Anthocyanins, which accumulate in leaves and stems in response to low temperature and changes in light intensity, are synthesized through the phenylpropanoid pathway that is controlled by key enzymes that include phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) In this work we demonstrate that PAL and CHS mRNAs accumulate in leaves of Arabidopsis thaliana (L) Heynh upon exposure to low temperature in a light-dependent manner The regulation of the PAL1 gene expression by low temperature and light was examined by analyzing the expression of the [beta]-glucuronidase (uidA) reporter gene in transgenic Arabidopsis plants containing the uidA gene of Escherichia coli under the control of the PAL1 promoter The results indicate that the accumulation of PAL1 mRNA is transcriptionally regulated Histochemical staining for [beta]-glucuronidase activity showed that the PAL1 promoter is preferentially activated in photosynthetically active cells, paralleling anthocyanin accumulation Moreover, we show that light may also be implicated in the regulation of the CHS gene in response to bacterial infiltration Finally, using two transparent testa Arabidopsis mutants that are unable to accumulate anthocyanins, we demonstrate that these pigments are not required for successful development of freezing tolerance in this species

/pdf/low-temperature-induces-the-accumulation-of-phenylalanine-2v8s5sq2ry.pdf

Low Temperature Induces the Accumulation of Phenylalanine Ammonia-Lyase and Chalcone Synthase mRNAs of Arabidopsis thaliana in a Light-Dependent Manner.

Crop models are used to estimate crop productivity under future climate projections, and modellers manage uncertainty by considering different scenarios and GCMs, using a range of crop simulators. Five crop models and 20 users were arranged in a randomized block design with four replicates. Parameters for maize (well studied by modellers) and rapeseed (almost ignored) were calibrated. While all models were accurate for maize (RRMSE from 16.5% to 25.9%), they were, to some extent, unsuitable for rapeseed. Although differences between biomass simulated by the models were generally significant for rapeseed, they were significant only in 30% of the cases for maize. This could suggest that in case of models well suited to a crop, user subjectivity (which explained 14% of total variance in maize outputs) can hide differences in model algorithms and, consequently, the uncertainty due to parameterization should be better investigated. Five crop models and 20 users were arranged in four randomized blocks.The significance of model factor for maize and rapeseed was evaluated.All models achieved good performance for maize and poor for rapeseed.Differences between models were significant only in 30% of the cases for maize.Parameterization uncertainty should be explicitly managed also in model ensembles.

Uncertainty in crop model predictions

In order to identify genes involved in cold acclimation, we have constructed a cDNA library from Brassica napus (cv. Samourai) cold-acclimated etiolated seedlings. By differential screening, a cDNA clone named pBnC24 (Brassica napus Cold), corresponding to a new cold-inducible plant gene, was isolated. Northern blot hybridizations using total RNA from acclimated and unacclimated seedlings confirmed that BnC24 represents a cold-regulated gene. In contrast with a number of cold-inducible plant genes, BnC24 does not seem to be responsive to abscisic acid (ABA). In addition, further screening of the ‘cold-acclimated’ cDNA library using pBnC24 cDNA as a probe, allowed the isolation of a second type of homologous cDNA. Sequence analysis showed that the two BnC24 genes encode basic 24 kDa proteins, which are highly hydrophilic and rich in alanine, lysine and arginine. The nucleotide and deduced amino acid sequences of these clones do not show any homology with other previously described cold-induced plants genes. However they have strong homology with a recently discovered human tumour gene, bbc1 (breast basic conserved), which seems to be highly conserved in eukaryotes.

Two related, low-temperature-induced genes from Brassica napus are homologous to the human tumour bbc1 (breast basic conserved) gene.

We have isolated a clone corresponding to a new cold-regulated gene from a cDNA library made from rapeseed (Brassica napus cv Samourai) cold-acclimated etiolated seedlings. Sequence analysis and homology searches showed that this clone encodes a protein highly homologous to the ATP-dependent phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.49) from Saccharomyces cerevisiae, Trypanosoma, Rhizobium sp., and Escherichia coli; we refer to the B. napus clone as BnPEPCK. A potential ATP-binding site existing in all PEPCK proteins was also found in BnPEPCK. Although there was a basal expression of BnPEPCK in seedlings grown at control, room temperature, the steady-state level of the transcripts increased at 4[deg]C and decreased to normal levels when the seedlings were returned to control temperature (22[deg]C). Using antibodies made against a recombinant histidine-BnPEPCK fusion protein, we demonstrated that BnPEPCK protein level is correlated with the accumulation of the BnPEPCK transcript.

A Rapeseed Cold-Inducible Transcript Encodes a Phosphoenolpyruvate Carboxykinase'

Similar changes in the m R N A population are also obvious when mRNAs obtained from coldtreated and control seedlings are translated in vitro in a cell-free system and then the trans­ lation products are compared. Several mRNAs are apparently more abundant at 0 ° C than at 18°C while others are less abundant or have completely disappeared. Differences were noticed in the response of the winter and spring varieties at the low temperatures. L-phenylalanine ammonia-lyase is induced specifically in the cold-tolerant cultivar, suggesting that it might be a useful biochemical marker in predicting the cold sensitivity of new variety or in improving a sensitive cultivar.

Cold resistance in rapeseed ( brassica napus ) seedlings . Searching a biochemical marker of cold - tolerance

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Cold resistance in rapeseed ( brassica napus ) seedlings . Searching a biochemical marker of cold - tolerance