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- Ivanov, A. G., et al.
(författare)
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Implications of alternative electron sinks in increased resistance of PSII and PSI photochemistry to high light stress in cold-acclimated Arabidopsis thaliana
- 2012
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Ingår i: Photosynthesis Research. - Dordrecht : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 113:1-3, s. 191-206
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Tidskriftsartikel (refereegranskat)abstract
- Exposure of control (non-hardened) Arabidopsis leaves to high light stress at 5 A degrees C resulted in a decrease of both photosystem II (PSII) (45 %) and Photosystem I (PSI) (35 %) photochemical efficiencies compared to non-treated plants. In contrast, cold-acclimated (CA) leaves exhibited only 35 and 22 % decrease of PSII and PSI photochemistry, respectively, under the same conditions. This was accompanied by an accelerated rate of P700(+) re-reduction, indicating an up-regulation of PSI-dependent cyclic electron transport (CET). Interestingly, the expression of the NDH-H gene and the relative abundance of the Ndh-H polypeptide, representing the NDH-complex, decreased as a result of exposure to low temperatures. This indicates that the NDH-dependent CET pathway cannot be involved and the overall stimulation of CET in CA plants is due to up-regulation of the ferredoxin-plastoquinone reductase, antimycin A-sensitive CET pathway. The lower abundance of NDH complex also implies lower activity of the chlororespiratory pathway in CA plants, although the expression level and overall abundance of the other well-characterized component involved in chlororespiration, the plastid terminal oxidase (PTOX), was up-regulated at low temperatures. This suggests increased PTOX-mediated alternative electron flow to oxygen in plants exposed to low temperatures. Indeed, the estimated proportion of O-2-dependent linear electron transport not utilized in carbon assimilation and not directed to photorespiration was twofold higher in CA Arabidopsis. The possible involvement of alternative electron transport pathways in inducing greater resistance of both PSII and PSI to high light stress in CA plants is discussed.
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| 2. |
- Norén, Louise, et al.
(författare)
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Circadian and Plastid Signaling Pathways Are Integrated to Ensure Correct Expression of the CBF and COR Genes during Photoperiodic Growth
- 2016
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 171:2, s. 1392-1406
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Tidskriftsartikel (refereegranskat)abstract
- The circadian clock synchronizes a wide range of biological processes with the day/night cycle, and correct circadian regulation is essential for photosynthetic activity and plant growth. We describe here a mechanism where a plastid signal converges with the circadian clock to fine-tune the regulation of nuclear gene expression in Arabidopsis (Arabidopsis thaliana). Diurnal oscillations of tetrapyrrole levels in the chloroplasts contribute to the regulation of the nucleus-encoded transcription factors C-REPEAT BINDING FACTORS (CBFs). The plastid signal triggered by tetrapyrrole accumulation inhibits the activity of cytosolic HEAT SHOCK PROTEIN90 and, as a consequence, the maturation and stability of the clock component ZEITLUPE (ZTL). ZTL negatively regulates the transcription factor LONG HYPOCOTYL5 (HY5) and PSEUDO-RESPONSE REGULATOR5 (PRR5). Thus, low levels of ZTL result in a HY5- and PRR5-mediated repression of CBF3 and PRR5-mediated repression of CBF1 and CBF2 expression. The plastid signal thereby contributes to the rhythm of CBF expression and the downstream COLD RESPONSIVE expression during day/night cycles. These findings provide insight into how plastid signals converge with, and impact upon, the activity of well-defined clock components involved in circadian regulation.
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| 6. |
- Stachula, Paulina, 1982-
(författare)
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Short and long term low temperature responses in Arabidopsis thaliana
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A unique aspect of plant biology is their ability to respond very rapidly to shifts in their ever-changing environment. To do this, plants need to have evolved mechanisms that enable them to sense their environment and to rapidly respond to different stresses and different combinations of stress. The main focus of my thesis has been on plant responses to low temperature. One way in which the plant cell is thought to sense low temperature is via the rigidification of the plasma membrane that occurs when the temperature falls rapidly. I showed that CRMK1, a leucine-rich-repeat-receptor-like kinase, located in the plasma membrane is a key component of the cold sensing machinery. I show that a T-DNA insertion mutant of CRMK1 attenuated the expression of marker cold genes in response to cold stress and decreased the plants ability to acquire freezing tolerance after 3 days of exposure to low temperature. I described a protective mechanism in the thylakoid membranes by which excess electrons, which can accumulate at low temperature and under high light in cold acclimated plants, can be dissipated. In order to properly respond to a changing surroundings cells not only have to sense the fluctuations but they need to communicate this changes to the nucleus and I showed that organelles such as the chloroplasts can act as a sensor of changing temperature and communicate this information to the nucleus to change the expression of cold regulated genes. I presented and identified factors in addition to low temperature that regulate the expression of genes for cold tolerance. I showed that a circadian signal, together with plastid and light signals, influence the expression of nuclear encoded cold tolerance genes (CBF3 and COR15). The response of plants to low temperature also depends on the duration of the cold stress. There are plants, such as over-wintering herbaceous and perennial woody plants, that have to survive and grow for prolonged periods at low temperature and there are those from extreme polar or alpine environments that spend entire life in cold. I provided a comprehensive overview of the biological processes and genes that enable plants to survive and develop the full cold acclimated state during long-term over wintering and growth in the low temperature.
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| 8. |
- Vergara, Alexander, et al.
(författare)
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Norway spruce deploys tissue-specific responses during acclimation to cold
- 2022
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Ingår i: Plant, Cell and Environment. - : John Wiley & Sons. - 0140-7791 .- 1365-3040. ; 45:2, s. 427-445
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Tidskriftsartikel (refereegranskat)abstract
- Climate change in the conifer-dominated boreal forest is expected to lead to warmer but more dynamic winter air temperatures, reducing the depth and duration of snow cover and lowering winter soil temperatures. To gain insight into the mechanisms that have enabled conifers to dominate extreme cold environments, we performed genome-wide RNA-Seq analysis from needles and roots of non-dormant two-year Norway spruce (Picea abies (L.) H. Karst), and contrasted these response to herbaceous model Arabidopsis We show that the main transcriptional response of Norway spruce needles exposed to cold was delayed relative to Arabidopsis, and this delay was associated with slower development of freezing tolerance. Despite this difference in timing, Norway spruce principally utilizes early response transcription factors (TFs) belonging to the same gene families as Arabidopsis, indicating broad evolutionary conservation of cold response networks. In keeping with their different metabolic and developmental states, needles and root of Norway spruce showed contrasting results. Regulatory network analysis identified both conserved TFs with known roles in cold acclimation (e.g. homologs of ICE1, AKS3, and of the NAC and AP2/ERF superfamilies), but also a root-specific bHLH101 homolog, providing functional insights into cold stress response strategies in Norway spruce.
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