Maize Cells Research Articles

HD-ZIP Gene Family: Potential Roles in Improving Plant Growth and Regulating Stress-Responsive Mechanisms in Plants

Exploring the molecular foundation of the gene-regulatory systems underlying agronomic parameters or/and plant responses to both abiotic and biotic stresses is crucial for crop improvement. Thus, transcription factors, which alone or in combination directly regulated the targeted gene expression levels, are appropriate players for enlightening agronomic parameters through genetic engineering. In this regard, homeodomain leucine zipper (HD-ZIP) genes family concerned with enlightening plant growth and tolerance to environmental stresses are considered key players for crop improvement. This gene family containing HD and LZ domain belongs to the homeobox superfamily. It is further classified into four subfamilies, namely HD-ZIP I, HD-ZIP II, HD-ZIP III, and HD-ZIP IV. The first HD domain-containing gene was discovered in maize cells almost three decades ago. Since then, with advanced technologies, these genes were functionally characterized for their distinct roles in overall plant growth and development under adverse environmental conditions. This review summarized the different functions of HD-ZIP genes in plant growth and physiological-related activities from germination to fruit development. Additionally, the HD-ZIP genes also respond to various abiotic and biotic environmental stimuli by regulating defense response of plants. This review, therefore, highlighted the various significant aspects of this important gene family based on the recent findings. The practical application of HD-ZIP biomolecules in developing bioengineered plants will not only mitigate the negative effects of environmental stresses but also increase the overall production of crop plants.

A Novel In Silico Method for Molecular Mimicry Detection Finds a Formin with the Potential to Manipulate the Maize Cell Cytoskeleton.

Molecular mimicry is one of the evolutionary strategies that parasites use to manipulate the host metabolism and perform an effective infection. This phenomenon has been observed in several animal and plant pathosystems. Despite the relevance of this mechanism in pathogenesis, little is known about it in fungus-plant interactions. For that reason, we performed an in silico method to select plausible mimicry candidates for the Ustilago maydis-maize interaction. Our methodology used a tripartite sequence comparison between the parasite, the host, and nonparasitic organisms' genomes. Furthermore, we used RNA sequencing information to identify gene coexpression, and we determined subcellular localization to detect potential cases of colocalization in the imitator-imitated pairs. With these approximations, we found a putative extracellular formin in U. maydis with the potential to rearrange the host cell cytoskeleton. In parallel, we detected at least two maize genes involved in the cytoskeleton rearrangement differentially expressed under U. maydis infection; thus, this find increases the expectation for the potential mimicry role of the fungal protein. The use of several sources of data led us to develop a strict and replicable in silico methodology to detect molecular mimicry in pathosystems with enough information available. Furthermore, this is the first time that a genomewide search has been performed to detect molecular mimicry in a U. maydis-maize system. Additionally, to allow the reproducibility of this experiment and the use of this pipeline, we created a Web server called Molecular Mimicry Finder.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Overexpression of a Sugarcane BAHD Acyltransferase Alters Hydroxycinnamate Content in Maize Cell Wall.

The purification of hydroxycinnamic acids [p-coumaric acid (pCA) and ferulic acid (FA)] from grass cell walls requires high-cost processes. Feedstocks with increased levels of one hydroxycinnamate in preference to the other are therefore highly desirable. We identified and conducted expression analysis for nine BAHD acyltransferase ScAts genes from sugarcane. The high conservation of AT10 proteins, together with their similar gene expression patterns, supported a similar role in distinct grasses. Overexpression of ScAT10 in maize resulted in up to 75% increase in total pCA content. Mild hydrolysis and derivatization followed by reductive cleavage (DFRC) analysis showed that pCA increase was restricted to the hemicellulosic portion of the cell wall. Furthermore, total FA content was reduced up to 88%, resulting in a 10-fold increase in the pCA/FA ratio. Thus, we functionally characterized a sugarcane gene involved in pCA content on hemicelluloses and generated a C4 plant that is promising for valorizing pCA production in biorefineries.

Elucidating compositional factors of maize cell walls contributing to stalk strength and lodging resistance

Lodging is one of the causes of maize (Zea mays L.) production losses worldwide and, at least, the resistance to stalk lodging has been positively correlated with stalk strength. In order to elucidate the putative relationship between cell wall, stalk strength and lodging resistance, twelve maize inbreds varying in rind penetration strength and lodging resistance were characterized for cell wall composition and structure. Stepwise multiple regression indicates that H lignin subunits confer a greater rind penetration strength. Besides, the predictive model for lodging showed that a high ferulic acid content increases the resistance to lodging, whereas those of diferulates decrease it. These outcomes highlight that the strength and lodging susceptibility of maize stems may be conditioned by structural features of cell wall rather than by the net amount of cellulose, hemicelluloses and lignin. The results presented here provide biotechnological targets in breeding programs aimed at improving lodging in maize.

Overexpression of ZmNF-YC13 Confers ER Stress Tolerance in Maize

Excessive accumulation of unfolded or misfolded proteins in the lumen of the endoplasmic reticulum (ER) can trigger ER stress. Although regulation of this stress response in plants is an important and effective means of mitigating the damage caused by stress, the associated genes and mechanisms in maize remain largely unknown. In this study, we identified the ER stress-responsive gene ZmNF-YC13, which encodes a protein localized in the nuclei and cytoplasm of maize cells. The overexpression of ZmNF-YC13 in maize and Arabidopsis was found to confer plant ER stress tolerance, and gene expression analyses revealed that the overexpression of this gene upregulates the expression of genes involved in protein folding and the ER-associated degradation (ERAD) system, including ERdj, BiP, and E3 ubiquitin ligase. Moreover, we established that ZmNF-YC13 activates the promoters of the chaperone genes ZmERdj and ZmBiP in protoplasts, which function in the elimination of unfolded and misfolded proteins in the ER. Based on our findings, we propose that ZmNF-YC13 positively regulates the ER stress response in maize by controlling chaperone genes, and we believe that these results could provide valuable information for further maize resistance breeding.

Direct Agroinoculation of Maize Seedlings by Injection with Recombinant Foxtail Mosaic Virus and Sugarcane Mosaic Virus Infectious Clones.

Agrobacterium-based inoculation approaches are widely used for introducing viral vectors into plant tissues. This study details a protocol for the injection of maize seedlings near meristematic tissue with Agrobacterium carrying a viral vector. Recombinant foxtail mosaic virus (FoMV) clones engineered for gene silencing and gene expression were used to optimize this method, and its use was expanded to include a recombinant sugarcane mosaic virus (SCMV) engineered for gene expression. Gene fragments or coding sequences of interest are inserted into a modified, infectious viral genome that has been cloned into the binary T-DNA plasmid vector pCAMBIA1380. The resulting plasmid constructs are transformed into Agrobacterium tumefaciens strain GV3101. Maize seedlings as young as 4 days old can be injected near the coleoptilar node with bacteria resuspended in MgSO4 solution. During infection with Agrobacterium, the T-DNA carrying the viral genome is transferred to maize cells, allowing for the transcription of the viral RNA genome. As the recombinant virus replicates and systemically spreads throughout the plant, viral symptoms and phenotypic changes resulting from the silencing of the target genes lesion mimic 22 (les22)orphytoene desaturase (pds) can be observed on the leaves, or expression of green fluorescent protein (GFP) can be detected upon illumination with UV light or fluorescence microscopy. To detect the virus and assess the integrity of the insert simultaneously, RNA is extracted from the leaves of the injected plant and RT-PCR is conducted using primers flanking the multiple cloning site (MCS) carrying the inserted sequence. This protocol has been used effectively in several maize genotypes and can readily be expanded to other viral vectors, thereby offering an accessible tool for viral vector introduction in maize.

Extraction, quantification, and biochemical characterization of cereal industry by‐product cell wall

The current study was aimed to extract and purify the cell walls of cereal industrial by-products, that is, maize, wheat, and barley bran, followed by their nutritional and biochemical properties. For the purpose, three varieties of wheat and barley were procured from Ayub Agriculture Research Institute, Faisalabad, Pakistan. Cell walls from industrial by-products were isolated and purified followed by the removal of starch and proteins from contaminating endosperm tissue. Moreover, their sugar and polysaccharide contents wall were determined through gas chromatography and alkaline treatment, respectively. Results revealed that cell wall content is more in barley (43.18 ± 0.58, 42.43 ± 1.07 and 42.08 ± 0.13 g/50 g than in wheat (39.30 ± 1.67, 38.72 ± 0.45, and 37.45 ± 0.23 g/50 g) and maize (34.00 ± 0.08, 34.56 ± 0.39, and 33.76 ± 1.21 g/50 g). Moreover, barley industry by-product cell wall has higher total sugars and total phenolic acids contents whereas, wheat industry by-product cell wall showed lower followed by maize cell wall. Conclusively, cell wall of barley industry by-product is more nutritious than that of wheat and maize industry by-product cell walls. Practical applications Cereals are the most abundant commodities widely used in the world as staple foods. Cereal bran cell wall has important bioactive components, which have the ability to combat different life-threatening diseases. Utilization of cell wall in cereal-based products can fulfill many objectives including improving product quality, shelf life, value addition, and maintaining good health of the consumers. Novel products with improved rheology can be introduced in market as functional foods against various diseases such as diabetes mellitus, cancer, and bacterial infections. Cereal bran cell wall can be probed in the baking industry to enhance the shelf life and stability of the baked goods.

Mutualism between Dark Septate Endophytes (DSEs) and their host plants under metal stress: a case study

In the current study, a model of ‘fungus-root’ interaction was designed using host Zea mays inoculated with a metal-tolerant dark septate endophyte (DSE) strain of Exophiala pisciphila H93 both under nutritional- (Zn0) and zinc-stressed (Zn550) conditions. We found that the co-cultured maize benefited from the alleviated excessive Zn toxicity by its root-associated E. pisciphila, through significantly decreasing root Zn under Zn550 conditions, or promoting the nutritional Zn in maize shoots and roots by 34.03% and 22.13% under Zn0 conditions, respectively, compared with non-inoculated controls. Interestingly, H93 further enhanced the maize Zn tolerance by the bioaugmented Zn compartmentation in root cell walls to reduce the proportion of Zn in maize root soluble fractions and cell organelles under Zn550 stress. In exchange for the maize carbon cost, the H93 extraradical hyphae tended to accumulate more toxic Zn, compared with H93 mycelia in the in vitro culture under Zn550 conditions, and vice versa the co-cultured maize also promoted Zn tolerance of H93 via the repartitioning of subcellular Zn. Our results suggest the potentially mutual association of E. pisciphila and its host maize, by trading carbon for the increased abiotic tolerance.

Feruloyl esterase activity and its role in regulating the feruloylation of maize cell walls

Cell walls of grasses have ferulic acid (FA) ester-linked to the arabinosyl substitutions of arabinoxylan (AX). Feruloyl esterases (FAE) are carboxylic acid esterases that release FA from cell walls and synthetic substrates. Despite the importance of FA for cell wall recalcitrance and in response to biotic and abiotic stresses, the physiological function of plant FAEs remains unclear. Here, we developed a simple method for the determination of FAE activity (ZmFAE) in maize using the total protein extract and investigated its role in regulating the feruloylation of cell wall. The method includes a single protein extraction and enzymatic reaction with protein concentration as low as 65 μg at 35 °C for 30 min, using methyl ferulate as the substrate. The methodology allowed the determination of the apparent Km (392.82 μM) and Vmax (79.15 pkat mg−1 protein). We also found that ZmFAE activity was correlated (r = 0.829) with the levels of FA in seedling roots, plant roots and leaves of maize. Furthermore, the exposure to osmotic stress resulted in a 50% increase in ZmFAE activity in seedling roots. These data suggest that FAE-catalyzed reaction is important for cell wall feruloylation during plant development and in response to abiotic stress. We conclude proposing a model for the feruloylation and deferuloylation of AX, which explains the role of FAE in regulating the levels of ester-linked FA. Our model might orient further studies investigating the role of plant FAEs and assist strategies for genetic engineering of grasses to obtain plants with reduced biomass recalcitrance.

Core Cell Cycle–Related Gene Identification and Expression Analysis in Maize

Cell cycle is precisely controlled by numerous regulators. Although extensive studies have identified the cell cycle regulators in rice and Arabidopsis and classified into different gene families, relatively few cell cycle regulators were identified in maize. In this study, 110 putative core cell cycle–related genes in the maize genome were identified through sequence alignment analysis. Among them, 54 members of cyclin family were divided into the A-, B-, C-, D-, F-, L-, T-, and SDS-type subfamilies; 16 members of CDK family were partitioned into the A-, B-, C-, E-, F-, and G-type subfamilies; 19 members of E2F-DP family were separated into the E2F, PAP, DPB, CK, and DEL subfamilies; the remaining genes were nine ICK/KRPs, three EL2/SIMs, three CKSs, five Rbs, and one Wee1 kinase. Maize cell cycle–related genes unequally distributed on all chromosomes, and thirty-six pairs of them were identified as paralogs. The prediction of protein interaction found that 91 proteins were able to interact with each other forming 939 pairs of interactions with a probability more than 0.7. The expression analyses revealed that most of the cell cycle–related genes were expressed in all tissues. The transcription level of some genes in young tissues was higher than that in mature tissues of maize. Meanwhile, some genes from different families shared the similar expression pattern. Overall, the sequence characteristics and expression patterns of maize cell cycle–related genes vary with different gene families. Our results provide basic information for elucidating the functions of these genes in maize.

H2O2, Ca2+, and K+ in subsidiary cells of maize leaves are involved in regulatory signaling of stomatal movement

The stomata of maize (Zea mays) contain a pair of guard cells and a pair of subsidiary cells. To determine whether H2O2, Ca2+, and K+ in subsidiary cells were involved in stomatal movement, we treated four-week-old maize (Zhengdan 958) leaves with H2O2, diphenylene iodonium (DPI), CaCl2, and LaCl3. Changes in content and distribution of H2O2, Ca2+, and K+ during stomatal movement were observed. When exogenous H2O2 was applied, Ca2+ increased and K+ decreased in guard cells, while both ions increased in subsidiary cells, leading to stomatal closure. After DPI treatment, Ca2+ decreased and K+ increased in guard cells, but both Ca2+ and K+ decreased in subsidiary cells, resulting in open stomata. Exogenous CaCl2 increased H2O2 and reduced K+ in guard cells, while significantly increasing them in subsidiary cells and causing stomatal closure. After LaCl3 treatment, H2O2 decreased and K+ increased in guard cells, whereas both decreased in subsidiary cells and stomata became open. Results indicate that H2O2 and Ca2+ correlate positively with each other and with K+ in subsidiary cells during stomatal movement. Both H2O2 and Ca2+ in subsidiary cells promote an inflow of K+, indirectly regulating stomatal closure.

Food/Feed and Environmental Risk Assessment of Insect-resistant Genetically Modified Maize MIR604 for Food and Feed Uses, Import and Processing under Regulation (EC) No 1829/2003 (EFSA/GMO/UK/2005/11)

Food/Feed and Environmental Risk Assessment of Insect-resistant Genetically Modified Maize MIR604 for Food and Feed Uses, Import and Processing under Regulation (EC) No 1829/2003 (EFSA/GMO/UK/2005/11)

Cytological effects of herbicide alachlor in somatic cells of maize (Zea mays L.) and soybean (Glycine max Merrill.)

Abstract The extensive application of the herbicides for weed control in modern agriculture practices exerts a risk on various crop plants by way of chromosomal damage to the plants. In the current study the cytological effects of alachlor was studied in the root tip cells of maize and soybean. The maize and soybean were subjected to different concentrations of alachlor treatment (1.0–10.0 ppm and 1.0–8.0 ppm) respectively at room temperature. The mitotic index and relative division rate were decreased considerably as the herbicide concentrations increased, on the other hand the mitotic inhibition percentage and the relative abnormality rate was found to be increased as the herbicide concentration increased. The most frequently occurred chromosomal aberrations were nuclear lesion, sticky chromosome, sticky anaphase, sticky metaphase, chromosomal bridges and micronuclei. From the findings of the present study it can be concluded that alachlor might be responsible for the negative effects on cell division in maize and soybean.

Comparative study of lignocellulosic biomass and its components as electrode modifiers for detection of lead and copper ions

Cellulose, xylan and lignin, as well as maize cell wall, were used as modifiers of carbon paste electrode. Comparative analysis of electrochemical performance of each modifier toward heavy metal detection was performed. A higher affinity of biomass constituents for lead ions than for copper ions influenced simultaneous detection of lead and copper ions. The new procedure for the simultaneous detection of lead and copper ions based on their co-adsorption was presented.

Biolistic DNA Delivery in Maize Immature Embryos.

One of the key factors for ensuring a successful genetic transformation is to effectively introduce genetic materials, such as plasmid DNA, into plant cells. A biolistic gun is one of the two best established and most popular tools for delivery of DNA into maize cells. It is the method that generated the first fertile transgenic maize plant. In this chapter, we describe steps involved in introducing single or paired plasmid DNAs into immature embryos of maize Hi II hybrid genotype, using Biolistic® PDS-1000/He particle delivery system. While we focus on the biolistic delivery process in the protocol presented here, we also provide step-by-step information required for successful regeneration of transgenic maize plants.

Phytotoxic and Cyto-Genotoxic Potential of Phytolacca americana on Zea mays

Pokeweed (Phytolacca americana L.) is an invasive weed commonly found in the Oltenia area (Romania). Considering the economic importance of maize crop, this study was carried out to investigate the phytotoxic, cytotoxic and genotoxic potential of pokeweed extracts on maize (Zea mays L.). The seeds of maize were treated with different concentrations (5%, 10% and 20%) of pokeweed extracts, under laboratory conditions, for macroscopic and microscopic analyses, respectively. A control (distilled water) was used for comparison. All extracts significantly decreased germination, root and shoot length of maize seedling, also inhibited root cell division by the reduction of the mitotic index and by the induction of chromosomal and nuclear abnormalities in the root cells of maize. Chromosome stickiness, C-mitosis, piknosis, laggards, micronuclei and nuclear erosion, were observed. Thus, the present study suggests that the allelochemicals in the extracts of P. americana have a highly toxic potential on maize, so prevention and control of this invasive plant in the agricultural fields, are really necessary.

Exploring the effect of cereal bran cell wall on rheological properties of wheat flour

The objective of present study was to probe the effect of cereal bran cell wall addition on farinographic and mixographic characteristics of wheat flour dough. For the purpose, bran cell wall was isolated from three varieties of each cereal (wheat, barley, maize) according to respective method. Additionally, cereal bran cell walls were added in wheat flour with concentrations of 1% and 2% and rheological properties were determined through farinograph and mixograph. Addition of cereal bran cell walls significantly improved rheological properties of wheat flour. Higher increase in water absorption capacity (71.55 ± 0.30%), dough stability (8.80 ± 0.09 min), peak height (74.11 ± 0.31 BU), and mixing tolerance index (74.54 ± 0.30%) of dough was observed with the addition of barley cell wall followed by wheat and maize bran cell walls at 2%. Moreover, dough development time (2.78 ± 0.38 min), mixing time (4.12 ± 0.27 min), and softness of dough (123.60 ± 0.79%) were decreased more significantly through barley cell wall than wheat and maize cell walls. Conclusively, exploitation of cereal bran cell wall in cereal-based products improves product quality. Practical applications Cereal bran cell walls were added in wheat flour and various properties of wheat dough such as water absorption capacity, dough development time, mixing time, softness of dough, dough stability, mixing tolerance index, and peak height were improved. Utilization of cell wall in cereal-based products can fulfill many objectives including improving product quality, shelf life, value addition, and maintaining good health of the consumers. Novel products with improved rheology can be introduced in market as functional foods against various diseases such as diabetes mellitus, cancer, and bacterial infections.

The role of cell wall phenolics during the early remodelling of cellulose-deficient maize cells

The habituation of cultured cells to cellulose biosynthesis inhibitors such as dichlobenil (dichlorobenzonitrile, DCB) has proven a valuable tool to elucidate the mechanisms involved in plant cell wall structural plasticity. Our group has demonstrated that maize cells cope with DCB through a modified cell wall in which cellulose is replaced by a more extensive network of highly cross-linked feruloylated arabinoxylans. In order to gain further insight into the contribution of phenolics to the early remodelling of cellulose-deficient cell walls, a comparative HPLC-PAD analysis was carried out of hydroxycinnamates esterified into nascent and cell wall polysaccharides obtained from non-habituated (NH) and habituated to low DCB concentrations (1.5 μM; H) maize suspension-cultured cells.Incipient DCB-habituated cell walls showed significantly higher levels of esterified ferulic acid and p-coumaric acid throughout the culture cycle. In terms of cell wall fortification, ferulic acid is associated to arabinoxylan crosslinking whereas the increase of p-coumaric suggests an early lignification response. As expected, the level of hydroxycinnamates esterified into nascent polysaccharides was also higher in DCB-habituated cells indicating an overexpression of phenylpropanoid pathway. Due to their key role in cell wall strengthening, special attention was paid into the dimerization pattern of ferulic acid. A quantitative comparison of diferulate dehydrodimers (DFAs) between cell lines and cell compartments revealed that an extra dimerization took place in H cells when both nascent and mature cell wall polysaccharides were analysed. In addition, qualitative differences in the ferulic acid coupling pattern were detected in H cells, allowing us to suggest that 8-O-4′-DFA and 8-5′-DFA featured the ferulic acid dimerization when it occurred in the protoplasmic and cell wall fractions respectively. Both qualitative and quantitative differences in the phenolic profile between NH and H cells point to a regioselectivity in the ferulate dehydrodimerization.

Expression profiles of cell-wall related genes vary broadly between two common maize inbreds during stem development

BackgroundThe cellular machinery for cell wall synthesis and metabolism is encoded by members of large multi-gene families. Maize is both a genetic model for grass species and a potential source of lignocellulosic biomass from crop residues. Genetic improvement of maize for its utility as a bioenergy feedstock depends on identification of the specific gene family members expressed during secondary wall development in stems.ResultsHigh-throughput sequencing of transcripts expressed in developing rind tissues of stem internodes provided a comprehensive inventory of cell wall-related genes in maize (Zea mays, cultivar B73). Of 1239 of these genes, 854 were expressed among the internodes at ≥95 reads per 20 M, and 693 of them at ≥500 reads per 20 M. Grasses have cell wall compositions distinct from non-commelinid species; only one-quarter of maize cell wall-related genes expressed in stems were putatively orthologous with those of the eudicot Arabidopsis. Using a slope-metric algorithm, five distinct patterns for sub-sets of co-expressed genes were defined across a time course of stem development. For the subset of genes associated with secondary wall formation, fifteen sequence motifs were found in promoter regions. The same members of gene families were often expressed in two maize inbreds, B73 and Mo17, but levels of gene expression between them varied, with 30% of all genes exhibiting at least a 5-fold difference at any stage. Although presence-absence and copy-number variation might account for much of these differences, fold-changes of expression of a CADa and a FLA11 gene were attributed to polymorphisms in promoter response elements.ConclusionsLarge genetic variation in maize as a species precludes the extrapolation of cell wall-related gene expression networks even from one common inbred line to another. Elucidation of genotype-specific expression patterns and their regulatory controls will be needed for association panels of inbreds and landraces to fully exploit genetic variation in maize and other bioenergy grass species.

Development of dwarfish and yield-effective GM maize through passivation of bioactive gibberellin.

During the Green Revolution in the 1960s, breeding dwarf cultivars turned out to be a landmark, leading to a significant increase in the global production of wheat and rice. The most direct and effective strategy for breeding dwarf crops, among others, would be to control endogenous gibberellin (GA) levels of the crops. GA 2-oxidases are a group of 2-oxoglutarate-dependent dioxygenases that catalyze the deactivation of bioactive GAs. The ArabidopsisAtGA2ox1 gene was transformed into maize with the aim of obtaining a height-reduced GM maize. The characterization of the GM maize revealed that the highest plant height reduction was accomplished by a 74% decline in GA1 level, and by approximately twofold increases in both chlorophyll content and root/shoot ratio over the wild-type (WT). Interestingly, the stem cells of the GM maize were condensed, and the typical vascular bundle structure was found to be deformed. Based on a 2-season field trial, the GM maize exhibited a higher harvest index (9-17%) and grain yield (10-14%) than the WT. The current results suggest that a modulation of the endogenous GA level would be a sensible approach for improving the crop architecture and grain yield in maize.