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61.
Vaughan Hurry Jan M. Anderson Murray R. Badger G. Dean Price 《Photosynthesis research》1996,50(2):159-169
We have examined tobacco transformed with an antisense construct against the Rieske-FeS subunit of the cytochromeb
6
f complex, containing only 15 to 20% of the wild-type level of cytochrome f. The anti-Rieske-FeS leaves had a comparable chlorophyll and Photosystem II reaction center stoichiometry and a comparable carotenoid profile to the wild-type, with differences of less than 10% on a leaf area basis. When exposed to high irradiance, the anti-Rieske-FeS leaves showed a greatly increased closure of Photosystem II and a much reduced capacity to develop non-photochemical quenching compared with wild-type. However, contrary to our expectations, the anti-Rieske-FeS leaves were not more susceptible to photoinhibition than were wild-type leaves. Further, when we regulated the irradiance so that the excitation pressure on photosystem II was equivalent in both the anti-Rieske-FeS and wild-type leaves, the anti-Rieske-FeS leaves experienced much less photoinhibition than wild-type. The evidence from the anti-Rieske-FeS tobacco suggests that rapid photoinactivation of Photosystem II in vivo only occurs when closure of Photosystem II coincides with lumen acidification. These results suggest that the model of photoinhibition in vivo occurring principally because of limitations to electron withdrawal from photosystem II does not explain photoinhibition in these transgenic tobacco leaves, and we need to re-evaluate the twinned concepts of photoinhibition and photoprotection.Abbreviations Chl
chlorophyll
- DCMU
3-(3,4-dichlophenyl)-1,-dimethylurea
- Fo and Fo
minimal fluorescence when all PS II reaction centers are open in dark- and light-acclimated leaves, respectively
- Fm and Fm
maximal fluorescence when all PS II reaction centers are closed in dark- and light-acclimated leaves, respectively
- Fv
variable fluorescence (Fm-Fo) in dark acclimated leaves
- Fv
variable fluorescence (Fm-Fo) in lightacclimated leaves
- NPQ
non-photochemical quenching of fluorescence
- PS I and PS II
Photosystem I and II
- P680
primary electron donor of the reaction center of PS II
- PFD
photosynthetic flux density
- QA
primary acceptor quinone of PS II
- qp
photochemical quenching of fluorescence
- V+A+Z
violaxanthin+antheraxanthin+zeaxanthin 相似文献
62.
Homologues of the human multidrug resistance genes MRP and MDR contribute to heavy metal resistance in the soil nematode Caenorhabditis elegans. 总被引:3,自引:1,他引:2 下载免费PDF全文
Acquired resistance of mammalian cells to multiple chemotherapeutic drugs can result from enhanced expression of the multidrug resistance-associated protein (MRP), which belongs to the ABC transporter superfamily. ABC transporters play a role in the protection of organisms against exogenous toxins by cellular detoxification processes. We have identified four MRP homologues in the soil nematode Caenorhabditis elegans, and we have studied one member, mrp-1, in detail. Using an mrp::lacZ gene fusion, mrp-l expression was found in cells of the pharynx, the pharynx-intestinal valve and the anterior intestinal cells, the rectum-intestinal valve and the epithelial cells of the vulva. Targeted inactivation of mrp-l resulted in increased sensitivity to the heavy metal ions cadmium and arsenite, to which wild-type worms are highly tolerant. The most pronounced effect of the mrp-1 mutation is on the ability of animals to recover from temporary exposure to high concentrations of heavy metals. Nematodes were found to be hypersensitive to heavy metals when both the MRP homologue, mrp-1, and a member of the P-glycoprotein (Pgp) gene family, pgp-1, were deleted. We conclude that nematodes have multiple proteins, homologues of mammalian proteins involved in the cellular resistance to chemotherapeutic drugs, that protect them against heavy metals. 相似文献
63.
Introduction of sense and antisense cDNA for branching enzyme in the amylose-free potato mutant leads to physico-chemical changes in the starch 总被引:5,自引:0,他引:5
E. Flipse L. Suurs C. J. A. M. Keetels J. Kossmann E. Jacobsen R. G. F. Visser 《Planta》1996,198(3):340-347
One isoform of the branching enzyme (BE; EC 2.4.1.18) of potato (Solarium tuberosum L.) is known and catalyses the formation of α-1,6 bonds in a glucan chain, resulting in the branched starch component amylopectin. Constructs containing the antisense or sense-orientated distal 1.5-kb part of a cDNA for potato BE were used to transform the amylose-free (amf) mutant of potato, the starch of which stains red with iodine. The expression of the endogenous BE gene was inhibited either largely or fully as judged by the decrease or absence of the BE mRNA and protein. This resulted in a low percentage of starch granules with a small blue core and large red outer layer. There was no effect on the amylose content, degree of branching or λmax of the iodine-stained starch. However, when the physico-chemical properties of the different starch suspensions were assessed, differences were observed, which although small indicated that starch in the transformants was different from that of theamf mutant. 相似文献
64.
Overproduction of Three Genes Leads to Camphor Resistance and Chromosome Condensation in Escherichia Coli 总被引:2,自引:0,他引:2 下载免费PDF全文
We isolated and characterized three genes, crcA, cspE and crcB, which when present in high copy confer camphor resistance on a cell and suppress mutations in the chromosomal partition gene mukB. Both phenotypes require the same genes. Unlike chromosomal camphor resistant mutants, high copy number crcA, cspE and crcB do not result in an increase in the ploidy of the cells. The cspE gene has been previously identified as a cold shock-like protein with homologues in all organisms tested. We also demonstrate that camphor causes the nucleoids to decondense in vivo and when the three genes are present in high copy, the chromosomes do not decondense. Our results implicate camphor and mukB mutations as interfering with chromosome condensation and high copy crcA, cspE and crcB as promoting or protecting chromosome folding. 相似文献
65.
Michael Dean J. Claiborne Stephens Cheryl Winkler Deborah A. Lomb Mark Ramsburg Raleigh Boaze Claudia Stewart Lauren Charbonneau David Goldman Bernard J. Albaugh James J. Goedert R. Palmer Beasley Lu-Yu Hwang Susan Buchbinder Michael Weedon Patricia A. Johnson Mary Eichelberger Stephen J. O'Brien 《American journal of human genetics》1994,55(4):788-808
A panel of 257 RFLP loci was selected on the basis of high heterozygosity in Caucasian DNA surveys and equivalent spacing throughout the human genome. Probes from each locus were used in a Southern blot survey of allele frequency distribution for four human ethnic groups: Caucasian, African American, Asian (Chinese), and American Indian (Cheyenne). Nearly all RFLP loci were polymorphic in each group, albeit with a broad range of differing allele frequencies (δ). The distribution of frequency differences (δ values) was used for three purposes: (1) to provide estimates for genetic distance (differentiation) among these ethnic groups, (2) to revisit with a large data set the proportion of human genetic variation attributable to differentiation within ethnic groups, and (3) to identify loci with high δ values between recently admixed populations of use in mapping by admixture linkage disequilibrium (MALD). Although most markers display significant allele frequency differences between ethnic groups, the overall genetic distances between ethnic groups were small (.066–.098), and <10% of the measured overall molecular genetic diversity in these human samples can be attributed to “racial” differentiation. The median δ values for pairwise comparisons between groups fell between .15 and .20, permitting identification of highly informative RFLP loci for MALD disease association studies. 相似文献
66.
Reinard Thomas; Sprunck Stefanie; Altherr Sandra; Jacobsen Hans-Jorg 《Journal of experimental botany》1994,45(11):1593-1601
A monoclonal antibody of IgM-type (TIM-11B2) was screened froma hybridoma library. The antibody recognizes a 40 kDa glycoprotein,p40, with high specificity. This protein was detected in allplant species examined so far and was found to be located bothsolubly and ionically-bound within the primary cell wall. The strongest immunobiochemical signals of p40 were found intissues undergoing elongation growth, whereas in other tissuesonly a faint signal could be detected. Those included the non-elongatingparts of different seedlings, such as the apical part of monocotprimary leaves or the leaves of dicots grown in light. Inhibitionof pea epicotyl growth by white light irradiation resulted ina strong decrease of the immunostain signal. On the other hand,induction of rapid coleoptile growth in rice seedlings inducedby submergence resulted in a strong increase of the immunobiochemicalsignal of p40. Time-course studies on the expression of p40during protoplast regeneration revealed that p40 is apparentlynot involved in cell wall formation. The hypothesis that p40is characteristic for tissues with the ability for elongationgrowth is discussed. Comparison of biochemical data and location of p40 with proteinsdescribed up to now indicate that this glycoprotein has notbeen characterized before. Key words: Cell wall protein, elongation growth, monoclonal antibody 相似文献
67.
68.
The variation pattern in the perennial Hordeum brachyantherum complex and in the annual H. depressum are described. The diploid form of H. brachyantherum s. lat., endemic to California in USA, previously recognized as a separate species is here treated as a subspecies ( H. brachyantherum ssp. californicum ). Despite its restricted distribution it shows a considerable variation and overlap in morphology with the tetraploid ssp. brachyantherum , and no unambiguous determination based on morphology between the two tax a is possible. The tetraploid cytotype has a large distribution area in western North America and easternmost Asia and a very wide morphological variation. It has also a small disjunct distribution area in easternmost Canada. A single hexaploid population from California is referred to ssp. brachyantherum . 相似文献
69.
70.
A. El-Kharbotly C. Leonards-Schippers D. J. Huigen E. Jacobsen A. Pereira W. J. Stiekema F. Salamini C. Gebhardt 《Molecular genetics and genomics : MGG》1994,242(6):749-754
Phytophthora infestans (Mont.) de Bary is the most important fungal pathogen of the potato (Solanum tuberosum). The introduction of major genes for resistance from the wild species S. demissum into potato cultivars is the earliest example of breeding for resistance using wild germplasm in this crop. Eleven resistance alleles (R genes) are known, differing in the recognition of corresponding avirulence alleles of the fungus. The number of R loci, their positions on the genetic map and the allelic relationships between different R variants are not known, except that the R1 locus has been mapped to potato chromosome V The objective of this work was the further genetic analysis of different R alleles in potato. Tetraploid potato cultivars carrying R alleles were reduced to the diploid level by inducing haploid parthenogenetic development of 2n female gametes. Of the 157 isolated primary dihaploids, 7 set seeds and carried the resistance alleles R1, R3 and R10 either individually or in combinations. Independent segregation of the dominant R1 and R3 alleles was demonstrated in two F1 populations of crosses among a dihaploid clone carrying R1 plus R3 and susceptible pollinators. Distorted segregation in favour of susceptibility was found for the R3 allele in 15 of 18 F1 populations analysed, whereas the RI allele segregated with a 1:1 ratio as expected in five F1 populations. The mode of inheritance of the R10 allele could not be deduced as only very few F1 hybrids bearing R10 were obtained. Linkage analysis in two F1 populations between R1, R3 and RFLP markers of known position on the potato RFLP maps confirmed the position of the R1 locus on chromosome V and localized the second locus, R3, to a distal position on chromdsome XI. 相似文献