The Diatom EST Database.

The Diatom EST database provides integrated access to expressed sequence tag (EST) data from two eukaryotic microalgae of the class Bacillariophyceae, Phaeodactylum tricornutum and Thalassiosira pseudonana. The database currently contains sequences of close to 30,000 ESTs organized into PtDB, the P.tricornutum EST database, and TpDB, the T.

The INO80 protein controls homologous recombination in Arabidopsis thaliana.

Homologous recombination (HR) serves a dual role in providing genetic flexibility and in maintaining genome integrity. Little is known about the regulation of HR and other repair pathways in the context of chromatin. We report on a mutant affected in the expression of the Arabidopsis INO80 ortholog of the SWI/SNF ATPase family, which shows a reduction of the HR frequency to 15% of that in wild-type plants.

Manipulation of DET1 expression in tomato results in photomorphogenic phenotypes caused by post-transcriptional gene silencing.

The tomato HIGH PIGMENT-2 gene encodes an orthologue of the Arabidopsis nuclear protein DE-ETIOLATED 1 (DET1). From genetic analyses it has been proposed that DET1 is a negative regulator of light signal transduction, and recent results indicate that it may control light-regulated gene expression at the level of chromatin remodelling. To gain further understanding about the function of DET1 during plant development, we generated a range of overexpression constructs and introduced them into tomato.

The genome of the diatom Thalassiosira pseudonana: ecology, evolution, and metabolism.

Diatoms are unicellular algae with plastids acquired by secondary endosymbiosis. They are responsible for approximately 20% of global carbon fixation. We report the 34 million-base pair draft nuclear genome of the marine diatom Thalassiosira pseudonana and its 129 thousand-base pair plastid and 44 thousand-base pair mitochondrial genomes.

Chromatin techniques for plant cells.

A large number of recent studies have demonstrated that many important aspects of plant development are regulated by heritable changes in gene expression that do not involve changes in DNA sequence. Rather, these regulatory mechanisms involve modifications of chromatin structure that affect the accessibility of target genes to regulatory factors that can control their expression. The central component of chromatin is the nucleosome, containing the highly conserved histone proteins that are known to be subject to a wide range of post-translational modifications, which act as recognition codes for the binding of chromatin-associated factors.

Manipulation of light signal transduction as a means of modifying fruit nutritional quality in tomato.

Fruit constitutes a major component of human diets, providing fiber, vitamins, and phytonutrients. Carotenoids are a major class of compounds found in many fruits, providing nutritional benefits as precursors to essential vitamins and as antioxidants. Although recent gene isolation efforts and metabolic engineering have primarily targeted genes involved in carotenoid biosynthesis, factors that regulate flux through the carotenoid pathway remain largely unknown.

The photomorphogenesis regulator DET1 binds the amino-terminal tail of histone H2B in a nucleosome context.

Light provides a major source of information from the environment during plant growth and development. Recent results suggest that the key events controlling light-regulated gene expression in plants are translocation of the phytochrome photoreceptors into the nucleus, followed by their binding to transcription factors such as PIF3. Coupled with this, the degradation of positively acting intermediates such as the transcription factor HY5 by COP1 and the COP9 signalosome appears to be an important process whereby photomorphogenesis is repressed in darkness (e.

Revealing the molecular secrets of marine diatoms.

Diatoms are unicellular photosynthetic eukaryotes that contribute close to one quarter of global primary productivity. In spite of their ecological success in the world's oceans, very little information is available at the molecular level about their biology. Their most well-known characteristic is the ability to generate a highly ornamented silica cell wall, which made them very popular study organisms for microscopists in the last century.

The role of calcium in oligogalacturonide-activated signalling in soybean cells.

Alpha-1,4-Linked oligogalacturonides (OGs) are pectic fragments of the plant cell wall that are perceived by the plant cell as signalling molecules. Using cytosolic aequorin-expressing soybean (Glycine max L.) cells, we have analysed cytosolic Ca(2+) changes and the oxidative burst induced by OGs with different degrees of polymerization.

Social factors regulate female-female aggression and affiliation in prairie voles.

Although patterns of aggression and affiliation may play a major role in social organization, the mechanisms underlying these behaviors are not well understood. The purpose of this study was to examine the effects of social and hormonal experience on female-female aggression and affiliation in prairie voles, Microtus ochrogaster. Prairie voles exhibit the traits of social monogamy and tend to live in communal families structured around a male-female pair.

Genome properties of the diatom Phaeodactylum tricornutum.

Diatoms are a ubiquitous class of microalgae of extreme importance for global primary productivity and for the biogeochemical cycling of minerals such as silica. However, very little is known about diatom cell biology or about their genome structure. For diatom researchers to take advantage of genomics and post-genomics technologies, it is necessary to establish a model diatom species.

Molecular insights into the novel aspects of diatom biology.

Diatoms are unicellular photosynthetic eukaryotes that are thought to contribute as much as 25% of global primary productivity. In spite of their ecological importance in the worlds oceans, very little information is available at the molecular level about the novel aspects of their biology. Recent advances, such as the development of gene transfer protocols, are now allowing the genetic dissection of diatom biology.

Perception of environmental signals by a marine diatom.

Diatoms are a key component of marine ecosystems and are extremely important for the biogeochemical cycling of silica and as contributors to global fixed carbon. However, the answers to fundamental questions such as what diatoms can sense in their environment, how they respond to external signals, and what factors control their life strategies are largely unknown. We generated transgenic diatom cells containing the calcium-sensitive photoprotein aequorin to determine whether changes in calcium homeostasis are used to respond to relevant environmental stimuli.

The role of calcium and activated oxygens as signals for controlling cross-tolerance.

Plants are confronted on a regular basis with a range of environmental stresses. These include abiotic insults caused by, for example, extreme temperatures, altered water status or nutrients, and biotic stresses generated by a plethora of plant pathogens. Many studies have shown that the cellular responses to these environmental challenges are rather similar, which might be why plants resistant to one stress are sometimes cross-tolerant to others.

Semi-quantitative RT-PCR analysis of photoregulated gene expression in marine diatoms.

The low cell densities of diatoms and other phytoplankton in culture has precluded the use of classical RNA analysis techniques for routine studies of gene expression in large numbers of samples. This has seriously hampered studies of the basic biology of such organisms. To circumvent this problem, we have developed a high-throughput semi-quantitative RT-PCR-based protocol and used it to monitor expression of a gene encoding a fucoxanthin, chlorophyll a/c-binding protein (FCP) in the centric planktonic diatom Thalassiosira weissflogii.

Transformation of Nonselectable Reporter Genes in Marine Diatoms.

: We report the genetic transformation of two marine diatoms by microparticle bombardment. The pennate diatom Phaeodactylum tricornutum was transformed with the bacterial gene Sh ble from Streptoalloteichus hindustanus, which confers resistance to the antibiotics phleomycin and zeocin. Transformants contained between 1 and 10 copies of the exogenous DNA integrated into the genome by illegitimate recombination at apparently random locations.

Phenotype of the tomato high pigment-2 mutant is caused by a mutation in the tomato homolog of DEETIOLATED1.

Tomato high pigment (hp) mutants are characterized by their exaggerated photoresponsiveness. Light-grown hp mutants display elevated levels of anthocyanins, are shorter and darker than wild-type plants, and have dark green immature fruits due to the overproduction of chlorophyll pigments. It has been proposed that HP genes encode negative regulators of phytochrome signal transduction.

Molecular cloning and characterization of a cDNA encoding asparagine synthetase from soybean (Glycine max L.) cell cultures.

A cDNA encoding glutamine-dependent asparagine synthetase was isolated from dark-adapted Glycine max cell culture. The deduced amino acid sequence showed 76-89% identity with other plant sequences. The gene for asparagine synthetase is expressed predominantly in shoots as compared to roots of etiolated plants and the level of expression decreases following light treatment, suggesting that the gene expression is down-regulated by light.

Molecular cloning and characterization of a cDNA encoding early light-inducible protein from soybean (Glycine max L.).

A cDNA for early light-inducible protein (ELIP) was isolated from Glycine max L. and the nucleotides were sequenced. The cDNA encodes a 192-residue polypeptide of 20.

Tuning in to the signals controlling photoregulated gene expression in plants.

Plants have developed flexible mechanisms to respond appropriately to environmental signals. These stimuli are transduced by largely unknown signalling pathways that are likely to be modulated by endogenous developmental signals to produce an integrated response that coordinately regulates gene expression. Light is a critical environmental signal that controls many aspects of plant development via a series of photoreceptors that are able to respond to different light wavelengths.

Phytochrome-regulated repression of gene expression requires calcium and cGMP.

The plant photoreceptor phytochrome A utilizes three signal transduction pathways, dependent upon calcium and/or cGMP, to activate genes in the light. In this report, we have studied the phytochrome A regulation of a gene that is down-regulated by light, asparagine synthetase (AS1). We show that AS1 is expressed in the dark and repressed in the light.

Cloning, subcellular localization and expression of CHL1, a subunit of magnesium-chelatase in soybean.

Mg-insertion is the first committed step in chlorophyll synthesis and is catalyzed by Mg-chelatase. In photosynthetic bacteria, bchI gene product was suggested to be a subunit of Mg-chelatase. We isolated a bchI homolog from a soybean cDNA library and designated it as chlI.