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Chlorophyll Synthase Under Epigenetic Surveillance Is Critical For Vitamin E Synthesis, And Altered Expression Affects Tocopherol Levels In Arabidopsis, Chunyu Zhang, Wei Zhang, Guodong Ren, Denli Li, Rebecca E. Cahoon, Ming Chen, Yongming Zhou, Bin Yu, Edgar B. Cahoon

Center for Plant Science Innovation: Faculty and Staff Publications

Chlorophyll synthase catalyzes the final step in chlorophyll biosynthesis: the esterification of chlorophyllide with either geranylgeranyl diphosphate or phytyl diphosphate (PDP). Recent studies have pointed to the involvement of chlorophyll-linked reduction of geranylgeranyl by geranylgeranyl reductase as a major pathway for the synthesis of the PDP precursor of tocopherols. This indirect pathway of PDP synthesis suggests a key role of chlorophyll synthase in tocopherol production to generate the geranylgeranyl-chlorophyll substrate for geranylgeranyl reductase. In this study, contributions of chlorophyll synthase to tocopherol formation in Arabidopsis (Arabidopsis thaliana) were explored by disrupting and altering expression of the corresponding gene …

Osmotic Stress Induces Phosphorylation Of Histone H3 At Threonine 3 In Pericentromeric Regions Of Arabidopsis Thaliana, Zhen Wang, Juan Armando Casas-Mollano, Jianping Xu, Jean-Jack M. Riethoven, Chi Zhang, Heriberto Cerutti

Center for Plant Science Innovation: Faculty and Staff Publications

Histone phosphorylation plays key roles in stress-induced transcriptional reprogramming in metazoans but its function(s) in land plants has remained relatively unexplored. Here we report that an Arabidopsis mutant defective in At3g03940 and At5g18190, encoding closely related Ser/Thr protein kinases, shows pleiotropic phenotypes including dwarfism and hypersensitivity to osmotic/salt stress. The double mutant has reduced global levels of phosphorylated histone H3 threonine 3 (H3T3ph), which are not enhanced, unlike the response in the wild type, by drought-like treatments. Genome-wide analyses revealed increased H3T3ph, slight enhancement in trimethylated histone H3 lysine 4 (H3K4me3), and a modest decrease in histone H3 occupancy …

Osmotic Stress Induces Phosphorylation Of Histone H3 At Threonine 3 In Pericentromeric Regions Of Arabidopsis Thaliana, Zhen Wang, Juan Casas-Mollano, Jianping Xu, Jean-Jack Riethoven, Chi Zhang, Heriberto D. Cerutti

Center for Plant Science Innovation: Faculty and Staff Publications

Histone phosphorylation plays key roles in stress-induced transcriptional reprogramming in metazoans but its function(s) in land plants has remained relatively unexplored. Here we report that an Arabidopsis mutant defective in At3g03940 and At5g18190, encoding closely related Ser/Thr protein kinases, shows pleiotropic phenotypes including dwarfism and hypersensitivity to osmotic/salt stress. The double mutant has reduced global levels of phosphorylated histone H3 threonine 3 (H3T3ph), which are not enhanced, unlike the response in the wild type, by drought-like treatments. Genome-wide analyses revealed increased H3T3ph, slight enhancement in trimethylated histone H3 lysine 4 (H3K4me3), and a modest decrease in histone H3 occupancy …

Combinatorial Effects Of Fatty Acid Elongase Enzymes On Nervonic Acid Production In Camelina Sativa, Dongxin Huai, Yuanyuan Zhang, Chunyu Zhang, Edgar B. Cahoon, Yongming Zhou

Center for Plant Science Innovation: Faculty and Staff Publications

Very long chain fatty acids (VLCFAs) with chain lengths of 20 carbons and longer provide feedstocks for various applications; therefore, improvement of VLCFA contents in seeds has become an important goal for oilseed enhancement. VLCFA biosynthesis is controlled by a multi-enzyme protein complex referred to as fatty acid elongase, which is composed of β-ketoacyl-CoA synthase (KCS), β-ketoacyl-CoA reductase (KCR), β-hydroxyacyl-CoA dehydratase (HCD) and enoyl reductase (ECR). KCS has been identified as the ratelimiting enzyme, but little is known about the involvement of other three enzymes in VLCFA production. Here, the combinatorial effects of fatty acid elongase enzymes on VLCFA production …

Sumoylation By A Stress-Specific Small Ubiquitin-Like Modifier E2 Conjugase Is Essential For Survival Of Chlamydomonas Reinhardtii Under Stress Conditions, Amy R. Knobbe, Kempton M. Horken, Thomas M. Plucinak, Eniko Balassa, Heriberto Cerutti, Donald P. Weeks

Center for Plant Science Innovation: Faculty and Staff Publications

Posttranslational modification of proteins by small ubiquitin-like modifier (SUMO) is required for survival of virtually all eukaryotic organisms. Attachment of SUMO to target proteins is catalyzed by SUMO E2 conjugase. All haploid or diploid eukaryotes studied to date possess a single indispensable SUMO conjugase. We report here the unanticipated isolation of a Chlamydomonas reinhardtii (mutant5 [mut5]), in which the previously identified SUMO conjugase gene C. reinhardtii ubiquitin-conjugating enzyme9 (CrUBC9) is deleted. This surprising mutant is viable and unexpectedly displays a pattern of protein SUMOylation at 25°C that is essentially identical to wild-type cells. However, unlike wild-type …

Toward Production Of Jet Fuel Functionality In Oilseeds: Identification Of Fatb Acyl-Acyl Carrier Protein Thioesterases And Evaluation Of Combinatorial Expression Strategies In Camelina Seeds, Hae Jin Kim, Jillian E. Silva, Hieu Sy Vu, Keithanne Mockaitis, Jeong-Won Nam, Edgar B. Cahoon

Center for Plant Science Innovation: Faculty and Staff Publications

Seeds of members of the genus Cuphea accumulate medium-chain fatty acids (MCFAs; 8:0–14:0). MCFA- and palmitic acid- (16:0) rich vegetable oils have received attention for jet fuel production, given their similarity in chain length to Jet A fuel hydrocarbons. Studies were conducted to test genes, including those from Cuphea, for their ability to confer jet fuel-type fatty acid accumulation in seed oil of the emerging biofuel crop Camelina sativa. Transcriptomes from Cuphea viscosissima and Cuphea pulcherrima developing seeds that accumulate >90% of C8 and C10 fatty acids revealed three FatB cDNAs (CpuFatB3, CvFatB1, and CpuFatB4) …

Fungal Morphogenesis, Xiaorong Lin, J. Andrew Alspaugh, Haoping Liu, Steven D. Harris

Center for Plant Science Innovation: Faculty and Staff Publications

Morphogenesis in fungi is often induced by extracellular factors and executed by fungal genetic factors. Cell surface changes and alterations of the microenvironment often accompany morphogenetic changes in fungi. In this review, we will first discuss the general traits of yeast and hyphal morphotypes and how morphogenesis affects development and adaptation by fungi to their native niches, including host niches. Then we will focus on the molecular machinery responsible for the two most fundamental growth forms, yeast and hyphae. Last, we will describe how fungi incorporate exogenous environmental and host signals together with genetic factors to determine their morphotype and …

Redirection Of Metabolic Flux For High Levels Of Omega-7 Monounsaturated Fatty Acid Accumulation In Camelina Seeds, Huu Tam Nguyen, Hyunwoo Park, Karen L. Koster, Rebecca E. Cahoon, Hanh Nguyen, John Shanklin, Thomas E. Clemente, Edgar B. Cahoon

Center for Plant Science Innovation: Faculty and Staff Publications

Seed oils enriched in omega-7 monounsaturated fatty acids, including palmitoleic acid (16:1Δ9) and cis-vaccenic acid (18:1Δ11), have nutraceutical and industrial value for polyethylene production and biofuels. Existing oilseed crops accumulate only small amounts (<2%) of these novel fatty acids in their seed oils. We demonstrate a strategy for enhanced production of omega-7 monounsaturated fatty acids in camelina (Camelina sativa) and soybean (Glycine max) that is dependent on redirection of metabolic flux from the typical Δ9 desaturation of stearoyl (18:0)-acyl carrier protein (ACP) to Δ9 desaturation of palmitoyl (16:0)-acyl carrier protein (ACP) and coenzyme A (CoA). This was achieved by seed-specific co-expression of a mutant Δ9-acyl-ACP and an acyl-CoA desaturase with high specificity for 16:0-ACP and CoA substrates, respectively. This strategy was most effective in camelina where seed oils with ~17% omega-7 monounsaturated fatty acids were obtained.

Further increases in omega-7 fatty acid accumulation to 60–65% of the total fatty acids in camelina seeds were achieved by inclusion of seed-specific suppression of 3-keto-acyl-ACP synthase II and the FatB 16:0-ACP thioesterase genes to increase substrate pool sizes of 16:0-ACP for the Δ9-acyl-ACP desaturase and by blocking C18 fatty acid elongation. Seeds from these lines also had total saturated fatty acids reduced to ~5% of …

Gene Silencing In Microalgae: Mechanisms And Biological Roles, Eun-Jeong Kim, Xinrong Ma, Heriberto Cerutti

Center for Plant Science Innovation: Faculty and Staff Publications

Microalgae exhibit enormous diversity and can potentially contribute to the production of biofuels and high value compounds. However, for most species, our knowledge of their physiology, metabolism, and gene regulation is fairly limited. In eukaryotes, gene silencing mechanisms play important roles in both the reversible repression of genes that are required only in certain contexts and the suppression of genome invaders such at transposons. The recent sequencing of several algal genomes is providing insights into the complexity of these mechanisms in microalgae. Collectively, glaucophyte, red, and green microalgae contain the machineries involved in repressive histone H3 lysine methylation, DNA cytosine …

The Role Of Ethylene In Plant Responses To K+ Deficiency, Daniel P. Schachtman

Center for Plant Science Innovation: Faculty and Staff Publications

Potassium is an essential macronutrient that is involved in regulating turgor , in driving plant growth, and in modulating enzyme activation. The changes in root morphology, root function, as well as cellular and molecular responses to low potassium conditions have been studied in the model plant Arabidopsis and in other plant species. In Arabidopsis ethylene plays a key role in roots in the transduction of the low potassium signal, which results in altered root function and growth. The first clues regarding the role of ethylene were detected through transcriptional profiling experiments showing changes in the expression of genes related to …

Modifications Of Membrane Lipids In Response To Wounding Of Arabidopsis Thaliana Leaves, Hieu Sy Vu, Rebecca Roston, Sunitha Shiva, Manhoi Hur, Eve Syrkin Wurtele, Xuemin Wang, Jyoti Shah, Ruth Welti

Center for Plant Science Innovation: Faculty and Staff Publications

Mechanical wounding of Arabidopsis thaliana leaves results in modifications of most membrane lipids within 6 hours. Here, we discuss the lipid changes, their underlying biochemistry, and possible relationships among activated pathways. New evidence is presented supporting the role of the processive galactosylating enzyme SENSITIVE TO FREEZING2 in the wounding response.

Sirna-Directed Dna Methylation In Plants, Meng Xie, Bin Yu

Center for Plant Science Innovation: Faculty and Staff Publications

DNA cytosine methylationis an important epigenetic process that is correlated with transgene silencing, transposon suppression, and gene imprinting. In plants, small interfering RNAs (siRNAs) can trigger DNA methylation at loci containing their homolog sequences through a process called RNAdirected DNA methylation (RdDM). In canonical RdDM, 24 nucleotide (nt) siRNAs (ra-siRNAs) will be loaded into their effector protein called ARGONAUTE 4 (AGO4) and subsequently targeted to RdDM loci through base-pairing with the non-coding transcripts produced by DNA-directed RNA Polymerase V. Then, the AGO4-ra-siRNA will recruit the DNA methyltransferase to catalyze de novo DNA methylation. Recent studies also identified non-canonical RdDM pathways …

Toward Production Of Jet Fuel Functionality In Oilseeds: Identification Of Fatb Acyl-Acyl Carrier Protein Thioesterases And Evaluation Of Combinatorial Expression Strategies In Camelina Seeds, Hae Jin Kim, Jillian E. Silva, Hieu Sy Vu, Keithanne Mockaitis, Jeong-Won Nam, Edgar B. Cahoon

Center for Plant Science Innovation: Faculty and Staff Publications

Seeds of members of the genus Cuphea accumulate medium-chain fatty acids (MCFAs; 8:0–14:0). MCFA- and palmitic acid- (16:0) rich vegetable oils have received attention for jet fuel production, given their similarity in chain length to Jet A fuel hydrocarbons. Studies were conducted to test genes, including those from Cuphea, for their ability to confer jet fuel-type fatty acid accumulation in seed oil of the emerging biofuel crop Camelina sativa. Transcriptomes from Cuphea viscosissima and Cuphea pulcherrima developing seeds that accumulate >90% of C8 and C10 fatty acids revealed three FatB cDNAs (CpuFatB3, CvFatB1, and CpuFatB4 …

The Taurine Biosynthetic Pathway Of Microalgae, Rahul Tevatia, James Allen, Deepak Rudrappa, Derrick White, Thomas E. Clemente, Heriberto Cerutti, Yaşar Demirel, Paul H. Blum

Center for Plant Science Innovation: Faculty and Staff Publications

Taurine (2-aminoethanesulfonic acid) is an amino acid–like compound widely distributed in animals and an essential nutrient in some species. Targeted metabolomics of marine and freshwater microalgae combined with medium supplementation identified biosynthetic pathway intermediates and necessary catalytic activities. Genomic analysis was then used to predict the first taurine biosynthetic pathway in these organisms. MRM-based electrospray ionization (ESI) LC–MS/MS analysis demonstrated that taurine is synthesized using a carbon backbone from L-serine combined with sulfur derived from sulfate. Metabolite analysis showed a nonuniform pattern in levels of pathway intermediates that were both species and supplement dependent. While increased culture salinity raised taurine …

Production Of High Levels Of Poly-3-Hydroxybutyrate In Plastids Of Camelina Sativa Seeds, Meghna R. Malik, Wenyu Tang, Nii Patterson, Jihong Tang, Rachel L. Wellinghoff, Mary L. Preuss, Claire Burkitt, Nirmala Sharma, Yuanyuan Ji, Joseph M. Jez, Oliver P. Peoples, Jan G. Jaworski, Edgar B. Cahoon, Kristi D. Snell

Center for Plant Science Innovation: Faculty and Staff Publications

Poly-3-hydroxybutyrate (PHB) production in plastids of Camelina sativa seeds was investigated by comparing levels of polymer produced upon transformation of plants with five different binary vectors containing combinations of five seed-specific promoters for expression of transgenes. Genes encoding PHB biosynthetic enzymes were modified at the N-terminus to encode a plastid targeting signal. PHB levels of up to 15% of the mature seed weight were measured in single sacrificed T1 seeds with a genetic construct containing the oleosin and glycinin promoters.

A more detailed analysis of the PHB production potential of two of the best performing binary vectors in a Camelina …

Variable Frequency Of Plastid Rna Editing Among Ferns And Repeated Loss Of Uridine-To-Cytidine Editing From Vascular Plants, Wenhu Guo, Felix Grewe, Jeffrey P. Mower

Center for Plant Science Innovation: Faculty and Staff Publications

The distinct distribution and abundance of C-to-U and U-to-C RNA editing among land plants suggest that these two processes originated and evolve independently, but the paucity of information from several key lineages limits our understanding of their evolution. To examine the evolutionary diversity of RNA editing among ferns, we sequenced the plastid transcriptomes from two early diverging species, Ophioglossum californicum and Psilotum nudum. Using a relaxed automated approach to minimize false negatives combined with manual inspection to eliminate false positives, we identified 297 C-to-U and three U-to-C edit sites in the O. californicum plastid transcriptome but only 27 C-to-U …

Microrna Biogenesis, Degradation And Activity In Plants, Meng Xie, Shuxin Zhang, Bin Yu

Center for Plant Science Innovation: Faculty and Staff Publications

microRNAs (miRNAs) are important regulators of gene expression. After excised from primary miRNA transcript by dicer-like1 (DCL1, an RNAse III enzyme), miRNAs bind and guide their effector protein named argonaute 1 (AGO1) to silence the expression of target RNAs containing their complementary sequences in plants. miRNA levels and activities are tightly controlled to ensure their functions in various biological processes such as development, metabolism and responses to abiotic and biotic stresses. Studies have identified many factors that involve in miRNA accumulation and activities. Characterization of these factors in turn greatly improves our understanding of the processes related to miRNAs. Here, …