Maize Roots Research Articles

Content Patterns of Maize Endogenous Hormones and Grain Yield Influenced by Field Phosphorus Application

The content of plant endogenous hormones could be influenced by fertilization, which play an important regulatory role in plant growth and yield formation. However, the effects of phosphate (P) application rates on the dynamical changes in the exogenous hormone content in maize plants to support high-yield production are still unclear. An experiment with six P application rates was designed (P1, 0 kg ha−1; P2, 20 kg ha−1; P3, 40 kg ha−1; P4, 60 kg ha−1; P5, 80 kg ha−1; and P6, 100 kg ha−1), aimed at determining the distribution or biosynthesis of phytohormones in maize roots and leaves, and clarifying the role of P fertilization in the formation of phytohormones. The results showed that P fertilization significantly increased the content of IAA, by 51.57%, and significantly decreased the contents of ABA and GA3, by 18.92% and 19.13% on average compared to P1. The highest increase in IAA was 99.02%, and the highest decreases in ABA and GA3 were 32.30% and 26.85%, respectively, in the P6 treatment in maize roots. Meanwhile, an increase in the IAA (41.34%), SA (27.58%), and GA3 (37.36%) contents and a decrease in the ABA (19.18%) content in maize leaves were observed. The highest increases in IAA, GA3, and SA in the P6 treatment in maize leaves were 57.5%, 62.50%, and 48.57%, respectively, and the highest decrease in ABA was 28.05%. Meanwhile, different contents of endogenous hormones in maize roots and leaves were observed at various maize growth stages. The maize phenotypes and soil available P content were increased with P application as well. A Pearson’s correlation analysis showed that endogenous hormones were significantly correlated with maize phenotypes and yield. Our results confirmed that P fertilization could change the content of endogenous hormones in maize roots and leaves; P6 was the best treatment for improving the endogenous hormone contents in maize plants, P3 was the best for improving the maize grain yield. Overall, 40 kg ha−1 is recommended as the best P application rate under the experimental conditions, considering the economic cost and environmental effects.

Impact of polystyrene microplastics on cadmium uptake in corn (Zea mays L.) in a cadmium‐contaminated calcareous soil

AbstractMicroplastics (MPs) are small plastic fragments that have spread globally, but the interaction between MPs and heavy metal soil contamination on plant growth has received little attention. In this study, the impact of polystyrene (PS) on maize growth in cadmium (Cd) polluted soil was examined through a randomized complete block design (RCBD) experiment. The results revealed that increasing PS levels in soil led to an increase in Cd concentration in maize shoots and roots compared to the control. Furthermore, the growth inhibiting impact of PS was enhanced by the presence of Cd. PS reduced the dry weights of the shoots and roots, resulting in lower overall dry weights. This study also demonstrated a distinct alteration in the soil pH following the addition of PS, with pH values increasing. PS enhanced the disruption of Cd and decreased the chlorophyll index, plant height, and leaf area by increasing the Cd concentration in the maize plant. These findings highlight the negative impact of PS on plant growth and the exacerbation of Cd contamination in soil. Proper disposal of plastic waste is crucial to mitigate its detrimental effects on the environment. Further research is needed to examine the impact of MPs on soil contamination and their interactions with plants. Understanding the mechanisms of the interactions between MPs and heavy metals will aid in developing strategies to reduce the risks associated with plastic waste and soil contamination. These findings underscore the need for effective waste management practices to prevent further contamination of the environment.

Purification effects show seed and root mucilage's ability to respond to changing rhizosphere conditions.

Mucilage, a polysaccharide-containing hydrogel, is hypothesized to play a key role in the rhizosphere as a self-organized system because it may vary its supramolecular structure with changes in the surrounding solution. However, there is currently limited research on how these changes are reflected in the physical properties of real mucilage. This study examines the role of solutes in maize root, wheat root, chia seed, and flax seed mucilage in relation to their physical properties. Two purification methods, dialysis and ethanol precipitation, were applied to determine the purification yield, cation content, pH, electrical conductivity, surface tension, viscosity, transverse 1 H relaxation time, and contact angle after drying of mucilage before and after purification. The two seed mucilage types contain more polar polymers that are connected to larger assemblies via multivalent cation crosslinks, resulting in a denser network. This is reflected in higher viscosity and water retention ability compared to root mucilage. Seed mucilage also contains fewer surfactants, making them better wettable after drying compared to the two root mucilage types. The root mucilage types, on the other hand, contain smaller polymers or polymer assemblies and become less wettable after drying. However, wettability not only depends on the amount of surfactants but also on their mobility, as well as the strength and mesh size of the network structure. The changes in physical properties and cation composition observed after ethanol precipitation and dialysis suggest that the polymer network of seed mucilage is more stable and specialized in protecting the seeds from unfavorable environmental conditions. In contrast, root mucilage is characterized by fewer cationic interactions and its network relies more on hydrophobic interactions. This allows root mucilage to be more flexible in responding to changing environmental conditions, facilitating nutrient and water exchange between root surfaces and the rhizosphere soil.

Co-Inoculation with Arbuscular Mycorrhizal Fungi and Dark Septate Endophytes under Drought Stress: Synergistic or Competitive Effects on Maize Growth, Photosynthesis, Root Hydraulic Properties and Aquaporins?

Arbuscular mycorrhizal fungi (AMF) and dark septate fungi (DSE) were simultaneously colonized in the root cells of maize. Single AMF and DSE symbiosis have been proven to improve the drought tolerance of maize. However, the effects of both fungi coexisting in maize roots under drought stress are not yet known. In this study, pot experiments of maize seedlings were conducted through four inoculation treatments (single AMF inoculation of Rhizophagus irregularis, single DSE inoculation of Exophiala pisciphila, co-inoculation of AMF + DSE and non-mycorrhizal inoculation) under well-watered (WW) and drought-stressed (DS) conditions. AMF and DSE colonization status, maize physiology and aquaporin gene expression in maize roots were investigated. The objective of this paper was to evaluate whether AMF and DSE had competitive, independent or synergistic effects on regulating the drought tolerance of maize. When maize seedlings of three inoculation treatments were subjected to drought stress, single AMF inoculation had the highest shoot and root dry weight, plant height, root length, osmotic root hydraulic conductivity and hydrostatic root hydraulic conductivity in maize seedlings. However, co-inoculation of AMF + DSE induced the highest stomatal conductance in maize leaves and the lowest H2O2 and O2•- concentration, membrane electrolyte leakage, intercellular CO2 concentration and gene expression level of ZmPIP1;1, ZmPIP1;2, ZmPIP2;1, ZmPIP2;5 and ZmPIP2;6. In addition, co-inoculation of AMF + DSE also obviously down-regulated the GintAQPF1 and GintAQPF2 expression in R. irregularis compared with single AMF inoculation treatment. Under DS stress, there were competitive relationships between AMF and DSE with regard to regulating mycorrhizal colonization, maize growth, root hydraulic conductivity and the gene expression of aquaporins in R. irregularis, but there were synergistic relationships with regard to regulating membrane electrolyte leakage, oxidative damage, photosynthesis and the aquaporin gene expression of maize seedlings. The obtained results improve our knowledge about how the mechanisms of AMF and DSE coexist, promoting the drought tolerance of host plants.

The changes in the maize root cell walls after exogenous application of auxin in the presence of cadmium.

Cadmium (Cd) is a transition metal and hazardous pollutant that has many toxic effects on plants. This heavy metal poses a health risk for both humans and animals. The cell wall is the first structure of a plant cell that is in contact with Cd; therefore, it can change its composition and/or ratio of wall components accordingly. This paper investigates the changes in the anatomy and cell wall architecture of maize (Zea mays L.) roots grown for 10 days in the presence of auxin indole-3-butyric acid (IBA) and Cd. The application of IBA in the concentration 10-9 M delayed the development of apoplastic barriers, decreased the content of lignin in the cell wall, increased the content of Ca2+ and phenols, and influenced the composition of monosaccharides in polysaccharide fractions when compared to the Cd treatment. Application of IBA improved the Cd2+ fixation to the cell wall and increased the endogenous concentration of auxin depleted by Cd treatment. The proposed scheme from obtained results may explain the possible mechanisms of the exogenously applied IBA and its effects on the changes in the binding of Cd2+ within the cell wall, and on the stimulation of growth that resulted in the amelioration of Cd stress.

Nitrogen fertilization and arbuscular mycorrhizal fungi do not mitigate the adverse effects of soil contamination with polypropylene microfibers on maize growth

Soil contamination with microplastics may adversely affect soil properties and functions and consequently crop productivity. In this study, we wanted to verify whether the adverse effects of microplastics in the soil on maize plants (Zea mays L.) are due to a reduction in nitrogen (N) availability and a reduced capacity to establish symbiotic relationships with arbuscular mycorrhizal (AM) fungi. To do this, we performed a pot experiment in which a clayey soil was exposed to two environmentally relevant concentrations of polypropylene (PP; one of the most used plastic materials) microfibers (0.4% and 0.8% w/w) with or without the addition of N fertilizer and with or without inoculation with AM fungi. The experiment began after the soil had been incubated at 23 °C for 5 months. Soil contamination with PP considerably reduced maize root and shoot biomass, leaf area, N uptake, and N content in tissue. The adverse effects increased with the concentration of PP in the soil. Adding N to the soil did not alleviate the detrimental effects of PP on plant growth, which suggests that other factors besides N availability played a major role. Similarly, although the presence of PP did not inhibit root colonization by AM fungi (no differences were observed for this trait between the uncontaminated and PP-contaminated soils), the addition of the fungal inoculum to the soil failed to mitigate the negative impact of PP on maize growth. Quite the opposite: mycorrhization further reduced maize root biomass accumulation. Undoubtedly, much research remains to be done to shed light on the mechanisms involved in determining plant behavior in microplastic-contaminated soils, which are most likely complex. This research is a priority given the magnitude of this contamination and its potential implications for human and environmental health.

Molecular identification of endophytes from maize roots and their biocontrol potential against toxigenic fungi of Nigerian maize.

Plants benefit from plant-associated microorganisms, of which endophytes are of particular interest as they are transmitted from generation to generation. This study characterises endophytes from maize roots and determines their biocontrol potential against toxigenic fungi in Nigerian maize. Maize roots were collected from farms in Lafia, and stored grain samples were collected from the six Northern States of Nigeria, from which endophytes and toxigenic fungal strains were isolated. Molecular identification employing 16SrRNA/internal transcribed spacer (ITS) sequences for isolated fungal endophytes was carried out, and mycotoxins produced by fungi were determined by high-performance liquid chromatography analysis. Biocontrol activity of the endophytes was determined using the dual culture confrontation test. Aspergillus and Fusarium genera were the prevalent isolated fungal species. Eight fungal endophytes were identified of which Trichoderma harzianum, Dichotomopilus erectus and Burkholderia spp. were the isolates with biocontrol activities, while 12 Aspergillus spp. were found to produce varying amounts of ochratoxin A and aflatoxin B1, respectively. T. harzianum showed the best inhibition (74%), followed by D. erectus (50%) and Burkholderia spp. (48%). T. harzianum showed poor inhibition of Aspergillus flavus (B7) at 30%. However, results from the Pakdaman Biological Control Index showed that T. harzianum has the best antifungal biocontrol activity of the three endophytes. The study concludes that antifungal biocontrol agents can be sourced from endophytes to obtain indigenous control activities that can check mycotoxin contamination of food and livestock feed, as well as elucidate possible metabolites for agricultural and industrial applications, which will help improve plant performance, increase crop yield and sustainability.

Exogenously applied sodium nitroprusside alleviates nickel toxicity in maize by regulating antioxidant activities and defense-related gene expression.

Nickel (Ni) stress adversely affects plant growth and biomass accumulation, posturing severe menace to crop production and food security. The current study aimed to determine the putative role of sodium nitroprusside (SNP) in mitigating Ni-induced phytotoxicity and identify the underlying defense mechanisms in maize, which are poorly understood. Our findings showed that SNP significantly augmented plant growth, biomass, and photosynthesis-related attributes (Fv/Fm, Fm, qP ETR, and ΦPSII) through diminishing Ni uptake and translocation in root and shoot tissues of maize under Ni stress conditions. In parallel, exogenous SNP substantially relieved maize seedlings from Ni-induced stress by enhancing enzymatic (SOD, CAT, and GPX) and non-enzymatic (phenol and flavonoids) antioxidant defenses and reducing oxidative stress indicators (MDA and H2 O2 ). The results revealed that SNP treatment increased the content of organic osmolyte glycine betaine and the activity of GST, concomitantly with ATP and ionic exchange capacity (including Ca2+ -ATPase and Mg2+ -ATPase), advocating its sufficiency to promote plant growth and avert Ni-induced stress in maize plants. The only exception was the production of organic acids (citric, oxalic, malic, and formic acids), which was reduced as SNP treatment relieved maize seedlings from Ni-induced oxidative damage. The application of SNP also displayed higher expression of defense- and detoxifying-related genes than in control treatments. Together, our data highlighted the mechanism involved in the amelioration of Ni toxicity by SNP; thus, suggesting a potential role of SNP in mitigating the adverse effects of Ni-contaminated soils to boost growth and yield of crop plants, that is, maize.

Effects of cover crops on maize establishment, root mycorrhizal colonization, plant growth and grain yield depend on their botanical family: A global meta-analysis

The current literature reports contradictory information regarding the effects of cover crops (CCs) on maize productivity. Quantifying the available information helps drawing robust conclusions that may have important implications for research and policy. Previous meta-analyses investigated the potential effects of CCs on maize biomass and grain yield but with a very narrow focus in terms of geographical areas, explanatory and response variables. A broader geographical coverage would help drawing robust conclusions regarding the effects of CCs on the subsequent maize crop performance. In light of this, we conducted a global meta-analysis to investigate whether management practices and environmental conditions related to CCs (i.e. explanatory variables) affect maize seed germination and seedling emergence, root colonization by arbuscular mycorrhizal fungi, plant height, biomass growth, and grain yield (i.e. response variables) compared to a no CC treatment (i.e. control). Our database included 5 185 comparisons totalling 53 127 observations from 275 publications between 1967 and 2022, worldwide. Overall, CCs reduced maize seed germination and seedling emergence while they enhanced maize root colonization by arbuscular mycorrhizal fungi, biomass and grain yield. When data were analyzed by CC families, three different groups were identified with Fabaceae, Brassicaceae and Poaceae showing the most beneficial, neutral and negative effects, respectively, on most of the response variables. While CC mixtures often enhanced maize performance, higher than three-species mixtures strongly affected maize grain yield. Overall, cover cropping into maize cropping systems, especially under low nitrogen fertilization, maintains or enhances maize productivity while also providing other ecosystem services.

Sugarcane mosaic virus reduced bacterial diversity and network complexity in the maize root endosphere.

Sugarcane mosaic virus (SCMV) causes mosaic disease in crops such as maize and sugarcane by its vector-an aphid-and is transmitted top-down into the root system. However, understanding of the effects of the aphid-borne virus on root-associated microbes after plant invasion remains limited. The current project investigated maize root-associated (rhizosphere and endosphere) bacterial communities, potential interspecies interaction, and assembly processes in response to SCMV invasion based on 16S rRNA gene amplicon sequencing. SCMV was detected in the roots 9 days after inoculation, and leaf mosaic and chlorosis appeared. The SCMV invasion markedly reduced the α-diversity of endosphere bacteria compared with uninoculated controls (Mock). The connectivity and complexity of the bacterial co-occurrence network in the root endosphere decreased after SCMV invasion, implying that the plant virus may alter root endophyte-microbial interactions. Moreover, a signature that deviates more from stochastic processes was observed in virus-infected plants. Unexpectedly, the rhizosphere bacterial communities were rarely affected by the viral invasion. This study lays the foundation for elucidating the fate of the microbial component of the plant holobiont following aphid-borne virus exposure. IMPORTANCE Biotic (e.g., soil-borne viruses) stress can alter root-associated bacterial communities, essential in maintaining host plant growth and health. However, the regulation of root-associated microorganisms by plant viruses from shoots is still largely unknown. Our results show that plant virus invasion leads to reduced and simpler inter-microbial communication in the maize endosphere. In addition, stochastic processes act on bacterial community assembly in both rhizosphere and endosphere, and bacterial communities in virus-invaded plant endosphere tend to shift toward deterministic processes. Our study highlights the negative effects of plant viruses on root endophytes from the microbial ecology perspective, which may be microbially mediated mechanisms of plant diseases.

Border row effects on the distribution of root and soil resources in maize–soybean strip intercropping systems

The cause of yield increase in crop strip intercropping is often inseparable from the boundary effect, and the distribution of roots and nutrients in the below-ground has an important influence on plant growth. However, previous studies on the boundary effect of intercropping have mainly focused on the above-ground part, and the state of the below-ground part is unknown. So we investigated the distribution of roots, water and NO3—N in the belowground part of the border row(adjacent rows of two crops in intercropping) in a maize and soybean strip intercropping system at different plant growth stage. There were three treatments in this experiment: maize monocrop, soybean monocrop and maize–soybean intercrop (four rows of maize and four rows of soybean). The distribution of maize roots extended beyond and below the border with the soybean rows and was concentrated in the 0–20 cm soil layer, while the growth of intercropped soybean roots was inhibited by maize. Intercropping increased the soil water content (SWC) in soybean rows at the podding stage and in maize rows at the drumming stage, and intercropping had a greatly effect on SWC of the system as a whole. Intercropping also increased the soil NO3—N content (SNC) in the intercropping system at the podding stage and had a negative effect at the drumming stage, and the effect of SNC in the intercropped maize rows was wider, while for intercropped soybean it was limited to the adjacent rows of soybean. The effect of intercropping on SWC and SNC occurred mainly in the 20–60 cm soil layer. Intercropping increased the grain weight of maize and decreased the grain weight and pods per soybean plant. Overall, the root system of maize in the border rows in the intercropping pattern extended into the soybean rows, intercropping increased soil water and soil nitrate-N levels in maize during the critical yield formation period, resulting in increased maize yields, while soybean was negatively affected in the intercropping pattern resulting in reduced yields, and we have calculated that intercropping maize and soybean has advantages in terms of land productivity and water use.

ZmmiR169q/ZmNF-YA8 is a module that homeostatically regulates primary root growth and salt tolerance in maize.

In response to salt stress, plants alter the expression of manifold gene networks, enabling them to survive and thrive in the face of adversity. As a result, the growth and development of plant roots could be drastically altered, with significant inhibition of the growth of root meristematic zones. Although it is known that root growth is primarily regulated by auxins and cytokinins, the molecular regulatory mechanism by which salt stress stunts root meristems remains obscure. In this study, we found that the ZmmiR169q/ZmNF-YA8 module regulates the growth of maize taproots in response to salt stress. Salt stress downregulates ZmmiR169q expression, allowing for significant upregulation of ZmNF-YA8, which, in turn, activates ZmERF1B, triggering the upregulation of ASA1 and ASA2, two rate-limiting enzymes in the biosynthesis of tryptophan (Trp), leading to the accumulation of auxin in the root tip, thereby inhibiting root growth. The development of the maize root is stymied as meristem cell division and meristematic zone expansion are both stifled. This study reveals the ZmmiR169q/ZmNF-YA8 module's involvement in maintaining an equilibrium in bestowing plant salt tolerance and root growth and development under salt stress, providing new insights into the molecular mechanism underlying the homeostatic regulation of plant development in response to salt stress.

Cell wall-related genes and lignin accumulation contribute to the root resistance in different maize (Zea mays L.) genotypes to Fusarium verticillioides (Sacc.) Nirenberg infection.

The fungal pathogen Fusarium verticillioides (Sacc.) Nirenberg (Fv) causes considerable agricultural and economic losses and is harmful to animal and human health. Fv can infect maize throughout its long agricultural cycle, and root infection drastically affects maize growth and yield. The root cell wall is the first physical and defensive barrier against soilborne pathogens such as Fv. This study compares two contrasting genotypes of maize (Zea mays L.) roots that are resistant (RES) or susceptible (SUS) to Fv infection by using transcriptomics, fluorescence, scanning electron microscopy analyses, and ddPCR. Seeds were infected with a highly virulent local Fv isolate. Although Fv infected both the RES and SUS genotypes, infection occurred faster in SUS, notably showing a difference of three to four days. In addition, root infections in RES were less severe in comparison to SUS infections. Comparative transcriptomics (rate +Fv/control) were performed seven days after inoculation (DAI). The analysis of differentially expressed genes (DEGs) in each rate revealed 733 and 559 unique transcripts that were significantly (P ≤0.05) up and downregulated in RES (+Fv/C) and SUS (+Fv/C), respectively. KEGG pathway enrichment analysis identified coumarin and furanocoumarin biosynthesis, phenylpropanoid biosynthesis, and plant-pathogen interaction pathways as being highly enriched with specific genes involved in cell wall modifications in the RES genotype, whereas the SUS genotype mainly displayed a repressed plant-pathogen interaction pathway and did not show any enriched cell wall genes. In particular, cell wall-related gene expression showed a higher level in RES than in SUS under Fv infection. Analysis of DEG abundance made it possible to identify transcripts involved in response to abiotic and biotic stresses, biosynthetic and catabolic processes, pectin biosynthesis, phenylpropanoid metabolism, and cell wall biosynthesis and organization. Root histological analysis in RES showed an increase in lignified cells in the sclerenchymatous hypodermis zone during Fv infection. These differences in the cell wall and lignification could be related to an enhanced degradation of the root hairs and the epidermis cell wall in SUS, as was visualized by SEM. These findings reveal that components of the root cell wall are important against Fv infection and possibly other soilborne phytopathogens.

Bio-converted organic wastes shape microbiota in maize rhizosphere: Localization and identification in enzyme hotspots

Organic fertilizers increase soil fertility, microbial diversity and heterogeneity of microbial activity hotspots. Black soldier fly (Hermetia illucens L.) frass (BSFF) derived from organic waste composts has been extensively marketed as organic fertilizer, but its effects on rhizosphere microbiota remain unknown. We compared the effects of BSFF from three organic wastes (straw, manure, and kitchen waste) on maize growth in acidic soils. Sufficient P, an optimal soil pH, and a satisfactory soil C/N ratio, as provided by the straw-derived frass, increased the maize growth more than the other frass types. Maize growth increased due to nutrient mobilization by active rhizosphere microbiota, which was localized using in situ soil zymography and identified through DNA amplicon sequencing and quantitative PCR. Specifically, the area of hotspots of acid phosphatase activity along the maize roots increased for 2.8 times after straw-derived frass application compared to unamended soils. Microbial diversity raised within these enzyme activity hotspots and was accompanied by the increased abundances of plant growth-promoting microbial taxa like Luteibacter, Chrysosporium, and Cladorrhinum. Microorganisms formed efficient and mutualistic networks within the rhizosphere hotspots induced by straw-derived frass to accelerate organic P mineralization, as inferred by random forest analysis and the quantitative of phoC and phoD genes. Concluding, the straw-derived frass benefits maize growth on acidic soils through abiotic (soil physico-chemical properties) and biotic (active rhizosphere microbiota) stimuli.

Partial replacement of chemical fertilizer by manure affects maize root traits in North China Plain

AbstractIn order to achieve high yields and environmental friendliness simultaneously, the replacement of chemical fertilizers by manure has become a research hotspot in recent years. Roots absorb nitrogen, participate in its assimilation and contribute to the cereal's dry matter accumulation. A 5‐year filed experiment in the North China Plain was initiated to assess the response of root morphology and distribution of summer maize (Zea mays L.) to fertilizer application and contribution to crop yield. The treatments included CK (unfertilized control), NPK (inorganic nitrogen/phosphorus/potassium fertilizer) and NPKM (manure + 70% NPK). We determined the root biomass, root diameter, root length density (RLD) of three diameters (>0.8 mm, 1stRLD; 0.2–0.8 mm, 2ndRLD; <0.2 mm, 3rdRLD) and the soil chemical properties at 60 cm with 10 cm increments. At 40–60 cm, NPKM significantly decreased the root diameter than NPK. Fertilization showed no effect on total RLD, 1stRLD, 2ndRLD and 3rdRLD for a 60‐cm soil profile. At 40–50 cm, the NPKM increased the RLD compared to NPK, mainly by increasing the 2ndRLD and 3rdRLD. Under CK and NPK, root lengths of 0–20 cm made up 62% and 57% of the total root length, respectively. Under NPKM, root lengths of 40–60 cm made up 46% of the total root length. Our results indicate that maize yield was preserved after replacing 30% of N fertilizer with manure, presumably depending on the change of root vertical distribution pattern and increase of the fine root length in deeper soil.

Single-cell RNA sequencing profiles reveal cell type-specific transcriptional regulation networks conditioning fungal invasion in maize roots.

Stalk rot caused by Fusarium verticillioides (Fv) is one of the most destructive diseases in maize production. The defence response of root system to Fv invasion is important for plant growth and development. Dissection of root cell type-specific response to Fv infection and its underlying transcription regulatory networks will aid in understanding the defence mechanism of maize roots to Fv invasion. Here, we reported the transcriptomes of 29 217 single cells derived from root tips of two maize inbred lines inoculated with Fv and mock condition, and identified seven major cell types with 21 transcriptionally distinct cell clusters. Through the weighted gene co-expression network analysis, we identified 12 Fv-responsive regulatory modules from 4049 differentially expressed genes (DEGs) that were activated or repressed by Fv infection in these seven cell types. Using a machining-learning approach, we constructed six cell type-specific immune regulatory networks by integrating Fv-induced DEGs from the cell type-specific transcriptomes, 16 known maize disease-resistant genes, five experimentally validated genes (ZmWOX5b, ZmPIN1a, ZmPAL6, ZmCCoAOMT2, and ZmCOMT), and 42 QTL or QTN predicted genes that are associated with Fv resistance. Taken together, this study provides not only a global view of maize cell fate determination during root development but also insights into the immune regulatory networks in major cell types of maize root tips at single-cell resolution, thus laying the foundation for dissecting molecular mechanisms underlying disease resistance in maize.

Microbial Syntrophy

While the gift economy is often considered a mechanism to strengthen social ties, the grift economy is often considered detrimental. However both systems rely on reciprocal play adding complexity to and questioning the ‘valuation’ mythology in contemporary free market logic. While traditional markets rely on so-called mutually agreed upon standards or market levers (value of currency, democratically decided upon regulations, legal precedents for civil behavior, global agreements for free exchange, supply-demand curves driving price), it is clear that this system has many games, loopholes, subsidies, institutional baggage, infrastructural lineages, national perversions, and theoretical distortions that make this free market, not actually free to correct its perversions on contemporary ‘value’ or inherited wealth inequity based on historic values. Gifters and grifters both contest value and do so by engaging existing social systems in unconventional ways. They work together, differently. In this presentation, I will playfully explore various theories about microbial economies that share gift/grift-like economies that support diverse bodies of life within a finite ecosystem of natural resources. For example, imagine a humanly visible maize root compared to an invisible microorganism; the single-celled bacteria cannot simply chew up the root that is orders of magnitude larger than itself (most microbes have a diameter between 0.5-10 microns, roughly the same range in size of ground corn starch). The scale of the opportunity for a microbe to eat a complex foodstuff like maize is Herculean! One form of microbial collaboration is called syntrophy. In this example, microbes living in environments without oxygen participate in an enzymatic potlatch. Different species contribute different enzymes to the extracellular matrix (outside the microbe body where the large molecule resides). Collectively these different donated enzymes with different capacities incrementally breakdown the complex substrate (the food). When the food is broken down into small enough metabolites, these basic building blocks of life in the extracellular matrix are now small enough to be absorbed by the small microbes (not unlike what happens in our stomachs) for maintenance, growth, or reproduction. Microbes share their genetic resources (in the form of donated enzymes) to then be able to collectively harvest the resulting metabolites in the commons of their extracellular space. In this case, it literally takes a village to make the village; losing certain species (and associated enzymes in the shared metabolic supply chain), breaks the collective system of metabolism to access the building blocks of the maize root. Just as in gift, grift, and current capitalist markets, the microbes deploy different agents to play different roles to access and distribute resources necessary for life. What is missing from this microbial system (in my anthropocentric read) is a perverse consent to value oneself and others’ worth, independent of the material needs of all. This talk will share observations from my art practice of transforming microbial ecosystems, present synopses of various theories on microbial ‘economies’, and then reflect back on two fringe human economies (gift/grift) to re-consider how we might build equitable and just collaborations to live sustainably within our own finite world.

Absorption, metabolism and distribution of carbosulfan in maize plants (Zea mays L.).

The insecticide carbosulfan is usually applied as a soil treatment or seed-coating agent, and so may be absorbed by crops and pose dietary risks. Understanding the uptake, metabolism and translocation of carbosulfan in crops is conducive to its safe application. In this study, we investigated the distribution of carbosulfan and its toxic metabolites in maize plants at both the tissue and subcellular levels, and explored the uptake and translocation mechanism of carbosulfan. Carbosulfan was mainly taken up by maize roots via the apoplast pathway, was preferentially distributed in cell walls (51.2%-57.0%) and most (85.0%) accumulated in roots with only weak upward translocation. Carbofuran, the main metabolite of carbosulfan in maize plants, was primarily stored in roots. However, carbofuran could be upwardly translocated to shoots and leaves because of its greater distribution in root-soluble components (24.4%-28.5%) compared with carbosulfan (9.7%-14.5%). This resulted from its greater solubility compared with its parent compound. The metabolite 3-hydroxycarbofuran was found in shoots and leaves. Carbosulfan could be passively absorbed by maize roots, mainly via the apoplastic pathway, and transformed into carbofuran and 3-hydroxycarbofuran. Although carbosulfan mostly accumulated in roots, its toxic metabolites carbofuran and 3-hydroxycarbofuran could be detected in shoots and leaves. This implies that there is a risk in the use of carbosulfan as a soil treatment or seed coating. © 2023 Society of Chemical Industry.

Response of soybean and maize roots and soil enzyme activities to biodegradable microplastics contaminated soil

Although biodegradable plastic film is a promising alternative product for reducing polyethylene plastic pollution in agricultural soils, the effects of its residues on plant growth and soil properties remain unclear. In this study, we conducted an experiment to investigate root properties and soil enzyme activities in Poly (butylene adipate-co-terephthalate) microplastics (PBAT-MPs) contaminated soil (0 % (CK), 0.1 %, 0.2 %, 0.5 % and 1 % of dry soil weight) with soybean (Glycine max (Linn.) Merr.) and maize (Zea mays L.). The results show that PBAT-MP accumulation in soil negatively affects root growth, and alter soil enzyme activities, which may then constrain C/N cycling and potential yields. For soybean, the total root length, total root surface area and root biomass decreased by 34 %− 58 %, 34 %− 54 % and 25 %− 40 % at the harvesting stage compared to CK, respectively. The negative effects of PBAT-MPs on maize roots were greater than on soybean roots. The total root length, root surface area and root biomass of maize decreased by 37 %− 71 %, 33 %− 71 % and 24 %− 64 % at the tasseling and harvesting stage, respectively (p < 0.05). Furthermore, a statistical analysis of the data indicates that the inhibition of soybean and maize root growth by PBAT-MP accumulation was mediated by the significantly different impacts of PBAT-MP addition on C-enzyme (β-xylosidase, cellobiohydrolase, β-glucosidase) and N-enzyme activities (leucine-aminopeptidase, N-acetyl-β-glucosaminidase, alanine aminotransferase) in rhizosphere and non-rhizosphere soil, possibly due to interactions with plant-specific root exudates and microbial communities. These findings show the potential risks posed by biodegradable microplastics on the plant-soil system, and suggest that biodegradable plastic film should be applied with caution.

Root cap is an important determinant of rhizosphere microbiome assembly.

Plants impact the development of their rhizosphere microbial communities. It is yet unclear to what extent the root cap and specific root zones contribute to microbial community assembly. To test the roles of root caps and root hairs in the establishment of microbiomes along maize roots (Zea mays), we compared the composition of prokaryote (archaea and bacteria) and protist (Cercozoa and Endomyxa) microbiomes of intact or decapped primary roots of maize inbred line B73 with its isogenic root hairless (rth3) mutant. In addition, we tracked gene expression along the root axis to identify molecular control points for an active microbiome assembly by roots. Absence of root caps had stronger effects on microbiome composition than the absence of root hairs and affected microbial community composition also at older root zones and at higher trophic levels (protists). Specific bacterial and cercozoan taxa correlated with root genes involved in immune response. Our results indicate a central role of root caps in microbiome assembly with ripple-on effects affecting higher trophic levels and microbiome composition on older root zones.