Explore the vast range of titles available.

Main conclusion Arabinogalactan protein content in both root extracellular trap and root exudates varies in three Sahelian woody plant species that are differentially tolerant to drought. At the root tip, mature root cap cells, mainly border cells (BCs)/border-like cells (BLCs) and their associated mucilage, form a web-like structure known as the “Root Extracellular Trap” (RET). Although the RET along with the entire suite of root exudates are known to influence rhizosphere function, their features in woody species is poorly documented. Here, RET and root exudates were analyzed from three Sahelian woody species with contrasted sensitivity to drought stress ( Balanites aegyptiaca , Acacia raddiana and Tamarindus indica ) and that have been selected for reforestation along the African Great Green Wall in northern Senegal. Optical and transmission electron microscopy show that Balanites aegyptiaca , the most drought-tolerant species, produces only BC, whereas Acacia raddiana and Tamarindus indica release both BCs and BLCs. Biochemical analyses reveal that RET and root exudates of Balanites aegyptiaca and Acacia raddiana contain significantly more abundant arabinogalactan proteins (AGPs) compared to Tamarindus indica, the most drought-sensitive species. Root exudates of the three woody species also differentially impact the plant soil beneficial bacteria Azospirillum brasilense growth. These results highlight the importance of root secretions for woody species survival under dry conditions.

Border cells (BCs) are a cell population of the root cap that, during the process of differentiation, separates from the surface of the root apex in the form of single cells, small aggregates, or cell sheets and passes into the rhizosphere space. The functional activity of BCs in the rhizosphere is realized through the production of exometabolites. The review discusses the role of BCs and the root extracellular trap formed from their exometabolites in the processes of adaptation of the root system to various abiotic factors and reactions of the root immune system.

Roots of many plants are known to produce large numbers of 'border' cells that play a central role in root protection and the interaction of the root with the rhizosphere. Unlike border cells, border-like cells were described only recently in the model plant Arabidopsis thaliana and other Brassicaceae species and very little is known about the functional properties of border-like cells as compared with 'classical' border cells. To stimulate discussion and future research on this topic, the function of border cells and the way border-like cells are organized, maintained, and possibly involved in plant protection is discussed here.

Background and Aims The impedance to root growth imposed by soil can be decreased by both mucilage secretion and the sloughing of border cells from the root cap. The aim of this study is to quantify the contribution of these two factors for maize root growth in compact soil. Methods These effects were evaluated by assessing growth after removing both mucilage (treatment I - intact) and the root cap (treatment D - decapped) from the root tip, and then by adding back 2 microliter of mucilage to both intact (treatment IM - intact plus mucilage) and decapped (treatment DM - decapped plus mucilage) roots. Roots were grown in either loose (0.9 Mg m-3) or compact (1.5 Mg m-3) loamy sand soils. Also examined were the effects of decapping on root penetration resistance at three soil bulk densities (1.3, 1.4 and 1.5 Mg m-3). Key Results In treatment I, mucilage was visible 12 h after transplanting to the compact soil. The decapping and mucilage treatments affected neither the root elongation nor the root widening rates when the plants were grown in loose soil for 12 h. Root growth pressures of seminal axes in D, DM, I and IM treatments were 0.328, 0.288, 0.272 and 0.222 MPa, respectively, when the roots were grown in compact soil (1.5 Mg m-3 density; 1.59 MPa penetrometer resistance). Conclusions The contributions of mucilage and presence of the intact root cap without mucilage to the lubricating effect of root cap (percentage decrease in root penetration resistance caused by decapping) were 43 % and 58 %, respectively. The lubricating effect of the root cap was about 30 % and unaffected by the degree of soil compaction (for penetrometer resistances of 0.52, 1.20 and 1.59 MPa).

Rhizodeposits, root exudates, and root border cells are vital components of the rhizosphere that significantly affect root colonization capacity and multiplication of rhizosphere microbes, as well as secretion of organic bioactive compounds. The rhizosphere is an ecological niche, in which beneficial bacteria compete with other microbiota for organic carbon compounds and interact with plants through root colonization activity to the soil. Some of these root-colonizing beneficial rhizobacteria also colonize endophytically and multiply inside plant roots. In the rhizosphere, these components contribute to complex physiological processes, including cell growth, cell differentiation, and suppression of plant pathogenic microbes. Understanding how rhizodeposits, root exudates, and root border cells interact in the rhizosphere in the presence of rhizobacterial populations is necessary to decipher their synergistic role for the improvement of plant health. This review highlights the diversity of plant growth-promoting rhizobacteria (PGPR) genera, their functions, and the interactions with rhizodeposits in the rhizosphere.

Sustainable enhancement in food production from less available arable land must encompass a balanced use of inorganic, organic, and biofertilizer sources of plant nutrients to augment and maintain soil fertility and productivity. The varied responses of microbial inoculants across fields and crops, however, have formed a major bottleneck that hinders its widespread adoption. This necessitates an intricate analysis of the inter-relationships between soil microbial communities and their impact on host plant productivity. The concept of “biased rhizosphere,” which evolved from the interactions among different components of the rhizosphere including plant roots and soil microflora, strives to garner a better understanding of the complex rhizospheric intercommunications. Moreover, knowledge on rhizosphere microbiome is essential for developing strategies for shaping the rhizosphere to benefit the plants. With the advent of molecular and “omics” tools, a better understanding of the plant-microbe association could be acquired which could play a crucial role in drafting the future “biofertilizers.” The present review, therefore aims to (a) to introduce the concepts of rhizosphere hotspots and microbiomes and (b) to detail out the methodologies for creating biased rhizospheres for plant-mediated selection of beneficial microorganisms and their roles in improving plant performance.

A key regulator of collective cell migrations, which drive development and cancer metastasis, is substrate stiffness. Increased substrate stiffness promotes migration and is controlled by Myosin. Using Drosophila border cell migration as a model of collective cell migration, we identify, for the first time, that the actin bundling protein Fascin limits Myosin activity in vivo. Loss of Fascin results in: increased activated Myosin on the border cells and their substrate, the nurse cells; decreased border cell Myosin dynamics; and increased nurse cell stiffness as measured by atomic force microscopy. Reducing Myosin restores on-time border cell migration in fascin mutant follicles. Further, Fascin’s actin bundling activity is required to limit Myosin activation. Surprisingly, we find that Fascin regulates Myosin activity in the border cells to control nurse cell stiffness to promote migration. Thus, these data shift the paradigm from a substrate stiffness-centric model of regulating migration, to uncover that collectively migrating cells play a critical role in controlling the mechanical properties of their substrate in order to promote their own migration. This understudied means of mechanical regulation of migration is likely conserved across contexts and organisms, as Fascin and Myosin are common regulators of cell migration.

Root cap–derived cells and mucilage provide the first line of defense of the plant against soil microbial pathogens. These cells form a mucilaginous root extracellular trap (RET), which also harbors a range of molecules including exDNA and defensive peptides and proteins much like the neutrophil extracellular trap (NET) of mammalians. Plant RETs resemble mucus structures found in mammalian systems and are rich in arabinogalactan proteins that have similarities to highly glycosylated human mucins. Human mucus and mucins regulate the intestinal flora microbiome through recruiting certain species of microbes and it is plausible that the arabinogalactan protein–rich mucilage found in plant roots fulfills a similar function by attracting specific microbes to the rhizosphere. The role of RETs in root defense functioning is highlighted.

Hippocampal place cells are known for their spatially selective firing and are believed to encode an animal’s location while forming part of a cognitive map of space. These cells exhibit marked tuning curves and rate changes when an animal’s environment is sufficiently manipulated, in a process known as remapping. Place cells are accompanied by many other spatially tuned cells, such as border cells and grid cells, but how these cells interact during navigation and remapping is unknown. In this work, we build a normative place cell model wherein a neural network is tasked with accurate position reconstruction and path integration. Motivated by the notion of a cognitive map, the network’s position is estimated directly from its learned representations. To obtain a position estimate, we propose a non-trainable decoding scheme applied to network output units, inspired by the localized firing patterns of place cells. We find that output units learn place-like spatial representations, while upstream recurrent units become boundary-tuned. When the network is trained to perform the same task in multiple simulated environments, its place-like units learn to remap like biological place cells, displaying global, geometric, and rate remapping. These remapping abilities appear to be supported by rate changes in upstream units. While the model does not learn grid-like units, its place unit centers form clusters organized in a hexagonal lattice in open fields. When we decode the center locations of CA1 place fields in mice, we find preliminary evidence of a similar clustering tendency. This suggests a potential mechanism for the interaction between place cells, border cells, and grid cells. Our model provides a normative framework for learning spatial representations previously reserved for biological place cells, providing new insight into place cell field formation and remapping.

Neurons of the medial entorhinal cortex (MEC) provide spatial representations critical for navigation. In this network, the periodic firing fields of grid cells act as a metric element for position. The location of the grid firing fields depends on interactions between self-motion information, geometrical properties of the environment and nonmetric contextual cues. Here, we test whether visual information, including nonmetric contextual cues, also regulates the firing rate of MEC neurons. Removal of visual landmarks caused a profound impairment in grid cell periodicity. Moreover, the speed code of MEC neurons changed in darkness and the activity of border cells became less confined to environmental boundaries. Half of the MEC neurons changed their firing rate in darkness. Manipulations of nonmetric visual cues that left the boundaries of a 1D environment in place caused rate changes in grid cells. These findings reveal context specificity in the rate code of MEC neurons.