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PubMed1987

Use of nuclear mutants in the analysis of chloroplast development.

Although a wide range of mutations in the nuclear genome also affect chloroplast biogenesis, their pleiotropic nature often limits their use in studying nuclear genes that regulate or facilitate chloroplast development. However, many mutations that cause a high-chlorophyll-fluorescent (hcf) phenotype exhibit limited pleiotrophy, causing the loss of functionally related sets of chloroplast polypeptides. Several hcf mutations are described that result in the loss of one specific protein complex from the thylakoid membrane. Chloroplast and cytosolic mRNAs coding for component polypeptides of the missing complex are unaffected in the mutants, suggesting that each mutation disrupts some process in the synthesis and assembly of the missing complex. Another hcf mutation causes both the loss of three protein complexes and grossly abnormal thylakoid membrane structures. The primary effect of this mutation might be in the assembly of thylakoid membranes or in the stable accumulation of the three protein complexes. Two other hcf mutations are more pleiotropic. Hcf*-38 causes a quantitative reduction of many chloroplast proteins and a reduction of some chloroplast RNAs, including several splicing intermediates. Hcf*-7 causes a major reduction of all chloroplast-encoded proteins examined. The range of pleiotropic effects of hcf mutations indicates that the mutations identify nuclear genes whose products are involved in a number of different steps in chloroplast development. Because some of the mutations described have been generated by transposon insertions, they can be cloned using the transposon to identify the mutant allele.

Cell Nucleus↗
PubMed1991

Effect of low temperature stress on the expression of sucrose synthetase in spring and winter wheat plants. Development of a monoclonal antibody against wheat germ sucrose synthetase.

A monoclonal antibody against wheat germ sucrose synthetase is developed and characterized. Its use in studying the effect of cold acclimation on the expression of sucrose synthetase in winter and spring wheat plants is described. The antibody shows cross-reactivity with sucrose synthetase from maize and pea plants, as well as carrot cells. A gradual accumulation of the enzyme as a function of time spent at 2 degrees C is observed in both wheat varieties. In contrast, an initial sharp rise in the mRNA level is observed, which agrees with the previously reported response of maize plants subjected to anaerobic stress.

Antibodies, Monoclonal↗
PubMed2006

Growth of Lygeum spartum in acid mine tailings: response of plants developed from seedlings, rhizomes and at field conditions.

Lygeum spartum is a native species in semiarid Mediterranean areas that grows spontaneously on acid mine tailings. We aimed to study the suitability of this plant for phytostabilization. L. spartum was grown from both seeds and rhizomes in acid mine tailings with various fertilizer and lime treatments. Untreated soils had a solution pH of 2.9 with high concentrations of dissolved salts (Electrical Conductivity 25 dS m(-1)) and Zn (3100 mg L(-1)). Plants grown on untreated soil had high shoot metal concentrations (>4000 mg kg(-1)Zn). Liming increased the solution pH to 5.5 and reduced the dissolved salts by more than 75%, resulting in lower shoot metal accumulation. Plants grown from rhizomes accumulated less metal than those grown from seeds. Plants collected in the field had metal concentrations an order of magnitude less than plants raised in the growth chamber. These differences may be due to the higher moisture content and homogeneous nature of the soils used in the pot experiment.

Anions↗
PubMed2006

AtEXO70A1, a member of a family of putative exocyst subunits specifically expanded in land plants, is important for polar growth and plant development.

The exocyst is a hetero-oligomeric protein complex involved in exocytosis and has been extensively studied in yeast and animal cells. Evidence is now accumulating that the exocyst is also present in plants. Bioinformatic analysis of genes encoding plant homologs of the exocyst subunit, Exo70, revealed that three Exo70 subgroups are evolutionarily conserved among angiosperms, lycophytes and mosses. Arabidopsis and rice contain 22 and approximately 39 EXO70 genes, respectively, which can be classified into nine clusters considered to be ancient in angiosperms (one has been lost in Arabidopsis). We characterized two independent T-DNA insertional mutants of the AtEXO70A1 gene (exo70A1-1 and exo70A1-2). Heterozygous EXO70A1/exo70A1 plants appear to be normal and segregate in a 1:2:1 ratio, suggesting that neither male nor female gametophytes are affected by the EXO70A1 disruption. However, both exo70A1-1 and exo70A1-2 homozygotes exhibit an array of phenotypic defects. The polar growth of root hairs and stigmatic papillae is disturbed. Organs are generally smaller, plants show a loss of apical dominance and indeterminate growth where instead of floral meristems new lateral inflorescences are initiated in a reiterative manner. Both exo70A1 mutants have dramatically reduced fertility. These results suggest that the putative exocyst subunit EXO70A1 is involved in cell and organ morphogenesis.

Arabidopsis↗
PubMed1995

Chalcone synthase localization in early stages of plant development. I. Immunohistochemical use of plasmolysis for localizing the enzyme in epidermal cell cytoplasm of illuminated buckwheat hypocotyls.

Immunohistochemical methods combined with progressive plasmolysis were used to localize chalcone synthase (CHS), an important enzyme for plant metabolism of aromatics in hypocotyls of illuminated buckwheat (Fagopyrum esculentum M.) seedlings. Illumination of etiolated seedlings with white light results in anthocyanin synthesis in the epidermal layer of the hypocotyl. Anthocyanin-containing epidermal peels, after fixation for 30 min in 4% paraformaldehyde, 2.5% glutaraldehyde, 0.1% caffeine, were treated with a specific rabbit anti-buckwheat CHS antibody and a 20 nm goat anti-rabbit IgG gold conjugate. CHS is specifically shown in epidermal cells as pink to dark red deposits. Progressive plasmolysis combined with our immunohistochemical method showed that CHS was located exclusively in the cytoplasm of the epidermal cells of buckwheat hypocotyls except for the guard cells, which contained no detectable CHS.

Acyltransferases↗
PubMed2005

An allelic series reveals essential roles for FY in plant development in addition to flowering-time control.

The autonomous pathway functions to promote flowering in Arabidopsis by limiting the accumulation of the floral repressor FLOWERING LOCUS C (FLC). Within this pathway FCA is a plant-specific, nuclear RNA-binding protein, which interacts with FY, a highly conserved eukaryotic polyadenylation factor. FCA and FY function to control polyadenylation site choice during processing of the FCA transcript. Null mutations in the yeast FY homologue Pfs2p are lethal. This raises the question as to whether these essential RNA processing functions are conserved in plants. Characterisation of an allelic series of fy mutations reveals that null alleles are embryo lethal. Furthermore, silencing of FY, but not FCA, is deleterious to growth in Nicotiana. The late-flowering fy alleles are hypomorphic and indicate a requirement for both intact FY WD repeats and the C-terminal domain in repression of FLC. The FY C-terminal domain binds FCA and in vitro assays demonstrate a requirement for both C-terminal FY-PPLPP repeats during this interaction. The expression domain of FY supports its roles in essential and flowering-time functions. Hence, FY may mediate both regulated and constitutive RNA 3'-end processing.

Alleles↗
PubMed2003

In situ hybridization analysis of protein kinase CK2 expression during plant development.

Protein kinase CK2 (EC 2.7.1.37) is a ubiquitous Ser/Thr kinase composed of two subunits, a subunit (catalytic) and a subunit (regulatory). Although CK2 is one of the components of the network that controls the eukaryotic cell cycle, very little is known about the developmental control of its expression, particularly in plants. Using in situ hybridization we have determined the pattern of expression of its two subunits in relation to plant morphogenesis. Our results show a cell-specific mRNA accumulation, equivalent for both subunits, which suggests a co-ordinate regulation during development. The spatial and temporal pattern of expression correlates with the appearance of the meristems, and high levels of transcripts are also present in differentiated tissues with high mitotic activity. These results confirm the transcriptional regulation of CK2 and establish a general correlation with cell proliferation in a developmental context. They also provide suggestive evidence for the requirement of CK2 expression for the initiation and organization of meristem activity.

Journal Article↗
PubMed1996

Regulation of a carotenoid biosynthesis gene promoter during plant development.

Carotenoids are terpenoid pigments which are accumulated in the chloroplasts of leaves and in the chromoplasts of many flowers and fruits. Phytoene desaturase (Pds), the second dedicated enzyme in carotenoid biosynthesis, is encoded in tomato by a single copy gene. A 2 kb fragment from the tomato Pds gene, comprising 1.5 kb from the promoter and 0.5 kb from the 5' non-translated region, is able to drive developmentally regulated expression of the GUS reporter gene in transgenic tomato and tobacco plants. In tomato, high levels of Pds/GUS expression are found in organs and at stages of development where chromoplasts are formed: petals, anthers and ripening fruits. Tobacco petals and fruits, which do not contain chromoplasts, show instead low levels of Pds/GUS expression. Transgenic tobacco seedlings were subjected to treatment with a range of inhibitors of carotenoid and chlorophyll biosynthesis. The results indicate that, in green tissues, carotenoid and chlorophyll levels are tightly co-regulated and that a chemically induced arrest in pigment biosynthesis results in activation of the Pds promoter. The promoter is also induced in etiolated seedlings, which contain much lower carotenoid levels than light-grown seedlings. These data suggest that in green tissues Pds gene transcription may respond to end-product regulation.

Base Sequence↗
PubMed1996

Application of diluted chlorine dioxide to radish and lettuce nurseries insignificantly reduced plant development.

The possible toxicity of a commercial chlorine dioxide preparation (Halox E-100) was evaluated on radish and lettuce seedlings growing in pots under controlled conditions. A single application of various dilutions to radish seedlings growing in a sterile or nonsterile commercial plant substrate only slightly decreased plant dry weight. At the end of the experiments, the plants appeared unaffected by the treatments. Other common plant parameters (root and stem length, number of true leaves) were unaffected or even enhanced. Halox did not reduce the total level of soil bacteria even after four consecutive applications at any dilution rate. In nonsterile soil, high Halox dilution (1:1000) significantly decreased plant dry weight, and the other concentrations (1:10,000; 1:50,000, and 1:100,000) had no apparent effect on the size of the plants. In sterile soil, high concentrations of Halox (1:1000 and 1:10,000) significantly decreased plant growth, but higher dilutions produced no significant reduction in plant dry weight. For radish plants growing in organic matter-free sand only, dilution of 1:10,000 reduced plant growth. On lettuce plants, dilutions from 1:5000 to 1:25,000 did not reduce plant growth. High levels of Halox (1:1000) were toxic to both radish and lettuce seedlings growing in sand and resulted in chlorosis and significant depression of plant growth. Further dilutions of Halox (equivalent to the level used in water disinfection) significantly decreased toxicity for both plant species. Low concentrations of Halox (> 1:50,000) had no apparent effect on the appearance of both plant species. In conclusion, this study suggests that chlorine dioxide-treated drinking water can be considered safe for growing plants; this treatment should be further evaluated using other plant species under more realistic growth conditions.

Chlorine↗
PubMed2005

Severe acute respiratory syndrome (SARS) S protein production in plants: development of recombinant vaccine.

In view of a recent spread of severe acute respiratory syndrome (SARS), there is a high demand for production of a vaccine to prevent this disease. Recent studies indicate that SARS-coronavirus (CoV) spike protein (S protein) and its truncated fragments are considered the best candidates for generation of the recombinant vaccine. Toward the development of a safe, effective, and inexpensive vaccine candidate, we have expressed the N-terminal fragment of SARS-CoV S protein (S1) in tomato and low-nicotine tobacco plants. Incorporation of the S1 fragment into plant genomes as well as its transcription was confirmed by PCR and RT-PCR analyses. High levels of expression of recombinant S1 protein were observed in several transgenic lines by Western blot analysis using specific antibodies. Plant-derived antigen was evaluated to induce the systemic and mucosal immune responses in mice. Mice showed significantly increased levels of SARS-CoV-specific IgA after oral ingestion of tomato fruits expressing S1 protein. Sera of mice parenterally primed with tobacco-derived S1 protein revealed the presence of SARS-CoV-specific IgG as detected by Western blot and ELISA analysis.

Amino Acid Sequence↗
PubMed2005

The ABC of auxin transport: the role of p-glycoproteins in plant development.

A surprising outcome of the Arabidopsis genome project was the annotation of a large number of sequences encoding members of the ABC transporter superfamily, including 22 genes encoding the p-glycoprotein (PGP) subfamily. As mammalian PGP orthologs are associated with multiple drug resistance, plant PGPs were initially presumed to function in detoxification, but were soon seen to have a developmental role. Here, we summarise recent studies of plant PGPs indicating that PGPs mediate the cellular and long-distance transport of the plant hormone auxin. One class of PGPs, represented by AtPGP1, catalyze auxin export, while another class with at least one member, AtPGP4, appears to function in auxin import. Current models on the physiological role of PGPs, their functional interaction and their involvement in cell-to cell (polar) auxin transport are discussed.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2005

Cell death and organ development in plants.

Programmed cell death (PCD) is an important feature of plant development; however, the mechanisms responsible for its regulation in plants are far less well understood than those operating in animals. In this review data from a wide variety of plant PCD systems is analyzed to compare what is known about the underlying mechanisms. Although senescence is clearly an important part of plant development, only what is known about PCD during senescence is dealt with here. In each PCD system the extracellular and intracellular signals triggering PCD are considered and both cytological and molecular data are discussed to determine whether a unique model for plant PCD can be derived. In the majority of cases reviewed, PCD is accompanied by the formation of a large vacuole, which ruptures to release hydrolytic enzymes that degrade the cell contents, although this model is clearly not universal. DNA degradation and the activation of proteases is also common to most plant PCD systems, where they have been studied; however, breakdown of DNA into nucleosomal units (DNA laddering) is not observed in all systems. Caspase-like activity has also been reported in several systems, but the extent to which it is a necessary feature of all plant PCD has not yet been established. The trigger for tonoplast rupture is not fully understood, although active oxygen species (AOS) have been implicated in several systems. In two systems, self incompatibility and tapetal breakdown as a result of cytoplasmic male sterility, there is convincing evidence for the involvement of mitochondria including release of cytochrome c. However, in other systems, the role of the mitochondrion is not clear-cut. How cells surrounding the cell undergoing PCD protect themselves against death is also discussed as well as whether there is a link between the eventual fate of the cell corpse and the mechanism of its death.

Apoptosis↗
PubMed2006

Chromatin assembly factor CAF-1 is required for cellular differentiation during plant development.

Chromatin assembly factor CAF-1 facilitates the formation of nucleosomes on newly replicated DNA in vitro. However, the role of CAF-1 in development is poorly understood because mutants are not available in most multicellular model organisms. Biochemical evidence suggests that FASCIATA1, FASCIATA2 and MSI1 form CAF-1 in Arabidopsis thaliana. Because fasciata mutants are viable, CAF-1 is not essential for cell division in plants. Arabidopsis CAF-1 mutants have defects in shoot apical meristems; in addition, CAF-1 is required to establish seedling architecture, leaf size and trichome differentiation. CAF-1 is needed to restrict branching of trichomes on rosette leaves. Increased trichome branching in CAF-1 mutants is not strictly correlated with increased nuclear DNA content. In addition, fas2 glabra3 double mutants show an additive genetic interaction, demonstrating that CAF-1 acts genetically parallel to the GLABRA3-containing, endoreduplication-coupled trichome branching pathway. However, CAF-1 is often needed to restrict endoreduplication, because seedlings of most CAF-1 mutants have increased ploidy. Notably, in the Landsberg erecta background, loss of CAF-1 does not affect ploidy, demonstrating that loss of CAF-1 can be compensated in some Arabidopsis accessions. These results reveal that the functions of FAS1, FAS2 and MSI1 are not restricted to meristems, but are also needed to control genome replication at multiple steps of development.

Animals↗
PubMed1990

Abnormal plant development and down-regulation of phenylpropanoid biosynthesis in transgenic tobacco containing a heterologous phenylalanine ammonia-lyase gene.

Biosynthesis of phenylpropanoid natural products in tobacco was perturbed by introduction of a heterologous (bean) phenylalanine ammonia-lyase (PAL; L-phenylalanine ammonia-lyase, EC 4.3.1.5) gene, modified by inclusion of cauliflower mosaic virus 35S enhancer sequences in its promoter. These transgenic plants can exhibit a series of unusual phenotypes including localized fluorescent lesions, altered leaf shape and texture, reduced signification in xylem, stunted growth, reduced pollen viability, and altered flower morphology and pigmentation. Genetic analysis of a transformant with severe symptoms showed that symptom development was inherited as a single, partially dominant trait and cosegregated with reduced levels of PAL activity and soluble phenylpropanoid products. Accumulation of transcripts encoded by the endogenous tobacco PAL genes was suppressed. We conclude that the transgene disrupts PAL regulation and that some of the phenotypes reflect interference with putative signals dependent on phenylpropanoid biosynthesis.

Journal Article↗
PubMed1994

Getting to the root of plant development: the genetics of Arabidopsis root formation.

Root development in Arabidopsis thaliana is amenable to molecular genetic analyses because of its simplicity and accessibility. Genetic screens have identified a rich collection of mutants that can be used to address a variety of fundamental questions in plant developmental biology. These mutants have defects in genes that govern organ formation, meristem activity, cell differentiation and response to environmental conditions.

Arabidopsis↗