| 1. |
- KROL, M, et al.
(author)
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CHLOROPHYLL A/B-BINDING PROTEINS, PIGMENT CONVERSIONS, AND EARLY LIGHT-INDUCED PROTEINS IN A CHLOROPHYLL B-LESS BARLEY MUTANT
- 1995
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In: Plant Physiology. - 0032-0889 .- 1532-2548. ; 107:3, s. 873-883
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Journal article (peer-reviewed)abstract
- Monospecific polyclonal antibodies have been raised against synthetic peptides derived from the primary sequences from different plant light-harvesting Chl a/b-binding (LHC) proteins. Together with other monospecific antibodies, these were used to quantify the levels of the 10 different LHC proteins in wild-type and chlorina 12 barley (Hordeum vulgare L.), grown under normal and intermittent light (ImL). Chlorina 12, grown under normal light, lacked Lhcb1 (type I LHC II) and Lhcb6 (CP24) and had reduced amounts of Lhcb2, Lhcb3 (types II and III LHC II), and Lhcb4 (CP 29). Chlorina f2 grown under ImL lacked all LHC proteins, whereas wild-type ImL plants contained Lhcb5 (CP 26) and a small amount of Lhcb2. The chlorina f2 ImL thylakoids were organized in large parallel arrays, but wild-type ImL thylakoids had appressed regions, indicating a possible role for Lhcb5 in grana stacking. Chlorina f2 grown under ImL contained considerable amounts of violaxanthin (2-3/reaction center), representing a pool of phototransformable xanthophyll cycle pigments not associated with LHC proteins. Chlorina f2 and the plants grown under ImL also contained early light-induced proteins (ELIPs) as monitored by western blotting. The levels of both ELIPs and xanthophyll cycle pigments increased during a 1 h of high light treatment, without accumulation of LHC proteins. These data are consistent with the hypothesis that ELIPs are pigment-binding proteins, and we suggest that ELIPs bind photoconvertible xanthophylls and replace ''normal'' LHC proteins under conditions of light stress.
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| 2. |
- KROL, M, et al.
(author)
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LOW-TEMPERATURE STRESS AND PHOTOPERIOD AFFECT AN INCREASED TOLERANCE TO PHOTOINHIBITION IN PINUS-BANKSIANA SEEDLINGS
- 1995
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In: Canadian Journal of Botany. - 0008-4026 .- 1480-3305. ; 73:8, s. 1119-1127
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Journal article (peer-reviewed)abstract
- The capacity to develop tolerance to photoinhibition of photosynthesis was assessed in jack pine seedlings (Pinus banksiana Lamb.). Photoinhibition induced at 5 degrees C in control jack pine seedlings grown at 20 degrees C was saturated above an irradiance of 1000 mu mol . m(-2). s(-1) but was detectable at an irradiance as low as 25 mu mol . m(-2). s(-1). However, 20 degrees C seedlings shifted to 5 degrees C were 2-fold more tolerant to photoinhibition than 20 degrees C unshifted control seedlings, as detected by either the light-dependent decrease in photochemical efficiency or the apparent quantum yield of O-2 evolution. The extent of this tolerance of photoinhibition was dependent upon time, photoperiod, and irradiance during exposure to the low-temperature shift. Furthermore, the tolerance of photoinhibition was correlated with anthocyanin accumulation in 20 degrees C grown seedlings shifted to 5 degrees C. In addition, seedlings shifted to 5 degrees C and an 8-h photoperiod exhibited a 2-fold higher yield of photosystem II electron transport, which was associated with an increased capacity to keep Q(A), the first stable quinone electron acceptor of photosystem II, oxidized at high irradiance. This was consistent with a 2-fold higher rate of photosynthesis on a chlorophyll basis. We propose that the combination of light attenuation by anthocyanin in the epidermis and enhanced rates of photosynthesis may, in part, account for the reduced sensitivity of jack pine to photoinhibition at low temperature.
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| 3. |
- Rojdestvenski, I, et al.
(author)
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Robustness and time-scale hierarchy in biological systems
- 1999
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In: Biosystems (Amsterdam. Print). - 0303-2647 .- 1872-8324. ; 50:1, s. 71-82
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Journal article (peer-reviewed)abstract
- This study addresses the issue of robustness of biological systems with respect to microscopic parameters, especially the emergence of robustness as a consequence of lime-scale hierarchy, applying naive thermodynamic and dynamic assumptions. Theoretical considerations of how the time-scale hierarchy can decouple physiological regulatory mechanisms are illustrated by two model systems involving the photosynthetic apparatus of green plants. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.
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| 4. |
- Soitamo, A J, et al.
(author)
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Over-production of the D1:2 protein makes Synechococcus cells more tolerant to photoinhibition of Photosystem II
- 1996
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In: Plant Molecular Biology. - 0167-4412 .- 1573-5028. ; 30:3, s. 467-478
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Journal article (peer-reviewed)abstract
- Over-expression of the psbAIII gene encoding for the D1 protein (form II; D1:2) of the photosystem II reaction centre in the Synechococcus sp. PCC 7942 was studied using a inc promoter and the lacI(Q) system. Over-expression was induced with 40 mu g/ml IPTG in the growth medium for either 6 or 12 h at growth irradiance (50 mu mol photons m(-2) s(-1)). This treatment doubled the amount of psbAII/III mRNA and the D1:2 protein in membranes but decreased the amount of psbAI messages and the D1:1 protein. The total amount of both heterodimeric reaction centre proteins, D1 and D2, remained constant under growth light conditions, indicating that the number of PSII centres in the membranes was not affected, only the form of the D1 protein was changed from D1:1 to D1:2 in most centres, When the cells were photoinhibited either at 500 or 1000 mu mol photons m(-2) s(-1), in the presence or absence of the protein synthesis inhibitor lincomycin, the D1:2 protein remained at a higher level in cells in which over-expression had been induced by IPTG. These cells were also less prone to photoinhibition of PSII. It is suggested that the tolerance of cells to photoinhibition increases when most PSII reaction centres contain the D1:2 protein at the beginning of high irradiance. This tolerance is further strengthened by maintaining psbAIII gene over-expression during the photoinhibitory treatment.
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