Arthur R. Grossman

Bio: Arthur R. Grossman is an academic researcher from Carnegie Institution for Science. The author has contributed to research in topics: Chlamydomonas reinhardtii & Chlamydomonas. The author has an hindex of 94, co-authored 321 publications receiving 29561 citations. Previous affiliations of Arthur R. Grossman include Rockefeller University & University of Idaho.

The Chlamydomonas Genome Reveals the Evolution of Key Animal and Plant Functions

Abstract: Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the approximately 120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella.

A pigment-binding protein essential for regulation of photosynthetic light harvesting

Abstract: Photosynthetic light harvesting in plants is regulated in response to changes in incident light intensity. Absorption of light that exceeds a plant's capacity for fixation of CO2 results in thermal dissipation of excitation energy in the pigment antenna of photosystem II by a poorly understood mechanism. This regulatory process, termed nonphotochemical quenching, maintains the balance between dissipation and utilization of light energy to minimize generation of oxidizing molecules, thereby protecting the plant against photo-oxidative damage. To identify specific proteins that are involved in nonphotochemical quenching, we have isolated mutants of Arabidopsis thaliana that cannot dissipate excess absorbed light energy. Here we show that the gene encoding PsbS, an intrinsic chlorophyll-binding protein of photosystem II, is necessary for nonphotochemical quenching but not for efficient light harvesting and photosynthesis. These results indicate that PsbS may be the site for nonphotochemical quenching, a finding that has implications for the functional evolution of pigment-binding proteins.

Arabidopsis mutants define a central role for the xanthophyll cycle in the regulation of photosynthetic energy conversion.

Abstract: A conserved regulatory mechanism protects plants against the potentially damaging effects of excessive light. Nearly all photosynthetic eukaryotes are able to dissipate excess absorbed light energy in a process that involves xanthophyll pigments. To dissect the role of xanthophylls in photoprotective energy dissipation in vivo, we isolated Arabidopsis xanthophyll cycle mutants by screening for altered nonphotochemical quenching of chlorophyll fluorescence. The npq1 mutants are unable to convert violaxanthin to zeaxanthin in excessive light, whereas the npq2 mutants accumulate zeaxanthin constitutively. The npq2 mutants are new alleles of aba1, the zeaxanthin epoxidase gene. The high levels of zeaxanthin in npq2 affected the kinetics of induction and relaxation but not the extent of nonphotochemical quenching. Genetic mapping, DNA sequencing, and complementation of npq1 demonstrated that this mutation affects the structural gene encoding violaxanthin deepoxidase. The npq1 mutant exhibited greatly reduced nonphotochemical quenching, demonstrating that violaxanthin deepoxidation is required for the bulk of rapidly reversible nonphotochemical quenching in Arabidopsis. Altered regulation of photosynthetic energy conversion in npq1 was associated with increased sensitivity to photoinhibition. These results, in conjunction with the analysis of npq mutants of Chlamydomonas, suggest that the role of the xanthophyll cycle in nonphotochemical quenching has been conserved, although different photosynthetic eukaryotes rely on the xanthophyll cycle to different extents for the dissipation of excess absorbed light energy.

An ancient light-harvesting protein is critical for the regulation of algal photosynthesis

Abstract: Light is necessary for photosynthesis, but its absorption by pigment molecules such as chlorophyll can cause severe oxidative damage and result in cell death. The excess absorption of light energy by photosynthetic pigments has led to the evolution of protective mechanisms that operate on the timescale of seconds to minutes and involve feedback-regulated de-excitation of chlorophyll molecules in photosystem II (qE). Despite the significant contribution of eukaryotic algae to global primary production, little is known about their qE mechanism, in contrast to that in flowering plants. Here we show that a qE-deficient mutant of the unicellular green alga Chlamydomonas reinhardtii, npq4, lacks two of the three genes encoding LHCSR (formerly called LI818). This protein is an ancient member of the light-harvesting complex superfamily, and orthologues are found throughout photosynthetic eukaryote taxa, except in red algae and vascular plants. The qE capacity of Chlamydomonas is dependent on environmental conditions and is inducible by growth under high light conditions. We show that the fitness of the npq4 mutant in a shifting light environment is reduced compared to wild-type cells, demonstrating that LHCSR is required for survival in a dynamic light environment. Thus, these data indicate that plants and algae use different proteins to dissipate harmful excess light energy and protect the photosynthetic apparatus from damage.

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。

ABC Transporters: From Microorganisms to Man

Abstract: INTRODUCTION .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 DOMAIN ORGANIZATION: The Typical ABC Transporter . . . . . . . . . . . . . . . . . 73 THE TRANSMEMBRANE DOMAINS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 The "Two-Times-Six" Helix Paradigm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Sequence Similarities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 THE ATP-BINDING DOMAINS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 PERIPLASMIC-BINDING PROTEINS ... . 84 SUBSTRATE SPECIFICITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 THE ROLE OF ATP : Coupling Energy to Transport . . . . . . . . . . . . . . . . . . . " . . . . . 88 COVALENT MODIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 CELLULAR FUNCTIONS OF ABC TRANSPORTERS . . . . . . . . . . . . . . . . . . . . . . . 9 1 Nutrient Uptake . . . . . . . . . . . . ....... . 9 1 Protein Export ....... . .... . . . . . . . . . . . . ... . ......... . ...... . ... . .. 93 Intracellular Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 Regulation of ABC Transporters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 Regulation by ABC Transporters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Drug and Antibiotic Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Channel Functions: CFTR and P-glycoprotein . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 MECHANISMS OF SOLUTE TRANSLOCATION . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Structure of the Transmembrane Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Channels and Transporters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 I Energy Coupling andlor Gating . 102 CONCLUDING REMARKS . 103

Phytozome: a comparative platform for green plant genomics

Abstract: The number of sequenced plant genomes and associated genomic resources is growing rapidly with the advent of both an increased focus on plant genomics from funding agencies, and the application of inexpensive next generation sequencing. To interact with this increasing body of data, we have developed Phytozome (http://www.phytozome.net), a comparative hub for plant genome and gene family data and analysis. Phytozome provides a view of the evolutionary history of every plant gene at the level of sequence, gene structure, gene family and genome organization, while at the same time providing access to the sequences and functional annotations of a growing number (currently 25) of complete plant genomes, including all the land plants and selected algae sequenced at the Joint Genome Institute, as well as selected species sequenced elsewhere. Through a comprehensive plant genome database and web portal, these data and analyses are available to the broader plant science research community, providing powerful comparative genomics tools that help to link model systems with other plants of economic and ecological importance.

Plant drought stress: effects, mechanisms and management

Abstract: Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.