Gautam Sarath

Bio: Gautam Sarath is an academic researcher from Agricultural Research Service. The author has contributed to research in topics: Panicum virgatum & Biotinylation. The author has an hindex of 55, co-authored 231 publications receiving 9615 citations. Previous affiliations of Gautam Sarath include University of Nebraska–Lincoln & United States Department of Agriculture.

The role of acid phosphatases in plant phosphorus metabolism

Abstract: Hydrolysis of phosphate esters is a critical process in the energy metabolism and metabolic regulation of plant ceils. This review summarizes the characteristics and putative roles of piant acid phosphatase lAPasel. Although immunologicaliy closely related, plant APases display remarkable heterogeneity w ith regards to their kinetic and molecular properties, and subcellular location. The secreted APa.ses of roots and cell cultures are relati\ ely non-specific enzymes that appear to be important in the hydrolysis and mobilization of P, from extracellular phosphomonoesters for plant nutrition. Intracelluiar APases are undoubtedly involved in the routine utilization of P, reserves or other P, containing compounds. A special class of intracellular APase exists that demonstrate a clear-cut (but generally nonabsoiute) substrate selectivity. These .^.Pases are hypothesized to have distinct metabolic functions and include; phytase, phosphoglycoiate phosphatase. 3-pbosphoglycerate phosphatase. phosphoenolpyruvate phosphatase. and phosphotyrosyl-protein phosphatase. APase expression is regulated by a variety of developmental and environmental factors. P, starvation induces de novo synthesis of extra- and intracellular APases in cell cultures as well as in whole plants. Recommendations are made to achieve uniformity in the analyses of the different .A.Pase isoforms normally encountered within and between different plant tissues.

The Electronic Plant Gene Register

Abstract: Plant Gene Register titles for PGR 99–174 to PGR 99–187 appear below. The sequences have beendeposited in GenBank and the articles listed online through the World Wide Web.To cite an electronic Plant Gene Register article as a bibliographic reference, follow the stylegiven below:Park S, Thornburg RW (1998) Characterization of UMP kinase cDNAs from rice (accession nos.AF187062 and AF187063) (PGR 99–174). Plant Physiol

Switchgrass as a biofuels feedstock in the USA

Abstract: Switchgrass (Panicum virgatum L.) has been identified as a model herbaceous energy crop for the USA. In this review, we selectively highlight current USDA-ARS research on switchgrass for biomass energy. Intensive research on switchgrass as a biomass feedstock in the 1990s greatly improved our understanding of the adaptation of switchgrass cultivars, production practices, and environmental benefits. Several constraints still remain in terms of economic production of switchgrass for biomass feedstock including reliable establishment practices to ensure productive stands in the seeding year, efficient use of fertilizers, and more efficient methods to convert lignocellulose to biofuels. Overcoming the biological constraints will require genetic enhancement, molecular biology, and plant breeding efforts to improve switchgrass cultivars. New genomic resources will aid in developing molecular markers, and should allow for marker-assisted selection of improved germplasm. Research is also needed on profitable mana...

Production of butanol (a biofuel) from agricultural residues: Part II – Use of corn stover and switchgrass hydrolysates☆

Abstract: Acetone butanol ethanol (ABE) was produced from hydrolysed corn stover and switchgrass using Clostridium beijerinckii P260. A control experiment using glucose resulted in the production of 21.06 g L−1 total ABE. In this experiment an ABE yield and productivity of 0.41 and 0.31 g L−1 h−1 was achieved, respectively. Fermentation of untreated corn stover hydrolysate (CSH) exhibited no growth and no ABE production; however, upon dilution with water (two fold) and wheat straw hydrolysate (WSH, ratio 1:1), 16.00 and 18.04 g L−1 ABE was produced, respectively. These experiments resulted in ABE productivity of 0.17–0.21 g L−1 h−1. Inhibitors present in CSH were removed by treating the hydrolysate with Ca(OH)2 (overliming). The culture was able to produce 26.27 g L−1 ABE after inhibitor removal. Untreated switchgrass hydrolysate (SGH) was poorly fermented and the culture did not produce more than 1.48 g L−1 ABE which was improved to 14.61 g L−1. It is suggested that biomass pretreatment methods that do not generate inhibitors be investigated. Alternately, cultures resistant to inhibitors and able to produce butanol at high concentrations may be another approach to improve the current process.

Improved Sugar Conversion and Ethanol Yield for Forage Sorghum (Sorghum bicolor L. Moench) Lines with Reduced Lignin Contents

Abstract: Lignin is known to impede conversion of lignocellulose into ethanol. In this study, forage sorghum plants carrying brown midrib (bmr) mutations, which reduce lignin contents, were evaluated as bioenergy feedstocks. The near-isogenic lines evaluated were: wild type, bmr-6, bmr-12, and bmr-6 bmr-12 double mutant. The bmr-6 and bmr-12 mutations were equally efficient at reducing lignin contents (by 13% and 15%, respectively), and the effects were additive (27%) for the double mutant. Reducing lignin content was highly beneficial for improving biomass conversion yields. Sorghum biomass samples were pretreated with dilute acid and recovered solids washed and hydrolyzed with cellulase to liberate glucose. Glucose yields for the sorghum biomass were improved by 27%, 23%, and 34% for bmr-6, bmr-12, and the double mutant, respectively, compared to wild type. Sorghum biomass was also pretreated with dilute acid followed by co-treatment with cellulases and Saccharomyces cerevisiae for simultaneous saccharification and fermentation (SSF) into ethanol. Conversion of cellulose to ethanol for dilute-acid pretreated sorghum biomass was improved by 22%, 21%, and 43% for bmr-6, bmr-12, and the double mutant compared to wild type, respectively. Electron microscopy of dilute-acid treated samples showed an increased number of lignin globules in double-mutant tissues as compared to the wild-type, suggesting the lignin had become more pliable. The mutations were also effective for improving ethanol yields when the (degrained) sorghum was pretreated with dilute alkali instead of dilute acid. Following pretreatment with dilute ammonium hydroxide and SSF, ethanol conversion yields were 116 and 130 mg ethanol/g dry biomass for the double-mutant samples and 98 and 113 mg/g for the wild-type samples.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

“Bioinformatics” 특집을 내면서

Abstract: BIOE 402. Medical Technology Assessment. 2 or 3 hours. Bioentrepreneur course. Assessment of medical technology in the context of commercialization. Objectives, competition, market share, funding, pricing, manufacturing, growth, and intellectual property; many issues unique to biomedical products. Course Information: 2 undergraduate hours. 3 graduate hours. Prerequisite(s): Junior standing or above and consent of the instructor.

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

Abstract: Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.

Lignin valorization: improving lignin processing in the biorefinery.

Abstract: Background Lignin, nature’s dominant aromatic polymer, is found in most terrestrial plants in the approximate range of 15 to 40% dry weight and provides structural integrity. Traditionally, most large-scale industrial processes that use plant polysaccharides have burned lignin to generate the power needed to productively transform biomass. The advent of biorefineries that convert cellulosic biomass into liquid transportation fuels will generate substantially more lignin than necessary to power the operation, and therefore efforts are underway to transform it to value-added products. Production of biofuels from cellulosic biomass requires separation of large quantities of the aromatic polymer lignin. In planta genetic engineering, enhanced extraction methods, and a deeper understanding of the structure of lignin are yielding promising opportunities for efficient conversion of this renewable resource to carbon fibers, polymers, commodity chemicals, and fuels. [Credit: Oak Ridge National Laboratory, U.S. Department of Energy] Advances Bioengineering to modify lignin structure and/or incorporate atypical components has shown promise toward facilitating recovery and chemical transformation of lignin under biorefinery conditions. The flexibility in lignin monomer composition has proven useful for enhancing extraction efficiency. Both the mining of genetic variants in native populations of bioenergy crops and direct genetic manipulation of biosynthesis pathways have produced lignin feedstocks with unique properties for coproduct development. Advances in analytical chemistry and computational modeling detail the structure of the modified lignin and direct bioengineering strategies for targeted properties. Refinement of biomass pretreatment technologies has further facilitated lignin recovery and enables catalytic modifications for desired chemical and physical properties. Outlook Potential high-value products from isolated lignin include low-cost carbon fiber, engineering plastics and thermoplastic elastomers, polymeric foams and membranes, and a variety of fuels and chemicals all currently sourced from petroleum. These lignin coproducts must be low cost and perform as well as petroleum-derived counterparts. Each product stream has its own distinct challenges. Development of renewable lignin-based polymers requires improved processing technologies coupled to tailored bioenergy crops incorporating lignin with the desired chemical and physical properties. For fuels and chemicals, multiple strategies have emerged for lignin depolymerization and upgrading, including thermochemical treatments and homogeneous and heterogeneous catalysis. The multifunctional nature of lignin has historically yielded multiple product streams, which require extensive separation and purification procedures, but engineering plant feedstocks for greater structural homogeneity and tailored functionality reduces this challenge.

Two transcription factors, DREB1 and DREB2, with an EREBP/AP2 DNA binding domain separate two cellular signal transduction pathways in drought- and low-temperature-responsive gene expression, respectively, in Arabidopsis.

Abstract: Plant growth is greatly affected by drought and low temperature. Expression of a number of genes is induced by both drought and low temperature, although these stresses are quite different. Previous experiments have established that a cis-acting element named DRE (for dehydration-responsive element) plays an important role in both dehydration- and low-temperature-induced gene expression in Arabidopsis. Two cDNA clones that encode DRE binding proteins, DREB1A and DREB2A, were isolated by using the yeast one-hybrid screening technique. The two cDNA libraries were prepared from dehydrated and cold-treated rosette plants, respectively. The deduced amino acid sequences of DREB1A and DREB2A showed no significant sequence similarity, except in the conserved DNA binding domains found in the EREBP and APETALA2 proteins that function in ethylene-responsive expression and floral morphogenesis, respectively. Both the DREB1A and DREB2A proteins specifically bound to the DRE sequence in vitro and activated the transcription of the b-glucuronidase reporter gene driven by the DRE sequence in Arabidopsis leaf protoplasts. Expression of the DREB1A gene and its two homologs was induced by low-temperature stress, whereas expression of the DREB2A gene and its single homolog was induced by dehydration. Overexpression of the DREB1A cDNA in transgenic Arabidopsis plants not only induced strong expression of the target genes under unstressed conditions but also caused dwarfed phenotypes in the transgenic plants. These transgenic plants also revealed freezing and dehydration tolerance. In contrast, overexpression of the DREB2A cDNA induced weak expression of the target genes under unstressed conditions and caused growth retardation of the transgenic plants. These results indicate that two independent families of DREB proteins, DREB1 and DREB2, function as trans-acting factors in two separate signal transduction pathways under low-temperature and dehydration conditions, respectively.