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1.
Photosystem I (PS I) from the primitive cyanobacterium Gloeobacter violaceus has been purified and characterised. Despite the fact that the isolated complexes have the same subunit composition as complexes
from other cyanobacteria, the amplitude of flash-induced absorption difference spectra indicates a much bigger antenna size
with about 150 chlorophylls per P700 as opposed to the usual 90. Image analysis of the PS I preparation from Gloeobacter reveals that the PS I particles exist both in a trimeric and in a monomeric form and that their size and shape closely resembles
other cyanobacterial PS I particles. However, the complexes exhibit a higher molecular weight as could be shown by gel filtration.
The preparation contains novel polypeptides not related to known Photosystem I subunits. The N-terminal sequence of one of
those polypeptides has been determined and reveals no homology to known or hypothetical proteins. Immunoblotting shows a cross-reaction
of three of the polypeptide bands with an antibody raised against the major LHC from the diatom Cyclotella cryptica. Electron microscopy reveals a novel T-shaped complex which has never been observed in any other cyanobacterial PS I preparation.
77 K spectra of purified PS I show an extreme blue-shift of the fluorescence emission, indicating an unusual organisation
of the PS I antenna system in Gloeobacter.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Three Chl–protein complexes were isolated from thylakoid membranes of Bryopsis maxima and Ulva pertusa, marine green algae that inhabit the intertidal zone of the Pacific Ocean off the eastern coast of Japan by dodecyl-β-d-maltoside polyacrylamide gel electrophoresis. The slowest-moving fractions showed low Chl a/b and Chl/P-700 ratios, indicating that this fraction corresponds to complexes in PS I, which is large in both algae. The intermediate and fastest-moving fractions showed the traits of PS II complexes, with some associated Chl a/b–protein complexes and LHC II, respectively. The spectral properties of the separated Chl–proteins were also determined. The absorption spectra showed a shallow shoulder at 540 nm derived from siphonaxanthin in Bryopsis maxima, but not in Ulva pertusa. The 77 K emission spectra showed a single peak in Bryopsis maxima and two peaks in Ulva pertusa. Besides the excitation spectra indicated that the excitation energy transfer to the PS I complexes differed quite a lot higher plants. This suggested that the mechanisms of energy transfer in both of these algae differ from those of higher plants. Considering the light environment of this coastal area, the large size of the antennae of PS I complexes implies that the antennae are arranged so as to balance light absorption between the two photosystems. In addition, we discuss the relationships among the photosystem stoichiometry, the energy transfer, and the distribution between the two photosystems. 相似文献
3.
van Roon H van Breemen JF de Weerd FL Dekker JP Boekema EJ 《Photosynthesis research》2000,64(2-3):155-166
A biochemical and structural analysis is presented of fractions that were obtained by a quick and mild solubilization of thylakoid
membranes from spinach with the non-ionic detergent n-dodecyl-α,D-maltoside, followed by a partial purification using gel filtration chromatography. The largest fractions consisted
of paired, appressed membrane fragments with an average diameter of about 360 nm and contain Photosystem II (PS II) and its
associated light-harvesting antenna (LHC II), but virtually no Photosystem I, ATP synthase and cytochrome b
6
f complex. Some of the membranes show a semi-regular ordering of PS II in rows at an average distance of about 26.3 nm, and
from a partially disrupted grana membrane fragment we show that the supercomplexes of PS II and LHC II represent the basic
structural unit of PS II in the grana membranes. The numbers of free LHC II and PS II core complexes were very high and very
low, respectively. The other macromolecular complexes of the thylakoid membrane occurred almost exclusively in dispersed forms.
Photosystem I was observed in monomeric or multimeric PS I-200 complexes and there are no indications for free LHC I complexes.
An extensive analysis by electron microscopy and image analysis of the CF0F1 ATP synthase complex suggests locations of the δ (on top of the F1 headpiece) and ∈ subunits (in the central stalk) and reveals that in a substantial part of the complexes the F1 headpiece is bended considerably from the central stalk. This kinking is very likely not an artefact of the isolation procedure
and may represent the complex in its inactive, oxidized form.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
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
5.
Using 77 K chlorophyll a (Chl a) fluorescence spectra in vivo, the development was studied of Photosystems II (PS II) and I (PS I) during greening of barley under intermittent light followed
by continuous light at low (LI, 50 μmol m−2 s−1) and high (HI, 1000 μmol m−2 s−1) irradiances. The greening at HI intermittent light was accompanied with significantly reduced fluorescence intensity from
Chl b excitation for both PS II (F685) and PS I (F743), in comparison with LI plants, indicating that assembly of light-harvesting
complexes (LHC) of both photosystems was affected to a similar degree. During greening at continuous HI, a slower increase
of emission from Chl b excitation in PS II as compared with PS I was observed, indicating a preferred reduction in the accumulation of LHC II. The
following characteristics of 77 K Chl a fluorescence spectra documented the photoprotective function of an elevated content of carotenoids in HI leaves: (1) a pronounced
suppression of Soret region of excitation spectra (410–450 nm) in comparison with the red region (670–690 nm) during the early
stage of greening indicated a strongly reduced excitation energy transfer from carotenoids to the Chl a fluorescing forms within PS I and PS II; (2) changes in the shape of the excitation band of Chl b and carotenoids (460–490 nm) during greening under continuous light confirmed that the energy transfer from carotenoids to
Chl a within PS II remained lower as compared with the LI plants.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
Palacios MA Standfuss J Vengris M van Oort BF van Stokkum IH Kühlbrandt W van Amerongen H van Grondelle R 《Photosynthesis research》2006,88(3):269-285
In this article we report the characterization of the energy transfer process in the reconstituted isoforms of the plant light-harvesting complex II. Homotrimers of recombinant Lhcb1 and Lhcb2 and monomers of Lhcb3 were compared to native trimeric complexes. We used low-intensity femtosecond transient absorption (TA) and time-resolved fluorescence measurements at 77 K and at room temperature, respectively, to excite the complexes selectively in the chlorophyll b absorption band at 650 nm with 80 fs pulses and on the high-energy side of the chlorophyll a absorption band at 662 nm with 180 fs pulses. The subsequent kinetics was probed at 30–35 different wavelengths in the region from 635 to 700 nm. The rate constants for energy transfer were very similar, indicating that structurally the three isoforms are highly homologous and that probably none of them play a more significant role in light-harvesting and energy transfer. No signature has been found in the transient absorption measurements at 77 K for Lhcb3 which might suggest that this protein acts as a relative energy sink of the excitations in heterotrimers of Lhcb1/Lhcb2/Lhcb3. Minor differences in the amplitudes of some of the rate constants and in the absorption and fluorescence properties of some pigments were observed, which are ascribed to slight variations in the environment surrounding some of the chromophores depending on the isoform. The decay of the fluorescence was also similar for the three isoforms and multi-exponential, characterized by two major components in the ns regime and a minor one in the ps regime. In agreement with previous transient absorption measurements on native LHC II complexes, Chl b → Chl a energy transfer exhibited very fast channels but at the same time a slow component (ps). The Chls absorbing at around 660 nm exhibited both fast energy transfer which we ascribe to transfer from ‘red’ Chl b towards ‘red’ Chl a and slow transfer from ‘blue’ Chl a towards ‘red’ Chl a. The results are discussed in the context of the new available atomic models for LHC II. 相似文献
7.
Efficient oxygenic photosynthesis not only requires synchronous turover and operation of photosystem I (PS I) and photosystem
II (PS II) but also the preferential turnover of PS I for cyclic photophosphorylation to maintain required ATP and NADPH ratio
during carbon dioxide reduction. Ohe initial higher rate of turnover of PS IIin viva is accounted by the fact that (i) PS I contains only about one-third of total chlorophylls, (ii) about 90% of light harvesting
a/b protein (LAC) which accounts for about 50% of the total chlorophylls, remains associated with PS II as PS II-LHC II complexes
(PS IIα and (iii) the ratio of PS II/PS I is always greater than unity, in the range of 1–2 : 1 under different environmental regimes.
Ohe initial preferential feeding of PS II, due to its larger antenna, is bound to result in faster rate of turn over of PS
II than PS I, leading to higher rate of reduction of an intersystem carrier than the rate of its oxidation by PS I. Ohe light
dependent phosphorylation of a ‘mobile’ and small pool (−20%) of LHC II of PS IIα (possibly located at the edge of appressed regions of the membranes) increases the repulsive forces of LHC II resulting in
its migration to non-appressed region associating itself with PS 1. Ohe phosphorylation itself is controlled by the redox
state of an intermediate of electron transport.
Several experimental approaches have provided evidence which suggest that (i) phosphorylation of LAC II involves interaction
of cyt b5-f complex with LAC II kinase and the interaction of QA with cyt b5-f complex and (ii) different kinases may be involved in phosphorylation of LHC IIversus PS II polypeptides. Ohe major purpose of light dependent LAC II phosphorylation and its consequent migration close to PS
I appears to balance the rate of cyclicversus non-cyclic photophosphorylation. Ohe mechanism by which cyt b5-f complex controls the activation of LAC II is not known. Ohe role of membrane bound ealmodulin, electron transfer through
cyt b6-f complex in activation of LAC II kinase should be explored. 相似文献
8.
Sánchez V Rebolledo O Picaso RM Cárdenas E Córdova J González O Samuels GJ 《Mycopathologia》2007,163(1):49-58
Seventy-nine Trichoderma strains were isolated from soil taken from 28 commercial plantations of Agave tequilana cv. ‘Azul’ in the State of Jalisco, Mexico. Nine of these isolates produced nonvolatile metabolites that completely inhibited the growth of Thielaviopsis paradoxa on potato dextrose agar plates. These isolates were identified as Trichoderma longibrachiatum on the basis of their morphology and DNA sequence analysis of two genes (ITS rDNA and translation elongation factor EF-1α).
Mycoparasitism of Th. paradoxa by T. longibrachiatum strains in dual cultures was examined by scanning electron microscopy. The Trichoderma hyphae grew alongside the Th. paradoxa hyphae, but penetration of Thielaviopsis hyphae by Trichoderma was no apparent. Aleurioconidia of Th. paradoxa were parasitized by Trichoderma. Both hyphae and aleurioconidia of Th. paradoxa lost turgor pressure, wrinkled, collapsed and finally disintegrated. In liquid cultures, all nine Trichoderma isolates produced proteases, β-1,3-glucanases and chitinases that would be responsible for the degradation of Thielaviopsis hyphae. These results demonstrate that the modes of action of T. longibrachiatum involved against Th. paradoxa in vitro experiments are mycoparasitism and the production of nonvolatile toxic metabolites. 相似文献
9.
J. Kenneth Hoober Richard A. White Dawn B. Marks Jerome L. Gabriel 《Photosynthesis research》1994,39(1):15-31
Recent results obtained by electron microscopic and biochemical analyses of greening Chlamydomonas reinhardtii y1 suggest that localized expansion of the plastid envelope is involved in thylakoid biogenesis. Kinetic analyses of the assembly of light-harvesting complexes and development of photosynthetic function when degreened cells of the alga are exposed to light suggest that proteins integrate into membrane at the level of the envelope. Current information, therefore, supports the earlier conclussion that the chloroplast envelope is a major biogenic structure, from which thylakoid membranes emerge. Chloroplast development in Chlamydomonas provides unique opportunities to examine in detail the biogenesis of thylakoids.Abbreviations Rubisco
ribulose bisphosphate carboxylase/oxygenase
- CAB
Chl a/b-binding (proteins)
- Chlide
chlorophyllide
- LHC I
light-harvesting complex of PS I
- LHC II
light-harvesting complex of PS II
- Pchlide
protochlorophyllide 相似文献
10.
Accumulation of additive effects generates a strong photoperiod sensitivity in the extremely late-heading rice cultivar ‘Nona Bokra’ 总被引:1,自引:0,他引:1
Uga Y Nonoue Y Liang ZW Lin HX Yamamoto S Yamanouchi U Yano M 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2007,114(8):1457-1466
Many rice cultivars that originated from lower-latitude regions exhibit a strong photoperiod sensitivity (PS) and show extremely
late heading under long-day conditions. Under natural day-length conditions during the cropping season in Japan, the indica rice cultivar ‘Nona Bokra’ from India showed extremely late heading (202 days to heading) compared to the japonica cultivar ‘Koshihikari’ (105 days), from Japan. To elucidate the genetic factors associated with such extremely late heading,
we performed quantitative trait locus (QTL) analyses of heading date using an F2 population and seven advanced backcross progeny (one BC1F2 and six BC2F2) derived from a cross between ‘Nona Bokra’ and ‘Koshihikari’. The analyses revealed 12 QTLs on seven chromosomes. The ‘Nona
Bokra’ alleles of all QTLs contributed to an increase in heading date. Digenic interactions were rarely observed between QTLs.
Based on the genetic parameters of the QTLs, such as additive effects and percentage of phenotypic variance explained, these
12 QTLs are likely generate a large proportion of the phenotypic variation observed in the heading dates between ‘Nona Bokra’
and ‘Koshihikari’. Comparison of chromosomal locations between heading date QTLs detected in this study and QTLs previously
identified in ‘Nipponbare’ × ‘Kasalath’ populations revealed that eight of the heading date QTLs were recognized nearby the
Hd1, Hd2, Hd3a, Hd4, Hd5, Hd6, Hd9, and Hd13. These results suggest that the strong PS in ‘Nona Bokra’ was generated mainly by the accumulation of additive effects of
particular alleles at previously identified QTLs. 相似文献
11.
Xingguo Zhang Chaozhi Ma Tingdong Fu Yuanyuan Li Tonghua Wang Qingfang Chen Jinxing Tu Jinxiong Shen 《Molecular breeding : new strategies in plant improvement》2008,21(3):305-315
‘SI1300’ is a self-incompatible Brassica napus line generated by introgressing an S haplotype from B. rapa ‘Xishuibai’ into a rapeseed cultivar ‘Huayou No. 1’. Five S-locus specific primer pairs were employed to develop cleaved amplified polymorphic sequences (CAPS) markers linked the S haplotype of ‘SI1300’. Two segregating populations (F2 and BC1) from the cross between ‘SI1300’ and self-compatible European spring cultivar ‘Defender’, were generated to verify the molecular
markers. CAPS analysis revealed no desirable polymorphism between self-incompatible and self-compatible plants. Twenty primer
pairs were designed based on the homology-based candidate gene method, and six dominant sequence characterized amplified region
(SCAR) markers linked with the S-locus were developed. Of the six markers, three were derived from the SRK and SP11 alleles of class II B. rapa
S haplotypes and linked with S haplotype of ‘SI1300’. The other three markers were designed from the SLG-A10 and co-segregated with S haplotype of ‘Defender’. We successfully combined two pairs of them and characterized two multiplex PCR markers which could
discriminate the homozygous and heterozygous genotypes. These markers were further validated in 24 F3 and 22 BC1F2 lines of ‘SI1300 × Defender’ and another two segregating populations from the cross ‘SI1300 × Yu No. 9’. Nucleotide sequences
of fragments linked with S-locus of ‘SI1300’ showed 99% identity to B. rapa class II S-60 haplotype, and fragments from ‘Defender’ were 97% and 94% identical to SLG and SRK of B. rapa class I S-47 haplotype, respectively. ‘SI1300’ was considered to carry two class II S haplotypes and the S haplotype on the A-genome derived from B. rapa ‘Xishuibai’ determines the SI phenotype, while ‘Defender’ carry a class I S haplotype derived from B. rapa and a class II S haplotype from B. oleracea. SCAR markers developed in this study will be helpful for improving SI lines and accelerating marker-assisted selection process
in rapeseed SI hybrid breeding program. 相似文献
12.
Reported crystallographic data and calculated molecular models indicated that chlorophyll (Chl) a and bacteriochlorophyll (BChl) a tend to bind the fifth ligand on the side of the macrocycle where the C132-(R)-methoxycarbonyl moiety protrudes (denoting the ‘back’ side). The crystal structures of 34 photosynthetic proteins possessing
(B)Chl cofactors revealed that most of Chl a and BChl a (and b) are coordinated by any peptidyl residue (e.g., histydyl-imidazolyl group), peptidyl backbone or water from the ‘back’ side.
Almost all the cofactors that bind a water molecule as the fifth ligand in these proteins have a ‘back’ configuration. Theoretical
model calculations for methyl chlorophyllide a (MeChlid a) and methyl bacteriochlorophyllide a (MeBChlid a) bound to an imidazole molecule indicated that the ‘back’ side is energetically favored for the ligand binding. These results
are consistent with the fact that ethyl chlorophyllide a (EtChlid a) dihydrate crystal consists of the ‘back’ complex. The modeling also showed that both removal and stereochemical inverse
of the C132-methoxycarbonyl group affect the relative stability between the ‘back’ and ‘face’ complexes. The effect of the C132-moiety on the choice of the macrocycle side for the ligand binding is discussed in relation to the function of P700.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
Summary cDNAs encoding three different LHC I polypeptides (Type I, Type II and Type III) from the gymnosperm Scots pine (Pinus sylvestris L.) were isolated and sequenced. Comparisons of the deduced amino acid sequences with the corresponding tomato sequences showed that all three proteins were highly conserved although less so than the LHC II proteins. The similarities between mature Scots pine and tomato Types I, II and III LHC I proteins were 80%, 87% and 85%, respectively. Two of the five His residues that are found in AXXXH sequences, which have been identified as putative chlorophyll ligands in the Type I and Type II proteins, were not conserved. The same two regions of high homology between the different LHC proteins, which have been identified in tomato, were also found in the Scots pine proteins. Within the conserved regions, the Type I and Type II proteins had the highest similarity; however, the Type II and Type III proteins also showed a similarity in the central region. The results suggest that all flowering plants (gymnosperms and angiosperms) probably have the same set of LHC polypeptides. A new nomenclature for the genes encoding LHC polypeptides (formerly cab genes) is proposed. The names lha and lhb are suggested for genes encoding LHC I and LHC II proteins, respectively, analogous to the nomenclature for the genes encoding other photosynthetic proteins. 相似文献
14.
J.-M. Lacape D. Dessauw M. Rajab J.-L. Noyer B. Hau 《Molecular breeding : new strategies in plant improvement》2007,19(1):45-58
A series of 320 mapped simple sequence repeats (SSRs) have been used to screen the allelic diversity of tetraploid Gossypium species. Fourty-seven genotypes were analyzed representing (i) the wide spectrum of diversity of the cultivated pool and
of the primitive landraces of species G. hirsutum (‘marie-galante’, ‘punctatum’, ‘richmondi’, ‘morrilli’, ‘palmeri’, and ‘latifolium’, and ‘yucatanense’), and (ii) species
G. barbadense, G. darwinii and G. tomentosum. The polymorphism of 201 SSR loci revealed 1128 allelic variants ranging from 3 to 17 per locus. Neighbor-joining (NJ) method
based on genetic dissimilarities produced groupings consistent with the assignments of accessions both at species and at race
level. Our data confirmed the proximity of the Galapagos endemic species G. darwinii to species G. barbadense. Within species G. hirsutum, and as compared to the other 6 races, race yucatanense appeared as the most distant from cultivated genotypes. Race yucatanense
also exhibited the highest number of unique alleles. The important informative heterogeneity of the 201 SSR loci was exploited
to select the most polymorphic ones that were assembled into three series of genome-wide (i.e. each homoeologous AD chromosome
pair being equally represented) and mutliplexable (× 3) SSRs. Using one of these ‘genotyping set’, consisting of 39 SSRs (one
3-plex for each of the 13 AD chromosomes pairs) or 45 loci, we were able to assess the relationships between accessions and
the topology in the genetic diversity sampled. Such genotyping set of highly informative SSR markers assembled in PCR-multiplex,
while increasing genotyping throughput, will be applicable for molecular genetic diversity studies of large germplasm collections.
Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
15.
Experiments were conducted to quantify parasitism of Colorado potato beetle,Leptinotarsa decemlineata (Say), by the egg parasitoid,Edovum puttleri Grissell, on 3 different cultivars of eggplant,Solanum melongena L. Levels of parasitism were higher (P<0.05) on ‘Black Pride’ than on other cultivars. The percentage of egg masses that
were parasitized was 1.2-fold higher (P<0.05) on ‘Black Pride’ than on ‘Harris Special’ and ‘White’. The number of eggs per
mass that were parasitized was 1.3- and 1.4- fold greater (P<0.05) on ‘Black Pride’ than on ‘Harris Special’ and ‘White’,
respectively. The percentage of eggs that were parasitized per mass and percentage of emerged adult parasitoids did not differ
(P>0.05) among cultivars; between 2.1- to 2.6- fold more females than males emerged from eggs on all cultivars during the
growing season.Edovum puttleri suppressed the 2nd generation ofL. decemlineata on ‘Black Pride’ and ‘Harris Special’, but did not suppress populations on ‘White’.
相似文献
16.
The protein secondary structure and pigments' microenvironment in photosystem 1 (PS1) complexes were studied in the temperature
range of 25–80 °C using Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopy, respectively. Quantitative
analysis of the component bands of the amide I band (1 700–1 600 cm−1) showed no significant change below 50 °C. However, apparent conformational changes occurred at 60 °C and further continued
at 70 and 80 °C accompanied with transitions of secondary structure mainly from α-helix to the β-sheet structures. CD analysis
demonstrated that the regular arrangement, viz. protein microenvironment of pigments of PS1 complexes, was destroyed by heat
treatment which might come from the changes of protein secondary structure of PS1. The CD signals at 645 nm contributed by
chlorophyll (Chl) b of light-harvesting complex 1 (LHC1) were easily destroyed at the beginning of heat treatment (25–60 °C). When temperature
reached 70 and 80 °C, the CD signals at 478 nm contributed mainly by Chl b of LHC1 and 498 nm contributed by carotenoids decreased most rapidly, indicating that LHC1 was more sensitive to high temperature
than core complexes. In addition, the oxygen uptake rate decreased by 90.81 % at 70 °C and was lost completely at 80 °C showing
that heat treatment damaged the regular function of PS1 complexes. This may be attributed to heat-induced changes of pigment
microenvironment and protein secondary structure, especially transmembrane α-helix located in PsaA/B of PS1. 相似文献
17.
Consequences of LHC II deficiency for photosynthetic regulation in chlorina mutants of barley 总被引:1,自引:0,他引:1
The light-harvesting chlorophyll a/b proteins associated with PS II (LHC II) are often considered to have a regulatory role in photosynthesis. The photosynthetic responses of four chlorina mutants of barley, which are deficient in LHC II to varying degrees, are examined to evaluate whether LHC II plays a regulatory role in photosynthesis. The efficiencies of light use for PS I and PS II photochemistry and for CO2 assimilation in leaves of the mutants were monitored simultaneously over a wide range of photon flux densities of white light in the presence and absence of supplementary red light. It is demonstrated that the depletions of LHC II in these mutants results in a severe imbalance in the relative rates of excitation of PS I and PS II in favour of PS I, which cannot be alleviated by preferential excitation of PS II. Analyses of xanthophyll cycle pigments and fluorescence quenching in leaves of the mutants indicated that the major LHC II components are not required to facilitate the light-induced quenching associated with zeaxanthin formation. It is concluded that LHC II is important to balance the distribution of excitation energy between PS I and PS II populations over a wide range of photon flux densities. It appears that LHC II may also be important in determining the quantum efficiency of PS II photochemistry by reducing the rate of quenching of excitation energy in the PS II primary antennae.Abbreviations Fm, Fv
maximal and variable fluorescence yields in a light adapted state
- LHC II
light harvesting chlorophyll a/b protein complex associated with PS II
- qp
photochemical quenching
- A820
light-induced absorbance change at 820 nm
- øPSI, øPSII
relative quantum efficiencies of PS I and PS II photochemistry
- øCO2
quantum yield of CO2 assimilation 相似文献
18.
Aswin Mangerich Harry Scherthan Jörg Diefenbach Ulrich Kloz Franciscus van der Hoeven Sascha Beneke Alexander Bürkle 《Transgenic research》2009,18(2):261-279
Here we report an approach to generate a knock-in mouse model using an ‘ends-out’ gene replacement vector to substitute the
murine Parp-1 (mParp-1) coding sequence (32 kb) with its human orthologous sequence (46 kb). Unexpectedly, examination of mutant ES cell clones
and mice revealed that site-specific homologous recombination was mimicked in three independently generated ES cell clones
by bidirectional extension of the vector homology arms using the endogenous mParp-1-flanking sequences as templates. This was followed by adjacent integration of the targeting vector, thus leaving the endogenous
mParp-1 locus functional. A related phenomenon termed ‘ectopic gene targeting’ has so far only been described for ‘ends-in’ integration-type
vectors in non-ES cell gene targeting. We provide reliable techniques to detect such ectopic gene targeting which represents
an unexpected caveat in mouse genetic engineering that should be considered in the design and validation strategy of future
gene knock-in approaches.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
Effect of water stress on photosystem 2 in two wheat cultivars 总被引:2,自引:0,他引:2
W. -J. Liu S. Yuan N. -H. Zhang T. Lei H. -G. Duan H. -G. Liang H. -H. Lin 《Biologia Plantarum》2006,50(4):597-602
20.
E. P. Storey R. Boghozian James L. Little Douglas W. Lowman R. Chakraborty 《Biometals》2006,19(6):637-649
The Rhizobia comprise one of the most important groups of beneficial bacteria, which form nodules on the roots (rarely on the stems) of leguminous plants. They live within the nodules and reduce atmospheric nitrogen to ammonia, which is further assimilated by plants into required nitrogenous compounds. The Rhizobia in return obtain nutrition from the plant. Rhizobia are free-living soil bacteria and have to compete with other microorganisms for the limited available iron in the rhizosphere. In order to acquire iron Rhizobia have been shown to express siderophore-mediated iron transport systems. Rhizobium leguminosarum IARI 917 was investigated for its ability to produce siderophore. It was found to produce a dihydroxamate type siderophore under iron restricted conditions. The siderophore was purified and chemically characterized. The ESMS, MS/MS and NMR analysis indicate the dihydroxamate siderophore to be ‘schizokinen’, a siderophore reported to be produced by Bacillus megaterium that shares a similar structure to ‘rhizobactin 1021’ produced by Sinorhizobium meliloti 1021. This is the first report of production of schizokinen by a strain of R. leguminosarum, therefore it was carefully investigated to confirm that it is indeed ‘schizokinen’ and not a degradation product of ‘rhizobactin 1021’. Since ferric–siderophore complexes are transported across the outer membrane (OM) into the periplasm via an OM receptor protein, R. leguminosarum IARI 917 was investigated for the presence of an OM receptor for ‘ferric–schizokinen’. SDS PAGE analysis of whole cell pellet and extracted OM fractions indicate the presence of a possible iron-repressible OM receptor protein with the molecular weight (MW) of approximately 74 kDa. 相似文献