[Show abstract][Hide abstract] ABSTRACT: TETRASPANIN (TET) genes encode conserved integral membrane proteins that are known in animals to function in cellular communication during gamete fusion, immunity reaction and pathogen recognition. In plants, functional information is limited to one of the 17 members of the Arabidopsis TET gene family and to expression data in reproductive stages. Here, the promoter activity of all 17 Arabidopsis TET genes was investigated by pAtTET::NLS-GFP/GUS reporter lines throughout the life cycle, which predicted functional divergence in the paralogous genes per clade. However, partial overlap was observed for many TET genes across the clades, correlating with few phenotypes in single mutants and therefore requiring double mutant combinations for functional investigation. Mutational analysis showed a role for TET13 in primary root growth and lateral root development, and redundant roles for TET5 and TET6 in leaf and root growth through negative regulation of cell proliferation. Strikingly, a number of TET genes were expressed in embryonic and seedling progenitor cells and remained expressed until the differentiation state in the mature plant, suggesting a dynamic function over developmental stages. cis-regulatory elements together with transcription factor binding data provided molecular insight into the site, conditions and perturbations that affect TET gene expression, and positioned the TET genes in different molecular pathways; the data represent a hypothesis-generating resource for further functional analyses.
[Show abstract][Hide abstract] ABSTRACT: Dehydrins belong to a protein family whose expression may be induced or enhanced by developmental process and environmental stresses that lead to cell dehydration. A dehydrin gene named OesDHN was isolated and characterized from oleaster (Olea europaea L. subsp. europaea, var. sylvestris), the wild form of olive. To elucidate the contribution of OesDHN in the development of drought tolerance, its expression levels were investigated in oleaster plants during development and under drought stress condition. The involvement of OesDHN in plant stress response was also evaluated in Arabidopsis transgenic lines, engineered to overexpress this gene, and exposed to a controlled mild osmotic stress. OesDHN expression was found to be modulated during development and induced under mild drought stress in oleaster plants. In addition, the Arabidopsis transgenic plants showed a better tolerance to osmotic stress than wild-type plants. The results demonstrated that OesDHN expression is induced by drought stress and is able to confer osmotic stress tolerance. We suggest a role for OesDHN, as a putative functional marker of plant stress tolerance.
[Show abstract][Hide abstract] ABSTRACT: Elongation is a dynamic and highly regulated step of eukaryotic gene transcription. A variety of transcript elongation factors (TEFs), including modulators of RNA polymerase II (RNAPII) activity, histone chaperones, and histone modifiers, have been characterized from plants. These factors control the efficiency of transcript elongation of subsets of genes in the chromatin context and thus contribute to tuning gene expression programs. We review here how genetic and biochemical analyses, primarily in Arabidopsis thaliana, have advanced our understanding of how TEFs adjust plant gene transcription. These studies have revealed that TEFs regulate plant growth and development by modulating diverse processes including hormone signaling, circadian clock, pathogen defense, responses to light, and developmental transitions.
[Show abstract][Hide abstract] ABSTRACT: The elongation phase of the RNA polymerase (RNAPII) transcription process is dynamic and regulated. Elongator and SPT4/SPT5 are transcript elongation factors that contribute to the regulation of mRNA synthesis by RNAPII in the chromatin context. Recently, the Elongator complex consisting of six subunits and the SPT4/SPT5 heterodimer were isolated from Arabidopsis. Mutant plants affected in the expression of Elongator or SPT4/SPT5 share various auxin signaling phenotypes. In line with that it was observed that auxin-related genes are prominent among the genes differentially expressed in these mutants. Exemplified by Elongator and SPT4/SPT5 we discuss here the role that transcript elongation factors may play in the control of plant growth and development.This article is protected by copyright. All rights reserved
[Show abstract][Hide abstract] ABSTRACT: In higher plants, genetic transformation, which is part of the toolbox for the study of living organisms, had been reported only 30 years ago, boosting basic plant biology research, generating superior crops, and leading to the new discipline of plant biotechnology. Here, we review its principles and the corresponding molecular tools. In vitro regeneration, through somatic embryogenesis or organogenesis, is discussed because they are prerequisites for the subsequent Agrobacterium tumefaciens-mediated transferred (T)-DNA or direct DNA transfer methods to produce transgenic plants. Important molecular components of the T-DNA are examined, such as selectable marker genes that allow the selection of transformed cells in tissue cultures and are used to follow the gene of interest in the next generations, and reporter genes that have been developed to visualize promoter activities, protein localizations, and protein-protein interactions. Genes of interest are assembled with promoters and termination signals in Escherichia coli by means of GATEWAY-derived binary vectors that represent the current versatile cloning tools. Finally, future promising developments in transgene technology are considered.
The International journal of developmental biology 10/2013; 57(6-7-8):483-494. DOI:10.1387/ijdb.130232mv · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This dialogue was held between the Guest Editors of the Special Issue on Plant Transgenesis of the Int. J. Dev. Biol. and Marc Van Montagu. Research in the group of Marc Van Montagu and Jeff Schell in the 1970s was essential to reveal how the phytopathogenic bacterium Agrobacterium tumefaciens transfers DNA to host plants to cause crown gall disease. Knowledge of the molecular mechanism underlying gene transfer, subsequently led to the development of plant transgene technology, an indispensable tool in fundamental plant research and plant improvement. In the early 1980s, Marc Van Montagu founded a start-up company, Plant Genetic Systems, which successfully developed insect-resistant plants, herbicide-tolerant plants and a hybrid seed production system based on nuclear male sterility. Even before the first transgenic plant had been produced, Marc Van Montagu realized that the less developed countries might benefit most from plant biotechnology and throughout his subsequent career, this remained a focus of his efforts. After becoming emeritus professor, he founded the Institute of Plant Biotechnology Outreach (IPBO), which aims to raise awareness of the major role that plant biotechnology can play in sustainable agricultural systems, especially in less developed countries. Marc Van Montagu has been honored with many prizes and awards, the most recent being the prestigious World Food Prize 2013. In this paper, we look to the past and present of plant biotechnology and to the promises this technology holds for the future, on the basis of the personal perspective of Marc Van Montagu.
The International journal of developmental biology 10/2013; 57(6-7-8):453-460. DOI:10.1387/ijdb.130295ga · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In 1983, the first transgenic tissues and plants were generated by means of disarmed Agrobacterium tumefaciens strains, in which the oncogenes had been replaced by antibiotic resistance markers. Hence, this Special Issue of The International Journal of Developmental Biology celebrates 30 years of transgenic research in plants! Eminent scientists working in the field of plant transformation or plant biotechnology have contributed to this publication and reviewed the state-of-the-art of their particular subdomain or summarized the importance of transgenic research in the discovery of new mechanisms and the establishment of an entirely new field, such as epigenetics.
The International journal of developmental biology 10/2013; 57(6-7-8):445-447. DOI:10.1387/ijdb.130062mv · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This dialogue was held between the Guest Editors of the Special Issue on Plant Transgenesis of the Int. J. Dev. Biol. and Marc De Block. He was one of the first scientists worldwide to obtain transgenic plants transformed with the chimeric selectable marker genes encoding neomycin phosphotransferase and bialaphos that confer resistance against the antibiotic kanamycin and the herbicide Basta®/glufosinate, respectively at the Department of Genetics of Ghent University and, later on, at the spin-off company, Plant Genetic Systems. Today, these two genes are still the most frequently utilized markers in transgene technology. Marc De Block chose to work on the improvement of crops in an industrial environment to help realize the production of superior seeds or products. He was part of the team that developed the male sterility/restorer system in canola (Brassica napus var. napus) that led to the first hybrid lines to be commercialized as successful products of transgene technology. In more than 30 years of research, he developed transformation procedures for numerous crops, designed histochemical, biochemical and physiological assays to monitor plant performance, and made original and innovative contributions to plant biology. Presently, he considers transgenic research part of the toolbox for plant improvement and essential for basic plant research.
The International journal of developmental biology 10/2013; 57(6-7-8):461-465. DOI:10.1387/ijdb.130063mv · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Until now, the availability of vectors for transgenic research in cereal crops has been rather limited. We present a novel collection of Agrobacterium tumefaciens binary T-DNA vectors compatible with Gateway recombinational cloning that facilitate the modular assembly of genes of interest together with new regulatory sequences, such as strong constitutive or endosperm-specific Brachypodium distachyon promoters. This resource aims at streamlining the creation of vectors and transgenes designed to explore gene functions in vital monocotyledonous crops.
[Show abstract][Hide abstract] ABSTRACT: Recently, we have identified circadian clock genes as targets of Histone Monoubiquitination1 (HUB1) in Arabidopsis from a transcriptome comparison between the hub1-1 mutant and HUB1 overexpression lines. HUB1 affected the amplitudes of the circadian clock gene expression profiles in the hub1-1 mutant that coincided with reduced monoubiquitination of histone H2B at their coding regions. Here we showed that parameters for plant fitness are altered in HUB1 mutant and overexpression lines, suggesting that the histone H2B monoubiquitination status affects plant fitness.
[Show abstract][Hide abstract] ABSTRACT: In recent years, an increasing number of mutations in what would appear to be 'housekeeping genes' have been identified as having unexpectedly specific defects in multicellular organogenesis. This is also the case for organogenesis in seed plants. Although it is not surprising that loss-of-function mutations in 'housekeeping' genes result in lethality or growth retardation, it is surprising when (1) the mutant phenotype results from the loss of function of a 'housekeeping' gene and (2) the mutant phenotype is specific. In this review, by defining housekeeping genes as those encoding proteins that work in basic metabolic and cellular functions, we discuss unexpected links between housekeeping genes and specific developmental processes. In a surprising number of cases housekeeping genes coding for enzymes or proteins with functions in basic cellular processes such as transcription, post-transcriptional modification, and translation affect plant development.
Journal of Plant Research 08/2012; 126(1). DOI:10.1007/s10265-012-0518-2 · 1.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ribosomes play a basic housekeeping role in global translation. However, a number of ribosomal-protein-defective mutants show common and rare developmental phenotypes including growth defects, changes in leaf development, and auxin-related phenotypes. This suggests that translational regulation may be occurring during development. In addition, proteomic and bioinformatic analyses have demonstrated a high heterogeneity in ribosome composition. Although this might be a sign of unequal roles of individual ribosomal proteins, it does not explain every ribosomal-protein-defective phenotype. Moreover, comprehensive interpretations concerning the relationship between ribosomal-protein-defective phenotypes and molecular changes in ribosome status are lacking. In this review, we address these phenotypes based on three models, ribosome insufficiency, heterogeneity, and aberrancy, to consider how ribosomes play developmental roles. We propose that the three models are not mutually exclusive, and ribosomal-protein-defective phenotypes can be explained with one or more of these models. The three models with reference to genetic, biochemical, and bioinformatic knowledge will serve as a foundation for future studies of translational regulation.
[Show abstract][Hide abstract] ABSTRACT: Previously, we identified HISTONE MONOUBIQUITINATION1 (HUB1) as an unconventional ubiquitin E3 ligase that is not involved in protein degradation but in the histone H2B modification that is implicated in transcriptional activation in plants. HUB1-mediated regulation of gene expression played a role in periodic and inducible processes such as the cell cycle, dormancy, flowering time and defense responses. Here, we determined the effects of the hub1-1 mutation on expression of a set of diurnally induced circadian clock genes identified from a comparative microarray analysis between the hub1-1 mutant and an HUB1 over-expression line. The hub1-1 mutation reduced the amplitudes of a number of induced clock gene expression peaks, as well as the HUB1-mediated histone H2BUb and H3K4Me3 marks associated with the coding regions, suggesting a role for HUB1 in facilitating transcriptional elongation in plants. Furthermore, double mutants between hub1-1 and elongata (elo) showed an embryo-lethal phenotype, indicating a synergistic genetic interaction. The double mutant embryos arrested at the torpedo stage, implying that together histone ubiquitination and acetylation marks are essential to activate expression of target genes in multiple pathways.
The Plant Journal 07/2012; 72(2):249-60. DOI:10.1111/j.1365-313X.2012.05071.x · 5.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tetraspanins represent a four-transmembrane protein superfamily with a conserved structure and amino acid residues that are present in mammals, insects, fungi and plants. Tetraspanins interact with each other or with other membrane proteins to form tetraspanin-enriched microdomains that play important roles in development, pathogenesis and immune responses via facilitating cell-cell adhesion and fusion, ligand binding and intracellular trafficking. Here, we emphasize evolutionary aspects within the plant kingdom based on genomic sequence information. A phylogenetic tree based on 155 tetraspanin genes of 11 plant species revealed ancient and fast evolving clades. Tetraspanins were only present in multicellular plants, were often duplicated in the plant genomes and predicted by the electronic Fluorescent Pictograph for gene expression analysis to be either functionally redundant or divergent. Tetraspanins contain a large extracellular loop with conserved cysteines that provide the binding sites for the interactions. The Arabidopsis thaliana TETRASPANIN1/TORNADO2/EKEKO has a function in leaf and root patterning and TETRASPANIN3 was identified in the plasmodesmatal proteome, suggesting a role in cell-cell communication during plant development.
[Show abstract][Hide abstract] ABSTRACT: Plant growth rate is largely determined by the transition between the successive phases of cell division and expansion. A key role for hormone signaling in determining this transition was inferred from genetic approaches and transcriptome analysis in the Arabidopsis root tip. We used the developmental gradient at the maize leaf base as a model to study this transition, because it allows a direct comparison between endogenous hormone concentrations and the transitions between dividing, expanding, and mature tissue. Concentrations of auxin and cytokinins are highest in dividing tissues, whereas bioactive gibberellins (GAs) show a peak at the transition zone between the division and expansion zone. Combined metabolic and transcriptomic profiling revealed that this GA maximum is established by GA biosynthesis in the division zone (DZ) and active GA catabolism at the onset of the expansion zone. Mutants defective in GA synthesis and signaling, and transgenic plants overproducing GAs, demonstrate that altering GA levels specifically affects the size of the DZ, resulting in proportional changes in organ growth rates. This work thereby provides a novel molecular mechanism for the regulation of the transition from cell division to expansion that controls organ growth and size.
Current biology: CB 06/2012; 22(13):1183-7. DOI:10.1016/j.cub.2012.04.065 · 9.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The biotechnological approach to improve performance or yield of crops or for engineering metabolic pathways requires the expression of a number of transgenes, each with a specific promoter to avoid induction of silencing mechanisms. In maize (Zea mays), used as a model for cereals, an efficient Agrobacterium tumefaciens-mediated transformation system has been established that is applied for translational research. In the current transformation vectors, the promoters of the 35S gene of the cauliflower mosaic virus and of the ubiquitin gene of maize are often used to drive the bialaphos-selectable marker and the transgene, respectively. To expand the number of promoters, genes with either constitutive or seed-specific expression were selected in Brachypodium distachyon, a model grass distantly related to maize. After the corresponding Brachypodium promoters had been fused to the β-glucuronidase reporter gene, their activity was followed throughout maize development and quantified in a fluorimetric assay with the 4-methylumbelliferyl β-D-glucuronide substrate. The promoters pBdEF1α and pBdUBI10 were constitutively and highly active in maize, whereas pBdGLU1 was clearly endosperm-specific, hence, expanding the toolbox for transgene analysis in maize. The data indicate that Brachypodium is an excellent resource for promoters for transgenic research in heterologous cereal species.
[Show abstract][Hide abstract] ABSTRACT: Leaf primordia are generated around the shoot apical meristem. Mutation of the ASYMMETRIC LEAVES2 (AS2) gene of Arabidopsis thaliana results in defects in repression of the meristematic and indeterminate state, establishment of adaxial-abaxial polarity and left-right symmetry in leaves. AS2 represses transcription of meristem-specific class 1 KNOX homeobox genes and of the abaxial-determinant genes ETTIN/ARF3, KANADI2 and YABBY5. To clarify the role of AS2 in the establishment of leaf polarity, we isolated mutations that enhanced the polarity defects associated with as2. We describe here the enhancer-of-asymmetric-leaves-two1 (east1) mutation, which caused the formation of filamentous leaves with abaxialized epidermis on the as2-1 background. Levels of transcripts of class 1 KNOX and abaxial-determinant genes were markedly higher in as2-1 east1-1 mutant plants than in the wild-type and corresponding single-mutant plants. EAST1 encodes the histone acetyltransferase ELONGATA3 (ELO3), a component of the Elongator complex. Genetic analysis, using mutations in genes involved in the biogenesis of a trans-acting small interfering RNA (ta-siRNA), revealed that ELO3 mediated establishment of leaf polarity independently of AS2 and the ta-siRNA-related pathway. Treatment with an inhibitor of histone deacetylases (HDACs) caused additive polarity defects in as2-1 east1-1 mutant plants, suggesting the operation of an ELO3 pathway, independent of the HDAC pathway, in the determination of polarity. We propose that multiple pathways play important roles in repression of the expression of class 1 KNOX and abaxial-determinant genes in the development of the adaxial domain of leaves and, thus, in the establishment of leaf polarity.
[Show abstract][Hide abstract] ABSTRACT: In situ RNA-RNA hybridization (ISH) is a molecular method for localization of gene transcripts at the cellular level and is widely used to provide spatial and temporal information regarding gene expression. However, standard protocols are complex and laborious to implement, restricting analysis to one or a few genes at any one time, each one observed on separate ISH preparations. Multi-probe whole-mount in situ hybridization is a powerful technique to compare the expression patterns of two or more genes simultaneously in the same tissue or organ. We describe for the first time in plants, the detection of three different mRNAs in a single fixed whole mount Arabidopsis seedling. A combination of bright fluorescent secondary antibodies was used for the detection of riboprobes differentially labeled by digoxigenin, biotin and fluorescein. The 3-D detection of each of the multiple fluorescent hybridization signals or in combination was obtained through confocal laser-scanning microscopy. The reliability of the method was tested in the root, using the PINFORMED (PIN) genes with non-overlapping temporal and spatial expression patterns. In the shoot, a class-I KNOTTED -like homeobox gene from Arabidopsis (KNAT1) with expression restricted to the shoot apical meristem was used in combination with ELONGATOR3 (ELO3) gene. In addition, the expression patterns of ELONGATOR complex gene (ELO2, ELO3) and HISTONE MONOUBIQUITINATION1 (HUB1) genes were analyzed in both shoot and root and a partial overlapping was observed. The whole procedure takes only 6 days.
The International journal of developmental biology 04/2011; 55(2):197-203. DOI:10.1387/ijdb.103132lb · 1.90 Impact Factor