Kernel Development Research Articles

Ergotism and Saint Anthony's fire

It has been widely accepted that ergot is a fungal disease caused by infection with the parasitic Claviceps purpurea leading to the development of typical black kernels n the plant. Ingestion of infected rye grains containing ergot alkaloids—usually in the form of contaminated rye bread—causes poisoning, also known as ergotism. The negative impacts of ergot contamination of grain on the health of humans and animals were first documented in ancient times. The history of ergotism shows the influence of food on human health. Although ergot has been known for ages, until the 18th century, its nature was not recognized. It was a part of the rye plant and it was used in traditional medicine. The diet was based was mostly on rye that led to neurologic disorders and gangrene. In the Middle Ages, in regions where rye was a dietary staple, many cases of a peculiar epidemic were recorded. Two names are usually used to describe it: “Saint Anthony's fire” and “holy fire,” although there are many more appellations. The history of ergotism is a very important part of history of dermatology. The saint who people prayed to for protection against the disease was Anthony the Great (251-356). Monks of the Order of Saint Anthony played a particular role in treating ergotism by natural methods and specialized in treating skin diseases. Ergot alkaloids still pose a risk to human and animal safety if they appear in food.

On the flame stabilization of turbulent lifted hydrogen jet flames in heated coflows near the autoignition limit: A comparative DNS study

Three-dimensional direct numerical simulations of turbulent lifted hydrogen jet flames in heated coflows are performed with a detailed H2/air chemical mechanism to understand their ignition dynamics and stabilization mechanisms. Turbulent lifted jet flames with four different coflow temperatures, Tc, between 750 K and 1100 K are investigated by examining the instantaneous/time-averaged values and conditional means of heat release rate and species critical to ignition, and by performing a displacement speed analysis and a local combustion mode analysis with an indicator, α. Although Tc at 950 K is higher than the autoignition limit, the flame is primarily stabilized by flame propagation rather than autoignition, while at 1100 K, flame stabilization is found to be highly affected by autoignition. The local combustion mode analysis further reveals that at 950 K, even if a local ignition mode with |α|<1 first appears in the near field of the jet, it develops into a local extinction mode with α<−1 as local temperature decreases due to the excessive mixing of heated coflow and cold H2 within vortical structures, which inhibits the ignition kernel development upstream of the flamebase. At 1100 K, however, a local ignition mode prevails upstream of the flamebase. To further identify the effect of a vortex on the early development of an ignition kernel in a mixing layer between the heated coflow and cold H2, a series of two-dimensional DNSs are performed, varying several vortex parameters and air temperature, as a reference for the more complicated corresponding 3-D turbulent DNS cases. The results substantiate that the development of a vortex in the mixing layer tends to retard the autoignition within the vortex, especially when its temperature is slightly above the autoignition limit.

Effects of fuel decomposition and stratification on the forced ignition of a static flammable mixture

In advanced propulsion systems such as scramjet engines, endothermic decomposition of onboard large hydrocarbon fuels can be used effectively for cooling and active thermal protection. During the cooling process, large hydrocarbon fuels absorb heat and decompose into small fragments. Since fuel decomposition changes the chemical and transport properties of the reactants, it is expected to affect the combustion afterwards. In this study, forced ignition in quiescent n-decane/air mixtures with fuel decomposition is investigated via a simplified model and transient numerical simulations considering detailed chemistry and transport. The emphasis is placed on assessing the effects of fuel decomposition on ignition kernel development and minimum ignition energy (MIE) in both homogenous and fuel-stratified mixtures. Fuel decomposition is modelled by a homogeneous ignition process in n-decane/air mixture at constant atmospheric pressure and with an initial temperature of 1300 K. Small fragments appear during the pyrolysis process. The partially-reacted mixture is frozen and cooled to a lower temperature and used as the initial mixture in forced ignition. For homogeneous mixtures, fuel decomposition can greatly promote ignition for fuel-lean decane/air mixtures while it has little effect for the stoichiometric case. Fuel decomposition also affects the duration of unsteady ignition kernel transition. Besides, fuel decomposition and fuel stratification are combined to further promote forced ignition. New flame regimes are observed and an optimum stratification radius is identified. In order to promote the forced ignition, only the fuel within the optimum stratification radius needs to be decomposed. Furthermore, laser and spark ignition experiments are conducted to measure the MIE of n-decane/ethylene/air mixtures with different equivalence ratios and ethylene blending ratios. The MIE measured in experiments cannot be directly compared with simulation results since the simulation model for forced-ignition is simplified. Nevertheless, the experimental results are consistent with simulation results and thus validate some conclusions mentioned above. The present results provide useful guidance to the fundamental understanding of forced ignition in a mixture with fuel decomposition.

Genome-wide Identification and Expression Analysis of NAC Transcription Factor Family Genes during Fruit and Kernel Development in Siberian Apricot

The NAC (NAM, ATAF1/2, and CUC2) family is a group of plant-specific transcription factors that have vital roles in the growth and development of plants, and especially in fruit and kernel development. This study aimed to identify members of the NAC gene (PsNACs) family and investigate their functions in siberian apricot (Prunus sibirica). A total of 102 predicted PsNAC proteins (PsNACs) were divided into 14 clades and the genes were mapped to the eight chromosomes in siberian apricot. The PsNACs of the same clade had similar structures. A synteny analysis showed that the PsNACs had close relationships with the NAC genes of japanese apricot (Prunus mume). An expression pattern analysis of the PsNACs revealed many differences in various tissues and at different stages of fruit and kernel development. All eight PsNACs in clade XI have crucial roles in fruit and kernel development. Seven PsNACs (PsNACs 18, 64, 23, 33, 9, 4, and 50) in clades I, III, VI, VII, and XIII are related to fruit development. Eight PsNACs (PsNACs 6, 13, 46, 51, 41, 67, 37, and 59) in clades I, II, V, VIII, and XIII are involved in fruit ripening. Five PsNACs (PsNACs 6, 94, 41, 32, and 17) in clades I, IV, V, VII, and XI regulated the rapid growth of the kernel. Four PsNACs (PsNACs 50, 4, 67, and 84) in clades I, III, V, and XIII affected the hardening of the kernel. Four PsNACs (PsNACs 17, 82, 13, and 51) in clades II, XI, and IX acted on kernel maturation. We have characterized the NAC genes in siberian apricot during this study. Our results will provide resources for future research of the biological roles of PsNACs in fruit and kernel development in siberian apricot.

Nonlinear Model Selection for Fruit and Kernel Development as a Function of Heat in Pistachio

Knowing a tree crop’s seasonal growth and development as a function of heat accumulation can facilitate scheduling of irrigation, pesticide applications, and harvest. Our objective was to compare the goodness of fit of applied models and determine which provides the best description of pistachio nut growth as a function of thermal unit accumulation. Three fruit growth traits of pistachio—pericarp (hull) + endocarp (shell) size, endocarp thickening and hardening, and embryo (kernel) size—exhibited clear nonlinear dependence on heat accumulation. We tested three nonlinear models—Michaelis–Menten, three-parameter logistic, and Gompertz—fitted to fruit development data to create a tool to forecast pest susceptibility and harvest timing. Observation of development began at full bloom and ended at harvest. Data were collected from six pistachio cultivars in one experimental and eight commercial orchards over 3 years. Analyses of residual distribution, parameter standard errors, coefficient of determination (R2) and the Akaike information criterion (AIC) all demonstrated the Gompertz function was the best model. Cultivars differed significantly in all the three parameters (Asym, b, and c) for all three traits with the Gompertz model, demonstrating the Gompertz model can adjust to incorporate cultivar differences. The growth curve of the three traits together provided integrated information on nut biomass accumulation that facilitates predicting the critical timing for multiple orchard management practices.

Identification of genes involved in the formation of soluble dietary fiber in winter rye grain and their expression in cultivars with different viscosities of wholemeal water extract

The grain of rye (Secale cereale L.) used for baking contains a large amount of non-starch polysaccharides, making it an excellent component of functional foods. But rye grain intended for alcohol production and forage use should have a reduced content of these polysaccharides. A comprehensive parameter that can predict the best field of application for winter rye grain is the viscosity of its wholemeal water extract. However, our understanding of the genetic background underlying this key trait and associated features of rye grain is poor. By analyzing six Russian winter rye cultivars, we identified the most contrasting forms and characterized the peculiarities of their water-soluble carbohydrates capable of influencing the viscosity of water extracts. Then, using phylogenetic and transcriptomic analyses, we identified in the rye genome many genes encoding putative glycosyltransferases and glycosylhydrolases responsible for the synthesis and degradation of arabinoxylans, mixed-linkage glucans, cellulose, and some other polysaccharides. We determined the dynamics of mRNA abundance for these genes at three stages of kernel development. Comparisons of gene expression levels in two contrasting cultivars revealed specific members of multigene families that may serve as promising targets for manipulating non-starch polysaccharide content in rye grain. High-viscosity cultivars were characterized by up-regulation of many glycosyltransferases involved in the biosynthesis of arabinoxylans and other cell-wall polysaccharides, whereas low-viscosity cultivars showed up-regulation of several genes encoding polysaccharide-degrading enzymes.

Multiomics analysis of kernel development in response to short-term heat stress at the grain formation stage in waxy maize.

Understanding the adaptive changes in maize kernels under high-temperature stress during grain formation stage is critical for developing strategies to alleviate the negative effects on yield and quality. In this study, we subjected waxy maize (Zea mays L. sinensis Kulesh) to four different temperature regimes from 1-15 d after pollination (DAP), namely normal day/normal night (control), hot day/normal night, normal day/hot night, and hot day/hot night. Compared to the control, the three high-temperature treatments inhibited kernel development and starch deposition. To understand how the kernels responded to high-temperature stress, their transcriptomes, proteomes, and metabolomes were studied at 10 DAP and 25 DAP. This showed that genes and proteins related to kernel development and starch deposition were up- and down-regulated, respectively, at 10 DAP, but this pattern was reversed at 25 DAP. Metabolome profiling under high-temperature stress showed that the accumulation patterns of metabolites at 10 DAP and 25 DAP were inversely related. Our multiomics analyses indicated that the response to high-temperature stress of signaling pathways mediated by auxin, abscisic acid, and salicylic acid was more active at 10 DAP than at 25 DAP. These results confirmed that high-temperature stress during early kernel development has a carry-over effect on later development. Taken together, our multiomics profiles of developing kernels under high-temperature stress provide insights into the processes that underlie maize yield and quality under high-temperature conditions.

Development of a Large-Eddy Simulation Methodology for the Analysis of Cycle-to-Cycle Combustion Variability of a Lean Burn Engine

Ultra-lean burn conditions (λ > 1.8) is seen as a way for improving efficiency and reducing emissions of spark-ignition engines. It raises fundamental issues in terms of combustion physics and its modeling, among which the significant reduction of the laminar flame speeds and increase of the laminar flame thickness, as well as an increased sensitivity to local fuel/air equivalence ratio variations are essential to be accounted for as compared to conventional stoichiometric mixture conditions. In particular, the effects of the modified laminar flame characteristics on flame stretch during the early flame development in a spark ignited gasoline engine can be expected to become of importance. In the present work, a Large-Eddy Simulation combustion approach is presented and applied to the study of the cycle-to-cycle combustion variations of a direct injection gasoline engine operating both in stoichiometric and ultra-lean burn conditions. The Coherent Flame Model approach is used and enriched via a correlation for the laminar flame velocity accounting for nonlinear stretch effects. The stretched flame calculations are validated against experimental results. Then, different engine operating points are computed in stoichiometric and ultra-lean burn conditions assessing the capacity of the approach to reproduce variations of combustion regimes. The results are analyzed in terms of cycle-to-cycle combustion variabilities and the influence of the spark-plug orientation is studied. Finally, a detailed analysis of the flame development is presented with a particular emphasis on the analysis of the initial flame kernel development accounting for stretch effects in lean conditions and the analysis of extreme cycles in lean burn. A strong reduction of the flame velocity by one third was observed for lean-burn conditions due to non-linear stretch effects occurring during the early stage of the flame development while almost no change was observed for stoichiometric conditions. Moreover, the proposed approach was capable of handling the various conditions featuring significantly different combustion regimes (one order of magnitude for the Karlovitz number) with only a minor change in the model parameterization.

Expression analysis of β-carotene hydroxylase1 and opaque2 genes governing accumulation of provitamin-A, lysine and tryptophan during kernel development in biofortified sweet corn.

Traditional sweet corn possesses low levels of provitamin-A (proA), lysine and tryptophan. Mutant version of β-carotene hydroxylase1 (crtRB1) gene affecting the accumulation of β-carotene (BC), β-cryptoxanthin (BCX) and proA, and opaque2 (o2) gene governing the enhancement of lysine and tryptophan were introgressed together into elite sweet corn inbreds through marker-assisted selection. Here, we analyzed the expression pattern of crtRB1 and o2 genes among introgressed and traditional sweet corn inbreds at 20-, 24- and 28-days after pollination (DAP). The introgressed inbreds possessed two- to sevenfolds higher BC, BCX, proA, lysine and tryptophan compared to their original inbreds. However, all the nutrients attained the peak at 20-DAP (BC: 9.95µg/g, BCX: 8.21µg/g, proA: 14.05µg/g, lysine: 0.301%, tryptophan: 0.074%), which gradually reduced through 24-DAP (BC: 8.24µg/g, BCX: 7.53µg/g, proA: 12.01µg/g, lysine: 0.273%, tryptophan: 0.057%) and 28-DAP (BC: 5.84µg/g, BCX: 5.82µg/g, proA: 8.75µg/g, lysine: 0.202%, tryptophan: 0.037%). Biofortified sweet corn inbreds possessed significantly lower expression levels of crtRB1 (4.1-fold) and o2 (2.2-fold) compared to their wild type alleles in traditional sweet corn inbreds across DAPs. The expression of crtRB1 and o2 increased from 20-DAP to attain the highest peak at 24-DAP, and further decreased by 28-DAP. The transcript levels of crtRB1 were negatively correlated with BC (r = - 0.83), BCX (r = - 0.79) and proA (r = - 0.83) across dates of harvest. Lysine (r = - 0.83) and tryptophan (r = - 0.73) were also inversely associated with o2 transcript levels. This is the first report on expression of crtRB1 and o2 genes during kernel development in biofortified sweet corn. This information holds immense promise in understanding the dynamics of gene-regulation during kernel development in sweet corn.

A C-terminal encoded peptide, ZmCEP1, is essential for kernel development in maize.

C-terminal encoded peptides (CEPs) are peptide hormones which act as mobile signals coordinating important developmental programs. Previous studies have unraveled that CEPs are able to regulate plant growth and abiotic stress via cell-to-cell communication in Arabidopsis and rice; however, little is known about their roles in maize. Here, we examined the spatiotemporal expression pattern of ZmCEP1 and showed that ZmCEP1 is highly expressed in young ears and tassels of maize, particularly in the vascular bundles of ears. Heterologous expression of ZmCEP1 in Arabidopsis results in smaller plants and seed size. Similarly, overexpression of ZmCEP1 in maize decreased the plant and ear height, ear length, kernel size, and 100-kernel weight. Consistently, exogenous application of the synthesized ZmCEP1 peptide to the roots of Arabidopsis and maize inhibited root elongation. Knock-out of ZmCEP1 through CRISPR/Cas9 significantly increased plant and ear height, kernel size and 100-kernel weight. Transcriptome analysis revealed that knock-out of ZmCEP1 up-regulated a subset of genes involved in nitrogen metabolism, nitrate transport, sugar transport and auxin response. Thus, these results provide new insights into the genetic and molecular function of ZmCEP1 in regulating kernel development and plant growth, providing novel opportunities for maize breeding.

Genetic Mapping and Validation of Loci for Kernel-Related Traits in Wheat (Triticum aestivum L.).

Kernel size (KS) and kernel weight play a key role in wheat yield. Phenotypic data from six environments and a Wheat55K single-nucleotide polymorphism array–based constructed genetic linkage map from a recombinant inbred line population derived from the cross between the wheat line 20828 and the line SY95-71 were used to identify quantitative trait locus (QTL) for kernel length (KL), kernel width (KW), kernel thickness (KT), thousand-kernel weight (TKW), kernel length–width ratio (LWR), KS, and factor form density (FFD). The results showed that 65 QTLs associated with kernel traits were detected, of which the major QTLs QKL.sicau-2SY-1B, QKW.sicau-2SY-6D, QKT.sicau-2SY-2D, and QTKW.sicau-2SY-2D, QLWR.sicau-2SY-6D, QKS.sicau-2SY-1B/2D/6D, and QFFD.sicau-2SY-2D controlling KL, KW, KT, TKW, LWR, KS, and FFD, and identified in multiple environments, respectively. They were located on chromosomes 1BL, 2DL, and 6DS and formed three QTL clusters. Comparison of genetic and physical interval suggested that only QKL.sicau-2SY-1B located on chromosome 1BL was likely a novel QTL. A Kompetitive Allele Specific Polymerase chain reaction (KASP) marker, KASP-AX-109379070, closely linked to this novel QTL was developed and used to successfully confirm its effect in two different genetic populations and three variety panels consisting of 272 Chinese wheat landraces, 300 Chinese wheat cultivars most from the Yellow and Huai River Valley wheat region, and 165 Sichuan wheat cultivars. The relationships between kernel traits and other agronomic traits were detected and discussed. A few predicted genes involved in regulation of kernel growth and development were identified in the intervals of these identified major QTL. Taken together, these stable and major QTLs provide valuable information for understanding the genetic composition of kernel yield and provide the basis for molecular marker–assisted breeding.

Maize ATR safeguards genome stability during kernel development to prevent early endosperm endocycle onset and cell death.

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.

Heterologous expression of ZmGS5 enhances organ size and seed weight by regulating cell expansion in Arabidopsis thaliana.

Maize ZmGS5 was reported to be positively associated with kernel-related traits, however, its regulatory mechanism on plant development and seed size remains unknown. In this study, ZmGS5 was demonstrated to be widely expressed in various maize tissues with the highest expression level in developing embryos, indicating its critical roles in early kernel development process. The ZmGS5 protein was subcellularly localized to both the nucleus and cytoplasm. Transgenic Arabidopsis plants overexpressing ZmGS5 under the control of either the constitutive maize Ubiquitin1 promotor or native ZmGS5 promoter resulted in increased plant size, biomass, seed size and weight, although no significant difference was observed between transgenic lines harboring the two constructs. In contrast, the antisense-ZmGS5 transgene resulted in opposite phenotypes. Our cytological data suggested that ZmGS5 enlarged petal size through enhancing cell expansion. Quantitative RT-PCR analysis indicated that ZmGS5 might enhance cell expansion and grain filling by upregulating expression levels of particular EXPA or SWEET genes. Collectively, these findings help us further understand the biological function and regulatory mechanism of ZmGS5 in improving organ size and seed weight, which imply its great potential for high-yield breeding in the future.

Knl1 participates in spindle assembly checkpoint signaling in maize

The Knl1-Mis12-Ndc80 (KMN) network is an essential component of the kinetochore-microtubule attachment interface, which is required for genomic stability in eukaryotes. However, little is known about plant Knl1 proteins because of their complex evolutionary history. Here, we cloned the Knl1 homolog from maize (Zea mays) and confirmed it as a constitutive central kinetochore component. Functional assays demonstrated their conserved role in chromosomal congression and segregation during nuclear division, thus causing defective cell division during kernel development when Knl1 transcript was depleted. A 145 aa region in the middle of maize Knl1, that did not involve the MELT repeats, was associated with the interaction of spindle assembly checkpoint (SAC) components Bub1/Mad3 family proteins 1 and 2 (Bmf1/2) but not with the Bmf3 protein. They may form a helical conformation with a hydrophobic interface with the TPR domain of Bmf1/2, which is similar to that of vertebrates. However, this region detected in monocots shows extensive divergence in eudicots, suggesting that distinct modes of the SAC to kinetochore connection are present within plant lineages. These findings elucidate the conserved role of the KMN network in cell division and a striking dynamic of evolutionary patterns in the SAC signaling and kinetochore network.

Proteomic analysis of ubiquitinated proteins in maize immature kernels

Protein ubiquitination is a dynamic post-translational modification involved in various biological processes in eukaryotes. To understand the function of ubiquitinated proteins in maize kernels, we used the specific K-GG antibody coupled with high-resolution LC-MS/MS to identify the ubiquitinated proteins in maize immature kernels. A total of 1999 lysine ubiquitination sites in 881 proteins were identified in maize kernels. Eight conserved ubiquitination motifs included KubD, GKub, EKub, KubXXXE, AKub, NXKub, KubXXXXXN, and KKub were found in ubiquitinated peptides. The ubiquitinated lysine neighborhoods are more frequently presented in ordered structures. Go and KEGG analysis showed the proteins involved in carbohydrate metabolism and protein processing were identified to be the targets of lysine ubiquitination. Other proteins, which related to RNA transport, spliceosome, endocytosis, ubiquitin-mediated proteolysis, proteasome, and MAPK signaling, were also found to be ubiquitinated. Protein–protein interaction network and KEGG analysis indicated that protein ubiquitination plays a major role in regulating many cellular processes and modulating diverse interactions in maize kernel development. The identification of the 881 ubiquitinated proteins in maize kernels provides a foundation for understanding the physiological roles of these ubiquitinated proteins. Our finding also provides a new insight view into the function of ubiquitinated proteins involved in maize kernel development. SignificanceWe reported here the comprehensive proteomic analysis of the ubiquitin-modified proteome in maize kernel. We found that there are some new characteristics of them in ubiquitome of maize immature kernels. The results suggested that protein ubiquitination, as a post-translation modification, plays an essential role in regulating many cellular processes in maize kernel development. This study expands our knowledge on the regulatory roles and mechanisms of protein ubiquitination in maize.and other plants.

Proteomic analysis of metabolic mechanisms associated with fatty acid biosynthesis during Styrax tonkinensis kernel development.

Styrax tonkinensis is a white-flowered tree with considerable potential as a feedstock source for biodiesel production from the oily seed contained within its nutlike drupes. Transcriptome changes during oil accumulation have been previously reported, but not concurrent changes in the proteome. Using proteomic analysis of samples collected at 50, 70, 100 and 130 days after flowering (DAF), we identified 1472 differentially expressed proteins (DEPs). Based on their expression patterns, we grouped the DEPs into nine clusters and analyzed the pathway enrichment. Proteins related to starch and sucrose metabolism were most abundant at 50 DAF. Proteins involved in fatty acid (FA) biosynthesis were mainly grouped into a cluster that peaked at 70 DAF. Proteins related to protein processing in endoplasmic reticulum had two major patterns, trending either upwards or downwards, while proteins involved in amino acid biosynthesis showed more complex relationships. We identified 42 key enzymes involved in lipid accumulation during kernel development, including the acetyl-CoA carboxylase complex (ACC) and the pyruvate dehydrogenase complex (PDC). One oil body membrane protein, oleosin, continuously increased during kernel development. A regulatory network of oil accumulation processes was built based on protein and available transcriptome expression data, which were in good temporal agreement. This analysis placed ACC and PDC in the center of the network, suggesting that the glycolytic provision of substrate plays a central regulatory role in FA biosynthesis and oil accumulation. © 2021 Society of Chemical Industry.

Transcriptomic analysis of \u03b1-linolenic acid content and biosynthesis in Paeonia ostii fruits and seeds

BackgroundPaeonia ostii is a potentially important oilseed crop because its seed yield is high, and the seeds are rich in α-linolenic acid (ALA). However, the molecular mechanisms underlying ALA biosynthesis during seed kernel, seed testa, and fruit pericarp development in this plant are unclear. We used transcriptome data to address this knowledge gap.ResultsGas chromatograph-mass spectrometry indicated that ALA content was highest in the kernel, moderate in the testa, and lowest in the pericarp. Therefore, we used RNA-sequencing to compare ALA synthesis among these three tissues. We identified 227,837 unigenes, with an average length of 755 bp. Of these, 1371 unigenes were associated with lipid metabolism. The fatty acid (FA) biosynthesis and metabolism pathways were significantly enriched during the early stages of oil accumulation in the kernel. ALA biosynthesis was significantly enriched in parallel with increasing ALA content in the testa, but these metabolic pathways were not significantly enriched during pericarp development. By comparing unigene transcription profiles with patterns of ALA accumulation, specific unigenes encoding crucial enzymes and transcription factors (TFs) involved in de novo FA biosynthesis and oil accumulation were identified. Specifically, the bell-shaped expression patterns of genes encoding SAD, FAD2, FAD3, PDCT, PDAT, OLE, CLE, and SLE in the kernel were similar to the patterns of ALA accumulation in this tissue. Genes encoding BCCP, BC, KAS I– III, and FATA were also upregulated during the early stages of oil accumulation in the kernel. In the testa, the upregulation of the genes encoding SAD, FAD2, and FAD3 was followed by a sharp increase in the concentrations of ALA. In contrast, these genes were minimally expressed (and ALA content was low) throughout pericarp development.ConclusionsWe used three tissues with high, moderate, and low ALA concentrations as an exemplar system in which to investigate tissue-specific ALA accumulation mechanisms in P. ostii. The genes and TFs identified herein might be useful targets for future studies of ALA accumulation in the tree peony. This study also provides a framework for future studies of FA biosynthesis in other oilseed plants.

Small kernel 501 (smk501) encodes the RUBylation activating enzyme E1 subunit ECR1 (E1 C-TERMINAL RELATED 1) and is essential for multiple aspects of cellular events during kernel development in maize.

RUBylation plays essential roles in plant growth and development through regulating Cullin-RING ubiquitin E3 ligase (CRL) activities and the CRL-mediated protein degradations. However, the function of RUBylation in regulating kernel development remains unclear. Through genetic and molecular analyses of a small kernel 501 (smk501) mutant in maize (Zea mays), we cloned the smk501 gene, revealed its molecular function, and defined its roles in RUBylation pathway and seed development. Smk501 encodes a RUBylation activating enzyme E1 subunit ZmECR1 (E1 C-TERMINAL RELATED 1) protein. Destruction in RUBylation by smk501 mutation resulted in less embryo and endosperm cell number and smaller kernel size. The transcriptome and proteome profiling, hormone evaluation and cell proliferation observation revealed that disturbing ZmECR1 expression mainly affects pathways on hormone signal transduction, cell cycle progression and starch accumulation during kernel development. In addition, mutant in zmaxr1 (Auxin resistant 1), another RUB E1 subunit, also showed similar defects in kernel development. Double mutation of zmecr1 and zmaxr1 lead to empty pericarp kernel phenotype. RUBylation is a novel regulatory pathway affecting maize kernel development, majorly through its functions in modifying multiple cellular progresses.

Association Mapping and Transcriptome Analysis Reveal the Genetic Architecture of Maize Kernel Size

Kernel length, kernel width, and kernel thickness are important traits affecting grain yield and product quality. Here, the genetic architecture of the three kernel size traits was dissected in an association panel of 309 maize inbred lines using four statistical methods. Forty-two significant single nucleotide polymorphisms (SNPs; p < 1.72E-05) and 70 genes for the three traits were identified under five environments. One and eight SNPs were co-detected in two environments and by at least two methods, respectively, and they explained 5.87–9.59% of the phenotypic variation. Comparing the transcriptomes of two inbred lines with contrasting seed size, three and eight genes identified in the association panel showed significantly differential expression between the two genotypes at 15 and 39 days after pollination, respectively. Ten and 17 genes identified by a genome-wide association study were significantly differentially expressed between the two development stages in the two genotypes. Combining environment−/method-stable SNPs and differential expression analysis, ribosomal protein L7, jasmonate-regulated gene 21, serine/threonine-protein kinase RUNKEL, AP2-EREBP-transcription factor 16, and Zm00001d035222 (cell wall protein IFF6-like) were important candidate genes for maize kernel size and development.

Gibberellin induced transcription factor bZIP53 regulates CesA1 expression in maize kernels.

Proper development of the maize kernel is of great significance for high and stable maize yield to ensure national food security. Gibberellin (GA), one of the hormones regulating plant growth, is involved in modulating the development of maize kernels. Cellulose, one of the main components of plant cells, is also regulated by gibberellin. The mechanism of hormone regulation during maize grain development is highly complicated, and reports on GA-mediated modulation of cellulose synthesis during maize grain development are rare. Our study revealed that during grain growth and development, the grain length and bulk density of GA-treated corn kernels improved significantly, and the cellulose content of grains increased, while seed coat thickness decreased. The transcription factor basic region/leucine zipper motif 53 (bZIP53), which is strongly correlated with cellulose synthase gene 1 (CesA1) expression, was screened by transcriptome sequencing and the expression of the cellulose synthase gene in maize grain development after GA treatment was determined. It was found that bZIP53 expression significantly promoted the expression of CesA1. Further, analysis of the transcription factor bZIP53 determined that the gene-encoded protein was localized in the cell and nuclear membranes, but the transcription factor bZIP53 itself showed no transcriptional activation. Further studies are required to explore the interaction of bZIP53 with CesA1.