PubMed · 11635076
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
C Laforêt. 1983. [Not Available].. https://pubmed.ncbi.nlm.nih.gov/11635076/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Oxygen evolution is inhibited when leaves of chilling-sensitive plants like cucumber are treated at 0 degrees C in the dark. The activity is restored by moderate illumination at room temperature. We examined the changes in the redox state of the Mn-cluster in cucumber leaves in the processes of dark-chilling inhibition and subsequent light-induced reactivation by means of thermoluminescence (TL). A TL B-band arising from S(2)Q(B)(-) charge recombination in PSII was observed upon single-flash illumination of untreated leaves, whereas four flashes were required to yield the B-band after dark-chilling treatment for 24 h. This three-step delay indicates that over-reduced states of the Mn-cluster such as the S(-2) state were formed during the treatment. Fitting analysis of the flash-number dependence of the TL intensities showed that the Mn-cluster was more reduced with a longer period of the treatment and that S(-3) was the lowest S-state detectable in the dark-chilled leaves. Measurements of the Mn content by atomic absorption spectroscopy showed that Mn atoms were gradually released from PSII during the dark-chilling treatment but re-bound to PSII by illumination at 30 degrees C. Thus, dark-chilling inhibition of oxygen evolution can be ascribed to the disintegration of the Mn-cluster due to its over-reduction. The observation of the S(-3) state in the present in vivo system strongly suggests that S(-3), which has been observed only by addition of exogenous reductants into in vitro preparations, is indeed a redox intermediate of the Mn-cluster in the processes of its disintegration and photoactivation.
Rice (Oryza sativa L.) is sensitive to chilling particularly during early seedling development. Given the biochemical complexity of tolerance mechanisms, genetic potential for this trait depends on highly coordinated expression of many genes. We used a simple cDNA subtraction strategy to develop Expressed Sequence Tags (ESTs) that represent an important subset of cold stress-upregulated genes. The 3,084 subtracted cDNA clones represent a total of 1,967 unigenes from 1,354 singletons and 613 contigs. As expected in the developing seedlings, genes involved in basic cellular processes, i.e., metabolism, growth and development, protein synthesis, folding and destination, cellular transport, cell division and DNA replication were widely represented. Genes with stress-related and regulatory functions comprised 23.17% of the total ESTs. These categories included proteins with known function in cellular defenses against abiotic (drought, cold and salinity) and biotic (pathogen) stresses, and proteins involved in developmental and stress response signalling and transcription. Based on the types of genes represented, tolerance mechanisms rely on precise integration of developmental processes with stress-related responses. A large fraction of the ESTs (38.7%) represents unknown proteins. This EST library is a rich source of cold stress-related genes, and supplements for other publicly available libraries for comprehensive analysis of the stress-response transcriptome.
Explore the source record for details and available documents.