RESUMEN
Leaf angle (LA) is a crucial factor that affects planting density and yield in maize. However, the regulatory mechanisms underlying LA formation remain largely unknown. In this study, we performed a comparative histological analysis of the ligular region across various maize inbred lines and revealed that LA is significantly influenced by a two-step regulatory process involving initial cell elongation followed by subsequent lignification in the ligular adaxial sclerenchyma cells (SCs). Subsequently, we performed both bulk and single-nucleus RNA sequencing, generated a comprehensive transcriptomic atlas of the ligular region, and identified numerous genes enriched in the hypodermal cells that may influence their specialization into SCs. Furthermore, we functionally characterized two genes encoding atypical basic-helix-loop-helix (bHLH) transcription factors, bHLH30 and its homolog bHLH155, which are highly expressed in the elongated adaxial cells. Genetic analyses revealed that bHLH30 and bHLH155 positively regulate LA expansion, and molecular experiments demonstrated their ability to activate the transcription of genes involved in cell elongation and lignification of SCs. These findings highlight the specialized functions of ligular adaxial SCs in LA regulation by restricting further extension of ligular cells and enhancing mechanical strength. The transcriptomic atlas of the ligular region at single-nucleus resolution not only deepens our understanding of LA regulation but also enables identification of numerous potential targets for optimizing plant architecture in modern maize breeding.
Asunto(s)
Regulación de la Expresión Génica de las Plantas , Hojas de la Planta , Proteínas de Plantas , Zea mays , Zea mays/genética , Zea mays/crecimiento & desarrollo , Zea mays/metabolismo , Zea mays/citología , Hojas de la Planta/genética , Hojas de la Planta/metabolismo , Hojas de la Planta/crecimiento & desarrollo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Perfilación de la Expresión Génica , Transcriptoma/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Núcleo Celular/metabolismo , Núcleo Celular/genéticaRESUMEN
It has been hypothesized that vacuolar occupancy in mature root cortical parenchyma cells regulates root metabolic cost and thereby plant fitness under conditions of drought, suboptimal nutrient availability, and increased soil mechanical impedance. However, the mechanistic role of vacuoles in reducing root metabolic cost was unproven. Here we provide evidence to support this hypothesis. We first show that root cortical cell size is determined by both cortical cell diameter and cell length. Significant genotypic variation for both cortical cell diameter (~1.1- to 1.5-fold) and cortical cell length (~ 1.3- to 7-fold) was observed in maize and wheat. GWAS and QTL analyses indicate cortical cell diameter and length are heritable and under independent genetic control. We identify candidate genes for both phenes. Empirical results from isophenic lines contrasting for cortical cell diameter and length show that increased cell size, due to either diameter or length, is associated with reduced root respiration, nitrogen content, and phosphorus content. RootSlice, a functional-structural model of root anatomy, predicts that an increased vacuolar: cytoplasmic ratio per unit cortical volume causes reduced root respiration and nutrient content. Ultrastructural imaging of cortical parenchyma cells with varying cortical diameter and cortical cell length confirms the in silico predictions and shows that an increase in cell size is correlated with increased vacuolar volume and reduced cytoplasmic volume. Vacuolar occupancy and its relationship with cell size merits further investigation as a phene for improving crop adaptation to edaphic stress.
Asunto(s)
Tamaño de la Célula , Raíces de Plantas , Sitios de Carácter Cuantitativo , Vacuolas , Zea mays , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Raíces de Plantas/citología , Zea mays/genética , Zea mays/metabolismo , Zea mays/fisiología , Zea mays/citología , Vacuolas/metabolismo , Sitios de Carácter Cuantitativo/genética , Triticum/genética , Triticum/metabolismo , Triticum/fisiología , Estudio de Asociación del Genoma Completo , Genotipo , Nitrógeno/metabolismoRESUMEN
Different plant species within the grasses were parallel targets of domestication, giving rise to crops with distinct evolutionary histories and traits1. Key traits that distinguish these species are mediated by specialized cell types2. Here we compare the transcriptomes of root cells in three grass species-Zea mays, Sorghum bicolor and Setaria viridis. We show that single-cell and single-nucleus RNA sequencing provide complementary readouts of cell identity in dicots and monocots, warranting a combined analysis. Cell types were mapped across species to identify robust, orthologous marker genes. The comparative cellular analysis shows that the transcriptomes of some cell types diverged more rapidly than those of others-driven, in part, by recruitment of gene modules from other cell types. The data also show that a recent whole-genome duplication provides a rich source of new, highly localized gene expression domains that favour fast-evolving cell types. Together, the cell-by-cell comparative analysis shows how fine-scale cellular profiling can extract conserved modules from a pan transcriptome and provide insight on the evolution of cells that mediate key functions in crops.
Asunto(s)
Productos Agrícolas , Setaria (Planta) , Sorghum , Transcriptoma , Zea mays , Secuencia de Bases , Regulación de la Expresión Génica de las Plantas/genética , Sorghum/citología , Sorghum/genética , Transcriptoma/genética , Zea mays/citología , Zea mays/genética , Setaria (Planta)/citología , Setaria (Planta)/genética , Raíces de Plantas/citología , Análisis de Expresión Génica de una Sola Célula , Análisis de Secuencia de ARN , Productos Agrícolas/citología , Productos Agrícolas/genética , Evolución MolecularRESUMEN
Most plant roots have multiple cortex layers that make up the bulk of the organ and play key roles in physiology, such as flood tolerance and symbiosis. However, little is known about the formation of cortical layers outside of the highly reduced anatomy of Arabidopsis. Here, we used single-cell RNA sequencing to rapidly generate a cell-resolution map of the maize root, revealing an alternative configuration of the tissue formative transcription factor SHORT-ROOT (SHR) adjacent to an expanded cortex. We show that maize SHR protein is hypermobile, moving at least eight cell layers into the cortex. Higher-order SHR mutants in both maize and Setaria have reduced numbers of cortical layers, showing that the SHR pathway controls expansion of cortical tissue to elaborate anatomical complexity.
Asunto(s)
Proteínas de Plantas/metabolismo , Raíces de Plantas/citología , Raíces de Plantas/metabolismo , Setaria (Planta)/metabolismo , Factores de Transcripción/metabolismo , Zea mays/metabolismo , Citometría de Flujo , Genoma de Planta , Proteínas de Plantas/genética , Raíces de Plantas/genética , RNA-Seq , Setaria (Planta)/citología , Setaria (Planta)/genética , Análisis de la Célula Individual , Factores de Transcripción/genética , Transcripción Genética , Zea mays/citología , Zea mays/genéticaRESUMEN
Maize leaf angle (LA) is a complex quantitative trait that is controlled by developmental signals, hormones, and environmental factors. However, the connection between histone methylation and LAs in maize remains unclear. Here, we reported that SET domain protein 128 (SDG128) is involved in leaf inclination in maize. Knockdown of SDG128 using an RNA interference approach resulted in an expanded architecture, less large vascular bundles, more small vascular bundles, and larger spacing of large vascular bundles in the auricles. SDG128 interacts with ZmGID2 both in vitro and in vivo. Knockdown of ZmGID2 also showed a larger LA with less large vascular bundles and larger spacing of vascular bundles. In addition, the transcription level of cell wall expansion family genes ZmEXPA1, ZmEXPB2, and GRMZM2G005887; transcriptional factor genes Lg1, ZmTAC1, and ZmCLA4; and auxin pathway genes ZmYUCCA7, ZmYUCCA8, and ZmARF22 was reduced in SDG128 and ZmGID2 knockdown plants. SDG128 directly targets ZmEXPA1, ZmEXPB2, LG1, and ZmTAC1 and is required for H3K4me3 deposition at these genes. Together, the results of the present study suggest that SDG128 and ZmGID2 are involved in the maize leaf inclination.
Asunto(s)
Hojas de la Planta/fisiología , Proteínas de Plantas/genética , Zea mays/fisiología , Proteínas F-Box/genética , Proteínas F-Box/metabolismo , Regulación de la Expresión Génica de las Plantas , Histonas , Ácidos Indolacéticos/metabolismo , Mutación , Hojas de la Planta/citología , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente , Interferencia de ARN , Zea mays/citologíaRESUMEN
Coupling assay for transposase-accessible chromatin sequencing (ATAC-seq) with microfluidic separation and cellular barcoding has emerged as a powerful approach to investigate chromatin accessibility of individual cells. Here, we define a protocol for constructing single-cell ATAC-seq libraries from maize seedling nuclei and the preliminary computational steps for assessing data quality. This protocol can be readily adapted to other plant species or tissues with minor changes to reveal chromatin accessibility variation among individual cells. For complete details on the use and execution of this protocol, please refer to Marand et al. (2021).
Asunto(s)
Secuenciación de Inmunoprecipitación de Cromatina/métodos , Cromatina , Células Vegetales/química , Análisis de la Célula Individual/métodos , Técnicas de Cultivo de Célula , Cromatina/química , Cromatina/genética , Plantones/citología , Zea mays/citologíaRESUMEN
KEY MESSAGE: A novel genic male-sterile mutant ms40 was obtained from EMS treated RP125. The key candidate gene ZmbHLH51 located on chromosome 4 was identified by map-based cloning. This study further enriched the male sterile gene resources for both production applications and theoretical studies of abortion mechanisms. Maize male-sterile mutant 40 (ms40) was obtained from the progeny of the ethyl methanesulfonate (EMS) treated inbred line RP125. Genetic analysis indicated that the sterility was controlled by a single recessive nuclear gene. Cytological observation of anthers revealed that the cuticles of ms40 anthers were abnormal, and no Ubisch bodies were observed on the inner surface of ms40 anthers through scanning electron microscopy(SEM). Moreover, its tapetum exhibited delayed degradation and then blocked the formation of normal microspores. Using map-based cloning strategy, the ms40 locus was found to locate in a 282-kb interval on chromosome 4, and five annotated genes were predicted within this region. PCR-based sequencing detected a single non-synonymous SNP (G > A) that changed glycine (G) to arginine (A) in the seventh exon of Zm00001d053895, while no sequence difference between ms40 and RP125 was found for the other four genes. Zm00001d053895 encodes the bHLH transcription factor ZmbHLH51 which is localized in the nucleus. Phylogenetic analysis showed that ZmbHLH51 had the highest homology with Sb04g001650, a tapetum degeneration retardation (TDR) bHLH transcription factor in Sorghum bicolor. Co-expression analysis revealed a total of 1192 genes co-expressed with ZmbHLH51 in maize, 647 of which were anther-specific genes. qRT-PCR results suggested the expression levels of some known genes related to anther development were affected in ms40. In summary, these findings revealed the abortion characteristics of ms40 anthers and lay a foundation for further studies on the mechanisms of male fertility.
Asunto(s)
Flores/crecimiento & desarrollo , Flores/genética , Infertilidad Vegetal/genética , Proteínas de Plantas/genética , Zea mays/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Cromosomas de las Plantas , Regulación de la Expresión Génica de las Plantas , Genes Recesivos , Mutación , Filogenia , Proteínas de Plantas/metabolismo , Polen/genética , Zea mays/citologíaRESUMEN
The ataxia-telangiectasia mutated (ATM) and ATM and Rad3-related (ATR) kinases coordinate the DNA damage response. The roles described for Arabidopsis thaliana ATR and ATM are assumed to be conserved over other plant species, but molecular evidence is scarce. Here, we demonstrate that the functions of ATR and ATM are only partially conserved between Arabidopsis and maize (Zea mays). In both species, ATR and ATM play a key role in DNA repair and cell cycle checkpoint activation, but whereas Arabidopsis plants do not suffer from the absence of ATR under control growth conditions, maize mutant plants accumulate replication defects, likely due to their large genome size. Moreover, contrarily to Arabidopsis, maize ATM deficiency does not trigger meiotic defects, whereas the ATR kinase appears to be crucial for the maternal fertility. Strikingly, ATR is required to repress premature endocycle onset and cell death in the maize endosperm. Its absence results in a reduction of kernel size, protein and starch content, and a stochastic death of kernels, a process being counteracted by ATM. Additionally, while Arabidopsis atr atm double mutants are viable, no such mutants could be obtained for maize. Therefore, our data highlight that the mechanisms maintaining genome integrity may be more important for vegetative and reproductive development than previously anticipated.
Asunto(s)
Reparación del ADN/genética , Endospermo/genética , Proteínas de Plantas/genética , Zea mays/genética , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de la Ataxia Telangiectasia Mutada/genética , Sistemas CRISPR-Cas , Muerte Celular/genética , Roturas del ADN de Doble Cadena , Replicación del ADN/genética , Endospermo/citología , Inestabilidad Genómica , Mutación , Células Vegetales , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente , Semillas/citología , Semillas/genética , Semillas/crecimiento & desarrollo , Zea mays/citología , Zea mays/crecimiento & desarrolloRESUMEN
The morphology, size and quantity of cells, starch granules and protein bodies in seed determine the weight and quality of seed. They are significantly different among different regions of seed. In order to view the morphologies of cells, starch granules and protein bodies clearly, and quantitatively analyze their morphology parameters accurately, the whole-seed-sized section is needed. Though the whole-seed-sized paraffin section can investigate the accumulation of storage materials in seeds, it is very difficult to quantitatively analyze the morphology parameters of cells and storage materials due to the low resolution of the thick section. The thin resin section has high resolution, but the routine resin sectioning method is not suitable to prepare the whole-seed-sized section of mature seeds with a large volume and high starch content. In this study, we present a simple dry sectioning method for preparing the whole-seed-sized resin section. The technique can prepare the cross and longitudinal whole-seed-sized sections of developing, mature, germinated, and cooked seeds embedded in LR White resin, even for large seeds with high starch content. The whole-seed-sized section can be stained with fluorescent brightener 28, iodine, and Coomassie brilliant blue R250 to specifically exhibit the morphology of cells, starch granules, and protein bodies clearly, respectively. The image obtained can also be analyzed quantitatively to show the morphology parameters of cells, starch granules, and protein bodies in different regions of seed.
Asunto(s)
Microtomía/métodos , Resinas Sintéticas/química , Semillas/química , Zea mays/química , Proteínas de Plantas/metabolismo , Semillas/citología , Coloración y Etiquetado , Almidón/metabolismo , Zea mays/citología , Zea mays/embriologíaRESUMEN
Plants maintain populations of pluripotent stem cells in shoot apical meristems (SAMs), which continuously produce new aboveground organs. We used single-cell RNA sequencing (scRNA-seq) to achieve an unbiased characterization of the transcriptional landscape of the maize shoot stem-cell niche and its differentiating cellular descendants. Stem cells housed in the SAM tip are engaged in genome integrity maintenance and exhibit a low rate of cell division, consistent with their contributions to germline and somatic cell fates. Surprisingly, we find no evidence for a canonical stem-cell organizing center subtending these cells. In addition, trajectory inference was used to trace the gene expression changes that accompany cell differentiation, revealing that ectopic expression of KNOTTED1 (KN1) accelerates cell differentiation and promotes development of the sheathing maize leaf base. These single-cell transcriptomic analyses of the shoot apex yield insight into the processes of stem-cell function and cell-fate acquisition in the maize seedling and provide a valuable scaffold on which to better dissect the genetic control of plant shoot morphogenesis at the cellular level.
Asunto(s)
Diferenciación Celular , Análisis de la Célula Individual , Células Madre/citología , Zea mays/citología , División Celular , Regulación de la Expresión Génica de las Plantas , Genoma de Planta , Meristema , Hojas de la Planta/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Transcripción Genética , Transcriptoma/genética , Zea mays/genéticaRESUMEN
Maize (Zea mays) thick aleurone1 (thk1-R) mutants form multiple aleurone layers in the endosperm and have arrested embryogenesis. Prior studies suggest that thk1 functions downstream of defective kernel1 (dek1) in a regulatory pathway that controls aleurone cell fate and other endosperm traits. The original thk1-R mutant contained an â¼2-Mb multigene deletion, which precluded identification of the causal gene. Here, ethyl methanesulfonate mutagenesis produced additional alleles, and RNA sequencing from developing endosperm was used to identify a candidate gene based on differential expression compared with the wild-type progenitor. Gene editing confirmed the gene identity by producing mutant alleles that failed to complement existing thk1 mutants and that produced multiple-aleurone homozygous phenotypes. Thk1 encodes a homolog of NEGATIVE ON TATA-LESS1, a protein that acts as a scaffold for the CARBON CATABOLITE REPRESSION4-NEGATIVE ON TATA-LESS complex. This complex is highly conserved and essential in all eukaryotes for regulating a wide array of gene expression and cellular activities. Maize also harbors a duplicate locus, thick aleurone-like1, which likely accounts for the ability of thk1 mutants to form viable cells. Transcriptomic analysis indicated that THK1 regulates activities involving cell division, signaling, differentiation, and metabolism. Identification of thk1 provides an important new component of the DEK1 regulatory system that patterns cell fate in endosperm.
Asunto(s)
Diferenciación Celular/genética , Endospermo/citología , Endospermo/crecimiento & desarrollo , Endospermo/genética , Zea mays/citología , Zea mays/crecimiento & desarrollo , Zea mays/genética , Productos Agrícolas/citología , Productos Agrícolas/genética , Productos Agrícolas/crecimiento & desarrollo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Variación Genética , Genotipo , Mutación , FenotipoRESUMEN
Autophagic recycling of proteins, lipids, nucleic acids, carbohydrates, and organelles is essential for cellular homeostasis and optimal health, especially under nutrient-limiting conditions. To better understand how this turnover affects plant growth, development, and survival upon nutrient stress, we applied an integrated multiomics approach to study maize (Zea mays) autophagy mutants subjected to fixed-carbon starvation induced by darkness. Broad metabolic alterations were evident in leaves missing the core autophagy component ATG12 under normal growth conditions (e.g., lipids and secondary metabolism), while changes in amino acid-, carbohydrate-, and nucleotide-related metabolites selectively emerged during fixed-carbon starvation. Through combined proteomic and transcriptomic analyses, we identified numerous autophagy-responsive proteins, which revealed processes underpinning the various metabolic changes seen during carbon stress as well as potential autophagic cargo. Strikingly, a strong upregulation of various catabolic processes was observed in the absence of autophagy, including increases in simple carbohydrate levels with a commensurate drop in starch levels, elevated free amino acid levels with a corresponding reduction in intact protein levels, and a strong increase in the abundance of several nitrogen-rich nucleotide catabolites. Altogether, this analysis showed that fixed-carbon starvation in the absence of autophagy adjusts the choice of respiratory substrates, promotes the transition of peroxisomes to glyoxysomes, and enhances the retention of assimilated nitrogen.
Asunto(s)
Aminoácidos/metabolismo , Autofagia/fisiología , Carbono/metabolismo , Zea mays/citología , Zea mays/metabolismo , Metabolismo de los Hidratos de Carbono/genética , Metabolismo de los Hidratos de Carbono/fisiología , Oscuridad , Regulación de la Expresión Génica de las Plantas , Metabolismo de los Lípidos/genética , Metabolismo de los Lípidos/fisiología , Mutación , Hojas de la Planta/metabolismo , Proteínas de Plantas/genética , Zea mays/genéticaRESUMEN
To understand the growth response to drought, we performed a proteomics study in the leaf growth zone of maize (Zea mays L.) seedlings and functionally characterized the role of starch biosynthesis in the regulation of growth, photosynthesis and antioxidant capacity, using the shrunken-2 mutant (sh2), defective in ADP-glucose pyrophosphorylase. Drought altered the abundance of 284 proteins overrepresented for photosynthesis, amino acid, sugar and starch metabolism, and redox-regulation. Changes in protein levels correlated with enzyme activities (increased ATP synthase, cysteine synthase, starch synthase, RuBisCo, peroxiredoxin, glutaredoxin, thioredoxin and decreased triosephosphate isomerase, ferredoxin, cellulose synthase activities, respectively) and metabolite concentrations (increased ATP, cysteine, glycine, serine, starch, proline and decreased cellulose levels). The sh2 mutant showed a reduced increase of starch levels under drought conditions, leading to soluble sugar starvation at the end of the night and correlating with an inhibition of leaf growth rates. Increased RuBisCo activity and pigment concentrations observed in WT, in response to drought, were lacking in the mutant, which suffered more oxidative damage and recovered more slowly after re-watering. These results demonstrate that starch biosynthesis contributes to maintaining leaf growth under drought stress and facilitates enhanced carbon acquisition upon recovery.
Asunto(s)
Sequías , Hojas de la Planta/crecimiento & desarrollo , Proteínas de Plantas/metabolismo , Almidón/metabolismo , Zea mays/fisiología , Aminoácidos/metabolismo , Antioxidantes/metabolismo , División Celular , Deshidratación , Regulación de la Expresión Génica de las Plantas , Mutación , Fotosíntesis/fisiología , Hojas de la Planta/fisiología , Proteínas de Plantas/genética , Estomas de Plantas/fisiología , Almidón/biosíntesis , Zea mays/citologíaRESUMEN
Although cell wall polymers play important roles in the tolerance of plants to abiotic stress, the effects of salinity on cell wall composition and metabolism in grasses remain largely unexplored. Here, we conducted an in-depth study of changes in cell wall composition and phenolic metabolism induced upon salinity in maize seedlings and plants. Cell wall characterization revealed that salt stress modulated the deposition of cellulose, matrix polysaccharides and lignin in seedling roots, plant roots and stems. The extraction and analysis of arabinoxylans by size-exclusion chromatography, 2D-NMR spectroscopy and carbohydrate gel electrophoresis showed a reduction of arabinoxylan content in salt-stressed roots. Saponification and mild acid hydrolysis revealed that salinity also reduced the feruloylation of arabinoxylans in roots of seedlings and plants. Determination of lignin content and composition by nitrobenzene oxidation and 2D-NMR confirmed the increased incorporation of syringyl units in lignin of maize roots. Salt stress also induced the expression of genes and the activity of enzymes enrolled in phenylpropanoid biosynthesis. The UHPLC-MS-based metabolite profiling confirmed the modulation of phenolic profiling by salinity and the accumulation of ferulate and its derivatives 3- and 4-O-feruloyl quinate. In conclusion, we present a model for explaining cell wall remodeling in response to salinity.
Asunto(s)
Pared Celular/química , Fenoles/metabolismo , Polisacáridos/metabolismo , Zea mays/citología , Zea mays/metabolismo , Pared Celular/metabolismo , Celulosa/análisis , Celulosa/química , Ácidos Cumáricos/metabolismo , Regulación de la Expresión Génica de las Plantas , Lignina/metabolismo , Monosacáridos/análisis , Células Vegetales/metabolismo , Raíces de Plantas/metabolismo , Polisacáridos/química , Estrés Salino/fisiología , Plantones/citología , Plantones/metabolismo , Xilanos/análisis , Xilanos/química , Xilanos/metabolismo , Zea mays/crecimiento & desarrolloRESUMEN
In flowering plants, gene expression in the haploid male gametophyte (pollen) is essential for sperm delivery and double fertilization. Pollen also undergoes dynamic epigenetic regulation of expression from transposable elements (TEs), but how this process interacts with gene expression is not clearly understood. To explore relationships among these processes, we quantified transcript levels in four male reproductive stages of maize (tassel primordia, microspores, mature pollen, and sperm cells) via RNA-seq. We found that, in contrast with vegetative cell-limited TE expression in Arabidopsis pollen, TE transcripts in maize accumulate as early as the microspore stage and are also present in sperm cells. Intriguingly, coordinate expression was observed between highly expressed protein-coding genes and their neighboring TEs, specifically in mature pollen and sperm cells. To investigate a potential relationship between elevated gene transcript level and pollen function, we measured the fitness cost (male-specific transmission defect) of GFP-tagged coding sequence insertion mutations in over 50 genes identified as highly expressed in the pollen vegetative cell, sperm cell, or seedling (as a sporophytic control). Insertions in seedling genes or sperm cell genes (with one exception) exhibited no difference from the expected 1:1 transmission ratio. In contrast, insertions in over 20% of vegetative cell genes were associated with significant reductions in fitness, showing a positive correlation of transcript level with non-Mendelian segregation when mutant. Insertions in maize gamete expressed2 (Zm gex2), the sole sperm cell gene with measured contributions to fitness, also triggered seed defects when crossed as a male, indicating a conserved role in double fertilization, given the similar phenotype previously demonstrated for the Arabidopsis ortholog GEX2. Overall, our study demonstrates a developmentally programmed and coordinated transcriptional activation of TEs and genes in pollen, and further identifies maize pollen as a model in which transcriptomic data have predictive value for quantitative phenotypes.
Asunto(s)
Elementos Transponibles de ADN/genética , Regulación de la Expresión Génica de las Plantas , Aptitud Genética , Polen/genética , Transcripción Genética , Zea mays/genética , Linaje de la Célula , Perfilación de la Expresión Génica , Genes de Plantas/genética , Genoma de Planta/genética , Meiosis , Mutagénesis Insercional , Mutación , Polinización , Reproducibilidad de los Resultados , Reproducción , Semillas/genética , Semillas/crecimiento & desarrollo , Regulación hacia Arriba , Zea mays/citología , Zea mays/crecimiento & desarrolloRESUMEN
Meiotic double-strand breaks (DSBs) are generated by the evolutionarily conserved SPO11 complex in the context of chromatin loops that are organized along axial elements (AEs) of chromosomes. However, how DSBs are formed with respect to chromosome axes and the SPO11 complex remains unclear in plants. Here, we confirm that DSB and bivalent formation are defective in maize spo11-1 mutants. Super-resolution microscopy demonstrates dynamic localization of SPO11-1 during recombination initiation, with variable numbers of SPO11-1 foci being distributed in nuclei but similar numbers of SPO11-1 foci being found on AEs. Notably, cytological analysis of spo11-1 meiocytes revealed an aberrant AE structure. At leptotene, AEs of wild-type and spo11-1 meiocytes were similarly curly and discontinuous. However, during early zygotene, wild-type AEs become uniform and exhibit shortened axes, whereas the elongated and curly AEs persisted in spo11-1 mutants, suggesting that loss of SPO11-1 compromised AE structural maturation. Our results reveal an interesting relationship between SPO11-1 loading onto AEs and the conformational remodeling of AEs during recombination initiation.
Asunto(s)
Endodesoxirribonucleasas/metabolismo , Recombinación Homóloga , Meiosis , Zea mays/citología , Zea mays/metabolismo , Núcleo Celular/genética , Núcleo Celular/metabolismo , Emparejamiento Cromosómico , Roturas del ADN de Doble Cadena , Endodesoxirribonucleasas/genética , Genes de Plantas/genética , Meiosis/genética , Mutación , Fenotipo , Zea mays/genéticaRESUMEN
BACKGROUND: Maize bsd2 (bundle sheath defective2) is a classical C4 mutant with defective C4 photosynthesis, accompanied with reduced accumulation of Rubisco (ribulose bisphosphate carboxylase oxygenase) and aberrant mature chloroplast morphology in the bundle sheath (BS) cells. However, as a hypothetical chloroplast chaperone, the effects of BSD2 on C4 chloroplast development have not been fully examined yet, which precludes a full appreciation of BSD2 function in C4 photosynthesis. The aims of our study are to find out the role ofBSD2 in regulating chloroplasts development in maize leaves, and to add new insights into our understanding of C4 biology. RESULTS: We found that at the chloroplast maturation stage, the thylakoid membranes of chloroplasts in the BS and mesophyll (M) cells became significantly looser, and the granaof chloroplasts in the M cells became thinner stacking in the bsd2 mutant when compared with the wildtype plant. Moreover, at the early chloroplast development stage, the number of dividing chloroplasts and the chloroplast division rate are both reduced in the bsd2 mutant, compared with wild type. Quantitative reverse transcriptase-PCR analysis revealed that the expression of both thylakoid formation-related genesand chloroplast division-related genes is significantly reduced in the bsd2 mutants. Further, we showed that BSD2 interacts physically with the large submit of Rubisco (LS) in Bimolecular Fluorescence Complementation assay. CONCLUSIONS: Our combined results suggest that BSD2 plays an essential role in regulating the division and differentiation of the dimorphic BS and M chloroplasts, and that it acts at a post-transcriptional level to regulate LS stability or assembly of Rubisco.
Asunto(s)
Cloroplastos/ultraestructura , Hojas de la Planta/citología , Proteínas de Plantas/genética , Zea mays , Cloroplastos/metabolismo , Mutación , Hojas de la Planta/metabolismo , Proteínas de Plantas/metabolismo , Ribulosa-Bifosfato Carboxilasa/metabolismo , Zea mays/citología , Zea mays/genética , Zea mays/metabolismo , Zea mays/ultraestructuraRESUMEN
Meiosis consists of two highly conserved nuclear divisions, which allow eukaryotes to maintain their chromosome number through sexual reproduction. The successful completion of meiosis depends on homologous chromosome pairing. Centromere interactions during early meiotic prophase I facilitate homologous chromosome pairing, but the underlying mechanism is unclear. Here, we performed chromatin immunoprecipitation-mass spectrometry analysis of maize (Zea mays) anthers during early meiotic prophase I using anti-centromeric histone H3 (CENH3) antibodies and determined that the cohesin subunit Structural Maintenance of Chromosome3 (SMC3) interacts with CENH3 during this period. SMC3 is enriched at centromeres and along chromosome arms in threads from leptotene to pachytene and might promote interactions between homologous centromeres. We observed dysfunctional SMC3 assembly in meiotic-specific maize mutants with defective centromere pairing. In SMC3 RNAi meiocytes, centromere pairing defects were observed during early meiotic prophase I, SMC3 was weakly associated with centromeres, and SMC3 did not localize to the chromosome arms. In wild-type mitosis, SMC3 is associated with chromatin and is enriched at centromeres from prophase to anaphase. CRISPR-Cas9-induced Zmsmc3 mutants showed premature loss of sister chromatid cohesion and mis-segregation of chromosomes in mitotic spreads. Our findings suggest that in addition to sister chromatid cohesion, ZmSMC3 participates in meiotic centromere pairing.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Centrómero/metabolismo , Proteínas Cromosómicas no Histona/metabolismo , Emparejamiento Cromosómico , Meiosis , Proteínas de Plantas/metabolismo , Subunidades de Proteína/metabolismo , Zea mays/citología , Zea mays/metabolismo , Cromátides/metabolismo , Cromosomas de las Plantas/genética , Profase Meiótica I , Mitosis , Mutación/genética , Fenotipo , Unión Proteica , Recombinación Genética/genética , Huso Acromático/metabolismo , CohesinasRESUMEN
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.
Asunto(s)
Pared Celular/metabolismo , Celulosa/metabolismo , Fenoles/metabolismo , Fitoquímicos/metabolismo , Zea mays/química , Pared Celular/química , Celulosa/química , Fenoles/química , Fitoquímicos/química , Zea mays/citología , Zea mays/metabolismoRESUMEN
The distribution of highly de-esterified homogalacturonans (HGs) in dividing protodermal cells of the monocotyledon Zea mays, the dicotyledon Vigna sinensis, and the fern Asplenium nidus was investigated in order to examine whether the cell wall region adjoining the preprophase band (PPB) is locally diversified. Application of immunofluorescence revealed that de-esterified HGs were accumulated selectively in the cell wall adjacent to the PPB in: (a) symmetrically dividing cells of stomatal rows of Z. mays, (b) the asymmetrically dividing protodermal cells of Z. mays, (c) the symmetrically dividing guard cell mother cells (GMCs) of Z. mays and V. sinensis, and (d) the symmetrically dividing protodermal cells of A. nidus. A common feature of the above cell types is that the cell division plane is defined by extrinsic cues. The presented data suggest that the PPB cortical zone-plasmalemma and the adjacent cell wall region function in a coordinated fashion in the determination/accomplishment of the cell division plane, behaving as a continuum. The de-esterified HGs, among other possible functions, might be involved in the perception and the transduction of the extrinsic cues determining cell division plane in the examined cells.