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C Somerville

Publications and source records attributed to C Somerville.

At least 19 recordsLinked to original sources
PubMed2001

Modifications of cellulose synthase confer resistance to isoxaben and thiazolidinone herbicides in Arabidopsis Ixr1 mutants.

In many higher plants, cellulose synthesis is inhibited by isoxaben and thiazolidinone herbicides such as 5-tert-butyl-carbamoyloxy-3-(3-trifluromethyl) phenyl-4-thiazolidinone. Semidominant mutations at the IXR1 and IXR2 loci of Arabidopsis confer isoxaben and thiazolidinone resistance. Isolation of the IXR1 gene by map-based cloning revealed that it encodes the AtCESA3 isoform of cellulose synthase. The two known mutant alleles contain point mutations that replace glycine 998 with aspartic acid, and threonine 942 with isoleucine, respectively. The mutations occur in a highly conserved region of the enzyme near the carboxyl terminus that is well separated from the proposed active site. Although the IXR1 gene is expressed in the same cells as the structurally related RSW1 (AtCESA1) cellulose synthase gene, these two CESA genes are not functionally redundant.

Alleles↗
PubMed2001

The Arabidopsis Information Resource (TAIR): a comprehensive database and web-based information retrieval, analysis, and visualization system for a model plant.

Arabidopsis thaliana, a small annual plant belonging to the mustard family, is the subject of study by an estimated 7000 researchers around the world. In addition to the large body of genetic, physiological and biochemical data gathered for this plant, it will be the first higher plant genome to be completely sequenced, with completion expected at the end of the year 2000. The sequencing effort has been coordinated by an international collaboration, the Arabidopsis Genome Initiative (AGI). The rationale for intensive investigation of Arabidopsis is that it is an excellent model for higher plants. In order to maximize use of the knowledge gained about this plant, there is a need for a comprehensive database and information retrieval and analysis system that will provide user-friendly access to Arabidopsis information. This paper describes the initial steps we have taken toward realizing these goals in a project called The Arabidopsis Information Resource (TAIR) (www.arabidopsis.org).

Arabidopsis↗
PubMed2000

Genomics. Plant biology in 2010.

The completion of the Arabidopsis sequence will be followed by a new ten-year project that will determine the function of all angiosperm genes. Funding for the U.S. component of this multinational project will originate from a new initiative from the U.S. National Science Foundation called the 2010 Project. Progress toward completion of this ambitious project will necessitate significant changes in how the plant biology community selects and approaches research objectives. The plan envisions that the project will facilitate the development of a computational model of a virtual plant that will allow predictive queries about basic mechanisms underlying plant growth and development.

Arabidopsis↗
PubMed1999

PICKLE is a CHD3 chromatin-remodeling factor that regulates the transition from embryonic to vegetative development in Arabidopsis.

The life cycle of angiosperms is punctuated by a dormant phase that separates embryonic and postembryonic development of the sporophyte. In the pickle (pkl) mutant of Arabidopsis, embryonic traits are expressed after germination. The penetrance of the pkl phenotype is strongly enhanced by inhibitors of gibberellin biosynthesis. Map-based cloning of the PKL locus revealed that it encodes a CHD3 protein. CHD3 proteins have been implicated as chromatin-remodeling factors involved in repression of transcription. PKL is necessary for repression of LEC1, a gene implicated as a critical activator of embryo development. We propose that PKL is a component of a gibberellin-modulated developmental switch that functions during germination to prevent reexpression of the embryonic developmental state.

Arabidopsis↗
PubMed1999

Plant functional genomics.

Nucleotide sequencing of the Arabidopsis genome is nearing completion, sequencing of the rice genome has begun, and large amounts of expressed sequence tag information are being obtained for many other plants. There are many opportunities to use this wealth of sequence information to accelerate progress toward a comprehensive understanding of the genetic mechanisms that control plant growth and development and responses to the environment.

Arabidopsis↗
PubMed1999

Genetic engineering of plant lipids.

Vegetable oils are a major component of human diets, comprising as much as 25% of average caloric intake. Until recently, it was not possible to exert significant control over the chemical composition of vegetable oils derived from different plants. However, the advent of genetic engineering has provided novel opportunities to tailor the composition of plant-derived lipids so that they are optimized with respect to food functionality and human dietary needs. In order to exploit this new capability, it is essential for food scientists and nutritionists to define the lipid compositions that would be most desirable for various purposes.

Dietary Fats, Unsaturated↗
PubMed1998

Catalytic plasticity of fatty acid modification enzymes underlying chemical diversity of plant lipids.

Higher plants exhibit extensive diversity in the composition of seed storage fatty acids. This is largely due to the presence of various combinations of double or triple bonds and hydroxyl or epoxy groups, which are synthesized by a family of structurally similar enzymes. As few as four amino acid substitutions can convert an oleate 12-desaturase to a hydroxylase and as few as six result in conversion of a hydroxylase to a desaturase. These results illustrate how catalytic plasticity of these diiron enzymes has contributed to the evolution of the chemical diversity found in higher plants.

Amino Acid Substitution↗
PubMed1998

A bifunctional oleate 12-hydroxylase: desaturase from Lesquerella fendleri.

LFAH12, an oleate 12-hydroxylase gene from Lesquerella fendleri (L.) was isolated on the basis of nucleotide sequence similarity to an oleate hydroxylase gene from Ricinus communis (L.). Transgenic Arabidopsis plants containing the Lesquerella gene under transcriptional control of the cauliflower mosaic virus 35S promoter accumulated ricinoleic, lesquerolic and densipolic acids in seeds, but not in leaves or roots. However, hydroxylase activity was detectable in crude extracts of vegetative tissues. The discrepancy between the presence of activity and the lack of hydroxy fatty acids suggests selective removal and breakdown of hydroxy fatty acids in vegetative organs. High levels of LFAH12 mRNA accumulation did not lead to correspondingly high levels of protein accumulation, suggesting that accumulation of the hydroxylase may be controlled post-transcriptionally. Expression of the L. fendleri gene in transgenic plants of a fad2 mutant of Arabidopsis, which is deficient in cytoplasmic oleate delta 12 desaturase activity, resulted in partial suppression of the mutant phenotype in roots. Thus, unlike the hydroxylase from R. communis, the L. fendleri enzyme has both hydroxylase and desaturase activities. Fusion of the 5' flanking region of the LFAH12 gene to the beta-glucuronidase coding sequence resulted in a high level of early seed-specific expression of beta-glucuronidase activity in transgenic Arabidopsis plants.

Arabidopsis↗
PubMed1997

Cellular differentiation regulated by gibberellin in the Arabidopsis thaliana pickle mutant.

The plant growth regulator gibberellin (GA) has a profound effect on shoot development and promotes developmental transitions such as flowering. Little is known about any analogous effect GA might have on root development. In a screen for mutants, Arabidopsis plants carrying a mutation designated pickle (pkl) were isolated in which the primary root meristem retained characteristics of embryonic tissue. Expression of this aberrant differentiation state was suppressed by GA. Root tissue from plants carrying the pkl mutation spontaneously regenerated new embryos and plants.

Arabidopsis↗
PubMed1997

Cloning in silico.

Cellulose is a major component of plant cell walls, but identification of the enzymes that synthesize it has proven difficult. Now, however, several candidate proteins with sequence homology to bacterial cellulose synthases have been identified by partial sequencing of anonymous cDNA clones from cotton fibers.

Bacteria↗
PubMed1997

Accumulation of ricinoleic, lesquerolic, and densipolic acids in seeds of transgenic Arabidopsis plants that express a fatty acyl hydroxylase cDNA from castor bean.

A cDNA encoding the oleate 12-hydroxylase from castor bean (Ricinus communis L.) has previously been shown to direct the synthesis of small amounts of ricinoleic acid (12-hydroxyoctadec-cis-9-enoic acid) in seeds of transgenic tobacco plants. Expression of the cDNA under control of the Brassica napus napin promoter in transgenic Arabidopsis thaliana plants resulted in the accumulation of up to 17% of seed fatty acids as ricinoleate and two novel fatty acids that have been identified by gas chromatography-mass spectrometry as lesquerolic (14-hydroxyeicos-cis-11-enoic acid) and densipolic (12-hydroxyoctadec-cis-9,15-dienoic acid) acids. Traces of auricolic acid were also observed. These results suggest that either the castor hydroxylase can utilize oleic acid and eicosenoic acid as substrates for ricinoleic and lesquerolic acid biosynthesis, respectively, or Arabidopsis contains an elongase that accepts ricinoleic acid as a substrate. These observations are also consistent with indirect biochemical evidence that an n-3 desaturase is capable of converting ricinoleic acid to densipolic acid. Expression of the castor hydroxylase also caused enhanced accumulation of oleic acid and a corresponding decrease in the levels of polyunsaturated fatty acids. Since the steady-state level of mRNA for the oleate-12 desaturase was not affected, it appears that the presence of the hydroxylase, directly or indirectly, causes posttranscriptional inhibition of desaturation.

Arabidopsis↗
PubMed1997

Isolation of mutants of Acinetobacter calcoaceticus deficient in wax ester synthesis and complementation of one mutation with a gene encoding a fatty acyl coenzyme A reductase.

Acinetobacter calcoaceticus BD413 accumulates wax esters and triacylglycerol under conditions of mineral nutrient limitation. Nitrosoguanidine-induced mutants of strain BD413 were isolated that failed to accumulate wax esters under nitrogen-limited growth conditions. One of the mutants, Wow15 (without wax), accumulated wax when grown in the presence of cis-11-hexadecenal and hexadecanol but not hexadecane or hexadecanoic acid. This suggested that the mutation may have inactivated a gene encoding either an acyl-acyl carrier protein or acyl-coenzyme A (CoA) reductase. The Wow15 mutant was complemented with a cosmid genomic library prepared from wild-type A. calcoaceticus BD413. The complementary region was localized to a single gene (acr1) encoding a protein of 32,468 Da that is 44% identical over a region of 264 amino acids to a product of unknown function encoded by an open reading frame associated with mycolic acid synthesis in Mycobacterium tuberculosis H37Ra. Extracts of Escherichia coli cells expressing the acr1 gene catalyzed the reduction of acyl-CoA to the corresponding fatty aldehyde, indicating that the gene encodes a novel fatty acyl-CoA reductase.

Acinetobacter calcoaceticus↗
PubMed1997

Hypoadrenocorticism in young related Nova Scotia duck tolling retrievers.

Five cases of hypoadrenocorticism in young related Nova Scotia duck tolling retrievers are discussed. Two were littermates and the others shared one or more common ancestors. No specific mode of inheritance was determined. Clinical and laboratory findings typical of hypoadrenocorticism were observed. Further documentation will be required to confirm a breed predisposition.

Adrenal Glands↗