Project description:Earlier findings indicated that light plays a critical role in the development of frost tolerance in winter cereals. However, the exact mechanism is still poorly understood. In the present work the effects of light during the cold acclimation period were studied in chilling-sensitive maize plants. The results show that although exposure to relatively high light intensities during cold acclimation at 15 °C causes various stress symptoms, it enhances the effectiveness of acclimation to chilling conditions (5 °C in the light). Interestingly, certain stress responses were light-dependent not only in the leaves, but also in the roots. A microarray study was also conducted to achieve a better understanding of the interaction of low temperature and light intensity during the cold hardening period. Numerous genes significantly differentially expressed were observed in almost all assimilation and metabolic pathways. Acclimation at moderately low temperature and low light intensity reduced the level of soluble sugars, while chilling increased it. Greater accumulation during hardening was detected at relatively high light intensity. It seems that the photoinhibition induced by low temperature is a necessary evil for cold acclimation processes in plants.
Project description:Exposure of plants to low temperature in the light may induce photoinhibitory stress symptoms, including oxidative damage. However, it is also known that light is a critical factor for the development of frost hardiness in cold tolerant plants. In the present work the effects of light during the cold acclimation period were studied in chilling-sensitive maize plants. Before exposure to chilling temperature at 5°C, plants were cold acclimated at non-lethal temperature (15°C) under different light conditions. Although exposure to relatively high light intensities during cold acclimation caused various stress symptoms, it also enhanced the effectiveness of acclimation processes to a subsequent severe cold stress. It seems that the photoinhibition induced by low temperature is a necessary evil for cold acclimation processes in plants. Greater accumulations of soluble sugars were also detected during hardening at relatively high light intensity. Certain stress responses were light-dependent not only in the leaves, but also in the roots. The comparison of the gene expression profiles based on a microarray study demonstrated that the light intensity is at least as important a factor as the temperature during the cold acclimation period. Differentially expressed genes were mainly involved in most of assimilation and metabolic pathways, namely photosynthetic light capture via the modification of chlorophyll biosynthesis and the dark reactions, carboxylic acid metabolism, cellular amino acid, porphyrin or glutathione metabolic processes, ribosome biogenesis and translation. Results revealed complex regulation mechanisms and interactions between cold and light signalling processes.
Project description:Heat acclimation (AC) allows its faster re-induction following its decline. Constitutively preserved euchromatin state in hsp70 promoter during acclimation decline/regain pushed forward the hypothesis that acclimation decline is a period of “dormant memory” involving molecular program including epigenetic controlled transcriptional regulation leading to heat acclimation mediated cytoprotective memory. We used microarray to uncover hallmark pathways in the induction of heat-acclimation-mediated memory, focusing on markers of epigenetic processes.
Project description:Plant acclimation to an ever-changing environment is decisive for growth, reproduction and survival. Light availability, as one crucial factor for plant growth, limits biomass production on both ends of the intensity spectrum, and a sophisticated light acclimation response evolved to counteract drawbacks from low and high light (HL) intensities in nature. Among others, adjustment of plant metabolism is central to HL acclimation and accumulation of photoprotective and antioxidative anthocyanins is commonly observed. Despite a good understanding of the biosynthesis, mechanisms and factors regulating anthocyanin accumulation and the associated HL acclimation response are less clear. Two Arabidopsis mutants of spliceosomal complex components exhibiting a pronounced anthocyanin overaccumulation in HL were isolated from a forward genetic screen aiming to isolate new factors crucial for plant acclimation. Time-resolved physiological, transcriptome and metabolome analysis within the first hours of HL exposure revealed a vital function of the spliceosomal complex components for rapidly adjusting gene expression and metabolism. More precisely, deficiency of INCREASED LEVEL OF POLPLOIDY1 (ILP1), its interaction partner NTC-RELATED PROTEIN 1 (NTR1), and PLEIOTROPIC REGULATORY LOCUS 1 (PRL1) resulted in a marked overaccumulation of carbohydrates and regulatory sugar phosphates and strongly diminished amino acid biosynthesis, one major sink for carbon blocks and nitrogen in HL. However, ilp1, ntr1 and prl1 mutants, which showed symptoms of nitrogen deficiency, were not affected in N assimilation but showed a limitation in the consumption of glutamate as the primary amino group donor for stimulated amino acid biosynthesis in HL. The comprehensive analysis revealed a critical function of the spliceosome in the conditional regulation of the C:N balance and the accumulation of protective compounds during HL acclimation. The importance of gene expression, metabolic regulation, and re-direction of carbon towards anthocyanin biosynthesis for HL acclimation is discussed.
Project description:Heat acclimation (AC) allows its faster re-induction following its decline. Constitutively preserved euchromatin state in hsp70 promoter during acclimation decline/regain pushed forward the hypothesis that acclimation decline is a period of M-bM-^@M-^\dormant memoryM-bM-^@M-^] involving molecular program including epigenetic controlled transcriptional regulation leading to heat acclimation mediated cytoprotective memory. We used microarray to uncover hallmark pathways in the induction of heat-acclimation-mediated memory, focusing on markers of epigenetic processes. Rats subjected to heat acclimation, deacclimation, reacclimation and untreated controls were used. We showed here that (i) AC2d provides the molecular switch for acclimation (ii) AC30 heart demonstrates qualitative adaptations (iii) specific molecular program encompassing up/down regulated gene during DeAC, of which epigenetic markers such as class A histones, chromatin modifiers and microRNA suggest epigenetic transcriptional regulation linked to acclimation memory (iv) constitutive upregulation of MAPK P38 module and targets as well as jak/stat and AKT associated pathways during DeAC imply its major role in this process. Noteworthy are players such as poly-(ADP-ribose)polymerase-1 (PARP1) and linker histones (histones H1 cluster in this process).
Project description:The acclimation of plants to environmental factors (light/temperature/nutrient availability) plays a crucial role in determining their tolerance to stress their ability to compete with other plants and the efficiency with which external inputs are used for growth and productivity. Some of the clearest responses involve the major modifications in the composition of the photosynthetic apparatus in response to light intensity. Photosynthetic acclimation. The acclimation response involves changes in the abundance of a large number of proteins in different cell compartments occurring at different intensity thresholds. The signal transduction chain is complex and involves crosstalk between redox control and other pathways that control photosynthetic gene expression but is poorly understood. Over the past 7 years we have laid the foundations for a molecular genetic approach by characterising the responses of Arabidopsis thaliana to growth in and transfer between high and low light conditions(1-6). Arabidopsis exhibits all the key features of photosynthetic acclimation: changes in maximum photosynthetic rate in leaf structure and in the levels of light-harvesting complexes photosystems and enzymes of carbon metabolism. Method: Samples A-1, A-2 and A-3 were grown at a light intensity of 400 umol.m-2.s-1 until rosette growth was complete. Plants for samples A-2 and A-3 were then transferred to 100 umol.m-2.s-1. Samples A-4, A-5 and A-6 were grown at 100umol.m-2.s-1 until rosette growth was complete, when plants for samples A-5 and A-6 were transferred to 400 umol.m-2.s-1. Samples were taken 24 hours after transfer to the different light intensity and samples A-3 and A-6 were taken 72 hours after transfer. Keywords: Photosynthesis
Project description:The sfr3-1 mutation causes freezing-sensitivity in Arabidopsis thaliana. The mutated gene has been identified by positional cloning and is currently being characterised. The mutant appears normal when grown in the warm (no phenotype has been identified associated with such growth). However, following cold acclimation and subsequent freezing mutant plants are severely damaged whilst wild type plants are not. This suggests that sfr3 is deficient in the cold acclimation process. Micro-array analysis will enable the identification of any transcriptional changes during the cold acclimation process. This information will then be used, together with information obtained by gene characterisation, in order to more fully understand the nature of the sfr3 mutation.
Project description:The acclimation of plants to environmental factors (light/temperature/nutrient availability) plays a crucial role in determining their tolerance to stress their ability to compete with other plants and the efficiency with which external inputs are used for growth and productivity. Some of the clearest responses involve the major modifications in the composition of the photosynthetic apparatus in response to light intensity. Photosynthetic acclimation. The acclimation response involves changes in the abundance of a large number of proteins in different cell compartments occurring at different intensity thresholds. The signal transduction chain is complex and involves crosstalk between redox control and other pathways that control photosynthetic gene expression but is poorly understood. Over the past 7 years we have laid the foundations for a molecular genetic approach by characterising the responses of Arabidopsis thaliana to growth in and transfer between high and low light conditions(1-6). Arabidopsis exhibits all the key features of photosynthetic acclimation: changes in maximum photosynthetic rate in leaf structure and in the levels of light-harvesting complexes photosystems and enzymes of carbon metabolism. Method: Samples A-1, A-2 and A-3 were grown at a light intensity of 400 umol.m-2.s-1 until rosette growth was complete. Plants for samples A-2 and A-3 were then transferred to 100 umol.m-2.s-1. Samples A-4, A-5 and A-6 were grown at 100umol.m-2.s-1 until rosette growth was complete, when plants for samples A-5 and A-6 were transferred to 400 umol.m-2.s-1. Samples were taken 24 hours after transfer to the different light intensity and samples A-3 and A-6 were taken 72 hours after transfer.