RESUMO
Land plants can grow to tremendous body sizes, yet even the most complex architectures are the result of iterations of the same developmental processes: organ initiation, growth, and pattern formation. A central question in plant biology is how these processes are regulated and coordinated to allow for the formation of ordered, 3D structures. All these elementary processes first occur in early embryogenesis, during which, from a fertilized egg cell, precursors for all major tissues and stem cells are initiated, followed by tissue growth and patterning. Here we discuss recent progress in our understanding of this phase of plant life. We consider the cellular basis for multicellular development in 3D and focus on the genetic regulatory mechanisms that direct specific steps during early embryogenesis.
Assuntos
Morfogênese , Sementes/embriologia , Padronização Corporal , Nicho de Células-TroncoRESUMO
The genetic control of the characteristic cell sizes of different species and tissues is a long-standing enigma. Plants are convenient for studying this question in a multicellular context, as their cells do not move and are easily tracked and measured from organ initiation in the meristems to subsequent morphogenesis and differentiation. In this article, we discuss cell size control in plants compared with other organisms. As seen from yeast cells to mammalian cells, size homeostasis is maintained cell autonomously in the shoot meristem. In developing organs, vacuolization contributes to cell size heterogeneity and may resolve conflicts between growth control at the cellular and organ levels. Molecular mechanisms for cell size control have implications for how cell size responds to changes in ploidy, which are particularly important in plant development and evolution. We also discuss comparatively the functional consequences of cell size and their potential repercussions at higher scales, including genome evolution.
Assuntos
Meristema/citologia , Células Vegetais/fisiologia , Ploidias , Tamanho Celular , Replicação do DNA , Células Eucarióticas/citologia , Meristema/crescimento & desenvolvimento , Mitose , Modelos Biológicos , Desenvolvimento Vegetal/genética , Leveduras/citologia , Leveduras/genéticaRESUMO
The formation of the plant body proceeds in a sequential post-embryonic manner through the action of meristems. Tightly coordinated meristem regulation is required for development and reproductive success, eventually determining yield in crop species. In maize (Zea mays), the RAMOSA1 ENHANCER LOCUS2 (REL2) family of transcriptional corepressors includes four members, REL2, RELK1 (REL2-LIKE1), RELK2, and RELK3. In a screen for rel2 enhancers, we identified shorter double mutants with enlarged ear inflorescence meristems (IMs) carrying mutations in RELK1. Expression and genetic analysis indicated that REL2 and RELK1 cooperatively regulate ear IM development by controlling genes involved in redox balance, hormone homeostasis, and differentiation, ultimately tipping the meristem toward an environment favorable to expanded expression of the ZmWUSCHEL1 gene, which encodes a key stem-cell promoting transcription factor. We further demonstrated that RELK genes have partially redundant yet diverse functions in the maintenance of various meristem types during development. By exploiting subtle increases in ear IM size in rel2 heterozygous plants, we also showed that extra rows of kernels are formed across a diverse set of F1 hybrids. Our findings reveal that the REL2 family maintains development from embryonic initiation to reproductive growth and can potentially be harnessed for increasing seed yield in a major crop species.
RESUMO
One of the challenges for global food security is to reliably and sustainably improve the grain yield of cereal crops. One solution is to modify the architecture of the grain-bearing inflorescence to optimize for grain number and size. Cereal inflorescences are complex structures, with determinacy, branching patterns, and spikelet/floret growth patterns that vary by species. Recent decades have witnessed rapid advancements in our understanding of the genetic regulation of inflorescence architecture in rice, maize, wheat, and barley. Here, we summarize current knowledge on key genetic factors underlying the different inflorescence morphologies of these crops and model plants (Arabidopsis and tomato), focusing particularly on the regulation of inflorescence meristem determinacy and spikelet meristem identity and determinacy. We also discuss strategies to identify and utilize these superior alleles to optimize inflorescence architecture and, ultimately, improve crop grain yield.
Assuntos
Hordeum , Inflorescência , Grão Comestível/genética , Grão Comestível/metabolismo , Poaceae/metabolismo , Hordeum/genética , Triticum/genética , Produtos Agrícolas/genética , Produtos Agrícolas/metabolismo , Meristema , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/metabolismoRESUMO
The superoxide anion radical (O2·-) is a one-electron reduction product of molecular oxygen. Compared with other forms of reactive oxygen species (ROS), superoxide has limited reactivity. Nevertheless, superoxide reacts with nitric oxide, ascorbate, and the iron moieties of [Fe-S] cluster-containing proteins. Superoxide has largely been neglected as a signalling molecule in the plant literature in favour of the most stable ROS form, hydrogen peroxide. However, superoxide can accumulate in plant cells, particularly in meristems, where superoxide dismutase activity and ascorbate accumulation are limited (or absent), or when superoxide is generated within the lipid environment of membranes. Moreover, oxidation of the nucleus in response to environmental stresses is a widespread phenomenon. Superoxide is generated in many intracellular compartments including mitochondria, chloroplasts, and on the apoplastic/cell wall face of the plasma membrane. However, nuclear superoxide production and functions remain poorly documented in plants. Accumulating evidence suggests that the nuclear pools of antioxidants such as glutathione are discrete and separate from the cytosolic pools, allowing compartment-specific signalling in the nucleus. We consider the potential mechanisms of superoxide generation and targets in the nucleus, together with the importance of antioxidant processing in regulating superoxide signalling.
Assuntos
Antioxidantes , Núcleo Celular , Transdução de Sinais , Superóxidos , Superóxidos/metabolismo , Antioxidantes/metabolismo , Núcleo Celular/metabolismo , Plantas/metabolismoRESUMO
Climate change-induced heat stress (HS) increasingly threatens potato (Solanum tuberosum L.) production by impacting tuberization and causing the premature sprouting of tubers grown during the hot season. However, the effects of post-harvest HS on tuber sprouting have yet to be explored. This study aims to investigate the effects of post-harvest HS on tuber sprouting and to explore the underlying transcriptomic changes in apical bud meristems. The results show that post-harvest HS facilitates potato tuber sprouting and negates apical dominance. A meticulous transcriptomic profiling of apical bud meristems unearthed a spectrum of differentially expressed genes (DEGs) activated in response to HS. During the heightened sprouting activity that occurred at 15-18 days of HS, the pathways associated with starch metabolism, photomorphogenesis, and circadian rhythm were predominantly suppressed, while those governing chromosome organization, steroid biosynthesis, and transcription factors were markedly enhanced. The critical DEGs encompassed the enzymes pivotal for starch metabolism, the genes central to gibberellin and brassinosteroid biosynthesis, and influential developmental transcription factors, such as SHORT VEGETATIVE PHASE, ASYMMETRIC LEAVES 1, SHOOT MERISTEMLESS, and MONOPTEROS. These findings suggest that HS orchestrates tuber sprouting through nuanced alterations in gene expression within the meristematic tissues, specifically influencing chromatin organization, hormonal biosynthesis pathways, and the transcription factors presiding over meristem fate determination. The present study provides novel insights into the intricate molecular mechanisms whereby post-harvest HS influences tuber sprouting. The findings have important implications for developing strategies to mitigate HS-induced tuber sprouting in the context of climate change.
Assuntos
Solanum tuberosum , Solanum tuberosum/metabolismo , Perfilação da Expressão Gênica , Resposta ao Choque Térmico/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Amido/metabolismo , Tubérculos/metabolismo , Regulação da Expressão Gênica de PlantasRESUMO
Why living forms develop in a relatively robust manner, despite various sources of internal or external variability, is a fundamental question in developmental biology. Part of the answer relies on the notion of developmental constraints: at any stage of ontogenesis, morphogenetic processes are constrained to operate within the context of the current organism being built. One such universal constraint is the shape of the organism itself, which progressively channels the development of the organism toward its final shape. Here, we illustrate this notion with plants, where strikingly symmetric patterns (phyllotaxis) are formed by lateral organs. This Hypothesis article aims first to provide an accessible overview of phyllotaxis, and second to argue that the spiral patterns in plants are progressively canalized from local interactions of nascent organs. The relative uniformity of the organogenesis process across all plants then explains the prevalence of certain patterns in plants, i.e. Fibonacci phyllotaxis.
Assuntos
Brotos de Planta/metabolismo , Plantas/metabolismo , Desenvolvimento Vegetal/fisiologia , Folhas de Planta/metabolismo , Folhas de Planta/fisiologia , Brotos de Planta/fisiologiaRESUMO
Robust agricultural yields require consistent flower production throughout fluctuating environmental conditions. Floral primordia are produced in the inflorescence meristem, which contains a pool of continuously dividing stem cells. Daughter cells of these divisions either retain stem cell identity or are pushed to the SAM periphery, where they become competent to develop into floral primordia after receiving the appropriate signal. Thus, flower production is inherently linked to regulation of the stem cell pool. The plant hormone auxin promotes flower development throughout its early phases and has been shown to interact with the molecular pathways regulating stem cell maintenance. Here, we will summarize how auxin signaling contributes to stem cell maintenance and promotes flower development through the early phases of initiation, outgrowth, and floral fate establishment. Recent advances in this area suggest that auxin may serve as a signal that integrates stem cell maintenance and new flower production.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismo , Mutação , Flores , Células-Tronco , Meristema , Regulação da Expressão Gênica de PlantasRESUMO
The WUSCHEL-related homeobox (WOX) is a family of specific transcription factors involved in plant development and response to stress, characterized by the presence of a homeodomain. This study represents the first comprehensive characterization of the WOX family in a member of the Asteraceae family, the sunflower (H. annuus L.). Overall, we identified 18 putative HaWOX genes divided by phylogenetic analysis in three major clades (i.e., ancient, intermediate, and WUS). These genes showed conserved structural and functional motifs. Moreover, HaWOX has homogeneously distributed on H. annuus chromosomes. In particular, 10 genes originated after whole segment duplication events, underpinning a possible evolution of this family along with the sunflower genome. In addition, gene expression analysis evidenced a specific pattern of regulation of the putative 18 HaWOX during embryo growth and in ovule and inflorescence meristem differentiation, suggesting a pivotal role for this multigenic family in sunflower development. The results obtained in this work improved the understanding of the WOX multigenic family, providing a resource for future study on functional analysis in an economically valuable species such as sunflower.
Assuntos
Helianthus , Helianthus/genética , Filogenia , Família Multigênica , Fatores de Transcrição/metabolismo , Genes Homeobox , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/genéticaRESUMO
Increasing the yield of rapeseed is required to meet the rapidly expanding demand for both edible vegetable oil and biofuel. Branching, an important determinant of yield potential in rapeseed, is controlled by a series of quantitative trait loci (QTLs). To explore the genetic mechanism regulating the natural variation of branching, a BC1F1 population derived from a cross between dense branching 2 (dense branching line) and L72 (normal branching line) was used to map QTL conferring branching in rapeseed. A major QTL, qDB.A03, for branching-related traits was identified by the BeadChip Array assisted bulked segregation analysis method, which was subsequently validated by the classical QTL mapping approach, and fine mapped to the 256 kb region. This interval contains 56 annotated or predicted genes, 8 of which are candidates for controlling the branching trait. Comparative and expression analysis revealed four promising candidate genes for qDB.A03. Fine mapping and identification of the candidate genes for qDB.A03 represents the first step toward unraveling the genetical and molecular mechanisms controlling branching in rapeseed.
Assuntos
Brassica napus , Brassica rapa , Brassica napus/genética , Brassica rapa/genética , Mapeamento Cromossômico/métodos , Fenótipo , Locos de Características Quantitativas/genética , Compostos de QuinolínioRESUMO
Asymmetric cell divisions are essential to generate different cellular lineages. In plants, asymmetric cell divisions regulate the correct formation of the embryo, stomatal cells, apical and root meristems, and lateral roots. Current knowledge of regulation of asymmetric cell divisions suggests that, in addition to the function of key transcription factor networks, epigenetic mechanisms play crucial roles. Therefore, we highlight the importance of epigenetic regulation and chromatin dynamics for integration of signals and specification of cells that undergo asymmetric cell divisions, as well as for cell maintenance and cell fate establishment of both progenitor and daughter cells. We also discuss the polarization and segregation of cell components to ensure correct epigenetic memory or resetting of epigenetic marks during asymmetric cell divisions.
Assuntos
Divisão Celular Assimétrica , Epigênese Genética , Diferenciação Celular , Linhagem da Célula , Desenvolvimento Vegetal/genéticaRESUMO
Meristems are highly regulated structures ultimately responsible for the formation of branches, lateral organs, and stems, and thus directly affect plant architecture and crop yield. In meristems, genetic networks, hormones, and signaling molecules are tightly integrated to establish robust systems that can adapt growth to continuous inputs from the environment. Here we characterized needle1 (ndl1), a temperature-sensitive maize mutant that displays severe reproductive defects and strong genetic interactions with known mutants affected in the regulation of the plant hormone auxin. NDL1 encodes a mitochondria-localized ATP-dependent metalloprotease belonging to the FILAMENTATION TEMPERATURE-SENSITIVE H (FTSH) family. Together with the hyperaccumulation of reactive oxygen species (ROS), ndl1 inflorescences show up-regulation of a plethora of stress-response genes. We provide evidence that these conditions alter endogenous auxin levels and disrupt primordia initiation in meristems. These findings connect meristem redox status and auxin in the control of maize growth.
Assuntos
Mitocôndrias/genética , Termotolerância/genética , Zea mays/genética , Trifosfato de Adenosina/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Meristema/metabolismo , Metaloproteases/genética , Metaloproteases/metabolismo , Mitocôndrias/metabolismo , Mutação , Reguladores de Crescimento de Plantas/genética , Reguladores de Crescimento de Plantas/metabolismo , Proteínas de Plantas/genética , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/fisiologiaRESUMO
MicroRNA171 (miR171), a group of 21-nucleotide single-strand small RNAs, is one ancient and conserved microRNA family in land plants. This review focuses on the recent progress in understanding the role of miR171 in plant stem cell homeostasis and developmental patterning, and the regulation of miR171 by developmental cues and environmental signals. Specifically, miR171 regulates shoot meristem activity and phase transition through repressing the HAIRYMERISTEM (HAM) family genes. In the model species Arabidopsis, miR171 serves as a short-range mobile signal, which initiates in the epidermal layer of shoot meristems and moves downwards within a limited distance, to pattern the apical-basal polarity of gene expression and drive stem cell dynamics. miR171 levels are regulated by light and various abiotic stresses, suggesting miR171 may serve as a linkage between environmental factors and cell fate decisions. Furthermore, miR171 family members also demonstrate both conserved and lineage-specific functions in land plants, which are summarized and discussed here.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Embriófitas , MicroRNAs/genética , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Embriófitas/genética , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Homeostase/genética , Meristema/genética , Meristema/metabolismo , Brotos de Planta/metabolismoRESUMO
Roots provide physical and nutritional support to plant organs that are above ground and play critical roles for adaptation via intricate movements and growth patterns. Through screening the effects of bacterial isolates from roots of halophyte Mesquite (Prosopis sp.) on Arabidopsis thaliana, we identified Achromobacter sp. 5B1 as a probiotic bacterium that influences plant functional traits. Detailed genetic and architectural analyses in Arabidopsis grown in vitro and in soil, cell division measurements, auxin transport and response gene expression and brefeldin A treatments demonstrated that root colonization with Achromobacter sp. 5B1 changes the growth and branching patterns of roots, which were related to auxin perception and redistribution. Expression analysis of auxin transport and signaling revealed a redistribution of auxin within the primary root tip of wild-type seedlings by Achromobacter sp. 5B1 that is disrupted by brefeldin A and correlates with repression of auxin transporters PIN1 and PIN7 in root provasculature, and PIN2 in the epidermis and cortex of the root tip, whereas expression of PIN3 was enhanced in the columella. In seedlings harboring AUX1, EIR1, AXR1, ARF7ARF19, TIR1AFB2AFB3 single, double or triple loss-of-function mutations, or in a dominant (gain-of-function) mutant of SLR1, the bacterium caused primary roots to form supercoils that are devoid of lateral roots. The changes in growth and root architecture elicited by the bacterium helped Arabidopsis seedlings to resist salt stress better. Thus, Achromobacter sp. 5B1 fine tunes both root movements and the auxin response, which may be important for plant growth and environmental adaptation.
Assuntos
Achromobacter/metabolismo , Ácidos Indolacéticos/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Raízes de Plantas/microbiologia , Achromobacter/efeitos dos fármacos , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Arabidopsis/microbiologia , Brefeldina A/farmacologia , Divisão Celular , Meristema/crescimento & desenvolvimento , Meristema/microbiologia , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Transdução de SinaisRESUMO
The two paralogous Arabidopsis genes MAINTENANCE OF MERISTEMS (MAIN) and MAINTENANCE OF MERISTEMS LIKE1 (MAIL1) encode a conserved retrotransposon-related plant mobile domain and are known to be required for silencing of transposable elements (TE) and for primary root development. Loss of function of either MAIN or MAIL1 leads to release of heterochromatic TEs, reduced condensation of pericentromeric heterochromatin, cell death of meristem cells and growth arrest of the primary root soon after germination. Here, we show that they act in one protein complex that also contains the inactive isoform of PROTEIN PHOSPHATASE 7 (PP7), which is named PROTEIN PHOSPHATASE 7-LIKE (PP7L). PP7L was previously shown to be important for chloroplast biogenesis and efficient chloroplast protein synthesis. We show that loss of PP7L function leads to the same root growth phenotype as loss of MAIL1 or MAIN. In addition, pp7l mutants show similar silencing defects. Double mutant analyses confirmed that the three proteins act in the same molecular pathway. The primary root growth arrest, which is associated with cell death of stem cells and their daughter cells, is a consequence of genome instability. Our data demonstrate so far unrecognized functions of an inactive phosphatase isoform in a protein complex that is essential for silencing of heterochromatic elements and for maintenance of genome stability in dividing cells.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Elementos de DNA Transponíveis/genética , Proteínas Nucleares/metabolismo , Fosfoproteínas Fosfatases/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Cloroplastos/metabolismo , Inativação Gênica , Germinação , Heterocromatina/genética , Isoenzimas , Meristema/genética , Meristema/crescimento & desenvolvimento , Meristema/fisiologia , Mutação , Proteínas Nucleares/genética , Fenótipo , Fosfoproteínas Fosfatases/genética , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/fisiologia , Retroelementos/genéticaRESUMO
It is commonly assumed that plants do not possess consciousness. Since the criterion for this assumption is usually human consciousness this assumption represents a top down attitude. It is obvious that plants are not animals and using animal criteria of consciousness will lead to its rejection in plants. However using a bottom up evolutionary approach and a leading theory of consciousness, Integrated Information Theory, we report that we find evidence that indicates that plant meristems act in a conscious fashion although probably at the level of minimal consciousness. Since many plants contain multiple meristems these observations highlight a very different evolutionary approach to consciousness in biological organisms.
Assuntos
Estado de Consciência/fisiologia , Teoria da Informação , Plantas/metabolismo , Animais , HumanosRESUMO
Plants are the primary producers of biomass on earth. As an almost stereotypic feature, higher plants generate continuously growing bodies mediated by the activity of different groups of stem cells, the meristems. Shoot and root thickening is one of the fundamental growth processes determining form and function of these bodies. Mediated by a group of cylindrical meristems located below organ surfaces, vascular and protective tissues are continuously generated in a highly plastic manner, a competence essential for the survival in an ever changing environment. Acknowledging the fundamental role of this process, which is overall designated as secondary growth, we discuss in this review our current knowledge about the evolution and molecular regulation of the vascular cambium. The cambium is the meristem responsible for the formation of wood and bast, the two types of vascular tissues important for long-distance transport of water and assimilates, respectively. Although regulatory patterns are only beginning to emerge, we show that cambium activity represents a highly rewarding model for studying cell fate decisions, tissue patterning and differentiation, which has experienced an outstanding phylogenetic diversification.
Assuntos
Câmbio/genética , Diferenciação Celular/genética , Proliferação de Células/genética , Genes de Plantas/genética , Plantas/genética , Câmbio/citologia , Câmbio/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Filogenia , Plantas/anatomia & histologia , Plantas/classificação , Células-Tronco/citologia , Células-Tronco/metabolismoRESUMO
Epigenetic changes influence gene expression and contribute to the modulation of biological processes in response to the environment. Transgenerational epigenetic changes in gene expression have been described in many eukaryotes. However, plants appear to have a stronger propensity for inheriting novel epialleles. This mini-review discusses how plant traits, such as meristematic growth, totipotency, and incomplete epigenetic erasure in gametes promote epiallele inheritance. Additionally, we highlight how plant biology may be inherently tailored to reap the benefits of epigenetic metastability. Importantly, environmentally triggered small RNA expression and subsequent epigenetic changes may allow immobile plants to adapt themselves, and possibly their progeny, to thrive in local environments. The change of epigenetic states through the passage of generations has ramifications for evolution in the natural and agricultural world. In populations containing little genetic diversity, such as elite crop germplasm or habitually self-reproducing species, epigenetics may provide an important source of heritable phenotypic variation. Basic understanding of the processes that direct epigenetic shifts in the genome may allow for breeding or bioengineering for improved plant traits that do not require changes to DNA sequence.
Assuntos
Epigênese Genética , Evolução Molecular , Plantas/genética , Regulação da Expressão Gênica de PlantasRESUMO
Unlike seed plants, ferns leaves are considered to be structures with delayed determinacy, with a leaf apical meristem similar to the shoot apical meristems. To better understand the meristematic organization during leaf development and determinacy control, we analyzed the cell divisions and expression of Class I KNOX genes in Mickelia scandens, a fern that produces larger leaves with more pinnae in its climbing form than in its terrestrial form. We performed anatomical, in situ hybridization, and qRT-PCR experiments with histone H4 (cell division marker) and Class I KNOX genes. We found that Class I KNOX genes are expressed in shoot apical meristems, leaf apical meristems, and pinnae primordia. During early development, cell divisions occur in the most distal regions of the analyzed structures, including pinnae, and are not restricted to apical cells. Fern leaves and pinnae bear apical meristems that may partially act as indeterminate shoots, supporting the hypothesis of homology between shoots and leaves. Class I KNOX expression is correlated with indeterminacy in the apex and leaf of ferns, suggesting a conserved function for these genes in euphyllophytes with compound leaves.
Assuntos
Dryopteridaceae/genética , Histonas/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Plantas/genética , Divisão Celular , Dryopteridaceae/crescimento & desenvolvimento , Meristema/genética , Meristema/crescimento & desenvolvimento , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Proteínas de Plantas/metabolismo , Brotos de Planta/genética , Brotos de Planta/crescimento & desenvolvimento , Distribuição TecidualRESUMO
A brief review of current data on the molecular biology of stem cells forming meristems and differentiating into various organs of angiosperms is presented. Different primary and secondary meristems are compared. The interactions of some hormones, regulatory gene networks, and signaling pathways in different types of meristems are described.