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Articles 1 - 11 of 11

Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

Functional Interactions Between Heterologously Expressed Starch-Branching Enzymes Of Maize And The Glycogen Synthases Of Brewer’S Yeast, Beom-Seok Seo, Seungtaek Kim, Marvin Paul Scott, George W. Singletary, Kit-Sum Wong, Martha G. James, Alan M. Myers Apr 2002

Functional Interactions Between Heterologously Expressed Starch-Branching Enzymes Of Maize And The Glycogen Synthases Of Brewer’S Yeast, Beom-Seok Seo, Seungtaek Kim, Marvin Paul Scott, George W. Singletary, Kit-Sum Wong, Martha G. James, Alan M. Myers

Agronomy Publications

Starch-branching enzymes (SBEs) catalyze the formation of α(1→6) glycoside bonds in glucan polymers, thus, affecting the structure of amylopectin and starch granules. Two distinct classes of SBE are generally conserved in higher plants, although the specific role(s) of each isoform in determination of starch structure is not clearly understood. This study used a heterologous in vivo system to isolate the function of each of the three known SBE isoforms of maize (Zea mays) away from the other plant enzymes involved in starch biosynthesis. The ascomycete Brewer's yeast (Saccharomyces cerevisiae) was employed as the host species. All ...


Weedy Adaptation In Setaria Spp. V. Effects Of Gaseous Environment On Giant Foxtail (Setaria Faberii) (Poaceae) Seed Germination, Jack H. Dekker, Mark S. Hargrove Mar 2002

Weedy Adaptation In Setaria Spp. V. Effects Of Gaseous Environment On Giant Foxtail (Setaria Faberii) (Poaceae) Seed Germination, Jack H. Dekker, Mark S. Hargrove

Agronomy Publications

The effects that naturally occurring gases (oxygen, nitrogen, carbon monoxide) may cause in dormant giant foxtail (Setaria faberii) seed germination under favorable temperature and moisture conditions were investigated. The germination responses to gas mixtures supported the hypothesis that S. faberii germination behavior is regulated by the amount of oxygen taken into hydrated seed over time. Setaria faberii seed germination was markedly affected by O2 concentration (in N2) above and below that of air (20% O2): the largest increase in germination (from 37 to 60%) occurred between 20–25% O2; between 0–10% O2, germination increased ...


Molecular Genetic Studies Of Acetyl-Coa Carboxylase And 3-Methylcrotonyl-Coa Carboxylase In Plants , Hui-Rong Qian Jan 2002

Molecular Genetic Studies Of Acetyl-Coa Carboxylase And 3-Methylcrotonyl-Coa Carboxylase In Plants , Hui-Rong Qian

Retrospective Theses and Dissertations

Similar reverse-genetics approach is applied to investigate the function of two biotin-containing enzymes at the interface between catabolism and anabolism: acetyl-CoA carboxylase (ACCase) and 3-methylcrotonyl-CoA carboxylase (MCCase).;Plastidic ACCase catalyzes the first committed step of de novo fatty acid biosynthesis. Antisense Arabidopsis expressing antisense RNA of CAC1-A, which encodes the biotin carboxyl carrier protein (BCCP) of plastidic ACCase under the direction of CaMV 35S promoter, have been obtained. CAC1-A antisense plants with reduced BCCP possess different degrees of similar morphological changes. These include slow growth, smaller plant size, and crinkly and variegated-yellow vegetative and cauline leaves eventually leading to premature ...


Functional Characterization Of Mitochondrial And Cytosolic Aldehyde Dehydrogenases In Maize (Zea Mays L) , Feng Liu Jan 2002

Functional Characterization Of Mitochondrial And Cytosolic Aldehyde Dehydrogenases In Maize (Zea Mays L) , Feng Liu

Retrospective Theses and Dissertations

Aldehyde dehydrogenases (ALDHs) are a group of enzymes that catalyze oxidation of aldehydes in the presence of coenzyme NAD+ or NADP+. Few plant ALDHs have been studied at protein level, although many ALDH genes have been cloned. To date no functional characterization of plant ALDHs has been reported. This dissertation is focused on functional characterization of four ALDHs from maize, RF2A, RF2B, RF2C and RF2D. RF2A and RF2B are targeted to mitochondria, while RF2C and RF2D are located in cytosol. RF2A is required for normal pollen development: the anthers in lower florets from spikelets of homozygous mutant rf2a plants in ...


Characterization Of The De Novo Pyrimidine Biosynthetic Pathway In Arabidopsis Thaliana , Christopher W. Kafer Jan 2002

Characterization Of The De Novo Pyrimidine Biosynthetic Pathway In Arabidopsis Thaliana , Christopher W. Kafer

Retrospective Theses and Dissertations

We have characterized the enzyme cytidine deaminase. The full length cDNA was expressed in E. coli and purified to apparent homogeneity using a Ni-NTA agarose column. The Km and Vmax for cytidine were determined to be 226uM and 39.7 umoles/min respectively. The enzyme was also able to use 2'-deoxycytidine as substrate with an apparent Km of 49 uM and Vmax of 24 umoles/min.;We have also developed a single tube semi-quantitative relative reverse transcription polymerase chain reaction (RT-PCR) assay. We have used this assay to quantitate the relative transcript levels of the UMP synthase gene and ...


Transcription Factors Involved In The Development Of Potato (Solanum Tuberosum L) , Faye Michelle Rosin Jan 2002

Transcription Factors Involved In The Development Of Potato (Solanum Tuberosum L) , Faye Michelle Rosin

Retrospective Theses and Dissertations

The objective of this study was to gain insight into how classes of regulatory genes affect the growth and development of potato, particularly, the molecular processes of tuberization. This was accomplished by generating transgenic potato plants that overexpress the homeobox gene, POTH1 , and by using an antisense approach to suppress levels of the MADS box gene, POTM1.;POTH1 was shown to be involved in vegetative pattern formation via mediation of hormone levels. Overexpression of POTH1 resulted in dwarf plants with a 'mouse-ear' leaf phenotype. Leaves were heart-shaped with a decreased midvein and palmate venation. POTH1 overexpression lines exhibited an increase ...


Atp-Citrate Lyase Has An Essential Role In Cytosolic Acetyl-Coa Production In Arabidopsis , Beth Leann Fatland Jan 2002

Atp-Citrate Lyase Has An Essential Role In Cytosolic Acetyl-Coa Production In Arabidopsis , Beth Leann Fatland

Retrospective Theses and Dissertations

Acetyl-CoA is both an essential primary and secondary metabolite, however, the source of cytosolic acetyl-CoA has been unclear. We identified two non-overlapping groups of plant cDNAs that encode proteins similar to the amino and carboxy portions of human ATP-citrate lyase. In Arabidopsis, three genes encode the 45 kD ACLA subunit (ACLA-1, At1g10670; ACLA-2, At1g60810; ACLA-3, At1g09430) and two genes encode the 65 kD ACLB subunit (ACLB-1, At3g06650; ACLB-2, At5g49460). Co-expression of ACLA-1 and ACLB-2 cDNAs in Saccharomyces cerevisiae yields ATP-citrate lyase activity, indicating both polypeptides are required for activity. The Arabidopsis holoprotein has a molecular weight of 500 kDa, which ...


Identification And Characterization Of Proteins Expressed In The Nectar Of Ornamental Tobacco , Clay Jeremy Carter Jan 2002

Identification And Characterization Of Proteins Expressed In The Nectar Of Ornamental Tobacco , Clay Jeremy Carter

Retrospective Theses and Dissertations

A small set of proteins, termed Nectarins, are secreted into the nectar of ornamental tobacco (Nicotiana langsdorffii x Nicotiana sanderae). The most highly expressed protein, Nectarin I (29 kD monomer), was originally identified as a germin-like protein (GLP) of unknown function. This remarkably stable protein was later shown to possess manganese dependent superoxide dismutase activity. Hydrogen peroxide, the product of SOD activity, was found to accumulate in nectar at levels up to 4 mM. The promoter (1.2 kb) of the Nectarin I gene was fused to the reporter gene chloramphenicol acetyl transferase (CAT) and shown to be expressed in ...


Enzyme Activities In Soils As Affected By Management Practices , Mine Ekenler Jan 2002

Enzyme Activities In Soils As Affected By Management Practices , Mine Ekenler

Retrospective Theses and Dissertations

Studies were undertaken to investigate the long-term effects of lime application and tillage systems (no-till, ridge-till, and chisel plow) on soil microbial biomass C (Cmic) and N (Nmic) and the activities of glycosidases (alpha- and beta-glucosidases, alpha- and beta-galactosidases and beta-glucosaminidase); phosphatases (acid and alkaline phosphatases and phosphodiesterase); amidohydrolases (L-asparaginase, L-glutaminase, amidase, urease, and L-aspartase); and arylamidase at their optimal pH values. With the exception of acid phosphatase, which was significantly but negatively correlated, all other enzyme activities were significantly and positively correlated with soil pH values at four sites in Iowa. Delta activity/Delta pH values showed that among ...


Backcross Introgression And Two-Stage Testing For Conversion Of Improved Tropical Germplasm To Temperate Environments , Freeman Callaway Whitehead Jan 2002

Backcross Introgression And Two-Stage Testing For Conversion Of Improved Tropical Germplasm To Temperate Environments , Freeman Callaway Whitehead

Retrospective Theses and Dissertations

The use of exotic maize (Zea mays L.) germplasm, particularly of tropical and subtropical adaptation, has been suggested to increase genetic variability and grain yield of maize breeding material in temperate environments. Lack of adaptation to temperate areas and photoperiod sensitivity may mask desirable traits and reduce breeding progress. The objectives of this study included two-stage evaluation and selection of segregating families in the central U.S. Corn Belt derived from the backcross introgression of previously improved tropical CIMMYT germplasm into adapted, elite U.S. Corn Belt germplasm. The U.S. Corn Belt heterotic patterns of Stiff Stalk and non-Stiff ...


Molecular Marker Analysis Of Seed Size In Soybean , Joseph Andrew Hoeck Jan 2002

Molecular Marker Analysis Of Seed Size In Soybean , Joseph Andrew Hoeck

Retrospective Theses and Dissertations

Seed size is an important attribute of soybean [Glycine max (L.) Merr.] for some food uses. The objectives of this study were to identify markers associated with quantitative trait loci for seed size (SSQTL), determine the influence of the environment on expression of the marker-SSQTL associations, and compare the efficiency of phenotypic selection and marker-assisted selection for the trait. Three small-seeded lines were crossed to a line or cultivar with normal seed size to form three two-parent populations. The parents of the populations were screened with 178 simple sequence repeat (SSR) markers to identify polymorphism. Population 1 (Pop 1) had ...