Biochemistry, Biophysics, and Structural Biology Commons^™

Editorial: Structure And Function Of Chloroplasts, Volume Iii, Hongbo Gao, Alistair J. Mccormick, Rebecca Roston, Yan Lu

Department of Biochemistry: Faculty Publications

Chloroplasts are endosymbiotic organelles derived from cyanobacteria. They have a double envelope membrane, including the outer envelope and the inner envelope. A complex membrane system, thylakoids, exists inside the chloroplast. It is the site of the light-dependent reactions of photosynthesis. The stroma is the main site of the carbon fixation reactions. Although photosynthesis is a very complicated process with many proteins involved, there are many other important processes that occur in chloroplasts, including the regulation of photosynthesis, the biogenesis and maintenance of the structures, carbohydrate, lipid, tetrapyrrole, amino acid, and isoprenoid metabolism, production of some phytohormones, production of specialized metabolites, …

Genetic Control Of Photoprotection And Photosystem Ii Operating Efficiency In Plants, Seema Sahay, Marcin Grzybowski, James Schnable, Katarzyna Głowacka

Department of Biochemistry: Faculty Publications

• Photoprotection against excess light via nonphotochemical quenching (NPQ) is indispensable for plant survival. However, slow NPQ relaxation under low light conditions can decrease yield of field-grown crops up to 40%.

• Using semi-high-throughput assay, we quantified the kinetics of NPQ and photosystem II operating efficiency (ΦPSII) in a replicated field trial of more than 700 maize (Zea mays) genotypes across 2 yr. Parametrized kinetics data were used to conduct genome-wide association studies.

• For six candidate genes involved in NPQ and ΦPSII kinetics in maize the loss of function alleles of orthologous genes in Arabidopsis (Arabidopsis thaliana) …

Guard-Cell-Targeted Overexpression Of Arabidopsis Hexokinase 1 Can Improve Water Use Efficiency In Field-Grown Tobacco Plants, Liana G. Acevedo-Siaca, Katarzyna Glowacka, Steven M. Driever, Coralie E. Salesse-Smith, Nitsan Lugassi, David Granot, Stephen P. Long, Johannes Kromdijk

Department of Biochemistry: Faculty Publications

Water deficit currently acts as one of the largest limiting factors for agricultural productivity worldwide. Additionally, limitation by water scarcity is projected to continue in the future with the further onset of effects of global climate change. As a result, it is critical to develop or breed for crops that have increased water use efficiency and that are more capable of coping with water scarce conditions. However, increased intrinsic water use efficiency (iWUE) typically brings a trade-off with CO₂ assimilation as all gas exchange is mediated by stomata, through which CO₂ enters the leaf while water vapor exits. …

Editorial: Structure And Function Of Chloroplasts - Volume Ii, Yan Lu, Lu Ning Liu, Rebecca L. Roston, Jurgen Soll, Hongbo Gao

Department of Biochemistry: Faculty Publications

No abstract provided.

The Genome Evolution And Domestication Of Tropical Fruit Mango, Peng Wang, Yingfeng Luo, Jianfeng Huang, Shenghan Gao, Guopeng Zhu, Zhiguo Dang, Jiangtao Gai, Meng Yang, Min Zhu, Huangkai Zhang, Xiuxu Ye, Aiping Gao, Xinyu Tan, Sen Wang, Shuangyang Wu, Edgar B. Cahoon, Beibei Bai, Zhichang Zhao, Qian Li, Junya Wei, Huarui Chen, Ruixiong Luo, Deyong Gong, Kexuan Tang, Bing Zhang, Zhangguang Ni, Guodi Huang, Songnian Hu, Yeyuan Chen

Department of Biochemistry: Faculty Publications

Background: Mango is one of the world’s most important tropical fruits. It belongs to the family Anacardiaceae, which includes several other economically important species, notably cashew, sumac and pistachio from other genera. Many species in this family produce family-specific urushiols and related phenols, which can induce contact dermatitis.

Results: We generate a chromosome-scale genome assembly of mango, providing a reference genome for the Anacardiaceae family. Our results indicate the occurrence of a recent whole-genome duplication (WGD) event in mango. Duplicated genes preferentially retained include photosynthetic, photorespiration, and lipid metabolic genes that may have provided adaptive advantages to sharp historical decreases …

Can Chilling Tolerance Of C4 Photosynthesis In Miscanthus Be Transferred To Sugarcane?, Katarzyna Glowacka, Aasifuddin Ahmed, Shailendra Sharma, Tom Abbott, Jack C. Comstock, Stephen P. Long, Erik J. Sacks

Department of Biochemistry: Faculty Publications

The goal of this study was to investigate whether chilling tolerance of C₄ photosynthesis in Miscanthus can be transferred to sugarcane by hybridization. Net leaf CO₂ uptake (A_sat) and the maximum operating efficiency of photosystem II (Ф_PSII) were measured in warm conditions (25 °C/20 °C), and then during and following a chilling treatment of 10 °C/5 °C for 11 day in controlled environment chambers. Two of three hybrids (miscanes), ‘US 84-1058’ and ‘US 87-1019’, did not differ significantly from the chilling tolerant M. xgiganteus ‘Illinois’ (Mxg), for A_sat, and Φ …

Phylogenetic Engineering At An Interface Between Large And Small Subunits Imparts Land-Plant Kinetic Properties To Algal Rubisco, Robert J. Spreitzer, Srinivasa R. Peddi, Sriram Satagopan

Department of Biochemistry: Faculty Publications

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the rate-limiting step of photosynthetic CO₂ fixation and, thus, limits agricultural productivity. However, Rubisco enzymes from different species have different catalytic constants. If the structural basis for such differences were known, a rationale could be developed for genetically engineering an improved enzyme. Residues at the bottom of the large-subunit α/β-barrel active site of Rubisco from the green alga Chlamydomonas reinhardtii (methyl-Cys-256, Lys-258, and Ile-265) were previously changed through directed mutagenesis and chloroplast transformation to residues characteristic of land-plant Rubisco (Phe-256, Arg-258, and Val-265). The resultant enzyme has decreases in carboxylation efficiency and CO₂/O …

Elimination Of The Chlamydomonas Gene Family That Encodes The Small Subunit Of Ribulose-1,5-Bisphosphate Carboxylaseyoxygenase, Irina Khrebtukova, Robert J. Spreitzer

Department of Biochemistry: Faculty Publications

Ribulose-1,5-bisphosphate carboxylasey oxygenase (EC 4.1.1.39) is the key photosynthetic enzyme that catalyzes the first step of CO₂ fixation. The chloroplastlocalized holoenzyme of plants and green algae contains eight nuclear-encoded small subunits and eight chloroplastencoded large subunits. Although much has been learned about the enzyme active site that resides within each large subunit, it has been difficult to assess the role of eukaryotic small subunits in holoenzyme function and expression. Small subunits are coded by a family of genes, precluding genetic screening or nuclear transformation approaches for the recovery of small-subunit mutants. In this study, the two small-subunit genes of …

Shared Thematic Elements In Photochemical Reaction Centers, John H. Golbeck

Department of Biochemistry: Faculty Publications

The structural, functional, and evolutionary relationships between photosystem II and the purple nonsulfur bacterial reaction center have been recognized for several years. These can be classified as "quinone type" (type I) photosystems because the terminal electron acceptor is a mobile quinone molecule. The analogous relationship between photosystem I and the green sulfur bacterial (and heliobacterial) reaction centers has only recently become dear. These can be dcassified as "iron-sulfur type" (type I) photosystems because the terminal electron acceptor consists of one or more bound iron-sulfur clusters. At a fundamental level, the quinone type and ironsulfur type reaction centers share a common …

Mutational Analysis Of The Structure And Biogenesis Of The Photosystem I Reaction Center In The Cyanobacterium Synechocystis Sp. Pcc 6803, Lawrence B. Smart, Patrick V. Warren, John H. Golbeck, Lee Mcintosh

Department of Biochemistry: Faculty Publications

We have utilized the unicellular cyanobacterium Synechocystis sp. PCC 6803 to incorporate site-directed amino acid substitutions into the photosystemn I (PSI) reactioncenter protein PsaB. A cysteine residue (position 565 of PsaB) proposed to serve as a ligand to the [4Fe-4S] center F_x was changed to serine, histidine, and aspartate. These three mutants- C565S, C565H, and C565D-all exhibited greatly reduced accumulation of PSI reaction-center proteins and failed to grow autotrophically, indicating that this cysteine most likely does coordinate F_x, which is crucial for PSI biogenesis. Interestingly, the strain C565S accumulated significantly more PSI than the other two cysteine …

Reduced Co2/O2 Specificity Of Ribulose-Bisphosphate Carboxylase/Oxygenase In A Temperature-Sensitive Chloroplast Mutant Of Chlamydomonas, Zhixiang Chen, Chris J. Chastain, Souhail R. Al-Abed, Raymond Chollet, Robert J. Spreitzer

Department of Biochemistry: Faculty Publications

The Chlamydomonas reinhardtii chloroplast mutant 68-4PP is phenotypically indistinguishable from wild type at 25°C but fails to grow photosynthetically at 35°C. It had about 30% of the wild-type level of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) holoenzyme and carboxylase activity when grown at 25°C, but less than 15% when grown at 35°C. Pulse-labeling with ³⁵S showed that the decrease in enzyme level at the restrictive temperature was not a result of reduced synthesis of enzyme subunits. The CO₂/O₂ specificity factor (V_cK_o/V_oK_c, where V_c and V_o are V_{max …}

Nonsense Mutations In The Chlamydomonas Chloroplast Gene That Codes For The Large Subunit Of Ribulosebisphosphate Carboxylase/Oxygenase, Robert J. Spreitzer, Michel Goldschmidt-Clermont, Michele Rahire, Jean-David Rochiax

Department of Biochemistry: Faculty Publications

The Chlamydomonas reinhardtii chloroplast mutants 18-SB and 18-7G lack both the chloroplast-encoded large subunit and nuclear-encoded small subunit of the chloroplast enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39). A chloroplast intergenic-suppression model has been postulated to account for the genetic instability of 18-5B revertants. Here, we have determined the molecular basis of the 18-SB and 18-7G mutants. They contain nonsense mutations close to the 3' and 5' ends of their large-subunit genes, respectively. Puls-chase experiments revealed that the 18-SB mutant produces a truncated large subunit that is unstable. In connection with previous experiments, this work identifies nonsense suppression in the chloroplast. Small …