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PubMed2005

Role of extracytoplasmic leucine rich repeat proteins in plant defence mechanisms.

Plant-pathogen interactions involve highly complex series of reactions in disease development. Plants are endowed with both, resistance and defence genes. The activation of defence genes after contact with avirulence gene products of pathogens depends on signals transduced by leucine-rich repeats (LRRs) contained in resistance genes. Additionally, LRRs play roles for various actions following ligand recognition. Polygalacturonase inhibiting proteins (PGIPs), the only plant LRR protein with known ligands, are pectinase inhibitors, bound by ionic interactions to the extracellular matrix (ECM) of plant cells. They have a high affinity for fungal endopolygalacturonases (endoPGs). PGIP genes are organised in families encoding proteins with similar physical characteristics but different specificities. They are induced by infection and stress related signals. The molecular basis of PG-PGIP interaction serves as a model to understand the evolution of plant LRR proteins in recognising non-self-molecules. Extensins form a different class of structural proteins with repetitive sequences. They are also regulated by wounding and pathogen infection. Linkage of extensins with LRR motifs is highly significant in defending host tissues against pathogen invasion. Overexpression of PGIPs or expression of several PGIPs in a plant tissue, and perhaps manipulation of extensin expression could be possible strategies for disease management.

Extracellular Matrix↗

PubMed2003

The release of genetically modified crops into the environment. Part II. Overview of ecological risk assessment.

Despite numerous future promises, there is a multitude of concerns about the impact of GM crops on the environment. Key issues in the environmental assessment of GM crops are putative invasiveness, vertical or horizontal gene flow, other ecological impacts, effects on biodiversity and the impact of presence of GM material in other products. These are all highly interdisciplinary and complex issues. A crucial component for a proper assessment is defining the appropriate baseline for comparison and decision. For GM crops, the best and most appropriately defined reference point is the impact of plants developed by traditional breeding. The latter is an integral and accepted part of agriculture. In many instances, the putative impacts identified for GM crops are very similar to the impacts of new cultivars derived from traditional breeding. When assessing GM crops relative to existing cultivars, the increased knowledge base underpinning the development of GM crops will provide greater confidence in the assurances plant science can give on the risks of releasing such crops.

Crops, Agricultural↗

PubMed2026

Plant cis-regulatory grammar: Decoding the multidimensional code of transcriptional regulation for programmable crop engineering.

Cis-regulatory elements (CREs) orchestrate the spatiotemporal precision of gene expression that underlies plant development, adaptation, and domestication. Decoding the cis-regulatory grammar of plant genomes remains a central challenge in modern biology, with profound implications for programmable crop engineering. Here, recent conceptual and technological advances are synthesized to reshape our understanding of plant CREs. This review first argues that CRE function is not only an intrinsic property of DNA sequence alone but also emerges from a multidimensional context, including chromatin accessibility, histone modifications, three-dimensional genome topology, and cell type-specific regulatory landscapes. Furthermore, the convergence of single-cell epigenomics, high-throughput functional assays, and CRISPR-based dissection has begun to unravel this contextual grammar, revealing the computational principles governing transcriptional regulation. Critically, we propose that artificial intelligence (AI) platforms are catalyzing an ongoing transition from descriptive discovery to predictive engineering, wherein these platforms outperform natural evolution in designing synthetic CREs. Finally, a roadmap is outlined toward a plant regulatory grammar foundation model, which will enable truly predictive engineering of gene expression when fine-tuned for specific tasks. Collectively, the integration of single-cell resolution maps, precise genome editing, AI-driven design, and regulatory-compliant delivery systems promises to transform our ability to reprogram plant gene regulation for next-generation agriculture, bridging the gap between foundational regulatory biology and tangible crop improvement.

artificial intelligence↗

PubMed1984

Isolated liver damage in chemical workers.

During a period of 18 months three workers were admitted to hospital with jaundice that had developed two to four months after beginning work at a chemical plant. Liver biopsies showed severe centrilobular, haemorrhagic liver cell necrosis. The pathological changes resolved within six to 18 months. No damage to other organs was observed. The only worker who resumed work at the plant developed clinical and biochemical evidence of relapse of liver damage. Exposure to carbon disulphide, isopropanol, toluene, and acrylonitrile among others was shown, but liver damage may have been caused by a synergistic, hepatotoxic reaction mediated through the hepatic microsomal enzyme system. It was not possible to decide which chemical was responsible.

Adult↗

PubMed2001

Efficient down-regulation of the major vegetative storage protein genes in transgenic soybean does not compromise plant productivity.

Soybean (Glycine max L. Merr.) contains two related and abundant proteins, VSP alpha and VSP beta, that have been called vegetative storage proteins (VSP) based on their pattern of accumulation, degradation, tissue localization, and other characteristics. To determine whether these proteins play a critical role in sequestering N and other nutrients during early plant development, a VspA antisense gene construct was used to create transgenic plants in which VSP expression was suppressed in leaves, flowers, and seed pods. Total VSP was reduced at least 50-fold due to a 100-fold reduction in VSP alpha and a 10-fold reduction in VSP beta. Transgenic lines were grown in replicated yield trials in the field in Nebraska during the summer of 1999 and seed harvested from the lines was analyzed for yield, protein, oil, and amino acid composition. No significant difference (alpha = 0.05) was found between down-regulated lines and controls for any of the traits tested. Young leaves of antisense plants grown in the greenhouse contained around 3% less soluble leaf protein than controls at the time of flowering. However, total leaf N did not vary. Withdrawing N from plants during seed fill did not alter final seed protein content of antisense lines compared with controls. These results indicate that the VSPs play little if any direct role in overall plant productivity under typical growth conditions. The lack of VSPs in antisense plants might be partially compensated for by increases in other proteins and/or non-protein N. The results also suggest that the VSPs could be genetically engineered or replaced without deleterious effects.

Down-Regulation↗

PubMed2005

Cell-to-cell movement of GFP during embryogenesis and early seedling development in Arabidopsis.

There is increasing evidence for intercellular trafficking of macromolecules through plasmodesmata (PD) during plant development. Here we study the ability of PD to traffic proteins during embryogenesis and early seedling development in Arabidopsis. Transgenic lines that induce GFP expression only in meristems, MSG (meristem-specific GFP), were used to monitor GFP movement. Cell-to-cell movement of different-sized GFP reporters reveals that embryos and young seedlings traffic proteins at least 54 kDa in size. Although 27-kDa soluble GFP (1 x sGFP) freely moves between cells throughout the entire embryo during all stages analyzed, 2 x sGFP movement becomes more restricted as development proceeds. After germination, cells near the apical meristem in seedlings show a higher size exclusion limit (SEL), whereas the SEL becomes more restricted as surrounding tissues develop identities. Although 1 x sGFP moves throughout leaf primordia, as the leaf develops only the basal part of leaf petioles, main vascular tissues, and leaf veins (not blades) allow 1 x sGFP movement. Although previous studies showed that embryos allow movement of small symplastic tracers (0.5 kDa), the present data demonstrate that the embryo constitutes a single symplast that allows transport of macromolecules as well. Even 2 x sGFP moves from its site of expression at the apical meristem in embryos and seedlings, yet the extent of movement is more limited than 1 x sGFP. Thus, PD have distinct SELs in different subregions of the embryo and seedling. These studies support the general concept that PD in younger tissues are more dilated and less restrictive than PD in older (nonvascular) tissues.

Arabidopsis↗

PubMed2004

Green fluorescent protein fusions to Arabidopsis fimbrin 1 for spatio-temporal imaging of F-actin dynamics in roots.

The visualization of green fluorescent protein (GFP) fusions with microtubule or actin filament (F-actin) binding proteins has provided new insights into the function of the cytoskeleton during plant development. For studies on actin, GFP fusions to talin have been the most generally used reporters. Although GFP-Talin has allowed in vivo F-actin imaging in a variety of plant cells, its utility in monitoring F-actin in stably transformed plants is limited particularly in developing roots where interesting actin dependent cell processes are occurring. In this study, we created a variety of GFP fusions to Arabidopsis Fimbrin 1 (AtFim1) to explore their utility for in vivo F-actin imaging in root cells and to better understand the actin binding properties of AtFim1 in living plant cells. Translational fusions of GFP to full-length AtFim1 or to some truncated variants of AtFim1 showed filamentous labeling in transient expression assays. One truncated fimbrin-GFP fusion was capable of labeling distinct filaments in stably transformed Arabidopsis roots. The filaments decorated by this construct were highly dynamic in growing root hairs and elongating root cells and were sensitive to actin disrupting drugs. Therefore, the fimbrin-GFP reporters we describe in this study provide additional tools for studying the actin cytoskeleton during root cell development. Moreover, the localization of AtFim1-GFP offers insights into the regulation of actin organization in developing roots by this class of actin cross-linking proteins.

Actins↗

PubMed2003

Chitosan improves development, and protects Vitis vinifera L. against Botrytis cinerea.

We evaluated the potential of chitosan both to stimulate plant development and to induce protection from Botrytis cinerea in Vitis vinifera L. plantlets. The presence of 1.75% (v/v) chitogel in the culture medium was the optimal concentration for in vitro grapevine plantlet growth, as determined by measurements on enhancement of root and shoot biomass. Photosynthesis and related parameters were also stimulated in chitogel-treated plantlets. Chitogel reduced the development of Botrytis cinerea and induced cytological alterations to the pathogen. When challenged with the fungus, a significant decrease in disease incidence was observed in plants growing on medium supplemented with chitogel. Furthermore, exogenous foliar applications of chitogel to plantlets growing on chitogel-free medium sensitized them so as to be protected against Botrytis cinerea attack. Our results indicate that chitogel can be used in the vineyard as a means to attain protection against Botrytis cinerea and that its application may counteract the wide use of chemical pesticides.

Botrytis↗

PubMed2005

The roothairless1 gene of maize encodes a homolog of sec3, which is involved in polar exocytosis.

The roothairless1 (rth1) mutant is impaired in root hair elongation and exhibits other growth abnormalities. Unicellular root hairs elongate via localized tip growth, a process mediated by polar exocytosis of secretory vesicles. We report here the cloning of the rth1 gene that encodes a sec3 homolog. In yeast (Saccharomyces cerevisiae) and mammals, sec3 is a subunit of the exocyst complex, which tethers exocytotic vesicles prior to their fusion. The cloning of the rth1 gene associates the homologs of exocyst subunits to an exocytotic process in plant development and supports the hypothesis that exocyst-like proteins are involved in plant exocytosis. Proteomic analyses identified four proteins that accumulate to different levels in wild-type and rth1 primary roots. The preferential accumulation in the rth1 mutant proteome of a negative regulator of the cell cycle (a prohibitin) may at least partially explain the delayed development and flowering of the rth1 mutant.

Chromosome Mapping↗

PubMed1999

Transgenic tobacco plants expressing the Drosophila Polycomb (Pc) chromodomain show developmental alterations: possible role of Pc chromodomain proteins in chromatin-mediated gene regulation in plants.

The chromodomain of the Drosophila Polycomb (Pc) protein has been introduced into tobacco nuclei to determine its location in the nucleus and its effect on plant development. Pc is a repressor of homeotic Drosophila genes that shares a well-conserved, although not identical, chromodomain with a structural heterochromatin component, Heterochromatin Protein 1. The chromodomains might therefore play a common role in chromatin repression. An analysis of transgenic plants expressing the Pc chromodomain, which was linked to the green fluorescent protein, suggested that the Pc chromodomain has distinct target regions in the plant genome. Transgenic plants expressing the Pc chromodomain had phenotypic abnormalities in their leaves and flowers, indicating a disruption in development. In axillary shoot buds of plants displaying altered leaf phenotypes, enhanced expression of a homeodomain gene, which is downregulated in wild-type leaves, was found. In Drosophila, Pc has been shown to possess distinct chromosome binding activity and to be involved in the regulation of development-specific genes. Our results support the assumptions that the heterologous chromodomain affects related functions in Drosophila and in plants, and that chromatin modification mechanisms are involved in the regulation of certain plant genes, in a manner similar to chromatin-mediated gene regulation in Drosophila.

Base Sequence↗

PubMed2000

Ozone impacts on allometry and root hydraulic conductance are not mediated by source limitation nor developmental age.

O(3)could reduce growth and carbohydrate allocation to roots by direct inhibition of photosynthesis and source strength. Alternatively, O(3) could reduce growth indirectly by inhibition of root hydraulic development through a primary lesion in carbohydrate translocation. Another alternative is that O(3) could slow the rate of plant development, only apparently altering carbohydrate allocation at a given plant age. Pima cotton (Gossypium barbadense L.) is used to address these possibilities, and four hypotheses were tested/ (1) O(3) exposure reduces leaf pools of soluble sugars; (2) pruning leaf area and reducing source strength to match that of O(3)-treated plants reproduces O(3)-effects; (3) pruning lower leaf area more closely reproduces O(3) effects than pruning upper leaf area; and (4) manipulating plant age and thereby plant size to match O(3)-treated plants reproduces O(3)-effects. All were falsified. Soluble sugars did not decline. Pruning upper and lower leaves and manipulating plant age all reduced biomass and leaf area similarly to O(3)-exposure, but neither reproduced O(3) effects on biomass allocation nor root function. It is concluded that O(3) induces an allometric shift in carbohydrate allocation that is not mediated by photosynthetic inhibition nor by alteration of developmental age. Effects of O(3) could be mediated by direct effects on phloem loading, with consequent inhibition of translocation to roots and root system development.

Biomass↗

PubMed1995

A Mutation Altering Auxin Homeostasis and Plant Morphology in Arabidopsis.

Many aspects of plant development are associated with changing concentrations of the phytohormone auxin. Several stages of root formation exhibit extreme sensitivities to exogenous auxin and are correlated with shifts in endogenous auxin concentration. In an effort to elucidate mechanisms regulating development of adventitious roots, an ethyl methanesulfonate-mutagenized M2 population of Arabidopsis was screened for mutants altered in this process. A recessive nuclear mutant, rooty (rty), displayed extreme proliferation of roots, inhibition of shoot growth, and other alterations suggesting elevated responses to auxin or ethylene. Wild-type Arabidopsis seedlings grown on auxin-containing media phenocopied rty, whereas rty seedlings were partially rescued on cytokinin-containing media. Analysis by gas chromatography-selected ion monitoring-mass spectrometry showed endogenous indole-3-acetic acid concentrations to be two to 17 times higher in rty than in the wild type. Dose-response assays with exogenous indole-3-acetic acid indicated equal sensitivities to auxin in tissues of the wild type and rty. Combining rty with mutations conferring resistance to auxin (axr1-3) or ethylene (etr1-1) suggested that root proliferation and restricted shoot growth are auxin effects, whereas other phenotypic alterations are due to ethylene. Four mutant alleles from independently mutagenized populations were identified, and the locus was mapped using morphological and restriction fragment length polymorphism markers to 3.9 centimorgans distal to marker m605 on chromosome 2. The wild-type RTY gene product may serve a critical role in regulating auxin concentrations and thereby facilitating normal plant growth and development.

Journal Article↗

PubMed1994

ENOD12, an early nodulin gene, is not required for nodule formation and efficient nitrogen fixation in alfalfa.

To demonstrate the importance of an extensively studied early nodulin gene ENOD12 in symbiotic nodule development, plants of different Medicago sativa subspecies were tested for the presence or absence of ENOD12 alleles. In M. s. ssp coerulea w2 (Mcw2), two ENOD12 genes were detected, whereas in M. s. ssp quasifalcata k93 (Mqk93) only one gene was present. In both plants, the ENOD12 genes were expressed in nodules induced by Rhizobium meliloti. The nucleotide sequence of the ENOD12 genes showed that the two Mcw2-specific genes were similar to the ENOD12A and ENOD12B genes of the tetraploid M. s. ssp sativa. ENOD12 from Mqk93 was similar to the corresponding gene found in M. truncatula. From the aligned ENOD12 sequences, an evolutionary tree was constructed. Genetic analysis of the progenies of a cross between Mqk93 and Mcw2 showed that several offspring in F1 carried a null allele originating from Mcw2, and among the F2 progenies, plants with the null allele only lacking the ENOD12 gene appeared. Surprisingly, the ENOD12-deficient plants were similar to their wild-type parents in viability, nodule development, nodule structure, and nitrogen fixation efficiency. Therefore, we concluded that in Medicago the ENOD12 gene is not required for symbiotic nitrogen fixation. Furthermore, we proposed that the heterozygous nature of these legumes can be exploited for the identification of mutated alleles of other known nodulin genes; this will permit the construction of plant mutants deficient in these genes.

Alleles↗

PubMed2002

HEN1 functions pleiotropically in Arabidopsis development and acts in C function in the flower.

Four classes of floral homeotic MADS domain proteins specify the identities of the four organ types in an Arabidopsis flower. While the activities of the MADS domain proteins are essentially confined to the flower or to the inflorescence, several genes, such as APETALA2, HUA1 and HUA2, also act outside the flower in addition to their organ identity functions inside the flower. We identified a new gene, HUA ENHANCER 1 (HEN1) from a sensitized genetic screen in the hua1-1 hua2-1 background that is compromised in floral homeotic C function. We showed that HEN1, like the C function gene AGAMOUS, acts to specify reproductive organ identities and to repress A function. HEN1 also shares AG's non-homeotic function in controlling floral determinacy. HEN1 may achieve these functions by regulating the expression of AG. hen1 single mutants exhibit pleiotropic phenotypes such as reduced organ size, altered rosette leaf shape and increased number of coflorescences, during most stages of development. Therefore, HEN1, like the A function gene AP2, plays multiple roles in plant development as well as acting in organ identity specification in the flower. HEN1 codes for a novel protein and is expressed throughout the plant.

Amino Acid Sequence↗

PubMed2004

A defect in atToc159 of Arabidopsis thaliana causes severe defects in leaf development.

Plastid protein import 2 (ppi2), a mutant of Arabidopsis thaliana, lacks a homologue of a component of the translocon at the outer envelope membrane of chloroplasts (Toc), designated Toc159 of the pea. Toc159 is thought to be essential for the import of photosynthetic proteins into chloroplasts. In order to investigate the effect of protein import on the plant development, we examined the morphologies of the developing leaves and the shoot apical meristems (SAM) in the ppi2 plants. Our histological analysis revealed that the development of leaves is severely affected in ppi2, while the structure of SAM is normal. Abnormalities in leaves became obvious in the later stages of leaf development, resulting in the generation of mature leaves with fewer mesophyll cells and more intercellular spaces as compared with the wild type. Palisade and spongy tissues of the mature leaves were indistinguishable in ppi2. Replication of chloroplast DNA was also suggested to be impaired in ppi2. Our results suggest that protein import into chloroplasts is important for the normal development of leaves.

Arabidopsis↗

PubMed1993

The importance of starch biosynthesis in the wrinkled seed shape character of peas studied by Mendel.

The wrinkled-seed mutant (rr) of pea (Pisum sativum L.) arose through mutation of the gene encoding starch-branching enzyme isoform I (SBE1) by insertion of a transposon-like element into the coding sequence. Two isoforms of starch-branching enzyme have been documented in the developing pea embryo. The second isoform, SBEII, is expressed towards the later stages of embryo development while SBEI is expressed highly in the early stages. Due to mutation of SBEI the total amount of starch and the proportion of amylopectin, a branched starch polymer, are greatly reduced in the wrinkled (rr) line as compared to that in the wild-type, round (RR) line. Consequently, the level of sucrose in the rr line is nearly two fold that of the RR line. Increased sucrose concentration in the developing embryos of this mutant line causes increased uptake of water and thereby increases the cell size and fresh weight. During seed maturation in these mutant seeds a greater loss of water occurs. As a result, the wrinkled seed phenotype develops. Besides this morphological variation, the mutation also causes changes in the amount of lipid and of one storage protein, legumin. This review article discusses the role of the SBEI enzyme in causing such metabolic changes in the developing embryos with the implication that metabolism can play a central role in plant development.

1,4-alpha-Glucan Branching Enzyme↗

PubMed2006

Spatial and temporal divergence of expression in duplicated barley germin-like protein-encoding genes.

Subfunctionalization is the process by which a pair of duplicated genes, or paralogs, experiences a reduction of individual expression patterns or function while still reproducing the complete expression pattern and function of the ancestral gene. Two germin-like protein (GLP)-encoding genes, GerB and GerF, are paralogs that belong to a small gene family in barley (Hordeum vulgare). Both genes share high nucleotide sequence similarity in coding and noncoding regions and encode identical apoplastic proteins. The use of RNA gel blots, coupled with single-stranded conformation polymorphism (SSCP) analysis of RT-PCR products, elucidated the developmental and tissue-specific expression patterns of each gene. Individual expression patterns provided evidence of both overlapping redundancy and early subfunctionalization. GerB is predominantly expressed in developing shoots, while GerF is predominantly expressed in seedling roots, developing spikes, and pericarp/testa. GerF promoter deletion studies located a region (-356/-97) responsible for high promoter activity and showed the ability of GerB and GerF upstream regions to drive gfp expression in coleoptiles, epicarps, and lemma/palea of developing spikes. The observed expression patterns are consistent with proposed roles in plant development and defense mechanisms for this gene family. These roles may explain why redundancy has been selectively maintained in this duplicate gene pair.

Base Sequence↗

PubMed1991

Developmental Regulation of a Plasma Membrane Arabinogalactan Protein Epitope in Oilseed Rape Flowers.

We have identified and characterized the temporal and spatial regulation of a plasma membrane arabinogalactan protein epitope during development of the aerial parts of oilseed rape using the monoclonal antibody JIM8. The JIM8 epitope is expressed by the first cells of the embryo and by certain cells in the sexual organs of flowers. During embryogenesis, the JIM8 epitope ceases to be expressed by the embryo proper but is still found in the suspensor. During differentiation of the stamens and carpels, expression of the JIM8 epitope progresses from one cell type to another, ultimately specifying the endothecium and sperm cells, the nucellar epidermis, synergid cells, and the egg cell. This complex temporal sequence demonstrates rapid turnover of the JIM8 epitope. There is no direct evidence for any cell-inductive process in plant development. However, if cell-cell interactions exist in plants and participate in flower development, the JIM8 epitope may be a marker for one set of them.

Journal Article↗