scholarly journals CHLOROPLAST STRUCTURE AND FUNCTION IN ac-20, A MUTANT STRAIN OF CHLAMYDOMONAS REINHARDI

1970 ◽  
Vol 44 (3) ◽  
pp. 547-562 ◽  
Author(s):  
Ursula W. Goodenough ◽  
R. P. Levine
Keyword(s):  
Mutant Strain ◽  
Minimal Medium ◽  
Structure And Function ◽  
Membrane Organization ◽  
Chloroplast Structure ◽  
Wild Type ◽  
Fold Reduction ◽  
Membrane Reorganization ◽  
And Function ◽  
Photosynthetic Properties

The fine structure of the ac-20 strain of Chlamydomonas reinhardi is described. Cells grown mixotrophically in the presence of acetate have a highly disordered chloroplast membrane organization and usually lack pyrenoids. Chloroplast ribosome levels are only 5–10% of wild-type levels. Cells grown phototrophically without acetate possess more chloroplast ribosomes and have more normal membrane and pyrenoid organization. Chloroplast ribosome levels rise rapidly when cells are transferred from acetate to minimal medium, whereas membrane reorganization occurs only after a lag. These results, combined with earlier studies of the photosynthetic properties of the mutant strain, suggest that proper membrane organization, Photosystem II activity, and ribulose-1,5-diphosphate carboxylase formation are dependent on the presence of chloroplast ribosomes. Other chloroplast components tested are unaffected by a 10-fold reduction in levels of chloroplast ribosomes.

scholarly journals CHLOROPLAST STRUCTURE AND FUNCTION IN ac-20, A MUTANT STRAIN OF CHLAMYDOMONAS REINHARDI

1970 ◽  
Vol 44 (3) ◽  
pp. 540-546 ◽  
Author(s):  
R. P. Levine ◽  
A. Paszewski
Keyword(s):  
Electron Transport ◽  
Mutant Strain ◽  
Electron Transport Chain ◽  
Co2 Fixation ◽  
Photosynthetic Electron Transport ◽  
Structure And Function ◽  
Wild Type ◽  
Carboxylase Activity ◽  
Transport Chain ◽  
And Function

Photosynthetic electron transport is markedly affected in mixotrophic cells of ac-20 because they lack the capacity to form the wild-type level of cytochrome 559, as well as Q, the quencher of fluorescence of photochemical system II. The other components of the electron-transport chain, as well as reactions dependent upon photochemical system I, are unaffected in the mutant strain. These observations are discussed in terms of the previously reported effects of the ac-20 mutation on CO2 fixation and ribulose-1,5-diphosphate carboxylase activity.

scholarly journals A Rubisco-binding protein is required for normal pyrenoid number and starch sheath morphology inChlamydomonas reinhardtii

2019 ◽  
Vol 116 (37) ◽  
pp. 18445-18454 ◽  
Author(s):  
Alan K. Itakura ◽  
Kher Xing Chan ◽  
Nicky Atkinson ◽  
Leif Pallesen ◽  
Lianyong Wang ◽  
...  
Keyword(s):  
Surface Area ◽  
Structure And Function ◽  
Binding Motif ◽  
Starch Granules ◽  
Wild Type ◽  
Bisphosphate Carboxylase ◽  
Biophysical Mechanism ◽  
Mechanism Function ◽  
And Function

A phase-separated, liquid-like organelle called the pyrenoid mediates CO2fixation in the chloroplasts of nearly all eukaryotic algae. While most algae have 1 pyrenoid per chloroplast, here we describe a mutant in the model algaChlamydomonasthat has on average 10 pyrenoids per chloroplast. Characterization of the mutant leads us to propose a model where multiple pyrenoids are favored by an increase in the surface area of the starch sheath that surrounds and binds to the liquid-like pyrenoid matrix. We find that the mutant’s phenotypes are due to disruption of a gene, which we call StArch Granules Abnormal 1 (SAGA1) because starch sheath granules, or plates, in mutants lacking SAGA1 are more elongated and thinner than those of wild type. SAGA1 contains a starch binding motif, suggesting that it may directly regulate starch sheath morphology. SAGA1 localizes to multiple puncta and streaks in the pyrenoid and physically interacts with the small and large subunits of the carbon-fixing enzyme Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), a major component of the liquid-like pyrenoid matrix. Our findings suggest a biophysical mechanism by which starch sheath morphology affects pyrenoid number and CO2-concentrating mechanism function, advancing our understanding of the structure and function of this biogeochemically important organelle. More broadly, we propose that the number of phase-separated organelles can be regulated by imposing constraints on their surface area.

scholarly journals Alterations in flight muscle ultrastructure and function in Drosophila tropomyosin mutants.

1996 ◽  
Vol 135 (3) ◽  
pp. 673-687 ◽  
Author(s):  
A J Kreuz ◽  
A Simcox ◽  
D Maughan
Keyword(s):  
Amino Acid ◽  
Power Output ◽  
Flight Muscle ◽  
Structure And Function ◽  
Wild Type ◽  
Muscle Tropomyosin ◽  
Ultrastructure And Function ◽  
And Function ◽  
Net Power Output ◽  
Current Report

Drosophila indirect flight muscle (IFM) contains two different types of tropomyosin: a standard 284-amino acid muscle tropomyosin, Ifm-TmI, encoded by the TmI gene, and two > 400 amino acid tropomyosins, TnH-33 and TnH-34, encoded by TmII. The two IFM-specific TnH isoforms are unique tropomyosins with a COOH-terminal extension of approximately 200 residues which is hydrophobic and rich in prolines. Previous analysis of a hypomorphic TmI mutant, Ifm(3)3, demonstrated that Ifm-TmI is necessary for proper myofibrillar assembly, but no null TmI mutant or TmII mutant which affects the TnH isoforms have been reported. In the current report, we show that four flightless mutants (Warmke et al., 1989) are alleles of TmI, and characterize a deficiency which deletes both TmI and TmII. We find that haploidy of TmI causes myofibrillar disruptions and flightless behavior, but that haploidy of TmII causes neither. Single fiber mechanics demonstrates that power output is much lower in the TmI haploid line (32% of wild-type) than in the TmII haploid line (73% of wild-type). In myofibers nearly depleted of Ifm-TmI, net power output is virtually abolished (< 1% of wild-type) despite the presence of an organized fibrillar core (approximately 20% of wild-type). The results suggest Ifm-TmI (the standard tropomyosin) plays a key role in fiber structure, power production, and flight, with reduced Ifm-TmI expression producing corresponding changes of IFM structure and function. In contrast, reduced expression of the TnH isoforms has an unexpectedly mild effect on IFM structure and function.

scholarly journals The plant circadian clock influences rhizosphere community structure and function

2017 ◽  
Author(s):  
Charley J. Hubbard ◽  
Marcus T. Brock ◽  
Linda T.A. van Diepen ◽  
Loïs Maignien ◽  
Brent E. Ewers ◽  
...  
Keyword(s):  
Community Structure ◽  
Microbial Community ◽  
Circadian Clock ◽  
Structure And Function ◽  
Plant Performance ◽  
Wild Type ◽  
Night Time ◽  
History Of ◽  
And Function ◽  
Rhizosphere Community

AbstractPlants alter chemical and physical properties of soil, and thereby influence rhizosphere microbial community structure. The structure of microbial communities may in turn affect plant performance. Yet, outside of simple systems with pairwise interacting partners, the plant genetic pathways that influence microbial community structure remain largely unknown, as are the performance feedbacks of microbial communities selected by the host plant genotype. We investigated the role of the plant circadian clock in shaping rhizosphere community structure and function. We performed 16S rRNA gene sequencing to characterize rhizosphere bacterial communities of Arabidopsis thaliana between day and night time points, and tested for differences in community structure between wild-type (Ws) vs. clock mutant (toc1-21, ztl-30) genotypes. We then characterized microbial community function, by growing wild-type plants in soils with an overstory history of Ws, toc1-21 or ztl-30 and measuring plant performance. We observed that rhizosphere community structure varied between day and night time points, and clock misfunction significantly altered rhizosphere communities. Finally, wild-type plants germinated earlier and were larger when inoculated with soils having an overstory history of wild-type in comparison to clock mutant genotypes. Our findings suggest the circadian clock of the plant host influences rhizosphere community structure and function.

scholarly journals Muscles of mice deficient in α-sarcoglycan maintain large masses and near control force values throughout the life span

2005 ◽  
Vol 22 (2) ◽  
pp. 244-256 ◽  
Author(s):  
Christina M. Consolino ◽  
Franck Duclos ◽  
Jane Lee ◽  
Roger A. Williamson ◽  
Kevin P. Campbell ◽  
...  
Keyword(s):  
Connective Tissue ◽  
Life Span ◽  
Structure And Function ◽  
Null Mouse ◽  
Control Force ◽  
Wild Type ◽  
Cross Sectional ◽  
Muscle Structure ◽  
And Function

α-Sarcoglycan-deficient ( Sgca-null) mice provide potential for elucidating the pathogenesis of limb girdle muscular dystrophy type 2D (LGMD 2D) as well as for studying the effectiveness of therapeutic strategies. Skeletal muscles of Sgca-null mice demonstrate an early onset of extensive fiber necrosis, degeneration, and regeneration, but the progression of the pathology and the effects on muscle structure and function throughout the life span are not known. Thus the phenotypic accuracy of the Sgca-null mouse as a model of LGMD 2D has not been fully established. To investigate skeletal muscle structure and function in the absence of α-sarcoglycan throughout the life span, we analyzed extensor digitorum longus and soleus muscles of male and female Sgca-null and wild-type mice at 3, 6, 12, and 18 mo of age. Maximum isometric forces and powers were measured in vitro at 25°C. Also determined were individual myofiber cross-sectional areas and numbers, water content, and the proportion of the cross section occupied by connective tissue. Muscle masses were 40–100% larger for Sgca-null compared with age- and gender-matched wild-type mice, with the majority of the increased muscle mass for Sgca-null mice attributable to greater connective tissue and water contents. Although the greater mass of muscles in Sgca-null mice was primarily noncontractile material, absolute forces and powers were maintained near control levels at all ages, indicating a successful adaptation to the deficiency in α-sarcoglycan not observed at any age in LGMD 2D patients.

The Structure and Function of Murine Factor V and Its Inactivation by Protein C

Blood ◽  
1998 ◽  
Vol 91 (12) ◽  
pp. 4593-4599 ◽  
Author(s):  
Tony L. Yang ◽  
Jisong Cui ◽  
Alnawaz Rehumtulla ◽  
Angela Yang ◽  
Micheline Moussalli ◽  
...  
Keyword(s):  
Amino Acid ◽  
Protein C ◽  
Mammalian Species ◽  
Structure And Function ◽  
Procoagulant Activity ◽  
Factor V ◽  
Cleavage Sites ◽  
Wild Type ◽  
Coding Region ◽  
And Function

Factor V (FV) is a central regulator of hemostasis, serving both as a critical cofactor for the prothrombinase activity of factor Xa and the target for proteolytic inactivation by the anticoagulant, activated protein C (APC). To examine the evolutionary conservation of FV procoagulant activity and functional inactivation by APC, we cloned and sequenced the coding region of murine FV cDNA and generated recombinant wild-type and mutant murine FV proteins. The murine FV cDNA encodes a 2,183-amino acid protein. Sequence comparison shows that the A1-A3 and C1-C2 domains of FV are highly conserved, demonstrating greater than 84% sequence identity between murine and human, and 60% overall amino acid identity among human, bovine, and murine FV sequences. In contrast, only 35% identity among all three species is observed for the poorly conserved B domain. The arginines at all thrombin cleavage sites and the R305 and R504 APC cleavage sites (corresponding to amino acid residues R306 and R506 in human FV) are invariant in all three species. Point mutants were generated to substitute glutamine at R305, R504, or both (R305/R504). Wild-type and all three mutant FV recombinant proteins show equivalent FV procoagulant activity. Single mutations at R305 or R504 result in partial resistance of FV to APC inactivation, whereas recombinant murine FV carrying both mutations (R305Q/R504Q) is nearly completely APC resistant. Thus, the structure and function of FV and its interaction with APC are highly conserved across mammalian species.

scholarly journals His···Asp Catalytic Dyad of Ribonuclease A:  Structure and Function of the Wild-Type, D121N, and D121A Enzymes†

Biochemistry ◽  
1998 ◽  
Vol 37 (25) ◽  
pp. 8886-8898 ◽  
Author(s):  
L. Wayne Schultz ◽  
David J. Quirk ◽  
Ronald T. Raines
Keyword(s):  
Ribonuclease A ◽  
Structure And Function ◽  
Wild Type ◽  
And Function ◽  
Catalytic Dyad

The intracellular reserve polysaccharide of Clostridium pasteurianum

1977 ◽  
Vol 23 (8) ◽  
pp. 947-953 ◽  
Author(s):  
A. G. Darvill ◽  
M. A. Hall ◽  
J. P. Fish ◽  
J. G. Morris
Keyword(s):  
Mutant Strain ◽  
Minimal Medium ◽  
Clostridium Pasteurianum ◽  
Wild Type ◽  
Methylation Analysis ◽  
Glucose Content ◽  
Glucose Minimal Medium ◽  
Intracellular Polysaccharide ◽  
Type Strains ◽  
Negative Mutant

An amylopectinlike polysaccharide (granulose) was the only glucan produced in significant quantities by six wild-type strains of Clostridium pasteurianum grown in glucose minimal medium. The intracellular polysaccharide granules laid down before sporulation contained only this amylopectin. No intracellular dextran was discovered in these wild-type strains, nor in a granulose-negative mutant strain of C. pasteurianum possessing an ADP glucose pyrophosphorylase (EC 2.7.7.27) but lacking a granulose synthase (i.e. ADPglucose-α-1,4-glucan glucosyl transferase, EC 2.4.1.21). Furthermore, methylation analysis demonstrated that (1 → 6) linked α-D-glucose units accounted for less than 2% of the entire glucose content of these organisms.

Effects of NaCl Salinity on Growth, Cation Accumulation, Chloroplast Structure and Function in Wheat Cultivars Differing in Salt Tolerance

1994 ◽  
Vol 144 (2) ◽  
pp. 241-247 ◽  
Author(s):  
Samir Salama ◽  
Shailja Trivedi ◽  
Mira Busheva ◽  
A.A. Arafa ◽  
Győző Garab ◽  
...  
Keyword(s):  
Salt Tolerance ◽  
Structure And Function ◽  
Wheat Cultivars ◽  
Chloroplast Structure ◽  
Nacl Salinity ◽  
And Function
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