arc6, an extreme chloroplast division mutant of Arabidopsis also alters proplastid proliferation and morphology in shoot and root apices

1995 ◽  
Vol 108 (9) ◽  
pp. 2937-2944 ◽  
Author(s):  
E.J. Robertson ◽  
K.A. Pyke ◽  
R.M. Leech
Keyword(s):  
Higher Plants ◽  
Nuclear Gene ◽  
Mesophyll Cell ◽  
Wild Type ◽  
Plastid Development ◽  
Plastid Differentiation ◽  
Root Cells ◽  
In The Wild ◽  
Variable Morphology ◽  
Root Apices

The arc6 (accumulation and replication of chloroplasts) mutant of Arabidopsis has only two greatly enlarged chloroplasts per mature leaf mesophyll cell compared with ninety chloroplasts per cell in the wild type. The mutation is a single nuclear gene and the plant phenotype is normal. Shoot and root apical meristems of arc6 plants have been examined to determine how early during plastid development the mutant arc6 phenotype can be recognised. In the cells of the arc6 apical meristem there are only two proplastids, which are larger than wild type with a highly variable morphology. In the cells of the leaf primordia where differentiation of proplastids to chloroplasts occurs arc6 plastids are larger and at a more advanced developmental stage than wild-type plastids. In arc6 root cells statoliths and other plastids also show grossly abnormal morphology and the statoliths are greatly increased in size. During arc6 stomatal guard cell development the perturbation in proplastid population dynamics affects plastid segregation and 30% of stomata lack plastids in one or both guard cells. Our evidence would suggest that ARC6 is expressed throughout the vegetative cells of the Arabidopsis seedling with major effects on both the proplastid phenotype and the proplastid population. ARC6 is the first gene to be identified in Arabidopsis which has a global effect on plastid development in cells arising from both the shoot and root meristems, and is of major importance in the nuclear control of plastid differentiation in higher plants.

scholarly journals Cytokinesis in fra2 Arabidopsis thaliana p60-katanin Mutant: Defects in Cell Plate/Daughter Wall Formation

2021 ◽  
Author(s):  
Emmanuel Panteris ◽  
Anna Kouskouveli ◽  
Dimitris Pappas ◽  
Ioannis-Dimosthenis S. Adamakis
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Cell Walls ◽  
Higher Plants ◽  
Cell Plate ◽  
Wild Type ◽  
Microtubule Organization ◽  
Root Cells ◽  
Wall Formation ◽  
In The Wild

Cytokinesis is accomplished in higher plants by the phragmoplast, creating and conducting the cell plate, to separate daughter nuclei by a new cell wall. The microtubule-severing enzyme p60-katanin plays an important role in the centrifugal expansion and timely disappearance of phragmoplast microtubules. Consequently, aberrant structure and delayed expansion rate of the phragmoplast occur in p60-katanin mutants. Here, the consequences of p60-katanin malfunction in cell plate/daughter wall formation were investigated by transmission electron microscopy (TEM), while deviations in the chemical composition of cell plate/new cell wall were identified by immunolabeling and confocal microscopy, in root cells of the fra2 Arabidopsis thaliana mutant. It was found that, apart from defective phragmoplast microtubule organization, cell plates/new cell walls appeared also faulty in structure, being unevenly thick and perforated by large gaps. In addition, demethylesterified homogalacturonans were prematurely present in fra2 cell plates, while callose content was significantly lower than in the wild-type. Furthermore, KNOLLE syntaxin disappeared from newly formed cell walls in fra2 earlier than in the wild-type. Taken together, these observations indicate that delayed cytokinesis, due to faulty phragmoplast organization and expansion, results in a loss of synchronization between cell plate growth and its chemical maturation.

scholarly journals Cytokinesis in fra2 Arabidopsis thaliana p60-Katanin Mutant: Defects in Cell Plate/Daughter Wall Formation

2021 ◽  
Vol 22 (3) ◽  
pp. 1405
Author(s):  
Emmanuel Panteris ◽  
Anna Kouskouveli ◽  
Dimitris Pappas ◽  
Ioannis-Dimosthenis S. Adamakis
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Cell Walls ◽  
Higher Plants ◽  
Cell Plate ◽  
Wild Type ◽  
Microtubule Organization ◽  
Root Cells ◽  
Wall Formation ◽  
In The Wild

Cytokinesis is accomplished in higher plants by the phragmoplast, creating and conducting the cell plate to separate daughter nuclei by a new cell wall. The microtubule-severing enzyme p60-katanin plays an important role in the centrifugal expansion and timely disappearance of phragmoplast microtubules. Consequently, aberrant structure and delayed expansion rate of the phragmoplast have been reported to occur in p60-katanin mutants. Here, the consequences of p60-katanin malfunction in cell plate/daughter wall formation were investigated by transmission electron microscopy (TEM), in root cells of the fra2 Arabidopsis thaliana loss-of-function mutant. In addition, deviations in the chemical composition of cell plate/new cell wall were identified by immunolabeling and confocal microscopy. It was found that, apart from defective phragmoplast microtubule organization, cell plates/new cell walls also appeared faulty in structure, being unevenly thick and perforated by large gaps. In addition, demethylesterified homogalacturonans were prematurely present in fra2 cell plates, while callose content was significantly lower than in the wild type. Furthermore, KNOLLE syntaxin disappeared from newly formed cell walls in fra2 earlier than in the wild type. Taken together, these observations indicate that delayed cytokinesis, due to faulty phragmoplast organization and expansion, results in a loss of synchronization between cell plate growth and its chemical maturation.

scholarly journals Two Mutants Affecting Adaptative Responses to Abiotic Stresses in Barley Seedlings

2011 ◽  
Vol 41 (No. 1) ◽  
pp. 1-10 ◽  
Author(s):  
A.E. Martínez ◽  
A. Landau ◽  
P.T. García ◽  
G. Polenta ◽  
M.C. Arias ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Photosystem I ◽  
Abiotic Stresses ◽  
Higher Plants ◽  
Nuclear Gene ◽  
The Other ◽  
Wild Type ◽  
Seedling Roots ◽  
In The Wild ◽  
Photosystem I And Ii

Two novel mutants which affect the adaptative responses of barley seedlings to different abiotic stresses are described. They allow us to explore some aspects of adaptative phenomena that are little known in higher plants. One of these mutants corresponds to a nuclear gene which under certain circumstances in the wild type barley induces additional ethylene production in the seedling roots. This mechanism seems to be involved in inducing a negative hydrotropic growth of the roots, a phenomenon that we interpret as a response avoiding waterlogging. The other mutant corresponds to a plastid encoded gene which is involved in photosystem I and II stability and, probably, indirectly affects the acclimation of the seedlings to higher temperatures, a fact which seems to occur through the control of unsaturation/saturation levels of the thylakoid membrane fatty acids.  

scholarly journals Pleiotropic Effects of Inactivating a Carboxyl-Terminal Protease, CtpA, in Borrelia burgdorferi

2004 ◽  
Vol 186 (7) ◽  
pp. 2074-2084 ◽  
Author(s):  
Yngve Östberg ◽  
James A. Carroll ◽  
Marija Pinne ◽  
Jonathan G. Krum ◽  
Patricia Rosa ◽  
...  
Keyword(s):  
Borrelia Burgdorferi ◽  
Higher Plants ◽  
Bacterial Species ◽  
Immunoblot Analysis ◽  
Pleiotropic Effect ◽  
Wild Type ◽  
Gene Encoding ◽  
Two Dimensional Gel Electrophoresis ◽  
In The Wild ◽  
Carboxyl Terminal

ABSTRACT A gene encoding a putative carboxyl-terminal protease (CtpA), an unusual type of protease, is present in the Borrelia burgdorferi B31 genome. The B. burgdorferi CtpA amino acid sequence exhibits similarities to the sequences of the CtpA enzymes of the cyanobacterium Synechocystis sp. strain PCC 6803 and higher plants and also exhibits similarities to the sequences of putative CtpA proteins in other bacterial species. Here, we studied the effect of ctpA gene inactivation on the B. burgdorferi protein expression profile. Total B. burgdorferi proteins were separated by two-dimensional gel electrophoresis, and the results revealed that six proteins of the wild type were not detected in the ctpA mutant and that nine proteins observed in the ctpA mutant were undetectable in the wild type. Immunoblot analysis showed that the integral outer membrane protein P13 was larger and had a more acidic pI in the ctpA mutant, which is consistent with the theoretical change in pI for P13 not processed at the carboxyl terminus. Matrix-assisted laser desorption ionization—time of flight data indicated that in addition to P13, the BB0323 protein may serve as a substrate for carboxyl-terminal processing by CtpA. Complementation analysis of the ctpA mutant provided strong evidence that the observed effect on proteins depended on inactivation of the ctpA gene alone. We show that CtpA in B. burgdorferi is involved in the processing of proteins such as P13 and BB0323 and that inactivation of ctpA has a pleiotropic effect on borrelial protein synthesis. To our knowledge, this is the first analysis of both a CtpA protease and different substrate proteins in a pathogenic bacterium.

scholarly journals Multiple Translational Control Sequences in the 5′ Leader of the Chloroplast psbC mRNA Interact With Nuclear Gene Products in Chlamydomonas reinhardtii

Genetics ◽  
2003 ◽  
Vol 163 (3) ◽  
pp. 895-904
Author(s):  
William Zerges ◽  
Andrea H Auchincloss ◽  
Jean-David Rochaix
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Reporter Gene ◽  
Translational Control ◽  
Nuclear Gene ◽  
Gene Products ◽  
Wild Type ◽  
Translation Initiation Region ◽  
Mrna Stabilization ◽  
In The Wild ◽  
Nuclear Loci

Abstract Translation of the chloroplast psbC mRNA in the unicellular eukaryotic alga Chlamydomonas reinhardtii is controlled by interactions between its 547-base 5′ untranslated region and the products of the nuclear loci TBC1, TBC2, and possibly TBC3. In this study, a series of site-directed mutations in this region was generated and the ability of these constructs to drive expression of a reporter gene was assayed in chloroplast transformants that are wild type or mutant at these nuclear loci. Two regions located in the middle of the 5′ leader and near the initiation codon are important for translation. Other deletions still allow for partial expression of the reporter gene in the wild-type background. Regions with target sites for TBC1 and TBC2 were identified by estimating the residual translation activity in the respective mutant backgrounds. TBC1 targets include mostly the central part of the leader and the translation initiation region whereas the only detected TBC2 targets are in the 3′ part. The 5′-most 93 nt of the leader are required for wild-type levels of transcription and/or mRNA stabilization. The results indicate that TBC1 and TBC2 function independently and further support the possibility that TBC1 acts together with TBC3.

scholarly journals TheS. cerevisiaeHAP Complex, a Key Regulator of Mitochondrial Function, Coordinates Nuclear and Mitochondrial Gene Expression

2003 ◽  
Vol 4 (1) ◽  
pp. 37-46 ◽  
Author(s):  
S. Buschlen ◽  
J-M Amillet ◽  
B. Guiard ◽  
A. Fournier ◽  
C. Marcireau ◽  
...  
Keyword(s):  
Gene Expression ◽  
Respiratory Chain ◽  
Mitochondrial Gene ◽  
Nuclear Gene ◽  
Negative Control ◽  
Nuclear Genes ◽  
Wild Type ◽  
Mitochondrial Translation ◽  
Respiratory Chain Complexes ◽  
In The Wild

We have comparedSaccharomyces cerevisiaeglobal gene expression in wild-type and mutants (Δhap2 and Δhap4) of the HAP transcriptional complex, which has been shown to be necessary for growth on respiratory substrates. Several hundred ORFs are under positive or negative control of this complex and we analyse here in detail the effect of HAP on mitochondria. We found that most of the genes upregulated in the wild-type strain were involved in organelle functions, but practically none of the downregulated ones. Nuclear genes encoding the different subunits of the respiratory chain complexes figure in the genes more expressed in the wild-type than in the mutants, as expected, but in this group we also found key components of the mitochondrial translation apparatus. This control of mitochondrial translation may be one of the means of coordinating mitochondrial and nuclear gene expression in elaborating the respiratory chain. In addition, HAP controls the nuclear genes involved in several other mitochondrial processes (import, mitochondrial division) that define the metabolic state of the cell, but not mitochondrial DNA replication and transcription. In most cases, a putative CCAAT-binding site is present upstream of the ORF, while in others no such sites are present, suggesting the control to be indirect. The large number of genes regulated by the HAP complex, as well as the fact that HAP also regulates some putative transcriptional activators of unknown function, place this complex at a hierarchically high position in the global transcriptional regulation of the cell.

scholarly journals Comparative analysis of the biogenesis of photosystem II in the wild-type and Y-1 mutant of Chlamydomonas reinhardtii.

1988 ◽  
Vol 106 (3) ◽  
pp. 609-616 ◽  
Author(s):  
P Malnoë ◽  
S P Mayfield ◽  
J D Rochaix
Keyword(s):  
Photosystem Ii ◽  
Chlamydomonas Reinhardtii ◽  
Oxygen Evolving Complex ◽  
Wild Type ◽  
Plastid Development ◽  
Photosynthetic System ◽  
In The Wild ◽  
Steady State Levels ◽  
Chloroplast Mrna ◽  
Oxygen Evolving

Expression of the genes of the photosystem II (PSII) core polypeptides D1 and D2, of three proteins of the oxygen evolving complex of PSII and of the light harvesting chlorophyll a/b binding proteins (LHCP) has been compared in wild-type (wt) and in the y-1 mutant of Chlamydomonas reinhardtii. Since wt, but not y-1 cells produce a fully developed photosynthetic system in the dark, comparison of the two has allowed us to distinguish the direct effect of light from the influence of plastid development on gene expression. The PSII core polypeptides and LHCP are nearly undetectable in dark-grown y-1 cells but they accumulate progressively during light induced greening. The levels of these proteins in wt are the same in the light and the dark. The amounts of the proteins of the oxygen evolving complex do not change appreciably in the light or in the dark for both wt and y-1. Steady state levels of chloroplast mRNA encoding the core PSII polypeptides remain nearly constant in the light or the dark and are not affected by the developmental stage of the plastid. Levels of nuclear encoded mRNAs for the oxygen evolving proteins and of LHCP increase during light growth in wt and y-1. In contrast to wt, synthesis of LHCP proteins is not detectable in y-1 cells in the dark but starts immediately after transfer to light, indicating that LHCP synthesis is controlled by a light-induced factor or process. While the rates of synthesis of D1 and D2 are immediately enhanced by light in wt, this increase occurs only after a lag in y-1 and thus must be dependent on an early light-induced event in the plastid. These results show that the biosynthesis of PSII is affected by light directly, by the stage of plastid development, and by the interaction of light and events associated with plastid development.

scholarly journals Phenotype, Inheritance, and Regulation of Expression of a New Virescent Mutant in Watermelon: Juvenile Albino

1996 ◽  
Vol 121 (4) ◽  
pp. 609-615 ◽  
Author(s):  
X.P. Zhang ◽  
B.B. Rhodes ◽  
W.V. Baird ◽  
H.T. Skorupska ◽  
W.C. Bridges
Keyword(s):  
Red Light ◽  
Nuclear Gene ◽  
Chlorophyll Synthesis ◽  
Early Spring ◽  
Wild Type ◽  
Regulation Of Expression ◽  
Gene Segregation ◽  
Young Leaves ◽  
In The Wild ◽  
Virescent Mutant

Juvenile albino, gene symbol ja, is a spontaneous virescent mutant, first observed in `Dixielee' and an F2 population of `G17AB' (msms) × `Dixielee' in 1992. Hypocotyls, new young leaves, shoot tips, tendrils and flowers on the main shoot of the ja mutant are all albino during early spring. The interior portions of albino leaves gradually become green, while the margins remain albino. Fruit rind color of the mutant is variegated. Growth of the ja mutant is severely impaired in the early spring. However, the mutant grows at a rate comparable to wild-type in the summer, and produces fruit of almost normal size. Genetic analysis of F1, F2, and BC1 populations derived from the ja mutant showed that the gene for the ja mutant is inherited as a single, recessive, nuclear gene. Segregation ratios in the F2 and BC1 progenies derived from the cross between the previously reported delayed green virescent mutant and the ja mutant indicate independent inheritance of the genes dg and ja. Temperature and red/far-red light had no differential effect on mutant and the wild-type plants. An increase of daylength from 8 to 15 hours increased fresh weight and chlorophyll content more in the ja mutant than in the wild-type. The mutant had a higher chlorophyll a: b ratio than the wild-type under long days. Chlorophyll synthesis or accumulation in the mutant is severely impaired under short days. This is the only virescent mutant in the family Cucurbitaceae whose expression is regulated by daylength.

Comparative Immunological Studies on the CF1-Complex in Mutants of N. tabacum, Exhibiting Different Capacities for Photosynthesis and Photorespiration and Different Chloroplast Structures

1989 ◽  
Vol 44 (7-8) ◽  
pp. 689-697 ◽  
Author(s):  
A. Radunz ◽  
G. H. Schmid
Keyword(s):  
Spinacia Oleracea ◽  
Higher Plants ◽  
Morphological Structure ◽  
Coupling Factor ◽  
Molar Ratio ◽  
Wild Type ◽  
Crossed Immunoelectrophoresis ◽  
Adsorption Surface ◽  
In The Wild ◽  
Normal Ratio

We have compared by means of rocket immunoelectrophoresis the amount of CF1-complex in N. tabacum mutants with that in the wild type N. tabacum var. John William’s Broadleaf. Some of these mutants differ from the wild type not only by higher photosynthetic and photorespiratory activities but also by their chloroplast structure. The amount of CF1, present was related to the chlorophyll content. However, no correlation between the amount of CF1, present and a higher photosynthetic and photorespiratory activity was found. On the other hand the molar ratio of CF1, to chlorophyll seems to depend in these tobacco mutants on the morphological structure of the chloroplasts. In chloroplasts of green phenotypes, in particular in those of the mutants N. tabacum var. Consolation, var. NC 95 and var. Xanthi with high grana stacking as well as in those of the wild type N. tabacum var. JWB one CF1-complex occurs per 470-770 chlorophyll molecules. Whereas in chloroplasts of the yellow-green phenotypes with relatively more stroma thylakoids the amount of CF1 seems to be increased only by a factor of 3-4. The yellow phenotypes contain on the average 1 CF1-complex per 60 chlorophyll molecules. The CF1-complex in the investigated chlorophyll-deficient tobacco mutants is immunochemically identical to that of the wild type N. tabacum var. John William’s Broadleaf as demonstrated by means of the tandem-crossed immunoelectrophoresis. However, between the CF1-complex of tobacco and that of other higher plants such as spinach Spinacia oleracea, only partial identity is observed. Comparative quantitative determinations have shown that one CF1-complex binds on the average 8-9 CF1-antibodies which shows that the CF1-complex of the ATPase is fully exposed in the thylakoid membrane, offering a large adsorption surface to the antibodies. Furthermore, it appears that in the immediate vicinity of the CF1-complex large amounts of monogalactolipids are located. Thus, we have calculated that in the variegated NC 95 mutant, chloroplasts of the yellow leaf areas, in which only stroma thylakoids occur, exhibiting only photosystem I activity, as well as in chloroplasts of green leaf areas with a normal ratio of grana and intergrana thylakoids, the molar ratio of monogalactolipids to CF1-complex is the same. It looks as if the functionality and activity of the coupling factor of photophosphorylation depended on a certain quantity of monogalactolipid molecules.

Freeze-substituted fungal cells of Nectria haematococca: A comparison of the macroconidial walls of the adhesion-competent wild type with an adhesion-reduced mutant

1990 ◽  
Vol 48 (3) ◽  
pp. 688-689
Author(s):  
Thecan Caesar-Ton That ◽  
Lynn Epstein
Keyword(s):  
Freeze Substitution ◽  
Uranyl Acetate ◽  
Wild Type ◽  
Nectria Haematococca ◽  
Fruit Extract ◽  
Dialysis Tubing ◽  
Tube Emergence ◽  
Contrast Microscopy ◽  
In The Wild ◽  
Freeze Damage

Nectria haematococca mating population I (anamorph, Fusarium solani) macroconidia attach to its host (squash) and non-host surfaces prior to germ tube emergence. The macroconidia become adhesive after a brief period of protein synthesis. Recently, Hickman et al. (1989) isolated N. haematococca adhesion-reduced mutants. Using freeze substitution, we compared the development of the macroconidial wall in the wild type in comparison to one of the mutants, LEI.Macroconidia were harvested at 1C, washed by centrifugation, resuspended in a dilute zucchini fruit extract and incubated from 0 - 5 h. During the incubation period, wild type macroconidia attached to uncoated dialysis tubing. Mutant macroconidia did not attach and were collected on poly-L-lysine coated dialysis tubing just prior to freezing. Conidia on the tubing were frozen in liquid propane at 191 - 193C, substituted in acetone with 2% OsO4 and 0.05% uranyl acetate, washed with acetone, and flat-embedded in Epon-Araldite. Using phase contrast microscopy at 1000X, cells without freeze damage were selected, remounted, sectioned and post-stained sequentially with 1% Ba(MnO4)2 2% uranyl acetate and Reynold’s lead citrate. At least 30 cells/treatment were examined.

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