora spp. in walnuts. This similarity could lead to misdiagnosis, highlighting the necessity for specific diagnostic tools to accurately identify the pathogen.

Metabolic and Nutritional Responses of Contrasting Aluminium-Tolerant Banana Genotypes Under Al Stress

Aluminum (Al) toxicity is a major constraint to crop productivity in acidic soils, frequently encountered in banana-growing regions. This study investigates physiological and biochemical responses to Al stress in two Cavendish banana genotypes, Baodao and Baxi (Musa acuminata L.), which exhibit contrasting levels of Al tolerance. Banana plantlets were grown hydroponically under three AlCl3 concentrations (0, 100, and 500 μM) for 24, 48, and 72 h. Root elongation was progressively inhibited with increasing Al concentrations, with Baodao showing greater inhibition than Baxi. Al primarily accumulated in roots and displayed genotype-specific distribution patterns: Baodao concentrated more Al in root tips, suggesting lower exclusion efficiency. In contrast, Baxi, the Al-tolerant genotype, translocated Al from roots to shoots more effectively, indicating potential sequestration mechanisms in less sensitive tissues. Al stress influenced enzyme activities, with Baxi exhibiting higher phosphoenolpyruvate carboxylase and citrate synthase activities at 100 µM Al, while both genotypes showed similar reductions at 500 µM. Baodao experienced more pronounced reductions in H+-ATPase activity. At 100 µM Al, Baxi retained higher levels of key nutrients (P, Zn, Mg, Mn, Fe, K, and B) in essential tissues than Baodao. However, nutrient levels were reduced in both genotypes at 500 µM Al. These findings highlight Baxi’s superior resilience under Al stress, making it a suitable genotype for cultivation and breeding in acidic soils.

Rainfall seasonality shapes belowground root trait dynamics in an Amazonian tropical rainforest: A test of the stress‐dominance hypothesis

Abstract The stress‐dominance hypothesis (SDH) predicts that trait variation at the community level increases with the availability of limiting resources, driving spatial and temporal patterns in above‐ground plant functional trait expression. Here, we test the assumption that the SDH also applies to fine roots responding to spatial and temporal fluctuations in soil resource availability. We monitored fine root mass and functional root traits associated with resource acquisition, that is specific root length (SRL), specific root tip abundance (SRTA) and branching index (BI), and traits related to stress tolerance, such as root diameter (RD) and tissue density (RTD) in a Central Amazonian tree community. To test for spatial differences in root traits, we separated the uppermost organic (O‐A horizon, 0–5 cm) and mineral soil (B horizon, 5–15 cm) layers, and for temporal fluctuations, we investigated the relationship of precipitation on community‐level root variation over a period of 27 months. In accordance with the SDH, we found that fine roots in the O‐A horizon have on average 15% higher SRL, 23% higher BI, 32% higher SRTA and 15% lower RTD than those in the B horizon. Similarly, precipitation shifted the community over time to higher mean SRL, BI and SRTA (r = 0.92, 0.84 and 0.94, p &lt; 0.0001 respectively), although trait shifts occurred in the trimester after the rainy season onset, revealing a time‐lag between rainfall patterns and community response. We also detected a positive increase in trait range for SRL and SRTA with lagged precipitation (r = 0.90 and 0.79, p &lt; 0.0001). On the other hand, traits related to stress showed a weaker negative relationship with instantaneous precipitation (r = −0.7 and −0.57, p = 0.046 and p = 0.1 for RD and RTD, respectively). Our results supported the SDH predictions that root systems will become more acquisitive in areas with more resources, and that the community will shift to more acquisitive but also broader trait dispersion as hydric stress decreases. We conclude that although higher resource availability may increase competition for acquisition, trait overdispersion seems to promote species coexistence. Our results highlight how dynamic root systems can be in response to environmental cues, cautioning the common practice of making conclusions about root traits adaptations to environmental gradients based on a single sampling observation. Read the free Plain Language Summary for this article on the Journal blog.

Root cap border cells as regulators of rhizosphere microbiota

Root cap border cells as regulators of rhizosphere microbiota

Silicon Nutrition Improves Lodging Resistance of Rice Under Dry Cultivation

Silicon (Si) has been proven to enhance the stress resistance of rice, but its effect on the lodging resistance of rice under dry cultivation (DCR) is still unclear. The purpose of this experiment is to clarify the appropriate amount of silicon fertilizer for DCR to resist lodging and to elucidate how it coordinates lodging resistance and yield. This experiment used the ‘Suigeng 18’ cultivar as the material and set six silicon fertilizers (SiO2) with dosages of 0, 15, 30, 45, 60, and 75 kg·ha−1 (Si0, Si1, Si2, Si3, Si4, Si5). Analyze the effects and key indicators of silicon on lodging resistance of DCR from the perspectives of plant weight distribution, stem structure and composition, and root architecture. The results showed that the Si3 treatment had the highest yield and the lowest lodging index (LI). Si3 increases the weight of the upper three leaves and 4–5 internodes, thereby promoting panicle weight and yield. An increase of 13.38% in 2/3PWSI (weight of the 4th–5th stems and upper three leaves/weight of the 1st–3rd stems and lower leaves) can reflect the promoting effect of silicon on stem and leaf development near the panicle. Si3 reduces the GA/IAA value, shortens the length of the second internode, and increases the diameters of the major and minor axes, thereby increasing culm thickness and section modulus (SM), achieving the effect of “short and thick”. Si3 also increases the content of silicon and non-structural carbohydrates (NSCs) in the second internode, and increases lignin and cellulose content by upregulating the expression levels of CAD7, PAL, COMT, and CesA4 genes, thereby increasing fullness and flexural strength (M), achieving “short, thick, and strong” and reducing LI. The 38.95% reduction in IFL (second internode length/fullness) reflects the positive effect of silicon on the “short, thick, and strong” stem. In the underground part, adding silicon reduces the CTK/IAA value of roots, and increases root length, root tip number, root surface area, and root weight. The key to coordinating the lodging resistance and yield of DCR with appropriate silicon dosage is to reduce the IFL in the second internode and increase 2/3 PWSI and root growth. The key to DCR and breeding is to focus on the relationship between basal internode length and fullness, as well as stem and leaf growth near the panicle.

Bacillus subtilis inoculated in organic compost could improve the root architecture and physiology of soybean under water deficit.

Bacillus subtilis is known to promote root growth and improve plant physiology, while organic compost enhances soil water retention. This study explored the combined effect of inoculating B. subtilis in organic compost on soybean growth under water deficit. The treatments included chemical fertilization, non-inoculated organic compost, and organic compost inoculated with B. subtilis which were assessed under well-watered and water-deficit conditions. The organic compost inoculated with B. subtilis increased root biomass, length, volume, and the number of root tips under well-watered conditions, although it reduced root diameter. Under water deficit, the organic compost inoculated with B. subtilis increased root tip number (∼150%), biomass (∼95%) and number (∼85%) of nodules. Water deficit negatively affected soybean physiology, reduced photosynthesis, transpiration, and stomatal conductance, while increased internal CO₂ concentration. However, the organic compost inoculated with B. subtilis mitigated these effects, enhancing photosynthesis (∼20%) and water use efficiency (∼25%). Under water deficit, this treatment also increased shoot biomass by 15% and the drought tolerance index by 51% compared to the control. The combination of B. subtilis and organic compost improved root architecture, nodulation, and drought tolerance. These results suggest that B. subtilis inoculated in the organic compost is a promising strategy for enhancing soybean productivity and resilience under water stress, offering a novel approach to mitigating drought effects in agriculture.

Combined Effects of Nitrogen Deposition and Climate on Root-to-Shoot Ratios and Root Morphology in Temperate Tree Regeneration

Nitrogen (N) availability is known to interact with the drought tolerance in plants, but its effects on the morphological acclimation of forest trees to low precipitation have rarely been investigated. Based on a Germany-wide field-study design covering different combinations of climatic conditions and atmospheric N deposition, we harvested young trees up to 70 cm in height of Fagus sylvatica, Quercus petraea, Pseudotsuga menziesii, and Abies alba. We tested the hypothesis that high N deposition decreases the root/shoot ratio, alters fine root morphology (for example, by reducing specific root length of absorptive roots) and reduces mycorrhizal colonization rate, which are factors that would reduce the capacity for water uptake under drought. European beech showed reduced root/shoot ratios at high N deposition and reduced specific root length and mycorrhizal colonization of absorptive roots at sites with both high N deposition and low precipitation. These observations were consistent with the optimal portioning theory, as less investment in belowground biomass was required to meet the N demand at high N deposition. Sessile oak showed no effect of N deposition or mean annual precipitation on the parameters studied, indicating that the gradients studied were not large enough to cause changes. Douglas-fir and silver fir expanded their root systems with increasing N deposition, with higher specific root length in Douglas-fir and a trend towards higher root tip abundance in silver fir. Thus, in contrast to European beech, we found no indication that the tree's ability to cope with drought was reduced by high N deposition in sessile oak, Douglas-fir, and silver fir. The combined negative effect of drought and high N deposition on the root system in European beech as Central Europe’s most dominant tree species in the natural vegetation emphasizes the need for curtailing N emissions, especially from agriculture.

Subgenome-informed statistical modeling of transcriptomes in 25 common wheat accessions reveals cis- and trans- regulation architectures.

Common wheat is allohexaploid, where it is difficult to obtain homoeolog-distinguished transcriptome data. Lasy-Seq, a type of 3' RNA-seq, is a technology efficient at obtaining homoeolog-distinguished transcriptomes. Here we applied Lasy-Seq to obtain transcriptome data from the seedlings, second leaves, and root tips of 25 common wheat lines mainly from East Asia. Roots and seedlings were similar to each other in transcriptome profiles, but they were different from the leaves. We then asked how three homoeologous genes from different subgenomes (i.e., triads) show different levels of expression. Specifically, we examined the effects of subgenomes, lines and their interaction on the expression levels of each homoeolog triad, separately in each tissue. Of the 19,805 homoeolog triads, 51-55% showed significant effect of subgenome, suggesting cis-regulation, whereas 24-30% showed significant effect line, suggesting trans-regulation. We also found that 7.7-9.0% triads showed significant effects of the interaction. Hierarchical clustering and co-trans regulation network analysis of homoeolog triads revealed that the patterns of expression polymorphisms among the lines were shared in different genes. Our results also implied that expression variation between lines is caused by changes in a smaller number of common trans-factors. We performed GO term enrichment analysis using newly annotated and substantially improved GO annotations, which revealed that GO terms related to each tissue type function were enriched in genes expressed in the leaves and roots. Our information provides fundamental knowledge for the future breeding of plants possessing complex gene regulatory networks such as common wheat.

Cyto-Genotoxic Assessment of Sulfoxaflor in Allium cepa Root Cells and DNA Docking Studies.

Sulfoxaflor (SFX) is an insecticide that is commonly used for the control of sap-feeding insects. Since SFX is extensively applied globally, it has been implicated in the substantial induction of environmental toxicity. Therefore, in this study, Allium cepa roots have been employed to elucidate the potential cytogenotoxic effects of SFX in non-target cells by examination of mitotic index (MI), chromosomal aberrations (CAs), and DNA damage. Physiological effects of SFX were evaluated by A. cepa root growth inhibition assay, while cytogenotoxic effects were assessed by A. cepa ana-telophase and comet assay. Moreover, DNA binding affinity and binding mode of SFX were examined using molecular docking simulations to shed light on the genotoxic mechanism of action. The half maximal effective concentration (EC50) on the growth of A. cepa cells calculated for SFX was found as 500 mg/L. Moreover, dose- and time-dependent decrease in MI, increase in CAs (disturbed ana-telophase, chromosomal laggards, stickiness, and anaphase chromosome bridge) and DNA damage were observed by the exposure of A. cepa root tips to SFX after 24-, 48-, 72-, and 96-h treatment periods. A 6-bp double-stranded DNA structure containing two intercalation sites (PDB ID: 1Z3F) was used for docking studies. According to DNA docking results, SFX exhibited an energetically more favorable binding affinity with DNA (ΔG = -5.05 kcal/mol) compared with the experimental mutagen methyl methanesulfonate (MMS) (ΔG = -2.94 kcal/mol), and preferentially snugly fits into the minor groove of DNA possessing an intercalation gap, thus, providing valuable mechanistic data into the formation of chromosome aberrations and DNA fragmentation induced by this pesticide in A. cepa.

A Glutamate Receptor-Like Gene AtGLR25 With Its Unusual Splice Variant Has a Role in Mediating Glutamate-Elicited Changes in Arabidopsis Root Architecture.

The occurrence of external L-glutamate at the Arabidopsis root tip triggers major changes in root architecture, but the mechanism of -L-Glu sensing is unknown. Members of the family of GLUTAMATE RECEPTOR-LIKE (GLR) proteins are known to act as amino acid-gated Ca2+-permeable channels and to have signalling roles in diverse plant processes. To investigate the possible role of GLRs in the root architectural response to L-Glu, we screened a collection of mutants with T-DNA insertions in each of the 20 AtGLR genes. Reduced sensitivity of root growth to L-Glu was found in mutants of one gene, GLR2.5. Interestingly, GLR2.5 was found to apparently produce four transcript variants encoding hypothetical proteins of 169-720 amino acids. One of these transcripts, GLR2.5c, encodes a truncated GLR protein lacking both the conserved amino-terminal domain and part of the ligand-binding domain. When a glr2.5 mutant was transformed with a construct constitutively expressing GLR2.5c, both L-Glu sensitivity of root growth and L-Glu-elicited Ca2+ currents in root tip protoplasts were restored. These results, along with homology modelling of the truncated ligand-binding domain of GLR2.5c, suggest that GLR2.5c has a regulatory or scaffolding role in heteromeric GLR complex(es) that may involve triggering the root architectural response to L-Glu.

Identification of EXPA4 as a key gene in cotton salt stress adaptation through transcriptomic and coexpression network analysis of root tip protoplasts

BackgroundSalinity stress impairs cotton growth and fiber quality. Protoplasts enable elucidation of early salt-responsive signaling. Elucidating crop tolerance mechanisms that ameliorate these diverse salinity-induced stresses is key for improving agricultural productivity under saline conditions.ResultsHerein, we performed transcriptome profiling of Gossypium arboreum root tips and root tips-derived protoplasts to uncover salt tolerance genes and mechanisms. Differentially expressed genes (DEGs) were significantly enriched in the plant hormone signal transduction and MAPK signaling pathways. Transcriptome based weighted gene coexpression network analysis (WGCNA) clustered 885 commonly differentially expressed genes into four distinct modules. Black and yellow modules were highly upregulated under salt treatment, containing hub genes integral to signaling and transport, highlighting their importance. Differential expression analysis revealed more dynamic changes in protoplasts, identifying key genes including the Ga-α-expansin 4 (GaEXPA4). Silencing of the GaEXPA4 gene through virus-induced gene silencing heightened cotton’s sensitivity to salt stress, leading to increased wilting, elevated lipid peroxidation, and impaired antioxidant activity under salt conditions compared to controls.ConclusionThese findings underscore the functional significance of GaEXPA4 in the salt stress response. Future research should focus on elucidating the precise mechanisms of putative salt tolerance genes like GaEXPA4 and evaluating the potential of signaling pathways, such as MAPK, for engineering enhanced salt resilience in cotton. Integrating multi-omics approaches could further expand the genetic resources available for improving cotton cultivation in saline environments.

Effects of aluminum on metabolism of reactive oxygen species and reactive nitrogen species in root tips of different Eucalyptus species

On acidified soil, the growth of Eucalyptus is seriously restricted by aluminum (Al) stress. Therefore, breeding Eucalyptus species with excellent Al tolerance, developing the genetic potential of species, and improving tolerance to Al stress are important for the sustainable development of artificial Eucalyptus forests. By observing the occurrence and distribution of the main reactive oxygen species (ROS) and reactive nitrogen species (RNS) in root tips of Eucalyptus seedlings under Al stress, this study analyzed change in the growth and physiological indexes of Eucalyptus seedlings under Al stress. The antioxidant enzymes activities of the root tips of different Eucalyptus species induced by Al stress resulted in different ROS and RNS contents, ultimately resulting in differing degrees of membrane lipid peroxidation. In addition to suppressions of root relative elongation and root activity, the accumulations of soluble sugar, soluble protein, and proline can be used as indicators of Al sensitivity in Eucalyptus species. This may be an important determinant of the differences in Al tolerance among Eucalyptus species. The accumulation of ROS and RNS in the roots of E. grandis and E. tereticornis resulted in severe oxidative and nitrification stress. The tolerance of E. urophylla and E. urophylla × E. grandis to Al stress was stronger than that of E. grandis and E. tereticornis. Differences in Al toxicity tolerance were related to long-term selection of the original habitat of the species; moreover, the Al tolerance was hereditary. Eucalyptus urophylla × E. grandis had stronger Al tolerance than its parents, which is indicative of heterosis. These results provide theoretical support for the breeding of tree species in areas with acidic soil.

Synthetic Microbial Communities Enhance Pepper Growth and Root Morphology by Regulating Rhizosphere Microbial Communities.

Synthetic microbial community (SynCom) application is efficient in promoting crop yield and soil health. However, few studies have been conducted to enhance pepper growth via modulating rhizosphere microbial communities by SynCom application. This study aimed to investigate how SynCom inoculation at the seedling stage impacts pepper growth by modulating the rhizosphere microbiome using high-throughput sequencing technology. SynCom inoculation significantly increased shoot height, stem diameter, fresh weight, dry weight, chlorophyll content, leaf number, root vigor, root tips, total root length, and root-specific surface area of pepper by 20.9%, 36.33%, 68.84%, 64.34%, 29.65%, 27.78%, 117.42%, 35.4%, 21.52%, and 39.76%, respectively, relative to the control. The Chao index of the rhizosphere microbial community and Bray-Curtis dissimilarity of the fungal community significantly increased, while Bray-Curtis dissimilarity of the bacterial community significantly decreased by SynCom inoculation. The abundances of key taxa such as Scedosporium, Sordariomycetes, Pseudarthrobacter, norankSBR1031, and norankA4b significantly increased with SynCom inoculation, and positively correlated with indices of pepper growth. Our findings suggest that SynCom inoculation can effectively enhance pepper growth and regulate root morphology by regulating rhizosphere microbial communities and increasing key taxa abundance like Sordariomycetes and Pseudarthrobacter, thereby benefiting nutrient acquisition, resistance improvement, and pathogen resistance of crops to ensure sustainability.

The use of a drug based on extracellular matrix biomimetics as a means of regenerative therapy during resection of the tip of the tooth root

Introduction. The operation of resection of the tip of the tooth root is one of the main dental–preserving surgical methods of dental treatment with destructive changes in periapical tissues. Despite the high efficiency and other positive aspects, there are some disadvantages of this method of treatment, among which one can single out a long period of healing of periapical tissues, which necessitates the search for remedies that contribute to solving this problem. The aim is to study the possibility of using a drug based on extracellular matrix biomimetics as a means of regenerative therapy during resection of the tip of the tooth root, to evaluate its effect on the healing time of periapical tissues and the occurrence of complications. Materials and methods. The study involved 42 patients with indications for resection of the tip of the tooth root. The patients were randomly divided into two equal groups (n = 21): the control group, which underwent a traditional operation of resection of the tip of the tooth root, and the study group, which additionally used a drug based on extracellular matrix biomimetics. The timing of complete healing of periapical tissues and the presence of complications (in the form of lack of healing) were assessed using targeted intraoral contact radiography and percussion 6 months after the operation. The collected data were statistically analyzed. The indicators of descriptive statistics included the number of objects, the average value, the mean square deviation (SKO), 95 % confidence interval (CI95 %), median, lower (Q1) and upper (Q3) quartiles, minimum and maximum values. The comparison of the healing time in the study and control groups was carried out using the nonparametric Mann – Whitney criterion for independent groups. The comparison of the groups by the number of complications was carried out using the exact Fisher criterion. Results. In the study group, healing occurred on average after 129.9 days. (COE = 8.6 days), DI95 % 126.0–133.8 days, minimum healing period – 117.0 days, maximum – 151.0 days, median – 128.0 days, lower and upper quartiles 124.0 days and 133.0 days accordingly. In the control group, the average healing time was 181.5 days. (COE = 9.0 days), DI95 % 177.4–185.6 days, minimum healing period – 167.0 days, maximum – 199.0 days, median – 181.0 days, lower quartile – 175.0, upper quartile – 188.0 days. A comparison of the groups by healing time using the nonparametric Mann – Whitney criterion for independent samples showed a statistically significant difference (p = 0.00000003). In the study group, healing was faster (on average 129.9 days) than in the control group (on average 181.5 days). A comparison of the groups by the proportion (%) of complications using the exact Fisher criterion showed that there was no statistically significant difference between the groups (p = 0.49). In the study group, healing was in 21 (100 %) patients, in the control group – in 19 (90.5 %), complications were in 2 (9.5 %) patients. Conclusion. The results obtained during the study indicate the effectiveness of using the drug based on extracellular matrix biomimetics after resection of the tip of the tooth root: its effect reduces the time for complete healing of periapical tissues and completely prevents the occurrence of complications in the form of lack of healing.

Distinct and redundant roles of the Arabidopsis OCTOPUS gene family in plant growth beyond phloem development.

The Arabidopsis root apical meristem is an excellent model for studying plant organ growth that involves a coordinated process of cell division, elongation, and differentiation, while each tissue type develops on its own schedule. Among these tissues, the protophloem is particularly important, differentiating early to supply nutrients and signalling molecules to the growing root tip. The OCTOPUS (OPS) protein and its homolog OPS-LIKE 2 (OPL2) are essential for proper root protophloem differentiation and, likely through this role, indirectly promote root growth. Here, we explored the roles of the other three OPS homologs in Arabidopsis, OPL1, OPL3, and OPL4. OPS/OPL genes exhibit overlapping expression patterns and functions, with a high degree of redundancy among them. Although higher-order mutants do not display more severe phloem defects, they exhibit significantly reduced root growth compared to the ops opl2 mutant. These results suggest a direct contribution of the investigated OPL genes to meristematic activity. While our focus was on root growth, the OPS/OPL gene family also plays a positive role in regulating shoot growth, emphasizing its broader impact on plant development. Furthermore, our analyses reiterate the central role of OPS and the phloem domain in controlling overall plant growth.