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1.
Enhancement of Oxygen-Evolution in Photosystem II-Phycobilisome Particles from Porphyridium cruentum
Oxygen-evolving photosystem II-phycobilisome particles froma red alga were inhibited 5080% by aging, dilution, lowpH and salt-washing. Bovine serum albumin, and dithiothreitolwere found to stimulate activity in all but salt-washed particles.CaCl2 and MnCl2 partially restored activity lost after agingor dilution.
1Current address: Waksman Institute of Microbiology, RutgersUniversity, Piscataway, New Jersey 08854-0759, U.S.A. (Received October 5, 1985; Accepted March 31, 1986) 相似文献
2.
Constant Phycobilisome Size in Chromatically Adapted Cells of the Cyanobacterium Tolypothrix tenuis, and Variation in Nostoc sp
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Phycobilisomes of Tolypothrix tenuis, a cyanobacterium capable of complete chromatic adaptation, were studied from cells grown in red and green light, and in darkness. The phycobilisome size remained constant irrespective of the light quality. The hemidiscoidal phycobilisomes had an average diameter of about 52 nanometers and height of about 33 nanometers, by negative staining. The thickness was equivalent to a phycocyanin molecule (about 10 nanometers). The molar ratio of allophycocyanin, relative to other phycobiliproteins always remained at about 1:3. Phycobilisomes from red light grown cells and cells grown heterotrophically in darkness were indistinguishable in their pigment composition, polypeptide pattern, and size. Eight polypeptides were resolved in the phycobilin region (17.5 to 23.5 kilodaltons) by isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Half of these were invariable, while others were variable in green and red light. It is inferred that phycoerythrin synthesis in green light resulted in a one for one substitution of phycocyanin, thus retaining a constant phycobilisome size. Tolypothrix appears to be one of the best examples of phycobiliprotein regulation with wavelength. By contrast, in Nostoc sp., the decrease in phycoerythrin in red light cells was accompanied by a decrease in phycobilisome size but not a regulated substitution. 相似文献
3.
4.
An electron microscopic examination of Porphyridium cruentum revealed the presence of mitochondria which had been reported absent in this aerobic organism. The chloroplast in this red alga was found to contain small granules (about 320 A) regularly arranged along the parallel chloroplast lamellae. The chloroplast granules differ in size and staining intensity from the ribosomes located in the cytoplasm. Two tubular elements are described. One type (450 to 550 A) is associated with the Golgi bodies. Another type (350 A), in the cell periphery, is believed to connect the endoplasmic reticulum and the cell membrane. Daughter nuclei were found to be positioned at opposite ends of the cell prior to commencement of cell division. Cytokinesis is accomplished by an annular median constriction causing the gradual separation of the chloroplast, pyrenoid, and other cell organelles, resulting in two equal daughter cells. No appreciable differences were observed between cells grown in high light (400 ft-c) and low light (40 ft-c). Structural differences between young and old cells were compared. 相似文献
5.
Light is required for the germination of spores of Matteuccia struthiopteris. Histochemical studies show that dormant spores contain no starch, but have an abundance of storage protein granules. Starch accumulates in the numerous chloroplasts of the spore on exposure to light and becomes gradually more extensive. Protein granules disappear as germination progresses. Following this, the centrally located nucleus migrates toward the proximal spore face. Concomitant with the nuclear migration, an increase of cytoplasmic RNA surrounding the nucleus occurs. An equal nuclear division and unequal cell division give rise to a 2-celled gametophyte consisting of a large prothallial cell and smaller rhizoidal cell. A new peripheral wall forms around the entire protoplast at the time of nuclear migration, while a transverse wall forms after nuclear division. The rhizoid emerges through the split raphe along the proximal spore face; it is rich in cytoplasmic RNA but contains very few chloroplasts and little starch. Electron microscopy of the 2-celled stage revealed a greater concentration of mitochondria, Golgi bodies, and a more extensive endoplasmic reticulum in the rhizoid than was found in the prothallial cell, which, however, was far richer in chloroplasts and lipid bodies. As the rhizoid elongates and becomes more vacuolated, cytoplasmic RNA decreases as cytoplasmic protein increases. The rhizoid undergoes no cell divisions, while the prothallial cell retains the potential for further cell division. The possible significance of the distribution of storage products, cell organelles, and other cell components were considered in relation to the non-equational cell division and differentiation of the 2 cells. 相似文献
6.
Pigment protein complexes and the concept of the photosynthetic unit: Chlorophyll complexes and phycobilisomes 总被引:5,自引:0,他引:5
Elisabeth Gantt 《Photosynthesis research》1996,48(1-2):47-53
The photosynthetic unit includes the reaction centers (RC 1 and RC 2) and the light-harvesting complexes which contribute to evolution of one O2 molecule. The light-harvesting complexes, that greatly expand the absorptance capacity of the reactions, have evolved along three principal lines. First, in green plants distinct chlorophyll (Chl) a/b-binding intrinsic membrane complexes are associated with RC 1 and RC 2. The Chl a/b-binding complexes may add about 200 additional chromophores to RC 2. Second, cyanobacteria and red algae have a significant type of antenna (with RC 2) in the form of phycobilisomes. A phycobilisome, depending on the size and phycobiliprotein composition adds from 700 to 2300 light-absorbing chromophores. Red algae also have a sizable Chl a-binding complex associated with RC 1, contributing an additional 70 chromophores. Third, in chromophytes a variety of carotenoid-Chl-complexes are found. Some are found associated with RC 1 where they may greatly enhance the absorptance capacity. Association of complexes with RC 2 has been more difficult to ascertain, but is also expected in chromophytes. The apoprotein framework of the complexes provides specific chromophore attachment sites, which assures a directional energy transfer whithin complexes and between complexes and reaction centers. The major Chl-binding antenna proteins generally have a size of 16–28 kDa, whether of chlorophytes, chromophytes, or rhodophytes. High sequence homology observed in two of three transmembrane regions, and in putative chlorophyll-binding residues, suggests that the complexes are related and probably did not evolve from widely divergent polyphyletic lines.Abbreviations APC
allophycocyanin
- B
phycoerythrin-large bangiophycean phycoerythrin
- Chl
chlorophyll
- LCM
linker polypeptide in phycobilisome to thylakoid
- FCP
fucoxanthin Chl a/c complex
- LHC(s)
Chl-binding light harvesting complex(s)
- LHC I
Chl-binding complex of Photosystem I
- LHC II
Chl-binding complex of Photosystem II
- PC
phycocyanin
- PCP
peridinin Chl-binding complex
- P700
photochemically active Chl a of Photosystem I
- PS I
Photosystem I
- PS II
Photosystem II
- RC 1
reaction center core of PS I
- RC 2
reaction center core of PS II
- R
phycoerythrin-large rhodophycean phycoerythrin
- sPCP
soluble peridinin Chl-binding complex 相似文献
7.
Robert G. Gregerson Susan S. Miller Mary Petrowski J. Stephen Gantt Carroll P. Vance 《Plant molecular biology》1994,25(3):387-399
Genomic clones encoding two isozymes of aspartate aminotransferase (AAT) were isolated from an alfalfa genomic library and their DNA sequences were determined. The AAT1 gene contains 12 exons that encode a cytosolic protein expressed at similar levels in roots, stems and nodules. In nodules, the amount of AAT1 mRNA was similar at all stages of development, and was slightly reduced in nodules incapable of fixing nitrogen. The AAT1 mRNA is polyadenylated at multiple sites differing by more than 250 bp. The AAT2 gene contains 11 exons, with 5 introns located in positions identical to those found in animal AAT genes, and encodes a plastid-localized isozyme. The AAT2 mRNA is polyadenylated at a very limited range of sites. The transit peptide of AAT2 is encoded by the first two and part of the third exon. AAT2 mRNA is much more abundant in nodules than in other organs, and increases dramatically during the course of nodule development. Unlike AAT1, expression of AAT2 is significantly reduced in nodules incapable of fixing nitrogen. Phylogenetic analysis of deduced AAT proteins revealed 4 separate but related groups of AAT proteins; the animal cytosolic AATs, the plant cytosolic AATs, the plant plastid AATs, and the mitochondrial AATs. 相似文献
8.
Shi Tan Gregory R. Wolfe Francis X. Cunningham Jr Elisabeth Gantt 《Photosynthesis research》1995,45(1):1-10
Thylakoids isolated from cells of the red alga Porphyridium cruentum exhibit an increased PS I activity on a chlorophyll basis with increasing growth irradiance, even though the stoichiometry of Photosystems I and II in such cells shows little change (Cunningham et al. (1989) Plant Physiol 91: 1179–1187). PS I activity was 26% greater in thylakoids of cells acclimated at 280 mol photons · m–2 · s–1 (VHL) than in cells acclimated at 10 mol photons · m–2 · s–1 (LL), indicating a change in the light absorbance capacity of PS I. Upon isolating PS I holocomplexes from VHL cells it was found that they contained 132±9 Chl/P700 while those obtained from LL cells had 165±4 Chl/P700. Examination of the polypeptide composition of PS I holocomplexes on SDS-PAGE showed a notable decrease of three polypeptides (19.5, 21.0 and 22 kDa) in VHL-complexes relative to LL-complexes. These polypeptides belong to a novel LHC I complex, recently discovered in red algae (Wolfe et al. (1994a) Nature 367: 566–568), that lacks Chl b and includes at least six different polypeptides. We suggest that the decrease in PS I Chl antenna size observed with increasing irradiance is attributable to changes occurring in the LHC I-antenna complex. Evidence for a Chl-binding antenna complex associated with PS II core complexes is lacking at this point. LHC II-type polypeptides were not observed in functionally active PS II preparations (Wolfe et al. (1994b) Biochimica Biophysica Acta 1188: 357–366), nor did we detect polypeptides that showed immunocross-reactivity with LHC II specific antisera (made to Chlamydomonas and Euglena LHC II).Abbreviations Bis-Tris
bis(2-hydroxyethyl)imino-tris(hydroxymethyl)methane
- DCPIP
2,6-dichlorophenol indophenol
- -dm
dodecyl--d-maltoside
- HL
high light of 150 mol photons · m–2 · s–1
- LGB
lower green band
- LHC I
light-harvesting complex of PS I
- LHC II
light-harvesting complex of PS II
- LL
low light of 10 mol photons · m–2 · s–1
- ML
medium light of 50 mol photons · m–2 · s–1
- MES
2-(N-morpholino) ethanesulfonic acid
- P700
reaction center of PS I
- PFD
photon flux density
- Trizma
tris(hydroxymethyl)aminomethane
- UGB
upper green band
- VHL
very high light of 280 mol photons · m–2 · s–1 相似文献
9.
A highly conserved nuclear gene for low-level phylogenetics: elongation factor-1 alpha recovers morphology-based tree for heliothine moths 总被引:8,自引:2,他引:6
Cho S; Mitchell A; Regier JC; Mitter C; Poole RW; Friedlander TP; Zhao S 《Molecular biology and evolution》1995,12(4):650-656
Molecular systematists need increased access to nuclear genes. Highly
conserved, low copy number protein-encoding nuclear genes have attractive
features for phylogenetic inference but have heretofore been applied mostly
to very ancient divergences. By virtue of their synonymous substitutions,
such genes should contain a wealth of information about lower-level
taxonomic relationships as well, with the advantage that amino acid
conservatism makes both alignment and primer definition straightforward. We
tested this postulate for the elongation factor-1 alpha (EF-1 alpha) gene
in the noctuid moth subfamily Heliothinae, which has probably diversified
since the middle Tertiary. We sequenced 1,240 bp in 18 taxa representing
heliothine groupings strongly supported by previous morphological and
allozyme studies. The single most parsimonious gene tree and the
neighbor-joining tree for all nucleotides show almost complete concordance
with the morphological tree. Homoplasy and pairwise divergence levels are
low, transition/transversion ratios are high, and phylogenetic information
is spread evenly across gene regions. The EF-1 alpha gene and presumably
other highly conserved genes hold much promise for phylogenetics of
Tertiary age eukaryote groups.
相似文献
10.