The discovery of an anti-inflammatory monoterpenoid, neoroseoside from the Zea mays

A new monoterpenoid, neoroseoside (1), along with two previously reported compounds, 2″-O-α-l-rhamnosyl-6-C-fucosylluteolin (2) and farobin A (3) were isolated from the Zea mays. The structure of compound 1 was determined through the analysis spectroscopic data, including mass spectrometry (MS), infrared (IR) spectroscopy, and nuclear magnetic resonance (NMR) data. The absolute configurations of 1 were deduced from the comparing the values of optical rotations and from the interpretation of electronic circular dichroism (ECD) spectra. Compounds 2 and 3 displayed moderate antibacterial activity against Streptococcus mutans ATCC 25175 (inhibition rates 24 % and 28 %, respectively) and Streptococcus sobrinus ATCC 33478 (inhibition rate of 26 %), at a concentration of 100 μg/mL, whereas compound 1 did not have any significant antibacterial activities. The compounds 1-3 also showed anti-inflammatory activity on cytokine IL-6 and TNF-α.

Diverging cell wall strategies for drought adaptation in two maize inbreds with contrasting lodging resistance

The plant cell wall is a plastic structure of variable composition that constitutes the first line of defence against environmental challenges. Lodging and drought are two stressful conditions that severely impact maize yield. In a previous work, we characterised the cell walls of two maize inbreds, EA2024 (susceptible) and B73 (resistant) to stalk lodging. Here, we show that drought induces distinct phenotypical, physiological, cell wall, and transcriptional changes in the two inbreds, with B73 exhibiting lower tolerance to this stress than EA2024. In control conditions, EA2024 stalks had higher levels of cellulose, uronic acids and p-coumarate than B73. However, upon drought EA2024 displayed increased levels of arabinose-enriched polymers, such as pectin-arabinans and arabinogalactan proteins, and a decreased lignin content. By contrast, B73 displayed a deeper rearrangement of cell walls upon drought, including modifications in lignin composition (increased S subunits and S/G ratio; decreased H subunits) and an increase of uronic acids. Drought induced more substantial changes in gene expression in B73 compared to EA2024, particularly in cell wall-related genes, that were modulated in an inbred-specific manner. Transcription factor enrichment assays unveiled inbred-specific regulatory networks coordinating cell wall genes expression. Altogether, these findings reveal that B73 and EA2024 inbreds, with opposite stalk-lodging phenotypes, undertake different cell wall modification strategies in response to drought. We propose that the specific cell wall composition conferring lodging resistance to B73, compromises its cell wall plasticity, and renders this inbred more susceptible to drought.

Uncovering the Infection Strategy of Phyllachora maydis During Maize Colonization: A Comprehensive Analysis

Tar spot, a disease caused by the ascomycete fungal pathogen Phyllachora maydis, is considered one of the most significant yield-limiting diseases of maize (Zea mays) within the United States. P. maydis may also be found in association with other fungi, forming a disease complex that is thought to result in the characteristic fisheye lesions. Understanding how P. maydis colonizes maize leaf cells is essential for developing effective disease control strategies. Here, we used histological approaches to elucidate how P. maydis infects and multiplies within susceptible maize leaves. We collected tar spot-infected maize leaf samples from four different fields in northern Indiana at three different time points during the growing season. Samples were chemically fixed and paraffin-embedded for high-resolution light and scanning electron microscopy. We observed a consistent pattern of disease progression in independent leaf samples collected across different geographical regions. Each stroma contained a central pycnidium that produced asexual spores. Perithecia with sexual spores developed in the stomatal chambers adjacent to the pycnidium, and a cap of spores formed over the stroma. P. maydis reproductive structures formed around but not within the vasculature. We observed P. maydis associated with two additional fungi, one of which is likely a member of the Paraphaeosphaeria genus; the other is an unknown fungi. Our data provide fundamental insights into how this pathogen colonizes and spreads within maize leaves. This knowledge can inform new approaches to managing tar spot, which could help mitigate the significant economic losses caused by this disease.

Autophagy receptor ZmNBR1 promotes the autophagic degradation of ZmBRI1a and enhances drought tolerance in maize

Drought stress is a crucial environmental factor that limits plant growth, development, and productivity. Autophagy of misfolded proteins can help alleviate the damage caused in plants experiencing drought. However, the mechanism of autophagy-mediated drought tolerance in plants remains largely unknown. Here, we cloned the gene for a maize (Zea mays) selective autophagy receptor, NEXT TO BRCA1 GENE 1 (ZmNBR1), and identified its role in the response to drought stress. We observed that drought stress increased the accumulation of autophagosomes. RNA sequencing and reverse transcription-quantitative polymerase chain reaction showed that ZmNBR1 is markedly induced by drought stress. ZmNBR1 overexpression enhanced drought tolerance, while its knockdown reduced drought tolerance in maize. Our results established that ZmNBR1 mediates the increase in autophagosomes and autophagic activity under drought stress. ZmNBR1 also affects the expression of genes related to autophagy under drought stress. Moreover, we determined that BRASSINOSTEROID INSENSITIVE 1A (ZmBRI1a), a brassinosteroid receptor of the BRI1-like family, interacts with ZmNBR1. Phenotype analysis showed that ZmBRI1a negatively regulates drought tolerance in maize, and genetic analysis indicated that ZmNBR1 acts upstream of ZmBRI1a in regulating drought tolerance. Furthermore, ZmNBR1 facilitates the autophagic degradation of ZmBRI1a under drought stress. Taken together, our results reveal that ZmNBR1 regulates the expression of autophagy-related genes, thereby increasing autophagic activity and promoting the autophagic degradation of ZmBRI1a under drought stress, thus enhancing drought tolerance in maize. These findings provide new insights into the autophagy degradation of brassinosteroid signaling components by the autophagy receptor NBR1 under drought stress.

A Summary of Two Decades of QTL and Candidate Genes That Control Seed Tocopherol Contents in Maize (Zea mays L.)

Tocopherols are secondary metabolites synthesized through the shikimate biosynthetic pathway in the plastids of most plants. It is well known that α-Tocopherol (vitamin E) has many health benefits for humans and animals; therefore, it is highly used in human and animal diets. Tocopherols vary considerably in most crop (and plant) species and within cultivars of the same species depending on environmental and growth conditions; tocopherol content is a polygenic, complex traits, and its inheritance is poorly understood. The objective of this review paper was to summarize all identified quantitative trait loci (QTL) that control seed tocopherols and related contents identified in maize (Zea mays) during the past two decades (2002-2022). Candidate genes identified within these QTL regions are also discussed. The QTL described here, and candidate genes identified within these genomic regions could be used in breeding programs to develop maize cultivars with high, beneficial levels of seed tocopherol contents.

Heterologous Biosynthesis of Kauralexin A1 in Saccharomyces cerevisiae through Metabolic and Enzyme Engineering

Kauralexin A1 (KA1) is a key intermediate of the kauralexin A series metabolites of maize phytoalexins. However, their application is severely limited by their low abundance in maize. In this study, an efficient biosynthetic pathway was constructed to produce KA1 in Saccharomyces cerevisiae. Also, metabolic and enzyme engineering strategies were applied to construct the high-titer strains, such as chassis modification, screening synthases, the colocalization of enzymes, and multiple genomic integrations. First, the KA1 precursor ent-kaurene was synthesized using the efficient diterpene synthase GfCPS/KS from Fusarium fujikuroi, and optimized to reach 244.36 mg/L in shake flasks, which displayed a 200-fold increase compared to the initial strain. Then, the KA1 was produced under the catalysis of ZmCYP71Z18 from Zea mays and SmCPR1 from Salvia miltiorrhiza, and the titer was further improved by integrating the fusion protein into the genome. Finally, an ent-kaurene titer of 763.23 mg/L and a KA1 titer of 42.22 mg/L were achieved through a single-stage fed-batch fermentation in a 5 L bioreactor. This is the first report of the heterologous biosynthesis of maize diterpene phytoalexins in S. cerevisiae, which lays a foundation for further pathway reconstruction and biosynthesis of the kauralexin A series maize phytoalexins.

A red seaweed Kappaphycus alvarezii-based biostimulant (AgroGain®) improves the growth of Zea mays and impacts agricultural sustainability by beneficially priming rhizosphere soil microbial community

The overuse of chemical-based agricultural inputs has led to the degradation of soil with associated adverse effects on soil attributes and microbial population. This scenario leads to poor soil health and is reportedly on the rise globally. Additionally, chemical fertilizers pose serious risks to the ecosystem and human health. In this study, foliar sprays of biostimulant (AgroGain/LBS6) prepared from the cultivated, tropical red seaweed Kappaphycus alvarezii increased the phenotypic growth of Zea mays in terms of greater leaf area, total plant height, and shoot fresh and dry weights. In addition, LBS6 improved the accumulation of chlorophyll a and b, total carotenoids, total soluble sugars, amino acids, flavonoids, and phenolics in the treated plants. LBS6 applications also improved the total bacterial and fungal count in rhizospheric soil. The V3-V4 region of 16S rRNA gene from the soil metagenome was analyzed to study the abundance of bacterial communities which were increased in the rhizosphere of LBS6-treated plants. Treatments were found to enrich beneficial soil bacteria, i.e., Proteobacteria, especially the classes Alphaproteobacteria, Cyanobacteria, Firmicutes, Actinobacteriota, Verrucomicrobiota, Chloroflexi, and Acidobacteriota and several other phyla related to plant growth promotion. A metagenomic study of those soil samples from LBS6-sprayed plants was correlated with functional potential of soil microbiota. Enrichment of metabolisms such as nitrogen, sulfur, phosphorous, plant defense, amino acid, co-factors, and vitamins was observed in soils grown with LBS6-sprayed plants. These results were further confirmed by a significant increase in the activity of soil enzymes such as urease, acid phosphatase, FDAse, dehydrogenase, catalase, and biological index of fertility in the rhizosphere of LBS6-treated corn plant. These findings conclude that the foliar application of LBS6 on Z. mays improves and recruits beneficial microbes and alters soil ecology in a sustainable manner.

Expansion and improvement of ChinaMu by MuT-seq and chromosome-level assembly of the Mu-starter genome

ChinaMu is the largest sequence-indexed Mutator (Mu) transposon insertional library in maize (Zea mays). In this study, we made significant improvements to the size and quality of the ChinaMu library. We developed a new Mu-tag isolation method Mu-Tn5-seq (MuT-seq). Compared to the previous method used by ChinaMu, MuT-seq recovered 1/3 more germinal insertions, while requiring only about 1/14 of the sequencing volume and 1/5 of the experimental time. Using MuT-seq, we identified 113,879 germinal insertions from 3,168 Mu-active F1 families. We also assembled a high-quality genome for the Mu-active line Mu-starter, which harbors the initial active MuDR element and was used as the pollen donor for the mutation population. Using the Mu-starter genome, we recovered 33,662 (15.6%) additional germinal insertions in 3,244 (7.4%) genes in the Mu-starter line. The Mu-starter genome also improved the assignment of 117,689 (54.5%) germinal insertions. The newly upgraded ChinaMu dataset currently contains 215,889 high-quality germinal insertions. These insertions cover 32,224 pan-genes in the Mu-starter and B73Ref5 genomes, including 23,006 (80.4%) core genes shared by the two genomes. As a test model, we investigated Mu insertions in the pentatricopeptide repeat (PPR) superfamily, discovering insertions for 92% (449/487) of PPR genes in ChinaMu, demonstrating the usefulness of ChinaMu as a functional genomics resource for maize.

Genetic Diversity and Population Structure of Maize (Zea mays L.) Inbred Lines in Association with Phenotypic and Grain Qualitative Traits Using SSR Genotyping

Maize (Zea mays L.) is an important cereal and is affected by climate change. Therefore, the production of climate-smart maize is urgently needed by preserving diverse genetic backgrounds through the exploration of their genetic diversity. To achieve this, 96 maize inbred lines were used to screen for phenotypic yield-associated traits and grain quality parameters. These traits were studied across two different environments (Anand and Godhra) and polymorphic simple sequence repeat (SSR) markers were employed to investigate the genetic diversity, population structure, and trait-linked association. Genotype-environment interaction (GEI) reveals that most of the phenotypic traits were governed by the genotype itself across the environments, except for plant and ear height, which largely interact with the environment. The genotypic correlation was found to be positive and significant among protein, lysine and tryptophan content. Similarly, yield-attributing traits like ear girth, kernel rows ear-1, kernels row-1 and number of kernels ear-1 were strongly correlated to each other. Pair-wise genetic distance ranged from 0.0983 (1820194/T1 and 1820192/4-20) to 0.7377 (IGI-1101 and 1820168/T1). The SSRs can discriminate the maize population into three distinct groups and shortlisted two genotypes (IGI-1101 and 1820168/T1) as highly diverse lines. Out of the studied 136 SSRs, 61 were polymorphic to amplify a total of 131 alleles (2-3 per loci) with 0.46 average gene diversity. The Polymorphism Information Content (PIC) ranged from 0.24 (umc1578) to 0.58 (umc2252). Similarly, population structure analysis revealed three distinct groups with 19.79% admixture among the genotypes. Genome-wide scanning through a mixed linear model identifies the stable association of the markers umc2038, umc2050 and umc2296 with protein, umc2296 and umc2252 with tryptophan, and umc1535 and umc1303 with total soluble sugar. The obtained maize lines and SSRs can be utilized in future maize breeding programs in relation to other trait characterizations, developments, and subsequent molecular breeding performances for trait introgression into elite genotypes.

RIP-Seq analysis of non-PPR chloroplast editing factors reveals broad RNA interactions and enrichment of less efficiently translated RNAs by OZ1 and ORRM1 complexes

C-to-U RNA editing in angiosperm chloroplasts requires a large suite of proteins bound together in the editosome. The editosome is comprised of PPR proteins, RIP/MORFs, OZ proteins, and ORRM proteins that physically interact in high molecular weight complexes. The specific functions of non-PPR editing factors in the editosome are unclear, however, specific subsets of editing sites are affected by absence of non-PPR editing factors. Unlike the PPR components of editosomes that have predictable nucleotide specificities, domains present in non-PPR editing factors make RNA associations difficult to predict. In this study, chloroplast extracts were isolated from juvenile maize seedlings. RNAs were immunoprecipitated using polyclonal antibodies targeting non-PPR editing factors RIP9, OZ1, and ORRM1. RNA libraries from duplicate experiments were compared. RIP9 was associated with most of the non-ribosomal RNA content of chloroplasts, consistent with a general binding function to PPR L-motifs and tethering of large ribonucleoprotein complexes. The breadth of RNA associations was greater than predicted and include mRNAs without predicted editing sites, tRNA sequences, and introns. OZ1 and ORRM1 were associated with a highly similar pool of RNAs that have a bias toward lower translational efficiency values in mature chloroplasts. Lower translational efficiency was also associated with the pool of edited RNAs compared to RNAs without editing sites. The unexpected breadth of interactions by non-PPR editing factors suggests the editosome is large, diverse, and associated with RNAs with lower relative translational efficiency in mature chloroplasts.

Hesperidin and chlorogenic acid mitigate arsenic-induced oxidative stress via redox regulation, photosystems-related gene expression, and antioxidant efficiency in the chloroplasts of Zea mays

The ubiquitous metalloid arsenic (As), which is not essential, can be found extensively in the soil and subterranean water of numerous nations, raising substantial apprehensions due to its impact on both agricultural productivity and sustainability. Plants exposed to As often display morphological, physiological, and growth-related abnormalities, collectively leading to reduced productivity. Polyphenols, operating as secondary messengers within the intricate signaling networks of plants, assume integral functions in the acquisition of resistance to diverse environmental stressors, including but not limited to drought, salinity, and exposure to heavy metals. The pivotal roles played by polyphenols in these adaptive processes underscore their profound significance in plant biology. This study aims to elucidate the impact of hesperidin (HP) and chlorogenic acid (CA), recognized as potent bioactive compounds, on maize plants exposed to As. To achieve this objective, the study examined the physiological and biochemical impacts, including growth parameters, photosynthesis, and chloroplastic antioxidants, of HP (100 μM) and CA (50 μM) on Zea mays plants exposed to arsenate stress (AsV, 100 μM - Na2HAsO4⋅7H2O). As toxicity led to reductions in fresh weight (FW) and dry weight (DW) by 33% and 26%, respectively. However, the application of As+HP and As + CA increased FW by 22% and 40% and DW by 14% and 17%, respectively, alleviating the effects of As stress. As toxicity resulted in the up-regulation of PSII genes (psbA and psbD) and PSI genes (psaA and psaB), indicating a potential response to the re-formation of degraded regions, likely driven by the heightened demand for photosynthesis. Exogenous HP or/and CA treatments effectively counteracted the adverse effects of As toxicity on the photochemical quantum efficiency of PSII (Fv/Fm). H2O2 content showed a 23% increase under As stress, and this increase was evident in guard cells when examining confocal microscopy images. In the presence of As toxicity, the chloroplastic antioxidant capacity can exhibit varying trends, with either a decrease or increase observed. After the application of CA and/or HP, a significant increase was observed in the activity of GR, APX, GST, and GPX enzymes, resulting in decreased levels of H2O2 and MDA. Additionally, the enhanced functions of MDHAR and DHAR have modulated the redox status of ascorbic acid (AsA) and glutathione (GSH). The HP or CA-mediated elevated levels of AsA and GSH content further contributed to the preservation of redox homeostasis in chloroplasts facing stress induced by As. In summary, the inclusion of HP and CA in the growth medium sustained plant performance in the presence of As toxicity by regulating physiological and biochemical characteristics, chloroplastic antioxidant enzymes, the AsA-GSH cycle and photosynthesis processes, thereby demonstrating their significant potential to confer resistance to maize through the mitigation of As-induced oxidative damage and the safeguarding of photosynthetic mechanisms.

ZmC2H2-149 negatively regulates drought tolerance by repressing ZmHSD1 in maize

Drought is a major abiotic stress that limits maize production worldwide. Therefore, it is of great importance to improve drought tolerance in crop plants for sustainable agriculture. In this study, we examined the roles of Cys2 /His2 zinc-finger-proteins (C2H2-ZFPs) in maize's drought tolerance as C2H2-ZFPs have been implicated for plant stress tolerance. By subjecting 150 Ac/Ds mutant lines to drought stress, we successfully identified a Ds-insertion mutant, zmc2h2-149, which shows increased tolerance to drought stress. Overexpression of ZmC2H2-149 in maize led to a decrease in both drought tolerance and crop yield. DAP-Seq, RNA-Seq, Y1H and LUC assays additionally showed that ZmC2H2-149 directly suppresses the expression of a positive drought tolerance regulator, ZmHSD1 (hydroxysteroid dehydrogenase 1). Consistently, the zmhsd1 mutants exhibited decreased drought tolerance and grain yield under water deficit conditions compared to their respective wild-type plants. Our findings thus demonstrated that ZmC2H2-149 can regulate ZmHSD1 for drought stress tolerance in maize, offering valuable theoretical and genetic resources for maize breeding programmes that aim for improving drought tolerance.

First report of severe tolpyralate sensitivity in corn (Zea mays) discovers a novel genetic factor conferring crop response to a herbicide

BACKGROUND

Tolpyralate, a relatively new inhibitor of 4-hydroxyphenylpyruvate dioxygenase (HPPD), is registered for postemergence use in all types of corn (Zea mays L.) and has a record of excellent crop tolerance. A report of severe crop injury to sweet corn inbred (XSEN187) led to the following objectives: (i) determine whether sensitivity to tolpyralate in XSEN187 exists, and if confirmed, (ii) determine the genetic basis of tolpyralate sensitivity, and (iii) screen other corn germplasm for sensitivity to tolpyralate.

RESULTS

Inbred XSEN187 was confirmed sensitive to tolpyralate. Inclusion of methylated seed oil or nonionic surfactant in the spray volume was necessary for severe crop injury. Tolpyralate sensitivity in XSEN187 is not conferred by alleles at Nsf1, a cytochrome P450-encoding gene (CYP81A9) conferring tolerance to many corn herbicides. Evidence suggests that tolpyralate sensitivity in XSEN187 is conferred by a single gene mapped to the Chr05: 283 240-1 222 909 bp interval. Moreover, tolpyralate sensitivity was observed in 48 other sweet corn and field corn inbreds.

CONCLUSIONS

Severe sensitivity to tolpyralate exists in sweet corn and field corn germplasm when the herbicide is applied according to label directions. Whereas the corn response to several other herbicides, including HPPD-inhibitors, is conferred by the Nsf1 locus, corn sensitivity to tolpyralate is the result of a different locus. The use of tolpyralate should consider herbicide tolerance in inbred lines from which corn hybrids were derived, whereas alleles that render corn germplasm sensitive to tolpyralate should be eliminated from breeding populations, inbreds, and commercial cultivars. © 2023 Illinois Foundation Seeds, Inc and The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Experimental assessment of laser scarecrows for reducing avian damage to sweet corn

BACKGROUND

Birds damage crops, costing millions of dollars annually, and growers utilize a variety of lethal and nonlethal deterrents in an attempt to reduce crop damage by birds. We experimentally tested laser scarecrows for their effectiveness at reducing sweet corn (Zea mays) damage. We presented 18 captive flocks of free-flying European starlings (Sturnus vulgaris) with fresh sweet corn ears distributed on two plots where laser and control treatments were alternated each day and allowed each flock to forage over 5 days. In 16 trials, fresh sweet corn ears were mounted on wooden sticks distributed from 0 to 32 m from laser units (Stick Trials), and in two trials birds foraged on ripe corn grown from seed in the flight pen (Natural Trials). We aimed to determine if laser-treated plots had significantly less damage overall and closer to the laser unit, and whether birds became more or less likely to forage in laser-treated plots over time.

RESULTS

Lasers reduced damage overall, marginally in Stick Trials and dramatically in Natural Trials. Damage increased during each week in both trial types. Damage increased significantly with distance from lasers, and significant treatment effects occurred up to ~20 m from lasers.

CONCLUSION

Our results concur with recent field trials demonstrating strong reductions in sweet corn damage when lasers are deployed. This study provides a first look at how birds respond to repeated laser exposure and whether damage increases with distance from lasers. Key differences between pen and field trials are discussed. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Efficacy of Event MON 87460 in drought-tolerant maize hybrids under optimal and managed drought-stress in eastern and southern africa

BACKGROUND

Frequent drought events due to climate change have become a major threat to maize (Zea mays L.) production and food security in Africa. Genetic engineering is one of the ways of improving drought tolerance through gene introgression to reduce the impact of drought stress in maize production. This study aimed to evaluate the efficacy of Event MON 87460 (CspB; DroughtGard®) gene in more than 120 conventional drought-tolerant maize hybrids in Kenya, South Africa, and Uganda for 3-6 years under managed drought-stress and optimal conditions and establish any additional yield contribution or yield penalties of the gene in traited hybrids relative to their non-traited isohybrids. Germplasm used in the study were either MON 87460 traited un-adapted (2008-2010), adapted traited DroughtTEGO® (2011-2013) or a mix of both under confined field trials.

RESULTS

Results showed significant yield differences (p < 0.001) among MON 87460 traited and non-traited hybrids across well-watered and managed drought-stress treatments. The gene had positive and significant effect on yield by 36-62% in three hybrids (CML312/CML445; WMA8101/CML445; and CML312/S0125Z) relative to non-traited hybrids under drought, and without significant yield penalty under optimum-moisture conditions in Lutzville, South Africa. Five traited hybrids (WMA2003/WMB4401; CML442/WMB4401; CML489/WMB4401; CML511/CML445; and CML395/WMB4401) had 7-13% significantly higher yield than the non-traited isohybrids out of 34 adapted DroughtTEGO® hybrids with same background genetics in the three countries for ≥ 3 years. The positive effect of MON 87460 was mostly observed under high drought-stress relative to low, moderate, or severe stress levels.

CONCLUSION

This study showed that MON 87460 transgenic drought tolerant maize hybrids could effectively tolerate drought and shield farmers against severe yield loss due to drought stress. The study signified that development and adoption of transgenic drought tolerant maize hybrids can cushion against farm yield losses due to drought stress as part of an integrated approach in adaptation to climate change effects.

Plant nucleoside N-ribohydrolases: riboside binding and role in nitrogen storage mobilization

Cells save their energy during nitrogen starvation by selective autophagy of ribosomes and degradation of RNA to ribonucleotides and nucleosides. Nucleosides are hydrolyzed by nucleoside N-ribohydrolases (nucleosidases, NRHs). Subclass I of NRHs preferentially hydrolyzes the purine ribosides while subclass II is more active towards uridine and xanthosine. Here, we performed a crystallographic and kinetic study to shed light on nucleoside preferences among plant NRHs followed by in vivo metabolomic and phenotyping analyses to reveal the consequences of enhanced nucleoside breakdown. We report the crystal structure of Zea mays NRH2b (subclass II) and NRH3 (subclass I) in complexes with the substrate analog forodesine. Purine and pyrimidine catabolism are inseparable because nucleobase binding in the active site of ZmNRH is mediated via a water network and is thus unspecific. Dexamethasone-inducible ZmNRH overexpressor lines of Arabidopsis thaliana, as well as double nrh knockout lines of moss Physcomitrium patents, reveal a fine control of adenosine in contrast to other ribosides. ZmNRH overexpressor lines display an accelerated early vegetative phase including faster root and rosette growth upon nitrogen starvation or osmotic stress. Moreover, the lines enter the bolting and flowering phase much earlier. We observe changes in the pathways related to nitrogen-containing compounds such as β-alanine and several polyamines, which allow plants to reprogram their metabolism to escape stress. Taken together, crop plant breeding targeting enhanced NRH-mediated nitrogen recycling could therefore be a strategy to enhance plant growth tolerance and productivity under adverse growth conditions.

The serine-threonine protein kinase Snf1 orchestrates the expression of plant cell wall-degrading enzymes and is required for full virulence of the maize pathogen Colletotrichum graminicola

Colletotrichum graminicola, the causal agent of maize leaf anthracnose and stalk rot, differentiates a pressurized infection cell called an appressorium in order to invade the epidermal cell, and subsequently forms biotrophic and necrotrophic hyphae to colonize the host tissue. While the role of force in appressorial penetration is established (Bechinger et al., 1999), the involvement of cell wall-degrading enzymes (CWDEs) in this process and in tissue colonization is poorly understood, due to the enormous number and functional redundancy of these enzymes. The serine/threonine protein kinase gene SNF1 identified in Sucrose Non-Fermenting yeast mutants mediates de-repression of catabolite-repressed genes, including many genes encoding CWDEs. In this study, we identified and functionally characterized the SNF1 homolog of C. graminicola. Δsnf1 mutants showed reduced vegetative growth and asexual sporulation rates on media containing polymeric carbon sources. Microscopy revealed reduced efficacies in appressorial penetration of cuticle and epidermal cell wall, and formation of unusual medusa-like biotrophic hyphae by Δsnf1 mutants. Severe and moderate virulence reductions were observed on intact and wounded leaves, respectively. Employing RNA-sequencing we show for the first time that more than 2,500 genes are directly or indirectly controlled by Snf1 in necrotrophic hyphae of a plant pathogenic fungus, many of which encode xylan- and cellulose-degrading enzymes. The data presented show that Snf1 is a global regulator of gene expression and is required for full virulence.

Harvest Timing of Standing Corn Using Near-Infrared Reflectance Spectroscopy

Harvesting corn at the proper maturity is important for managing its nutritive value as livestock feed. Standing whole-plant moisture content is commonly utilized as a surrogate for corn maturity. However, sampling whole plants is time consuming and requires equipment not commonly found on farms. This study evaluated three methods of estimating standing moisture content. The most convenient and accurate approach involved predicting ear moisture using handheld near-infrared reflectance spectrometers and applying a previously established relationship to estimate whole-plant moisture from the ear moisture. The ear moisture model was developed using a partial least squares regression model in the 2021 growing season utilizing reference data from 610 corn plants. Ear moisture contents ranged from 26 to 80 %w.b., corresponding to a whole-plant moisture range of 55 to 81 %w.b. The model was evaluated with a validation dataset of 330 plants collected in a subsequent growing year. The model could predict whole-plant moisture in 2022 plants with a standard error of prediction of 2.7 and an R2P of 0.88. Additionally, the transfer of calibrations between three spectrometers was evaluated. This revealed significant spectrometer-to-spectrometer differences that could be mitigated by including more than one spectrometer in the calibration dataset. While this result shows promise for the method, further work should be conducted to establish calibration stability in a larger geographical region.

Potent pollen gene regulation by DNA glycosylases in maize

Although DNA methylation primarily represses transposable elements (TEs) in plants, it also represses select endosperm and pollen genes. These genes, or their cis-regulatory elements, are methylated in plant body tissues but are demethylated by DNA glycosylases (DNGs) in endosperm and pollen, enabling their transcription. Activity of either one of two DNGs, MDR1 or DNG102, is essential for pollen viability in maize. Using single-pollen mRNA sequencing on pollen segregating mutations in both genes, we identified 58 candidate DNG target genes, whose expression is strongly decreased in double mutant pollen (124-fold decrease on average). These genes account for 11.1% of the wild-type pollen polyadenylated transcriptome, but they are silent or barely detectable in the plant body. They are unusual in their tendency to lack introns but even more so in their having TE-like methylation in their coding DNA sequence. Moreover, they are strongly enriched for predicted functions in cell wall modification. While some may support development of the pollen grain cell wall, expansins and pectinases in this set of genes suggest a function in cell wall loosening to support the rapid tip growth characteristic of pollen tubes as they carry the sperm cells through maternal apoplast and extracellular matrix of the pistil. These results suggest a critical role for DNA methylation and demethylation in regulating maize genes with potential for extremely high expression in pollen but constitutive silencing elsewhere.

Forage cactus as an additive in corn without the cob silages of feedlot sheep diets

This study aimed to assess the impact of adding forage cactus as an additive to the production of corn silage without the cob on the performance of feedlot sheep and subsequent silage losses. The experimental design was completely randomized, consisting of three treatments: corn silage without cob; 0% = 100% corn plant without the cob; 10% = 90% corn plant without cob + 10% forage cactus; 20% = 80% corn plant without cob + 20% forage cactus. Significant effects were observed for dry matter intake (P = 0.0201), organic matter (P = 0.0152), ether extract (P = 0.0001), non-fiber carbohydrates (P = 0.0007). Notably, nutrient digestibility showed significant differences in organic matter (P = 0.0187), ether extract (P = 0.0095), neutral detergent fiber (P = 0.0005), non-fiber carbohydrates (P = 0.0001), and metabolizable energy (P = 0.0001). Performance variables, including total weight gain (P = 0.0148), average daily weight gain (P = 0.0148), feeding efficiency, and rumination efficiency of dry matter (P = 0.0113), also exhibited significant effects. Consequently, it is recommended to include 20% forage cactus in corn silage, which, based on natural matter, helps meet animals' water needs through feed. This inclusion is especially vital in semi-arid regions and aids in reducing silage losses during post-opening silo disposal.

The maize striate leaves2 (sr2) gene encodes a conserved DUF3732 domain and is homologous to the rice yss1 gene

Maize striate leaves2 (sr2) is a mutant that causes white stripes on leaves that has been used in mapping studies for decades though the underlying gene has not been identified. The sr2 locus has been previously mapped to small regions of normal chromosome 10 (N10) and a rearranged variant called abnormal chromosome 10 (Ab10). A comparison of assembled genomes carrying N10 and Ab10 revealed only five candidate sr2 genes. Analysis of a stock carrying the sr2 reference allele (sr2-ref) showed that one of the five genes has a transposon insertion that disrupts its protein sequence and has a severe reduction in mRNA. An independent Mutator transposon insertion in the gene (sr2-Mu) failed to complement the sr2-ref mutation, and plants homozygous for sr2-Mu showed white striped leaf margins. The sr2 gene encodes a DUF3732 protein with strong homology to a rice gene with a similar mutant phenotype called young seedling stripe1 (yss1). These and other published data suggest that sr2 may have a function in plastid gene expression.

Soil fertility and agro-physiological responses of maize (Zea mays) irrigated by treated domestic wastewater by hybrid multi-soil-layering technology

The depletion of water resources has gained global attention, particularly in arid climates, where there is growing interest in reusing treated wastewater for irrigation. This study focuses on the impact of irrigating treated wastewater using a hybrid multi-soil-layering (MSL) technology on soil physicochemical properties and the agro-physiological characteristics of maize (Zea mays) cultivated in Morocco, a region characterized by arid conditions. To achieve this research goals, three plots were cultivated with Zea mays and subjected to irrigation with water of varying qualities: raw wastewater (RWW), treated wastewater (TWW), and well water (WW). This experiment ran for five months, covering one crop season. The physicochemical and microbiological parameters in the soil and water were investigated, and the agro-physiological characteristics of the maize crops were assessed. The findings revealed significant differences in physicochemical and microbial parameters within both water and soil, as well as in the physiological responses of the maize crop, among the three water treatments. TWW's quality met the permissible limits for direct wastewater discharge, as prescribed by Moroccan norms, making it suitable for potential irrigation reuse. Moreover, the higher content of key elements (Na, K, Ca, and Mg) in WW indicated that TWW was more suitable for irrigation. Zea mays irrigated with RWW and TWW exhibited a higher accumulation of protein and sugar content compared to WW irrigation. Furthermore, the biomass parameters, including root, aerial, and grain dry weight, showed a positive effect on Zea mays irrigated with RWW and TWW compared to WW. Total chlorophyll content, on the other hand, was highest in plants irrigated with WW, followed by TWW. Plants irrigated with RWW produced the highest amounts of nitrogen, phosphorus, and potassium. Conversely, plants irrigated with WW had a higher content of Ca, Na, and Mg. TWW yielded medium concentrations of N, P, K, Ca, Mg, and Na compared to RWW and WW, attributed to the nutrients provided by irrigation with TWW using the hybrid MSL technology. In conclusion, aside from their use as irrigation water, treated wastewater emerges as a valuable source of plant nutrients and soil fertilizers. They offer significant nutritive value, enhancing plant growth, reducing the need for additional fertilizer application, lowering mineral fertilization costs, and increasing the productivity of infertile soils. This highlights the potential of treated wastewater to improve agricultural sustainability in arid regions like Morocco.

The Overexpression of Zea mays Strigolactone Receptor Gene D14 Enhances Drought Resistance in Arabidopsis thaliana L

Strigolactones (SLs) represent a recently identified class of plant hormones that are crucial for plant tillering and mycorrhizal symbiosis. The D14 gene, an essential receptor within the SLs signaling pathway, has been well-examined in crops, like rice (Oryza sativa L.) and Arabidopsis (Arabidopsis thaliana L.), yet the research on its influence in maize (Zea mays L.) remains scarce. This study successfully clones and establishes Arabidopsis D14 gene overexpression lines (OE lines). When compared with the wild type (WT), the OE lines exhibited significantly longer primary roots during germination. By seven weeks of age, these lines showed reductions in plant height and tillering, alongside slight decreases in rosette and leaf sizes, coupled with early aging symptoms. Fluorescence-based quantitative assays indicated notable hormonal fluctuations in OE lines versus the WT, implying that D14 overexpression disrupts plant hormonal homeostasis. The OE lines, exposed to cold, drought, and sodium chloride stressors during germination, displayed an especially pronounced resistance to drought. The drought resistance of OE lines, as evident from dehydration-rehydration assays, outmatched that of the WT lines. Additionally, under drought conditions, the OE lines accumulated less reactive oxygen species (ROS) as revealed by the assessment of the related physiological and biochemical parameters. Upon confronting the pathogens Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), post-infection, fluorescence quantitative investigations showed a significant boost in the salicylic acid (SA)-related gene expression in OE lines compared to their WT counterparts. Overall, our findings designate the SL receptor D14 as a key upregulator of drought tolerance and a regulator in the biotic stress response, thereby advancing our understanding of the maize SL signaling pathway by elucidating the function of the pivotal D14 gene.

under salt stress

Salinity is known to have a greater impact on shoot growth than root growth. Na+ buildup in plant tissue under salt stress has been proposed as one of the main issues that causes growth inhibition in crops via ionic imbalances, osmotic stress and pH disturbances. However, the evidence for apoplastic Na+ buildup and the role of silicon in Na+ accumulation at the subcellular level is still enigmatic. The current study focuses on the accumulation of Na+ in the apoplast and symplast of younger and older leaves of two maize varieties (Iqbal as salt-tolerant and Jalal as salt-sensitive) using hydroponic culture along with silicon supplementation under short-term salinity stress. Subcellular ion analysis indicated that silicon nutrition decreased Na+ concentration in both apoplastic washing fluid and symplastic fluid of maize under salt stress. The addition of silicon under NaCl treatment resulted in considerable improvement in fresh biomass, relative water content, chlorophyll content, and concentration of important subcellular ions (i.e., Ca2+, Mg2+, and K+). Knowledge of subcellular ion analysis is essential for solving the mechanisms underlying vital cellular functions e.g. in the current study, the soluble Na+ concentration in the apoplast of older leaves was found to be significantly greater (36.1 mM) in the salt-sensitive variety under NaCl treatment, which was 42.4% higher when compared to the Na+ concentration in the salt-tolerant variety under the same treatment which can influence permeability of cell membrane, signal transduction pathways and provides insights into how ion compartmentalization can contributes to salt tolerance. Calcium silicate enrichment can contribute to increased growth and improved ionic homeostasis by minimizing leaf electrolyte leakage, improving mechanical functions of cell wall and reducing water loss, and improved photosynthetic function. In current investigation, increased water content and intracellular ionic homeostasis along with reduced concentration of Na+ in the maize leaf apoplast suggest that calcium silicate can be used to ameliorate the adverse effects of salt stress and obtain yield using marginal saline lands.

Genetic variation in ZmKW1 contributes to kernel weight and size in dent corn and popcorn

Kernel weight is a critical factor that essentially affects maize (Zea mays) yield. In natural inbred lines, popcorn kernels exhibit overtly smaller sizes compared to dent corn kernels, and kernel weight, which is controlled by multiple genetic loci, varies widely. Here, we characterized a major quantitative trait locus on chromosome 1, responsible for controlling kernel weight (qKW1) and size. The qKW1 locus encodes a protein containing a seven in absentia domain with E3 ubiquitin ligase activity, expressed prominently from the top to the middle region of the endosperm. The presence and function of qKW1 were confirmed through ZmKW1 gene editing, where the mutations in ZmKW1 within dent corn significantly increased kernel weight, consistent with alterations in kernel size, while overexpression of ZmKW1 had the opposite effect. ZmKW1 acts as a negative regulator of kernel weight and size by reducing both the number and size of the endosperm cells and impacting endosperm filling. Notably, the popcorn allele qKW1N and the dent corn allele qKW1D encode identical proteins; however, the differences in promoter activity arise due to the insertion of an Indel-1346 sequence in the qKW1N promoter, resulting in higher expression levels compared to qKW1D , thus contributing to the variation in kernel weight and size between popcorn and dent corn kernels. Linkage disequilibrium analysis of the 2.8 kb promoter region of ZmKW1 in a dataset comprising 111 maize association panels identified two distinct haplotypes. Our results provide insight into the mechanisms underlying kernel development and yield regulation in dent corn and popcorn, with a specific focus on the role of the ubiquitination system.

Stomatal closure prevents xylem transport of green leaf volatiles and impairs their systemic function in plants

Plants perceive environmental stresses as whole organisms via distant signals conveying danger messages through their vasculature. In parallel to vascular transport, airborne plant volatile compounds, including green leaf volatiles (GLVs), can bypass the lack of vascular connection. However, some small volatile compounds move through the vasculature; such vascular transport is little known about GLVs. Here we illustrate GLV alcohols as solutes move within xylem vessels in Zea mays. We describe GLV alcohols, including Z-3-hexen-ol and its isomer E-3-hexen-ol, which is not synthesized in maize, moving through the transpiration stream via xylem vessels. Since transpiration is mediated by the stomatal aperture, closing stomata by two independent methods diminishes the transport of GLV alcohol and its isomer. In addition, the lower transport of GLV alcohols impairs their function in inducing terpenoid biosynthesis, suggesting that xylem transport of GLV alcohols plays a significant role in their systemic function. Our study suggests that GLV alcohols, in addition to airborne signals, are transported through xylem vessels. Our findings can be critical in future studies about the perception and function of these compounds in plants.

Structure-activity relationship of volatile compounds that induce defense-related genes in maize seedlings

Volatile organic compounds mediate plant-to-plant communication, and plants receiving volatile cues can acquire greater defenses against attackers. It has been expected that volatiles are received by factors that eventually lead to the induction of defense-related gene expression; however, the nature of these factors remain unclear. Structure-activity relationship analysis of gene expression induction by volatiles should provide insights into the nature of these factors. We conducted a structure-activity relationship study using maize seedlings and (Z)-3-hexen-1-yl acetate (Z3HAC) as the lead compound. The acid portion of Z3HAC was not essential, and (Z)-3-hexen-1-ol (Z3HOL), which is formed after the hydrolysis of Z3HAC, is likely the structure essential for the upregulation of the genes. The double bond of Z3HOL is essential; however, its geometry is indistinguishable. Strict specificity was detected regarding the length of the methylene chain on the α- and ω-sides of the double bond, and therefore, the 3-hexen-1-ol structure was found to be the ultimate structure. This finding provides insight into the nature of the factors that interact with a volatile compound and subsequently activate signaling pathways, leading to the upregulation of a subset of defense genes.

Cloning and expression study of a high-affinity nitrate transporter gene from Zea mays L

A nitrate transporter gene, named B46NRT2.1, from salt-tolerant Zea mays L. B46 has been cloned. B46NRT2.1 contained the same domain belonging to the major facilitator superfamily (PLN00028). The results of the phylogenetic tree indicated that B46NRT2.1 exhibits sequence similarity and the closest relationship with those known nitrate transporters of the NRT2 family. Through RT-qPCR, we found that the expression of B46NRT2.1 mainly happens in the root and leaf. Moreover, the treatment with NaCl, Na₂CO₃, and NaHCO₃ could significantly increase the expression of B46NRT2.1. B46NRT2.1 was located in the plasma membrane. Through the study of yeast and plant salt response brought by B46NRT2.1 overexpression, we have preliminary knowledge that the expression of B46NRT2.1 makes yeast and plants respond to salt shock. There are 10 different kinds of cis-acting regulatory elements (CRES) in the promotor sequences of B46NRT2.1 gene using the PlantCARE web server to analyze. It mainly includes hormone response, abscisic acid, salicylic acid, gibberellin, methyl jasmonate, and auxin. The B46NRT2.1 gene's co-expression network showed that it was co-expressed with a number of other genes in several biological pathways, including regulation of NO₃ long-distance transit, modulation of nitrate sensing and metabolism, nitrate assimilation, and transduction of Jasmonic acid-independent wound signal. The results of this work should serve as a good scientific foundation for further research on the functions of the NRT2 gene family in plants (inbred line B46), and this research adds to our understanding of the molecular mechanisms under salt tolerance.

ZnO nanoparticles mediated by Azadirachta indica as nano fertilizer: Improvement in physiological and biochemical indices of Zea mays grown in Cr-contaminated soil

The current investigation aimed at evaluating the impact of Azadirachta indica-mediated zinc oxide nanoparticles (Ai-ZnONPs) on the growth and biochemical characteristics of maize (sweet glutinous 3000) under exposure to 50 mg kg-1Ai-ZnONPs with Cr (VI) concentrations of 50 and 100 mg kg-1. The results indicate that plants exposed to Cr (VI) only experienced a decline in growth parameters. Conversely, the inclusion of Ai-ZnONPs caused a noteworthy increase in physiological traits. Specifically, shoot and root fresh weight increased by 28.02% and 16.51%, and 63.11% and 97.91%, respectively, when compared to Cr-50 and 100 treatments. Additionally, the SPAD chlorophyll of the shoot increased by 91.08% and 15.38% compared to Cr-50 and 100 treatments, respectively. Moreover, the antioxidant enzyme traits of plant shoot and root, such as superoxide dismutase (SOD 7.44% and 2.70%, and 4.45% and 3.53%), catalase (CAT 1.18% and 3.20%, and 5.03% and 5.78%), and peroxidase (POD 0.31% and 5.55%, and 4.72% and 3.61%), exhibited significant increases in Cr 50 and 100 treatments, respectively. The addition of Ai-ZnONPs to the soil also enhanced soil nutrient status and reduced Cr (VI) concentrations by 40.69% and 19.82% compared to Cr-50 and 100 treated soils. These findings suggest that Ai-ZnONPs can trigger the activation of biochemical pathways that enable biomass accumulation in meristematic cells. Further investigations are required to elucidate the mechanisms involved in growth promotion.

Genome-wide association analysis of plant architecture traits using doubled haploid lines derived from different cycles of the Iowa Stiff Stalk Synthetic maize population

Selection in the Iowa Stiff Stalk Synthetic (BSSS) maize population for high yield, grain moisture, and root and stalk lodging has indirectly modified plant architecture traits that are important for adaptation to high plant density. In this study, we developed doubled haploid (DH) lines from the BSSS maize population in the earliest cycle of recurrent selection (BSSS), cycle 17 of reciprocal recurrent selection, [BSSS(R)17] and the cross between the two cycles [BSSS/BSSS(R)C17]. We aimed to determine the phenotypic variation and changes in agronomic traits that have occurred through the recurrent selection program in this population and to identify genes or regions in the genome associated with the plant architecture changes observed in the different cycles of selection. We conducted a per se evaluation of DH lines focusing on high heritability traits important for adaptation to high planting density and grain yield. Trends for reducing flowering time, anthesis-silking interval, ear height, and the number of primary tassel branches in BSSS(R)17 DH lines compared to BSSS and BSSS/BSSS(R)C17 DH lines were observed. Additionally, the BSSS(R)C17 DH lines showed more upright flag leaf angles. Using the entire panel of DH lines increased the number of SNP markers identified within candidate genes associated with plant architecture traits. The genomic regions identified for plant architecture traits in this study may help to elucidate the genetic basis of these traits and facilitate future work about marker-assisted selection or map-based cloning in maize breeding programs.

Root growth of monocotyledons and dicotyledons is limited by different tissues

Plant growth and morphogenesis are determined by the mechanical properties of its cell walls. Using atomic force microscopy, we have characterized the dynamics of cell wall elasticity in different tissues in developing roots of several plant species. The elongation growth zone of roots of all species studied was distinguished by a reduced modulus of elasticity of most cell walls compared to the meristem or late elongation zone. Within the individual developmental zones of roots, there were also significant differences in the elasticity of the cell walls of the different tissues, thus identifying the tissues that limit root growth in the different species. In cereals, this is mainly the inner cortex, whereas in dicotyledons this function is performed by the outer tissues-rhizodermis and cortex. These differences result in a different behaviour of the roots of these species during longitudinal dissection. Modelling of longitudinal root dissection using measured properties confirmed the difference shown. Thus, the morphogenesis of monocotyledonous and dicotyledonous roots relies on different tissues as growth limiting, which should be taken into account when analyzing the localization of associated molecular events. At the same time, no matrix polysaccharide was found whose immunolabelling in type I or type II cell walls would predict their mechanical properties. However, assessment of the degree of anisotropy of cortical microtubules showed a striking correlation with the elasticity of the corresponding cell walls in all species studied.

Lines

Phenophase durations, including the timing of flowering and ripeness, were characterized in 20 inbred lines of the maize Zea mays L. Expression of key flowering initiation genes (CONZ1, GIGZ1a, GIGZ1b, ZmFKF1a, and ZmFKF1b) under long-photoperiod conditions was studied in seedlings of six maize lines that differed in ripeness time. Significantly lower transcription levels of all of the five genes were found in early-ripening lines compared with late-ripening lines. Similar expression patterns were observed for the GIGZ1a and GIGZ1b paralogous genes, while ZmFKF1a significantly predominated in expression over its paralog ZmFKF1b.

Two New Alkaloids from Roots of Zea mays and Their Cytotoxic Activity against Hep3B and SW480 Cells

Two undescribed alkaloids, along with seven known compounds, were isolated from the roots of Zea mays (RM). Their chemical structures were elucidated based on extensive analyses of HR-ESI-MS, 1D and 2D NMR, and CD spectra. Two new alkaloids exhibited moderate inhibition of Hep3B (IC50 values of 11.7±2.4 and 14.2±3.6 μM) and SW480 cells (IC50 values of 33.4±8.2 and 47.3±5.8 μM) compared to that of the positive control compound, Oxaliplatin, IC50 value of 8.4±1.7 and 45.8±5.6 μM, respectively.

Cell wall anisotropy plays a key role in Zea mays stomatal complex movement: the possible role of the cell wall matrix

The opening of the stomatal pore in Zea mays is accomplished by the lateral displacement of the central canals of the dumbbell-shaped guard cells (GCs) towards their adjacent deflating subsidiary cells that retreat locally. During this process, the central canals swell, and their cell wall thickenings become thinner. The mechanical forces driving the outward displacement of the central canal are applied by the asymmetrically swollen bulbous ends of the GCs via the rigid terminal cell wall thickenings of the central canal and the polar ventral cell wall (VW) ends. During stomatal pore closure, the shrinking bulbous GC ends no longer exert the mechanical forces on the central canals, allowing them to be pushed back inwards, towards their initial position, by the now swelling subsidiary cells. During this process, the cell walls of the central canal thicken. Examination of immunolabeled specimens revealed that important cell wall matrix materials are differentially distributed across the walls of Z. mays stomatal complexes. The cell walls of the bulbous ends and of the central canal of the GCs, as well as the cell walls of the subsidiary cells were shown to be rich in methylesterified homogalacturonans (HGs) and hemicelluloses. Demethylesterified HGs were, in turn, mainly located at the terminal cell wall thickenings of the central canal, at the polar ends of the VW, at the lateral walls of the GCs and at the periclinal cell walls of the central canal. During stomatal function, a spatiotemporal change on the distribution of some of the cell wall matrix materials is observed. The participation of the above cell wall matrix polysaccharides in the well-orchestrated response of the cell wall during the reversible movements of the stomatal complexes is discussed.

Genome-wide analysis of sugar transporter genes in maize (Zea mays L.): identification, characterization and their expression profiles during kernel development

Sugar transporters (STs) play a crucial role in the development of maize kernels. However, very limited information about STs in maize is known. In this study, sixty-eight ZmST genes were identified from the maize genome and classified into eight major groups based on phylogenetic relationship. Gene structure analysis revealed that members within the same group shared similar exon numbers. Synteny analysis indicated that ZmSTs underwent 15 segmental duplication events under purifying selection. Three-dimensional structure of ZmSTs demonstrated the formation of a compact helix bundle composed of 8-13 trans-membrane domains. Various development-related cis-acting elements, enriched in promoter regions, were correlated with the transcriptional response of ZmSTs during kernel development. Transcriptional expression profiles exhibited expression diversity of various ZmST genes in roots, stems, leaves, tassels, cobs, embryos, endosperms and seeds tissues. During kernel development, the expression of 24 ZmST genes was significantly upregulated in the early stage of grain filling. This upregulation coincided with the sharply increased grain-filling rate observed in the early stage. Overall, our findings shed light on the characteristics of ZmST genes in maize and provide a foundation for further functional studies.

Variations in Nitrogen Accumulation and Use Efficiency in Maize Differentiate with Nitrogen and Phosphorus Rates and Contrasting Fertilizer Placement Methodologies

Balanced nitrogen (N) and phosphorus (P) rates, coupled with rational fertilization methodology, could promote crop N accumulation, N use efficiency, and yield production, particularly in semi-arid and arid regions. To test these characteristics, a two-year (2018 and 2019) pot experiment was performed by growing summer maize in a rain-proof glass greenhouse under nine combined N (112, 150, and 187 kg ha-1, urea) and P (45, 60, and 75 kg ha-1 calcium superphosphate) rates and three contrasting fertilizer placements. The fertilizers were placed by broadcast on the soil surface (Broadcast), a side band on a 4 cm strip of soil surface within 7 cm from the sowing line (Side band), and a deep band on a 4 cm strip below 7 cm soil depth within 7 cm from the sowing line (Deep band). Results from three maize growth stages (eight-leaf, 45 days after sowing, DAS; tasseling, 60 DAS; and harvest, 115 DAS) showed that leaf, stem, root N accumulation, and total soil N were significantly increased under Deep band than under both Side band and Broadcast at N150P60, N187P60, N150P75, and N187P75, but not at N112P45, N150P45, N187P45, N112P60, and N112P75. Significantly greater leaf, stem, and root N accumulations were also displayed at N150 and N187 than at N112 for the same P60 or P75 under the Deep band at 60 DAS and 115 DAS; while for leaf and stem, N accumulations were greater at P75 and P60 than at P45 for the same N150 under Deep band at 45 DAS, 60 DAS, and 115 DAS. Significantly greater agronomy N use efficiency, partial factor productivity, and N use efficiency were exhibited under the Deep band than under the Side band and Broadcast at N150P75 and N187P75, but at N150P60 and N187P60 for NUE only. In addition, leaf, stem, seed, and root N concentrations positively correlated with their own N accumulations or soil N concentrations at the tasseling and harvest stages. Our results demonstrate that a synchronized N150P60, N187P60, N150P75, or N187P75 fertilization rate with Deep band placement can improve soil N availability and root N uptake, and thereby, increase aboveground N accumulation, N use efficiency, and yield production of maize, which is particularly practical for small-holder farmers globally.

Heavy metals mitigation and growth promoting effect of endophytic Agrococcus terreus (MW 979614) in maize plants under zinc and nickel contaminated soil

Introduction

Heavy metals such as iron, copper, manganese, cobalt, silver, zinc, nickel, and arsenic have accumulated in soils for a long time due to the dumping of industrial waste and sewage. Various techniques have been adapted to overcome metal toxicity in agricultural land but utilizing a biological application using potential microorganisms in heavy metals contaminated soil may be a successful approach to decontaminate heavy metals soil. Therefore, the current study aimed to isolate endophytic bacteria from a medicinal plant (Viburnum grandiflorum) and to investigate the growth-promoting and heavy metal detoxification potential of the isolated endophytic bacteria Agrococus tereus (GenBank accession number MW 979614) under nickel and zinc contamination.

Methods

Zinc sulfate and nickel sulfate solutions were prepared at the rate of 100 mg/kg and 50 mg/kg in sterilized distilled water. The experiment was conducted using a completely random design (CRD) with three replicates for each treatment.

Results and Discussion

Inoculation of seeds with A. tereus significantly increased the plant growth, nutrient uptake, and defense system. Treatment T4 (inoculated seeds), T5 (inoculated seeds + Zn100 mg/kg), and T6 (inoculated seeds + Ni 100 mg/kg) were effective, but T5 (inoculated seeds + Zn100 mg/kg) was the most pronounced and increased shoot length, root length, leaf width, plant height, fresh weight, moisture content, and proline by 49%, 38%, 89%, 31%, 113%, and 146%, respectively. Moreover the antioxidant enzymes peroxidase and super oxidase dismutase were accelerated by 211 and 68% in contaminated soil when plants were inoculated by A. tereus respectively. Similarly the inoculation of A. tereus also enhanced maize plants' absorption of Cu, Mn, Ni, Na, Cr, Fe, Ca, Mg, and K significantly. Results of the findings concluded that 100 mg/kg of Zn and Ni were toxic to maize growth, but seed inoculation with A. tereus helped the plants significantly in reducing zinc and nickel stress. The A. tereus strain may be employed as a potential strain for the detoxification of heavy metals.

The bundle sheath in Zea mays leaves functions as a protective barrier against the toxic effect of lead

Lead is a highly toxic metal. It impairs the metabolism of living organisms. Plants show different sensitivity to the action of this element. One of the plants with relatively high lead tolerance is Zea mays, where even in detached leaves treated with Pb2+ ions, the photosynthesis rate remains very high compared to other plant species. This study set out to determine the mechanism responsible for the high resistance of maize photosynthetic tissue to the toxic effect of this metal. For this purpose, the cut leaves of Z. mays were incubated in Pb(NO3)2 solutions at different concentrations. Regions of lead accumulation in tissues and cells were located using histochemical methods and transmission electron microscopy. The experiments showed a diverse distribution of lead ions in the leaf blade of Z. mays. Most of the accumulated Pb2+ ions were observed in the vascular bundle and the bundle sheath, while minimal traces of metal were transferred to the mesophyll. In Pisum sativum leaves, although Pb(NO3)2 concentration in the solution was two-fold lower, lead accumulated in all the leaf tissues - mainly in the vascular bundle, epidermis, sclerenchyma, and mesophyll. Thus, bundle sheath cells in maize leaves were able to inhibit the flow of Pb2+ ions to the ground tissue. Therefore, the influence of the toxic metal on photosynthesis in mesophyll cells remained minimal. These experiments show that the structure of Z. mays leaf, with a layer of bundle sheath cells (characteristic of C4 plants), contributes to the protecting photosynthetic tissue against the toxic effect of lead.

Seed bio-priming enhanced salt stress tolerance of maize (Zea mays L.) seedlings by regulating the antioxidant system and miRNA expression

Maize (Zea mays) is moderately sensitive to salt stress. Therefore, increasing salinity in soil causes the arrestment of physiological processes and retention of growth and development, consequently leading to yield loss. Although many strategies have been launched to improve salt stress tolerance, plant growth-promoting rhizobacteria (PGPR) are considered the most promising approach due to being more environmentally friendly and agronomically sustainable than chemicals. Therefore, this study aims to investigate the potential of Bacillus spp. and the role of microRNA-mediated genetic regulation in maize subjected to seed bio-priming application to mitigate salt stress effects. To this end, maize seeds were bio-primed with the vegetative form of B. pumilus, B. licheniformis, and B. coagulans both individually or combined, subsequently treated to NaCl, and the seedlings were screened morphologically, physiologically, and transcriptionally. The study revealed that seed bio-priming with B. licheniformis reduced the stress effects of maize seedlings by increasing catalase (CAT) and ascorbate peroxidase (APX) activities by 2.5- and 3-fold, respectively, tolerating the decrease in chlorophyll content (CC), upregulating miR160d expression which led to a 36% increase in root fresh weight (RFW) and a 39% increase in shoot fresh weight (SFW). In conclusion, Bacillus spp. successfully alleviated salt stress effects on maize by modulating antioxidant enzymes and miRNA expression.

Improved image processing for 3D virtual object construction from serial sections reveals tissue patterns in root tips of Zea mays

Premise

Previously we described methods for generating three-dimensional (3D) virtual reconstructions of plant tissues from transverse thin sections. Here, we report the applicability of longitudinal sections and improved image-processing steps that are simpler to perform and utilize free applications.

Methods

In order to obtain improved digital images and a virtual 3D object (cuboid), GIMP 2.10 and ImageJ 2.3.0 running on a laptop computer were used. Sectional views of the cuboid and 3D visualization were realized with use of the plug-ins "Volume Viewer" and "3D Viewer" in ImageJ.

Results

A 3D object was constructed and sectional views along several cutting planes were generated. The 3D object consisted of selected tissues inside the cuboid that were extracted and visualized from the original section data, and an animated video of the 3D construct was also produced.

Discussion

Virtual cuboids can be constructed by stacking longitudinal images along the transverse depth direction or stacking transverse images vertically along the organ axis, with both generating similar 3D objects. Which to use depends on the purpose of the investigation: if the vertical cell structures need close examination, the former method may be better, but for more general spatial evaluations or for evaluation of organs over longer tissue distances than can be accommodated with longitudinal sectioning, the latter method should be chosen.

Low expression of lipoxygenase 3 (LOX3) enhances the retention of kernel tocopherols in maize during storage

BACKGROUND

Deficiency of vitamin E results in several neurological and age-related disorders in humans. Utilization of maize mutants with favourable vte4-allele led to the development of several α-tocopherol (vitamin E) rich (16-19 µg/g) maize hybrids worldwide. However, the degradation of tocopherols during post-harvest storage substantially affects the efficacy of these genotypes.

METHODS AND RESULTS

We studied the role of lipoxygenase enzyme and Lipoxygenase 3 (LOX3) gene on the degradation of tocopherols at monthly intervals under traditional storage up to six months in two vte4-based contrasting-tocopherol retention maize inbreds viz. HKI323-PVE and HKI193-1-PVE. The analysis revealed significant degradation of tocopherols across storage intervals in both the inbreds. Lower retention of α-tocopherol was noticed in HKI193-1-PVE. HKI323-PVE with the higher retention of α-tocopherol showed lower lipoxygenase activity throughout the storage intervals. LOX3 gene expression was higher (~ 1.5-fold) in HKI193-1-PVE compared to HKI323-PVE across the storage intervals. Both lipoxygenase activity and LOX3 expression peaked at 120 days after storage (DAS) in both genotypes. Further, a similar trend was observed for LOX3 expression and lipoxygenase activity. The α-tocopherol exhibited a significantly negative correlation with lipoxygenase enzyme and expression of LOX3 across the storage intervals.

CONCLUSIONS

HKI323-PVE with high tocopherol retention, low -lipoxygenase activity, and -LOX3 gene expression can act as a potential donor in the vitamin E biofortification program. Protein-protein association network analysis also indicated the independent effect of vte4 and LOX genes. This is the first comprehensive report analyzing the expression of the LOX3 gene and deciphering its vital role in the retention of α-tocopherol in biofortified maize varieties under traditional storage.

Overexpression of ZmSTOP1-A Enhances Aluminum Tolerance in Arabidopsis by Stimulating Organic Acid Secretion and Reactive Oxygen Species Scavenging

Aluminum (Al) toxicity and low pH are major factors limiting plant growth in acidic soils. Sensitive to Proton Rhizotoxicity 1 (STOP1) transcription factors respond to these stresses by regulating the expression of multiple Al- or low pH-responsive genes. ZmSTOP1-A, a STOP1-like protein from maize (Zea mays), was localized to the nucleus and showed transactivation activity. ZmSTOP1-A was expressed moderately in both roots and shoots of maize seedlings, but was not induced by Al stress or low pH. Overexpression of ZmSTOP1-A in Arabidopsis Atstop1 mutant partially restored Al tolerance and improved low pH tolerance with respect to root growth. Regarding Al tolerance, ZmSTOP1-A/Atstop1 plants showed clear upregulation of organic acid transporter genes, leading to increased organic acid secretion and reduced Al accumulation in roots. In addition, the antioxidant enzyme activity in roots and shoots of ZmSTOP1-A/Atstop1 plants was significantly enhanced, ultimately alleviating Al toxicity via scavenging reactive oxygen species. Similarly, ZmSTOP1-A could directly activate ZmMATE1 expression in maize, positively correlated with the number of Al-responsive GGNVS cis-elements in the ZmMATE1 promoter. Our results reveal that ZmSTOP1-A is an important transcription factor conferring Al tolerance by enhancing organic acid secretion and reactive oxygen species scavenging in Arabidopsis.

Diterpenoid and phenolic constituents from corn silk (Zea mays) with PTP1B inhibitory activity

Chemical investigation of corn silk resulted in the isolation of nine secondary metabolites, including a new ent-kaurane diterpenoid, zeamaysditerpene A (1) and eight known compounds, stigmaydene A (2), stigmaydene J (3), stigmaydene L (4), stigmane D (5), demethyltorosaflavone D (6), chrysoeriol 6-C-β-boivinopyranosyl-7-O-β-D-glucopyranoside (7), deoxypodophyllotoxin (8), and α-peltatin glucoside (9). Their structures were elucidated using a combination of spectroscopic methods, including 1D and 2D NMR and HRESIQTOF mass spectra. The absolute configuration of 1 was deduced by applying electronic circular dichroism (ECD) calculation method. Among the isolates, only 6 displayed significant inhibition against PTP1B activity in a dose-dependent manner, with an IC50 value of 10.7 ± 0.1 µM. Furthermore, molecular docking simulation was carried out to explore the action perspective of 6 inside the enzyme PTP1B. This finding suggests that 6 might be a potential lead for the development of a new anti-diabetic agent.

Combination of transcriptomic, proteomic, and degradomic profiling reveals common and distinct patterns of pathogen-induced cell death in maize

Regulated cell death (RCD) is crucial for plant development, as well as in decision-making in plant-microbe interactions. Previous studies revealed components of the molecular network controlling RCD, including different proteases. However, the identity, the proteolytic network as well as molecular components involved in the initiation and execution of distinct plant RCD processes, still remain largely elusive. In this study, we analyzed the transcriptome, proteome, and N-terminome of Zea mays leaves treated with the Xanthomonas effector avrRxo1, the mycotoxin Fumonisin B1 (FB1), or the phytohormone salicylic acid (SA) to dissect plant cellular processes related to cell death and plant immunity. We found highly distinct and time-dependent biological processes being activated on transcriptional and proteome levels in response to avrRxo1, FB1, and SA. Correlation analysis of the transcriptome and proteome identified general, as well as trigger-specific markers for cell death in Zea mays. We found that proteases, particularly papain-like cysteine proteases, are specifically regulated during RCD. Collectively, this study characterizes distinct RCD responses in Z. mays and provides a framework for the mechanistic exploration of components involved in the initiation and execution of cell death.

Silencing ZmPP2C-A10 with a foxtail mosaic virus (FoMV) derived vector benefits maize growth and development following water limitation

Global climate change is causing more frequent and severe droughts, which can have negative impacts on plant growth and crop productivity. Under drought conditions, plants produce the hormone ABA (abscisic acid), which regulates adaptive responses, such as stomatal closure and root elongation. Plant viruses have been used in the lab to convey new traits to plants and could also be used to increase production of ABA or to enhance downstream plant drought resistance responses. In this study, foxtail mosaic virus (FoMV) was used to silence ZmPP2C-A10, a negative regulator of ABA signalling, in maize (Zea mays L.). Both silenced and control plants were exposed to an 8-day drought treatment, followed by a 30-day period of rewatering, after which indicators of drought resistance were measured. After drought treatment, we observed a nearly twofold increase in expression of a stress-mitigation gene, ZmRAB17, reduced chlorophyll fluorescence changes (indicator of stress), and increased plant biomass and development in the ZmPP2C-A10-silenced maize compared to controls. These results demonstrate that the FoMV system can be used to silence endogenous expression of ZmPP2C-A10 and increase maize tolerance to drought. This could offer a useful tool to improve crop traits and reduce yield loss during the growing season.

Maize plant expresses SWEET transporters differently when interacting with Trichoderma asperellum and Fusarium verticillioides, two fungi with different lifestyles

Most Trichoderma species are beneficial fungi that promote plant growth and resistance, while Fusarium genera cause several crop damages. During the plant-fungi interaction there is a competition for sugars in both lifestyles. Here we analyzed the plant growth promotion and biocontrol activity of T. asperellum against F. verticillioides and the effect of both fungi on the expression of the maize diffusional sugar transporters, the SWEETs. The biocontrol activity was done in two ways, the first was by observing the growth capacity of both fungus in a dual culture. The second one by analyzing the infection symptoms, the chlorophyl content and the transcript levels of defense genes determined by qPCR in plants with different developmental stages primed with T. asperellum conidia and challenged with F. verticillioides. In a dual culture, T. asperellum showed antagonist activity against F. verticillioides. In the primed plants a delay in the infection disease was observed, they sustained chlorophyll content even after the infection, and displayed upregulated defense-related genes. Additionally, the T. asperellum primed plants had longer stems than the nonprimed plants. SWEETs transcript levels were analyzed by qPCR in plants primed with either fungus. Both fungi affect the transcript levels of several maize sugar transporters differently. T. asperellum increases the expression of six SWEETs on leaves and two at the roots and causes a higher exudation of sucrose, glucose, and fructose at the roots. On the contrary, F. verticillioides reduces the expression of the SWEETs on the leaves, and more severely when a more aggressive strain is in the plant. Our results suggest that the plant is able to recognize the lifestyle of the fungi and respond accordingly by changing the expression of several genes, including the SWEETs, to establish a new sugar flux.

Development of a Sensitive, Easy and High-Throughput Compliant Protocol for Maize and Soybean DNA Extraction and Quantitation Using a Plant-Specific Universal Taqman Minor Groove Binder Probe

We report the optimization of a high-throughput, compliant DNA extraction method that uses standard format 96-well plates and a commercial automated DNA purification system (ABI PRISM® 6100 Nucleic Acid PrepStation). The procedure was set up for maize and soybean, the most common GMO crops and the main ingredients of several foodstuffs, and compared with an EU-validated CTAB-based method. Optimization of the DNA extraction was achieved by applying self-prepared buffers (for DNA extraction, binding, and washing) on the PrepStation loaded with proprietary glass-fiber-coated purification plates. Quantification of extracted DNA was performed by real-time PCR using previously reported endogenous soybean lectin and maize starch synthase genes and a novel plant-specific universal TaqMan MGB probe that targets the 18S rRNA multiple copy gene. Using serial dilutions of both maize and soybean genomic DNAs, we show low PCR sensitivity and efficiency for the official TransPrep DNA extraction protocol compared to the CTAB-based one. On the other hand, using serial dilutions of a standard reference plasmid containing a 137 bp sequence cloned from the 18S rRNA plant-specific ribosomal gene, we demonstrate the high PCR sensitivity and efficiency of the optimized DNA extraction protocol setup with self-prepared buffers. The limits of detection and quantification of the 18S rDNA reiteration were consistent with the calculated values, supporting the suitability of the DNA extraction procedure for high-throughput analyses of large populations and small amounts of tissue.

Multiresponse optimization of the extrusion process for ready-to-eat snacks from pineapple byproducts and maize flour

This research aimed to optimize the processing conditions to obtain ready-to-eat extruded snacks with a high fiber content from mixtures of pineapple byproduct powder (PBP) and nixtamalized maize flour (PBP-NMF) or maize flour (PBP-MF). The effects of barrel temperature, feed moisture content, and PBP were evaluated. The increase in barrel temperature has a negative effect on the bulk density, the water absorption index, and the texture in both mixtures (PBP-MF and PBP-NMF) and increases the expansion index and the water solubility index in the mixture with MF. The increase in the feed moisture content increased the bulk density and water absorption index in both mixtures and the texture in the mixtures with MF. The increasing PBP decreases the expansion index and increases the water solubility index in both mixtures. The increase in PBP in the mixtures with MF decreases the water absorption index, texture, and bulk density. From the optimization, four products were obtained, two for the NMF mixture and two for the MF mixtures. The optimal formulations can be considered a good source of total fiber (12.46-12.78 g/100 g) and protein (8.27-8.85 g/100 g) with good acceptance by consumers. PRACTICAL APPLICATION: Pineapple byproducts in combination with nixtamalized and nonnixtamalized maize flour are viable raw materials for the development of ready-to-eat extruded snacks with a high content of dietary fiber and good acceptance by consumers. Due to their characteristic nutritional properties, the consumption of this ready-to-eat snack could present potential benefits for human health.

A systematic in silico report on iron and zinc proteome of Zea mays

Zea mays is an essential staple food crop across the globe. Maize contains macro and micronutrients but is limited in essential mineral micronutrients such as Fe and Zn. Worldwide, serious health concerns have risen due to the deficiencies of essential nutrients in human diets, which rigorously jeopardizes economic development. In the present study, the systematic in silico approach has been used to predict Fe and Zn binding proteins from the whole proteome of maize. A total of 356 and 546 putative proteins have been predicted, which contain sequence and structural motifs for Fe and Zn ions, respectively. Furthermore, the functional annotation of these predicted proteins, based on their domains, subcellular localization, gene ontology, and literature support, showed their roles in distinct cellular and biological processes, such as metabolism, gene expression and regulation, transport, stress response, protein folding, and proteolysis. The versatile roles of these shortlisted putative Fe and Zn binding proteins of maize could be used to manipulate many facets of maize physiology. Moreover, in the future, the predicted Fe and Zn binding proteins may act as relevant, novel, and economical markers for various crop improvement programs.

Microsatellite marker-based genetic diversity assessment among exotic and native maize inbred lines of Bangladesh

Hybrid development is basically dependent on the variability among available genetic resources. Polymorphism among the maize inbreds is essentially needed for maize hybridization. This study aimed at the assessment of diversity among 22 maize inbreds by 18 microsatellite markers. The study identified 187 alleles at 18 SSR loci. The amplified allele frequency per microsatellite locus was 10.4 and the highest allele per locus was 17 in SSR primer pair phi026. SSR primer set p-umc1292, phi074 and phi090 showed the lowest 6 alleles per genotype per locus. The locus phi026 showed the highest degree of gene diversity (0.92), and the locus p-umc1292 had the lowest of gene diversity (0.77) with a mean value of 0.862 among the microsatellites. At each site, the most prevalent allele varied between 0.14 (bnlg371) and 0.36. (p-umc1292). At any given locus, an average of 0.22 out of the 22 selected maize inbred lines had a common major allele. The average value of the polymorphic information content (PIC) was 0.85, within the range of 0.74 at the lowest to 0.92 at the highest. The higher PIC values of phi026 and nc013 established them to be the best markers for maize inbred lines. The UPGMA clustering generated seven distinct groups having 12.5% of similarity coefficient. The results revealed that inbred lines E10, E27, E19, E34, E35, E4, E43, E28, E11, E21, E17, E38, E25, E34, E14, E16, E39 and E3 were more diversified. These lines are promising to be used as parent materials for hybrid maize development in the future.