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At least 991 records · Page 55Linked to original sources

PubMed1998

The retinoblastoma pathway in plant cell cycle and development.

The activity of cyclin-dependent kinases (CDKs) on specific targets mediates the temporal regulation of plant cell cycle transitions. The sequential activity of CDKs and the spatial regulation of cell proliferation during plant development, however, are still poorly understood. Understanding these aspects depends on the identification of the downstream targets and upstream modulators of CDKs and their regulation in response to mitogenic and/or differentiation signals. Current efforts to elucidate the answers to these questions are very promising; in particular, recent works reveal the essential role that the retinoblastoma pathway plays in controlling cell cycle progression and, presumably, some developmental events.

Amino Acid Sequence↗

PubMed2000

Engineering direct fructose production in processed potato tubers by expressing a bifunctional alpha-amylase/glucose isomerase gene complex.

Manipulation of starch biosynthesis/degradation and formation of novel molecules in storage organs of plants through genetic engineering is an attractive but technically challenging goal. We report here, for the first time, that starch was degraded and glucose and fructose were produced directly when crushed potato tubers expressing a starch degrading bifunctional gene were heated for 45 minutes at 65 degrees C. To achieve this, we have constructed a fusion gene encoding the thermostable enzymes: alpha-amylase (Bacillus stearothermophilus) and glucose isomerase (Thermus thermophilus). The chimeric gene was placed under the control of the granule-bound-starch synthase promoter. This enzymatic complex produced in transgenic tubers was only active at high temperature (65 degrees C). More than 100 independent transgenic potato plants were regenerated. Molecular analyses confirmed the stable integration of the chimeric gene into the potato genome. The biochemical analyses performed on young and old tubers after high-temperature treatment (65 degrees C) revealed an increase in the formation rate of fructose and glucose by a factor of 16.4 and 5. 7, respectively, in the transgenic tubers as compared to untransformed control tubers. No adverse discernible effect on plant development and metabolism including tuber formation and starch accumulation was observed in the transgenic plants before heat treatment. Our results demonstrate that it is possible to replace starch degradation using microbial enzymes via a system where the enzymes are produced directly in the plants, but active only at high temperature, thus offering novel and viable strategies for starch-processing industries.

Aldose-Ketose Isomerases↗

PubMed2004

Lipid function in plant cell polarity.

The establishment and maintenance of cell polarity play pivotal roles during plant development. During the past five years, proteins that are required for different aspects of plant cell polarity have been identified. However, the functions of lipids and their interactions with proteins that mediate polarity remained largely unaddressed. Recent genetic studies have discovered cell and tissue polarity mutants that have defects in sterol composition, glycosylphosphatidylinositol-anchored proteins, glycosylphosphatidylinositol biosynthesis and phospholipid signalling. Analyses of the affected gene products have provided a first glance at the roles of lipids in cell polarity signalling, as well as in the trafficking and anchoring of polar proteins.

Arabidopsis↗

PubMed2002

Leaf urea metabolism in potato. Urease activity profile and patterns of recovery and distribution of (15)N after foliar urea application in wild-type and urease-antisense transgenics.

The influence of urease activity on N distribution and losses after foliar urea application was investigated using wild-type and transgenic potato (Solanum tuberosum cv Désirée) plants in which urease activity was down-regulated. A good correlation between urease activity and (15)N urea metabolism (NH(3) accumulation) was found. The general accumulation of ammonium in leaves treated with urea indicated that urease activity is not rate limiting, at least initially, for the assimilation of urea N by the plant. It is surprising that there was no effect of urease activity on either N losses or (15)N distribution in the plants after foliar urea application. Experiments with wild-type plants in the field using foliar-applied (15)N urea demonstrated an initial rapid export of N from urea-treated leaves to the tubers within 48 h, followed by a more gradual redistribution during the subsequent days. Only 10% to 18% of urea N applied was lost (presumably because of NH(3) volatilization) in contrast to far greater losses reported in several other studies. The pattern of urease activity in the canopy was investigated during plant development. The activity per unit protein increased up to 10-fold with leaf and plant age, suggesting a correlation with increased N recycling in senescing tissues. Whereas several reports have claimed that plant urease is inducible by urea, no evidence for urease induction could be found in potato.

Enzyme Induction↗

PubMed1994

Complementation of the Tomato anthocyanin without (aw) Mutant Using the Dihydroflavonol 4-Reductase Gene.

We isolated the dihydroflavonol 4-reductase (DFR) gene from tomato (Lycopersicon esculentum) using a previously characterized cDNA as probe. Earlier studies had indicated that the DFR gene is present in tomato as a single gene located on chromosome 2 near the locus anthocyanin without (aw). Mutant alleles of the aw locus result in the complete absence of anthocyanin pigmentation throughout all stages of plant development. When the genomic DFR clone was introduced by Agrobacterium-mediated transformation into plants bearing the aw mutation, primary transgenic seedlings accumulated anthocyanins that could be observed while the plants were still in tissue culture and which continued to be observed as the plants matured. Progeny of self pollinated and backcrossed transgenic plants segregated for anthocyanin pigmentation, and Southern hybridization analyses indicated the presence of the DFR transgene exclusively in those plants with pigmentation. These data indicate that the aw locus likely corresponds to the structural gene for DFR and that DFR can be used as a visual, nondestructive, plant-derived marker gene for tomato.

Journal Article↗

PubMed2005

Cloning and characterization of micro-RNAs from moss.

Micro-RNAs (miRNAs) are one class of endogenous tiny RNAs that play important regulatory roles in plant development and responses to external stimuli. To date, miRNAs have been cloned from higher plants such as Arabidopsis, rice and pumpkin, and there is limited information on their identity in lower plants including Bryophytes. Bryophytes are among the oldest groups of land plants among the earth's flora, and are important for our understanding of the transition to life on land. To identify miRNAs that might have played a role early in land plant evolution, we constructed a library of small RNAs from the juvenile gametophyte (protonema) of the moss Physcomitrella patens. Sequence analysis revealed five higher plant miRNA homologues, including three members of the miR319 family, previously shown to be involved in the regulation of leaf morphogenesis, and miR156, which has been suggested to regulate several members of the SQUAMOSA PROMOTER BINDING-LIKE (SPL) family in Arabidopsis. We have cloned PpSBP3, a moss SPL homologue that contains an miR156 complementary site, and demonstrated that its mRNA is cleaved within that site suggesting that it is an miR156 target in moss. Six additional candidate moss miRNAs were identified and shown to be expressed in the gametophyte, some of which were developmentally regulated or upregulated by auxin. Our observations suggest that miRNAs play important regulatory roles in mosses.

Base Sequence↗

PubMed2003

[Expression of a thermostable bacterial cellulase in transgenic tobacco plants].

The bacterial gene of the thermostable endo-beta-1,4-glucanase (cellulase) was shown to retain its activity and substrate specificity when expressed in transgenic tobacco plants. The leader peptide of the carrot extensin was efficient in transferring the bacterial enzyme into the apoplast. The expression of the bacterial cellulase gene leads to changes in the plant tissue morphology. In the transgenic plant lines, regeneration of primary shoots from callus occurred at the three to five times higher cytokinin (6-BAP) concentration than in control plants. The transgenic plants that expressed the bacterial gene exhibited increased business and altered leaf shape. The transgenic plants developed can be used as models for studying the cellulases role and function in plants.

Bacterial Proteins↗

PubMed1997

Comparative genetics of flowering time.

Analysis of genes controlling flowering time (heading date) contributes to our understanding of fundamental principles of plant development and is of practical importance because of the effects of flowering time on plant adaptation and crop yield. This review discusses the extent to which plants may share common genetic mechanisms for the control of flowering time and the implications of such conservation for gene isolation from the major cereal crops. Gene isolation may exploit the small genome of rice in map-based approaches, utilizing the conservation of gene order that is revealed when common DNA markers are mapped in different species. Alternatively, mechanisms may be conserved within plants as a whole, in which case genes cloned from the model dicot Arabidopsis thaliana provide an alternative route.

Arabidopsis↗

PubMed1990

OCSBF-1, a maize ocs enhancer binding factor: isolation and expression during development.

The ocs-elements comprise a family of related 20-base pair DNA sequences with dyad symmetry that are functional components of the promoters of several genes introduced into the plant nucleus by Agrobacterium transformation or infection by DNA viruses. We describe the isolation and characterization of a maize cDNA that encodes a protein, OCSBF-1, that binds specifically to ocs-element sequences. The 21-kilodalton OCSBF-1 protein was encoded by a single copy, intron-less gene. The gene was differentially expressed in maize plants. Developing leaves had a gradient of OCSBF-1 mRNA with the basal portion of the leaves, which contain dividing and differentiating cells, having 40-fold to 50-fold higher levels of OCSBF-1 transcripts than the apical portion of the leaves, where the cells are fully differentiated. Roots and shoots of young plants had levels of OCSBF-1 mRNA similar to the basal portions of developing leaves. OCSBF-1 contained a small basic amino acid region and a potential leucine zipper motif homologous to the DNA-binding domains of the basic region-leucine zipper family of transcription factors such as Jun and GCN4. A truncated protein with the amino-terminal 76 amino acids of OCSBF-1, encompassing the basic domain and leucine zipper motif, still bound to ocs-element sequences in vitro. OCSBF-1 was able to bind to a site within each half of the ocs-element as well as to animal AP-1 and CREB sites.

Amino Acid Sequence↗

PubMed2025

Chromatin accessibility analysis reveals functional cis-regulatory regions related to fruit development and domestication in tomato.

Non-coding DNA sequences harbor vast regulatory programs that ensure the precise spatiotemporal control of gene expression, which is essential for proper plant development and trait formation. Chromatin accessibility analysis could identify functional DNA regions within the extensive non-coding sequences and infer regulatory elements, serving as a crucial approach to unravel the mysteries of non-coding DNA sequences. Tomato fruit, a fleshy organ, provides a special system for studying fruit development and trait formation. However, the role of cis-accessible chromatin regions (cis-ACRs) during tomato fruit development, particularly in comparison with protein-coding DNA sequences, remains poorly understood. Here, we used ATAC-seq to define the landscape of cis-ACRs during fruit development and domestication in tomato. Temporal differential analysis revealed the dynamic opening and closing of cis-ACRs during fruit development. Comparative analysis of cis-ACRs between cultivated and wild tomatoes highlighted their significant contributions to fruit domestication. Combining analysis with genomic structural variations (SVs) suggested that SVs are likely a key factor in the formation of specific accessible cis-ACRs in cultivated tomatoes. Moreover, using gene editing, we identified a functional cis-ACR within the intron of the MBP3 gene that regulates fruit development and size traits. Overall, our findings provide a comprehensive perspective on the roles of cis-ACRs in tomato fruit development and domestication.

Solanum lycopersicum↗

PubMed2006

[Analysis of shoot apical anatomic changes during the development of Brassica plants].

In this study, we analyzed shoot apical anatomic changes during the development of Brassica plants including cauliflower (Brasscia oleracea L.var. botrytis), broccoli (B. oleracea L.var italica), Chinese cabbage (Brasscia compestris spp. pekinensis) and cabbage (Brasscia oleracea.L.). It has been showed that all of their apical meristems changed from the original tunica-corpus structure to the intergrade subarea, to typical 5-subarea structure and to 4-subarea structure when they went into reproductive development. The shoot apical meristem (SAM) cells were undergoing in different developmental way among these plants after they began reproductive development. The bilateral cells of sub-tunica of Chinese cabbage and cabbage divided into apical leafy primordial, in which lateral inflorescence meristem arised. While the bilateral cells of sub-tunica of cauliflower and broccoli divided into inflorescence meristem, which proliferated into curd or head. The results presented here provide the base for further investigation of anatomic identity of inflorescence phenotype formation and molecular events associated with meristem fate.

Brassica↗

PubMed2005

Seasonal development of ozone-induced foliar injury on tall milkweed (Asclepias exaltata) in Great Smoky Mountains National Park.

The goals of this study were to document the development of ozone-induced foliar injury, on a leaf-by-leaf basis, and to develop ozone exposure relationships for leaf cohorts and individual tall milkweeds (Asclepias exaltata L.) in Great Smoky Mountains National Park. Plants were classified as either ozone-sensitive or insensitive based on the amount of foliar injury. Sensitive plants developed injury earlier in the season and to a greater extent than insensitive plants. Older leaf cohorts were more likely to belong to high injury classes by the end of each of the two growing seasons. In addition, leaf loss was more likely for older cohorts (2000) and lower leaf positions (2001) than younger cohorts and upper leaves, respectively. Most leaves abscised without prior ozone-like stippling or chlorosis. Failure to take this into account can result in underestimation of the effects of ozone on these plants.

Air Pollutants↗

PubMed1995

Ectopic expression of the Arabidopsis transcriptional activator Athb-1 alters leaf cell fate in tobacco.

The Arabidopsis thaliana Athb-1 is a homeobox gene of unknown function. By analogy with homeobox genes of other organisms, its gene product, Athb-1, is most likely a transcription factor involved in developmental processes. We constructed a series of Athb-1-derived genes to examine the roles of Athb-1 in transcriptional regulation and plant development. Athb-1 was found to transactivate a promoter linked to a specific DNA binding site by transient expression assays. In transgenic tobacco plants, overexpression of Athb-1 or its chimeric derivatives with heterologous transactivating domains of the yeast transcription factor GAL4 or herpes simplex virus transcription factor VP16 conferred deetiolated phenotypes in the dark, including cotyledon expansion, true leaf development, and an inhibition of hypocotyl elongation. Expression of Athb-1 or the two chimeric derivatives also affected the development of palisade parenchyma under normal growth conditions, resulting in light green sectors in leaves and cotyledons, whereas other organs in the transgenic plants remained normal. Both developmental phenotypes were induced by glucocorticoid in transgenic plants expressing a chimeric transcription factor comprising the Athb-1 DNA binding domain, the VP16 transactivating domain, and the glucocorticoid receptor domain. Plants with severe inducible phenotypes showed additional abnormality in cotyledon expansion. Our results suggest that Athb-1 is a transcription activator involved in leaf development.

Arabidopsis↗

PubMed2006

Simplified and improved somatic embryogenesis for clonal propagation of Pinus pinaster (Ait.).

In this study, several improvements and simplifications of SE protocols in Pinus pinaster (Ait.), a species of economic importance in the regions of Western Europe, are described. These improvements pertained to all stages of SE including high initiation frequencies in eight control pollinated seed families, relatively high somatic embryo maturation yield when cells were coated with particles of activated charcoal and a rapid production of plants directly in a shade house. The SE initiation frequency from isolated zygotic embryos was high (up to 100%) and plants were produced from 11 embryogenic lines representing all crosses. Based on these results, the estimated number of somatic embryos required to produce 1,000 plants varied from slightly more than the required number of plants to more than double this number depending on the line. Such an estimate is critical in developing plant production strategy when a number of embryogenic lines are considered for production of clonal plants.

Acclimatization↗

PubMedDate not supplied

[Characteristics of Triticum vulgare in the early phases of development (ontogenesis) in space flight].

The effect of space flight factors on the growth and development of wheat grown in a Svetoblock-M unit on the orbital station Mir was investigated. The data obtained allow the conclusion that wheat plants develop flight-induced changes. When compared to control plants, experimental plants show a delayed growth in terms of biometric parameters, different distribution of biogenic elements, lower phytoncidal activity, increased bacterial and fungal contamination, and a changed pigment and lipid composition.

Space Flight↗

PubMed2003

Divalent metal-dependent catalysis and cleavage specificity of CSP41, a chloroplast endoribonuclease belonging to the short chain dehydrogenase/reductase superfamily.

CSP41 is a ubiquitous chloroplast endoribonuclease belonging to the short chain dehydrogenase/reductase (SDR) superfamily. To help elucidate the role of CSP41 in chloroplast gene regulation, the mechanisms that determine its substrate recognition and catalytic activity were investigated. A divalent metal is required for catalysis, most probably to provide a nucleophile for cleavage 5' to the phosphodiester bond, and may also participate in cleavage site selection. This requirement distinguishes CSP41 from other Rossman fold-containing proteins from the SDR superfamily, including several RNA-binding proteins and endonucleases. CSP41 is active only in the presence of MgCl2 and CaCl2. Although Mg2+- and Ca2+-activated CSP41 cleave at identical sites in the single-stranded regions of a stem-loop-containing substrate, Mg2+-activated CSP41 was also able to cleave within the double-stranded region of the stem-loop. Mixed metal experiments with Mg2+ and Ca2+ suggest that CSP41 contains a single divalent metal-binding site which is non-selective, since Mn2+, Co2+ and Zn2+ compete with Mg2+ for binding, although there is no activity in their presence. Using site-directed mutagenesis, we identified three residues, Asn71, Asp89 and Asp103, which may form the divalent metal-binding pocket. The activation constant for Mg2+ (K(A,Mg) = 2.1 +/- 0.4 mM) is of the same order of magnitude as the stromal Mg2+ concentrations, which fluctuate between 0.5 and 10 mM as a function of light and of leaf development. These changes in stromal Mg2+ concentration may regulate CSP41 activity, and thus cpRNA stability, during plant development.

Base Sequence↗

PubMed1996

Plasmodesmal cell-to-cell transport of proteins and nucleic acids.

The complexity associated with post-translational processing, in terms of protein sorting and delivery is now well understood. Although such studies have been focused almost exclusively on the fate of proteins within the cell in which they are synthesized, recent studies indicate that it is time to broaden this focus to incorporate the concept of intercellular targeting of proteins. Direct evidence is now available that viral and endogenous proteins can be synthesized in a particular cell and subsequently transported into neighboring (or more distant) cells. Plasmodesmata, plasma membrane-lined cytoplasmic pores, are thought to establish the intercellular pathway responsible for this cell-to-cell trafficking of macromolecules (proteins and nucleic acids). These recent findings establish a new paradigm for understanding the manner in which higher plants exert control over developmental processes. We discuss the concept that programming of plant development involves supracellular control achieved by plasmodesmal trafficking of informational molecules, herein defined as supracellular control proteins (SCPs). This novel concept may explain why, in plants, cell fate is determined by position rather than cell lineage. Finally, the circulation of long-distance SCPs, within the phloem, may provide the mechanism by which the plant signals to the shoot apical meristem that it is time to switch to the reproductive phase of its development.

Biological Transport↗

PubMed1993

Genetic control of fungal differentiation: the three sporulation pathways of Neurospora crassa.

Sporulation in the mold Neurospora crassa can proceed along three very different pathways, leading to the production of three types of spores. Two asexual sporulation pathways that lead to the formation of macroconidia and microconidia involve budding from hyphae by two different mechanisms. A much more complex sexual reproductive pathway involves the formation of a fruiting body called a perithecium, in which meiosis takes place and ascospores are formed in sac-like cells called asci. Numerous mutations exist that affect these developmental pathways and genes have been isolated that are expressed preferentially during sporulation. The Neurospora sporulation pathways offer a simple system with which to study mechanisms and regulation of development that are usually obscured by complex cell-cell interactions involved in animal and plant development.

Genes, Fungal↗