Control of sexuality by the sk1-encoded UDP-glycosyltransferase of maize

Silkless1 gene in maize: development and validation of the gene-based markers for breeding silkless baby corn

BACKGROUND

The role of the silkless1 (sk1) gene in developing silkless baby corn, a distinctive trait in maize has been investigated. So far, no sk1 gene-specific marker has been available for accelerated development of silkless baby corn hybrids.

METHODS & RESULTS

We developed sk1 gene-based markers and validated them in backcross (BC) and F2 segregating generations, revealing a polymorphic marker corresponding to a silkless phenotype. Among all the developed markers, the MGU_sk1-1 marker (141 bp size in sk1-mutant allele) validated its association with the silkless trait. The chi square (χ2) analysis revealed that the segregation of alleles Sk1Sk1 (219): Sk1sk1 (414): sk1sk1 (188) is as per the Mendelian ratio (1:2:1) in the F2 population. In 821 F2 plants, we found a 3:1 phenotypic ratio among the population with silked (633) and silkless (188) plants. We studied 349 BC plants and found a 1:1 phenotypic ratio between silked and silkless plants, as well as a genotypic ratio (1:1) between heterozygotes (Sk1sk1) and homozygous recessives (sk1sk1). Additionally, double mutants (sk1sk1/ts1ts1 and sk1sk1/ts2ts2) were identified using the sk1-based marker.

CONCLUSIONS

This study is the first to show the practical use of sk1 gene in marker-assisted selection (MAS). This research also reports the development of novel genetic resources for innovative silkless baby corn breeding.

Hormonal influence on maize inflorescence development and reproduction

KEY MESSAGE

Different plant hormones contribute to maize reproductive success. Maize is a major crop species and significantly contributes directly and indirectly to human calorie uptake. Its success can be mainly attributed to its unisexual inflorescences, the tassel and the ear, whose formation is regulated by complex genetic and hormonal networks, and is influenced by environmental cues such as temperature, and nutrient and water availability. Traditional genetic analysis of classic developmental mutants, together with new molecular approaches, have shed light on many crucial aspects of maize reproductive development including the influence that phytohormones exert on key developmental steps leading to successful reproduction and seed yield. Here we will review both historical and recent findings concerning the main roles that phytohormones play in maize reproductive development, from the commitment to reproductive development to sexual reproduction.

Progressive meristem and single-cell transcriptomes reveal the regulatory mechanisms underlying maize inflorescence development and sex differentiation

Maize develops separate ear and tassel inflorescences with initially similar morphology but ultimately different architecture and sexuality. The detailed regulatory mechanisms underlying these changes still remain largely unclear. In this study, through analyzing the time-course meristem transcriptomes and floret single-cell transcriptomes of ear and tassel, we revealed the regulatory dynamics and pathways underlying inflorescence development and sex differentiation. We identified 16 diverse gene clusters with differential spatiotemporal expression patterns and revealed biased regulation of redox, programmed cell death, and hormone signals during meristem differentiation between ear and tassel. Notably, based on their dynamic expression patterns, we revealed the roles of two RNA-binding proteins in regulating inflorescence meristem activity and axillary meristem formation. Moreover, using the transcriptional profiles of 53 910 single cells, we uncovered the cellular heterogeneity between ear and tassel florets. We found that multiple signals associated with either enhanced cell death or reduced growth are responsible for tassel pistil suppression, while part of the gibberellic acid signal may act non-cell-autonomously to regulate ear stamen arrest during sex differentiation. We further showed that the pistil-protection gene SILKLESS 1 (SK1) functions antagonistically to the known pistil-suppression genes through regulating common molecular pathways, and constructed a regulatory network for pistil-fate determination. Collectively, our study provides a deep understanding of the regulatory mechanisms underlying inflorescence development and sex differentiation in maize, laying the foundation for identifying new regulators and pathways for maize hybrid breeding and improvement.

Factors specifying sex determination in maize

Plant architecture is an important feature for agronomic performance in crops. In maize, which is a monoecious plant, separation of floral organs to produce specific gametes has been studied from different perspectives including genetic, biochemical and physiological. Maize mutants affected in floral organ development have been key to identifying genes, hormones and other factors like miRNAs important for sex determination. In this review, we describe floral organ formation in maize, representative mutants and genes identified with a function in establishing sexual identity either classified as feminizing or masculinizing, and its relationship with hormones associated with sexual organ identity as jasmonic acid, brassinosteroid and gibberellin. Finally, we discuss the challenges and scopes of future research in maize sex determination.

Genome-wide identification of ZmMYC2 binding sites and target genes in maize

BACKGROUND

Jasmonate (JA) is the important phytohormone to regulate plant growth and adaption to stress signals. MYC2, an bHLH transcription factor, is the master regulator of JA signaling. Although MYC2 in maize has been identified, its function remains to be clarified.

RESULTS

To understand the function and regulatory mechanism of MYC2 in maize, the joint analysis of DAP-seq and RNA-seq is conducted to identify the binding sites and target genes of ZmMYC2. A total of 3183 genes are detected both in DAP-seq and RNA-seq data, potentially as the directly regulating genes of ZmMYC2. These genes are involved in various biological processes including plant growth and stress response. Besides the classic cis-elements like the G-box and E-box that are bound by MYC2, some new motifs are also revealed to be recognized by ZmMYC2, such as nGCATGCAnn, AAAAAAAA, CACGTGCGTGCG. The binding sites of many ZmMYC2 regulating genes are identified by IGV-sRNA.

CONCLUSIONS

All together, abundant target genes of ZmMYC2 are characterized with their binding sites, providing the basis to construct the regulatory network of ZmMYC2 and better understanding for JA signaling in maize.

Large-scale single-cell profiling of stem cells uncovers redundant regulators of shoot development and yield trait variation

Stem cells in plant shoots are a rare population of cells that produce leaves, fruits and seeds, vital sources for food and bioethanol. Uncovering regulators expressed in these stem cells will inform crop engineering to boost productivity. Single-cell analysis is a powerful tool for identifying regulators expressed in specific groups of cells. However, accessing plant shoot stem cells is challenging. Recent single-cell analyses of plant shoots have not captured these cells, and failed to detect stem cell regulators like CLAVATA3 and WUSCHEL . In this study, we finely dissected stem cell-enriched shoot tissues from both maize and arabidopsis for single-cell RNA-seq profiling. We optimized protocols to efficiently recover thousands of CLAVATA3 and WUSCHEL expressed cells. A cross-species comparison identified conserved stem cell regulators between maize and arabidopsis. We also performed single-cell RNA-seq on maize stem cell overproliferation mutants to find additional candidate regulators. Expression of candidate stem cell genes was validated using spatial transcriptomics, and we functionally confirmed roles in shoot development. These candidates include a family of ribosome-associated RNA-binding proteins, and two families of sugar kinase genes related to hypoxia signaling and cytokinin hormone homeostasis. These large-scale single-cell profiling of stem cells provide a resource for mining stem cell regulators, which show significant association with yield traits. Overall, our discoveries advance the understanding of shoot development and open avenues for manipulating diverse crops to enhance food and energy security.

Striking a growth-defense balance: Stress regulators that function in maize development

Maize (Zea mays) cultivation is strongly affected by both abiotic and biotic stress, leading to reduced growth and productivity. It has recently become clear that regulators of plant stress responses, including the phytohormones abscisic acid (ABA), ethylene (ET), and jasmonic acid (JA), together with reactive oxygen species (ROS), shape plant growth and development. Beyond their well established functions in stress responses, these molecules play crucial roles in balancing growth and defense, which must be finely tuned to achieve high yields in crops while maintaining some level of defense. In this review, we provide an in-depth analysis of recent research on the developmental functions of stress regulators, focusing specifically on maize. By unraveling the contributions of these regulators to maize development, we present new avenues for enhancing maize cultivation and growth while highlighting the potential risks associated with manipulating stress regulators to enhance grain yields in the face of environmental challenges.

Genetic evidence that brassinosteroids suppress pistils in the maize tassel independent of the jasmonic acid pathway

The developmental genetics of reproductive structure control in maize must consider both the staminate florets of the tassel and the pistillate florets of the ear synflorescences. Pistil abortion takes place in the tassel florets, and stamen arrest is affected in ear florets to give rise to the monoecious nature of maize. Gibberellin (GA) deficiency results in increased tillering, a dwarfed plant syndrome, and the retention of anthers in the ear florets of maize. The silkless1 mutant results in suppression of silks in the ear. We demonstrate in this study that jasmonic acid (JA) and GA act independently and show additive phenotypes resulting in androecious dwarf1;silkless1 double mutant plants. The persistence of pistils in the tassel can be induced by multiple mechanisms, including JA deficiency, GA excess, genetic control of floral determinacy, and organ identity. The silkless1 mutant can suppress both silks in the ear and the silks in the tassel of JA-deficient and AP2 transcription factor tasselseed mutants. We previously demonstrated that GA production was required for brassinosteroid (BR) deficiency to affect persistence of pistils in the tassel. We find that BR deficiency affects pistil persistence by an independent mechanism from the silkless1 mutant and JA pathway. The silkless1 mutant did not prevent the formation of pistils in the tassel by nana plant2 in double mutants. In addition, we demonstrate that there is more to the silkless1 mutant than just a suppression of pistil growth. We document novel phenotypes of silkless1 mutants including weakly penetrant ear fasciation and anther persistence in the ear florets. Thus, the JA/AP2 mechanism of pistil retention in the tassel and silk growth in the ear are similarly sensitive to loss of the SILKLESS1 protein, while the BR/GA mechanism is not.

Novel insights into maize (Zea mays) development and organogenesis for agricultural optimization

In maize, intrinsic hormone activities and sap fluxes facilitate organogenesis patterning and plant holistic development; these hormone movements should be a primary focus of developmental biology and agricultural optimization strategies. Maize (Zea mays) is an important crop plant with distinctive life history characteristics and structural features. Genetic studies have extended our knowledge of maize developmental processes, genetics, and molecular ecophysiology. In this review, the classical life cycle and life history strategies of maize are analyzed to identify spatiotemporal organogenesis properties and develop a definitive understanding of maize development. The actions of genes and hormones involved in maize organogenesis and sex determination, along with potential molecular mechanisms, are investigated, with findings suggesting central roles of auxin and cytokinins in regulating maize holistic development. Furthermore, investigation of morphological and structural characteristics of maize, particularly node ubiquity and the alternate attachment pattern of lateral organs, yields a novel regulatory model suggesting that maize organ initiation and subsequent development are derived from the stimulation and interaction of auxin and cytokinin fluxes. Propositions that hormone activities and sap flow pathways control organogenesis are thoroughly explored, and initiation and development processes of distinctive maize organs are discussed. Analysis of physiological factors driving hormone and sap movement implicates cues of whole-plant activity for hormone and sap fluxes to stimulate maize inflorescence initiation and organ identity determination. The physiological origins and biogenetic mechanisms underlying maize floral sex determination occurring at the tassel and ear spikelet are thoroughly investigated. The comprehensive outline of maize development and morphogenetic physiology developed in this review will enable farmers to optimize field management and will provide a reference for de novo crop domestication and germplasm improvement using genome editing biotechnologies, promoting agricultural optimization.

The power of classic maize mutants: Driving forward our fundamental understanding of plants

Since Mendel, maize has been a powerhouse of fundamental genetics research. From testing the Mendelian laws of inheritance, to the first genetic and cytogenetic maps, to the use of whole-genome sequencing data for crop improvement, maize is at the forefront of genetics advances. Underpinning much of this revolutionary work are the classic morphological mutants; the "freaks" that stood out in the field to even the untrained eye. Here we review some of these classic developmental mutants and their importance in the history of genetics, as well as their key role in our fundamental understanding of plant development.

GIF1 controls ear inflorescence architecture and floral development by regulating key genes in hormone biosynthesis and meristem determinacy in maize

BACKGROUND

Inflorescence architecture and floral development in flowering plants are determined by genetic control of meristem identity, determinacy, and maintenance. The ear inflorescence meristem in maize (Zea mays) initiates short branch meristems called spikelet pair meristems, thus unlike the tassel inflorescence, the ears lack long branches. Maize growth-regulating factor (GRF)-interacting factor1 (GIF1) regulates branching and size of meristems in the tassel inflorescence by binding to Unbranched3. However, the regulatory pathway of gif1 in ear meristems is relatively unknown.

RESULT

In this study, we found that loss-of-function gif1 mutants had highly branched ears, and these extra branches repeatedly produce more branches and florets with unfused carpels and an indeterminate floral apex. In addition, GIF1 interacted in vivo with nine GRFs, subunits of the SWI/SNF chromatin-remodeling complex, and hormone biosynthesis-related proteins. Furthermore, key meristem-determinacy gene RAMOSA2 (RA2) and CLAVATA signaling-related gene CLV3/ENDOSPERM SURROUNDING REGION (ESR) 4a (CLE4a) were directly bound and regulated by GIF1 in the ear inflorescence.

CONCLUSIONS

Our findings suggest that GIF1 working together with GRFs recruits SWI/SNF chromatin-remodeling ATPases to influence DNA accessibility in the regions that contain genes involved in hormone biosynthesis, meristem identity and determinacy, thus driving the fate of axillary meristems and floral organ primordia in the ear-inflorescence of maize.

Ectopic Expression of the Transcriptional Regulator silky3 Causes Pleiotropic Meristem and Sex Determination Defects in Maize Inflorescences

Maize (Zea mays) is a monoecious plant, in which inflorescence morphogenesis involves complicated molecular regulatory mechanisms. Although many related genes have been cloned, our understanding of the molecular mechanism underlying maize inflorescence development remains limited. Here, we identified a maize semi-dominant mutant Silky3 (Si3), which displays pleiotropic defects during inflorescence development, including loss of determinacy and identity in meristems and floral organs, as well as the sexual transformation of tassel florets. We cloned the si3 gene using a map-based approach. Functional analysis reveals that SI3 is a nuclear protein and may act as a transcriptional regulator. Transcriptome analysis reveals that the ectopic expression of si3 strongly represses multiple biological processes, especially the flower development pathways. RNA in situ hybridization similarly shows that the expression patterns of genes responsible for flower development are changed in the Si3 mutant. In addition, the homeostasis of jasmonic acid and gibberellic acid are altered in the Si3 young tassels, and application of exogenous jasmonic acid can rescue the sex reversal phenotype of Si3 The defects we characterized in various regulatory pathways can explain the complex phenotypes of Si3 mutant, and this study deepens our knowledge of maize inflorescence development.

3D genome architecture coordinates trans and cis regulation of differentially expressed ear and tassel genes in maize

BACKGROUND

Maize ears and tassels are two separate types of inflorescence which are initiated by similar developmental processes but gradually develop distinct architectures. However, coordinated trans and cis regulation of differentially expressed genes determining ear and tassel architecture within the 3D genome context is largely unknown.

RESULTS

We identify 56,055 and 52,633 open chromatin regions (OCRs) in developing maize ear and tassel primordia using ATAC-seq and characterize combinatorial epigenome features around these OCRs using ChIP-seq, Bisulfite-seq, and RNA-seq datasets. Our integrative analysis of coordinated epigenetic modification and transcription factor binding to OCRs highlights the cis and trans regulation of differentially expressed genes in ear and tassel controlling inflorescence architecture. We further systematically map chromatin interactions at high-resolution in corresponding tissues using in situ digestion-ligation-only Hi-C (DLO Hi-C). The extensive chromatin loops connecting OCRs and genes provide a 3D view on cis- and trans-regulatory modules responsible for ear- and tassel-specific gene expression. We find that intergenic SNPs tend to locate in distal OCRs, and our chromatin interaction maps provide a potential mechanism for trait-associated intergenic SNPs that may contribute to phenotypic variation by influencing target gene expression through chromatin loops.

CONCLUSIONS

Our comprehensive epigenome annotations and 3D genome maps serve as valuable resource and provide a deep understanding of the complex regulatory mechanisms of genes underlying developmental and morphological diversities between maize ear and tassel.

Peroxisomes: versatile organelles with diverse roles in plants

Peroxisomes are small, ubiquitous organelles that are delimited by a single membrane and lack genetic material. However, these simple-structured organelles are highly versatile in morphology, abundance and protein content in response to various developmental and environmental cues. In plants, peroxisomes are essential for growth and development and perform diverse metabolic functions, many of which are carried out coordinately by peroxisomes and other organelles physically interacting with peroxisomes. Recent studies have added greatly to our knowledge of peroxisomes, addressing areas such as the diverse proteome, regulation of division and protein import, pexophagy, matrix protein degradation, solute transport, signaling, redox homeostasis and various metabolic and physiological functions. This review summarizes our current understanding of plant peroxisomes, focusing on recent discoveries. Current problems and future efforts required to better understand these organelles are also discussed. An improved understanding of peroxisomes will be important not only to the understanding of eukaryotic cell biology and metabolism, but also to agricultural efforts aimed at improving crop performance and defense.

Epigenetic aspects of floral homeotic genes in relation to sexual dimorphism in the dioecious plant Mercurialis annua

In plants, dioecy characterizes species that carry male and female flowers on separate plants and it occurs in about 6% of angiosperms; however, the molecular mechanisms that underlie dioecy are essentially unknown. The ability for sex-reversal by hormone application raises the hypothesis that the genes required for the expression of both sexes are potentially functional but are regulated by epigenetic means. In this study, proteomic analysis of nuclear proteins isolated from flower buds of females, males, and feminized males of the dioecious plant Mercurialis annua revealed differential expression of nuclear proteins that are implicated in chromatin structure and function, including floral homeotic proteins. Focusing on floral genes, we found that class B genes were mainly expressed in male flowers, while class D genes, as well as SUPERMAN-like genes, were mainly expressed in female flowers. Cytokinin-induced feminization of male plants was associated with down-regulation of male-specific genes concomitantly with up-regulation of female-specific genes. No correlation was found between the expression of class B and D genes and the changes in DNA methylation or chromatin conformation of these genes. Thus, we could not confirm DNA methylation or chromatin conformation of floral genes to be the major determinant regulating sexual dimorphisms. Instead, determination of sex in M. annua might be controlled upstream of floral genes by one or more sex-specific factors that affect hormonal homeostasis. A comprehensive model is proposed for sex-determination in M. annua.

Peroxisomes in plant reproduction and seed-related development

Peroxisomes are small multi-functional organelles essential for plant development and growth. Plant peroxisomes play various physiological roles, including phytohormone biosynthesis, lipid catabolism, reactive oxygen species metabolism and many others. Mutant analysis demonstrated key roles for peroxisomes in plant reproduction, seed development and germination and post-germinative seedling establishment; however, the underlying mechanisms remain to be fully elucidated. This review summarizes findings that reveal the importance and complexity of the role of peroxisomes in the pertinent processes. The β-oxidation pathway plays a central role, whereas other peroxisomal pathways are also involved. Understanding the biochemical and molecular mechanisms of these peroxisomal functions will be instrumental to the improvement of crop plants.

Tasselseed5 overexpresses a wound-inducible enzyme, ZmCYP94B1, that affects jasmonate catabolism, sex determination, and plant architecture in maize

Maize is monecious, with separate male and female inflorescences. Maize flowers are initially bisexual but achieve separate sexual identities through organ arrest. Loss-of-function mutants in the jasmonic acid (JA) pathway have only female flowers due to failure to abort silks in the tassel. Tasselseed5 (Ts5) shares this phenotype but is dominant. Positional cloning and transcriptomics of tassels identified an ectopically expressed gene in the CYP94B subfamily, Ts5 (ZmCYP94B1). CYP94B enzymes are wound inducible and inactivate bioactive jasmonoyl-L-isoleucine (JA-Ile). Consistent with this result, tassels and wounded leaves of Ts5 mutants displayed lower JA and JA-lle precursors and higher 12OH-JA-lle product than the wild type. Furthermore, many wounding and jasmonate pathway genes were differentially expressed in Ts5 tassels. We propose that the Ts5 phenotype results from the interruption of JA signaling during sexual differentiation via the upregulation of ZmCYP94B1 and that its proper expression maintains maize monoecy.

Physiological and iTRAQ-based proteomic analyses reveal the function of exogenous γ-aminobutyric acid (GABA) in improving tea plant (Camellia sinensis L.) tolerance at cold temperature

BACKGROUND

Internal γ-Aminobutyric Acid (GABA) interacting with stress response substances may be involved in the regulation of differentially abundant proteins (DAPs) associated with optimum temperature and cold stress in tea plants (Camellia sinensis (L.) O. Kuntze).

RESULTS

Tea plants supplied with or without 5.0 mM GABA were subjected to optimum or cold temperatures in this study. The increased GABA level induced by exogenous GABA altered levels of stress response substances - such as glutamate, polyamines and anthocyanins - in association with improved cold tolerance. Isobaric tags for relative and absolute quantification (iTRAQ) - based DAPs were found for protein metabolism and nucleotide metabolism, energy, amino acid transport and metabolism other biological processes, inorganic ion transport and metabolism, lipid metabolism, carbohydrate transport and metabolism, biosynthesis of secondary metabolites, antioxidant and stress defense.

CONCLUSIONS

The iTRAQ analysis could explain the GABA-induced physiological effects associated with cold tolerance in tea plants. Analysis of functional protein-protein networks further showed that alteration of endogenous GABA and stress response substances induced interactions among photosynthesis, amino acid biosynthesis, and carbon and nitrogen metabolism, and the corresponding differences could contribute to improved cold tolerance of tea plants.

Jasmonates: News on Occurrence, Biosynthesis, Metabolism and Action of an Ancient Group of Signaling Compounds

: Jasmonic acid (JA) and its related derivatives are ubiquitously occurring compounds of land plants acting in numerous stress responses and development. Recent studies on evolution of JA and other oxylipins indicated conserved biosynthesis. JA formation is initiated by oxygenation of α-linolenic acid (α-LeA, 18:3) or 16:3 fatty acid of chloroplast membranes leading to 12-oxo-phytodienoic acid (OPDA) as intermediate compound, but in Marchantiapolymorpha and Physcomitrellapatens, OPDA and some of its derivatives are final products active in a conserved signaling pathway. JA formation and its metabolic conversion take place in chloroplasts, peroxisomes and cytosol, respectively. Metabolites of JA are formed in 12 different pathways leading to active, inactive and partially active compounds. The isoleucine conjugate of JA (JA-Ile) is the ligand of the receptor component COI1 in vascular plants, whereas in the bryophyte M. polymorpha COI1 perceives an OPDA derivative indicating its functionally conserved activity. JA-induced gene expressions in the numerous biotic and abiotic stress responses and development are initiated in a well-studied complex regulation by homeostasis of transcription factors functioning as repressors and activators.

Evolution of intron-poor clades and expression patterns of the glycosyltransferase family 47

A large-scale bioinformatics analysis revealed the origin and evolution of GT47 gene family, and identified two clades of intron-poor genes with putative functions in drought stress responses and seed development in maize. Glycosyltransferase family 47 (GT47) genes encode β-galactosyltransferases and β-glucuronyltransferases that synthesize pectin, xyloglucans and xylan, which are important components of the plant cell wall. In this study, we performed a systematic and large-scale bioinformatics analysis of GT47 gene family using 352 GT47 proteins from 15 species ranging from cyanobacteria to seed plants. The analysis results showed that GT47 family may originate in cyanobacteria and expand along the evolutionary trajectory to moss. Further analysis of 47 GT47 genes in maize revealed that they can divide into five clades with diverse exon-intron structures. Among these five clades, two were mainly composed with intron-poor genes, which may originate in the moss. Gene duplication analysis revealed that the expansion of GT47 gene family in maize was significantly driven from tandem duplication events and segmental duplication events. Significantly, almost all duplicated genes are intron-poor genes. Expression analysis indicated that several intron-poor GT47 genes may be involved in the drought stress response and seed development in maize. This work provides insight into the origin and evolutionary process, expansion mechanisms and expression patterns of GT47 genes, thus facilitating their functional investigations in the future.

Mapping and Functional Analysis of a Maize Silkless Mutant sk-A7110

The maize (Zea mays) stigma, which is commonly known as silk, is indispensable for reproduction and thus for grain yield. Here, we isolated a spontaneous mutant sk-A7110, which completely lacks silk; scanning electron microscopy showed that the sk-A7110 pistils degenerated during late floret differentiation. Genetic analysis confirmed that this trait was controlled by a recessive nuclear gene and sk-A7110 was mapped to a 74.13-kb region on chromosome 2 between the simple sequence repeat markers LA714 and L277. Sequence analysis of candidate genes in this interval identified a single-nucleotide insertion at position 569 downstream of the transcriptional start site in Zm00001d002970, which encodes a UDP-glycosyltransferase; this insertion produces a frameshift and premature translational termination. RNA-sequencing analysis of young ears identified 258 differentially expressed genes (DEGs) between sk-A7110 and the wild type (WT), including 119 up- and 139 down-regulated genes. Interestingly, most DEGs related to jasmonic acid (JA) synthesis were up-regulated in the mutant compared to WT. Consistent with this, the JA and JA-Isoleucine (JA-Ile) contents were significantly higher in sk-A7110 ears than in WT. At the same time, RNA-sequencing analysis of tassels showed that sk-A7110 could reduce the number of tassel branches in maize by down-regulating the expression of UB2 and UB3 genes. Our identification of the sk-A7110 mutant and the responsible gene will facilitate further studies on female infertility research or maize breeding.

Peroxisome Function, Biogenesis, and Dynamics in Plants

Recent advances highlight understanding of the diversity of peroxisome contributions to plant biology and the mechanisms through which these essential organelles are generated.

Maize network analysis revealed gene modules involved in development, nutrients utilization, metabolism, and stress response

BACKGROUND

The advent of big data in biology offers opportunities while poses challenges to derive biological insights. For maize, a large amount of publicly available transcriptome datasets have been generated but a comprehensive analysis is lacking.

RESULTS

We constructed a maize gene co-expression network based on the graphical Gaussian model, using massive RNA-seq data. The network, containing 20,269 genes, assembles into 964 gene modules that function in a variety of plant processes, such as cell organization, the development of inflorescences, ligules and kernels, the uptake and utilization of nutrients (e.g. nitrogen and phosphate), the metabolism of benzoxazionids, oxylipins, flavonoids, and wax, and the response to stresses. Among them, the inflorescences development module is enriched with domestication genes (like ra1, ba1, gt1, tb1, tga1) that control plant architecture and kernel structure, while multiple other modules relate to diverse agronomic traits. Contained within these modules are transcription factors acting as known or potential expression regulators for the genes within the same modules, suggesting them as candidate regulators for related biological processes. A comparison with an established Arabidopsis network revealed conserved gene association patterns for specific modules involved in cell organization, nutrients uptake & utilization, and metabolism. The analysis also identified significant divergences between the two species for modules that orchestrate developmental pathways.

CONCLUSIONS

This network sheds light on how gene modules are organized between different species in the context of evolutionary divergence and highlights modules whose structure and gene content can provide important resources for maize gene functional studies with application potential.