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Complementary regulation of four Eucalyptus CBF genes under various cold conditions.

Navarro M, Marque G, Ayax C, Keller G, Borges JP, Marque C, Teulières C - J. Exp. Bot. (2009)

Bottom Line: This basal level, significant for the four genes, greatly influences the final EguCBF1 transcript level in the cold.The differential expression of the four EguCBF1 genes under these cold regimes suggests that there is a complementary regulation.The high accumulation of the CBF transcript, observed in response to the different types of cold conditions, might be a key for the winter survival of this evergreen broad-leaved tree.

View Article: PubMed Central - PubMed

Affiliation: Université de Toulouse (UT3): ERT1045-UMR5546, Pôle de Biotechnologie Végétale, 24 Chemin de Borde Rouge BP 42617 Auzeville, 31326 Castanet-Tolosan, France.

ABSTRACT
CBF transcription factors play central roles in the control of freezing tolerance in plants. The isolation of two additional CBF genes, EguCBF1c and EguCBF1d, from E. gunnii, one of the cold-hardiest Eucalyptus species, is described. While the EguCBF1D protein sequence is very similar to the previously characterized EguCBF1A and EguCBF1B sequences, EguCBF1C is more distinctive, in particular in the AP2-DBD (AP2-DNA binding domain). The expression analysis of the four genes by RT-qPCR reveals that none of them is specific to one stress but they are all preferentially induced by cold, except for the EguCBF1c gene which is more responsive to salt. The calculation of the transcript copy number enables the quantification of constitutive CBF gene expression. This basal level, significant for the four genes, greatly influences the final EguCBF1 transcript level in the cold. A cold shock at 4 degrees C, as well as a progressive freezing which mimics a natural frost episode, trigger a fast and strong response of the EguCBF1 genes, while growth at acclimating temperatures results in a lower but more durable induction. The differential expression of the four EguCBF1 genes under these cold regimes suggests that there is a complementary regulation. The high accumulation of the CBF transcript, observed in response to the different types of cold conditions, might be a key for the winter survival of this evergreen broad-leaved tree.

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Time-course of EguCBF1 gene expression at 4 °C in the dark. Total RNA was extracted from a pool of leaves harvested before cold exposure (control), after 15 min, 30 min, 2 h, 5 h, and 24 h. (A) The relative EguCBF1 transcript abundance was determined as described in the legend of Fig. 2. (B) Copy number ng−1 of cDNA of EguCBF1 genes was calculated using a standard curve (see the Materials and methods for details). For transcript copy number ng−1 of cDNA values, closed circles, open triangles, open circles, closed triangles, and closed squares correspond to EguCBF1a, EguCBF1b, EguCBF1c, EguCBF1d genes, and the total amount of the EguCBF1 genes, respectively.
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fig3: Time-course of EguCBF1 gene expression at 4 °C in the dark. Total RNA was extracted from a pool of leaves harvested before cold exposure (control), after 15 min, 30 min, 2 h, 5 h, and 24 h. (A) The relative EguCBF1 transcript abundance was determined as described in the legend of Fig. 2. (B) Copy number ng−1 of cDNA of EguCBF1 genes was calculated using a standard curve (see the Materials and methods for details). For transcript copy number ng−1 of cDNA values, closed circles, open triangles, open circles, closed triangles, and closed squares correspond to EguCBF1a, EguCBF1b, EguCBF1c, EguCBF1d genes, and the total amount of the EguCBF1 genes, respectively.

Mentions: The expression of the four EguCBF1 genes was then quantified in plantlets during a 24 h cold exposure in the dark, after a direct transfer from 22 °C to 4 °C. The four EguCBF1 genes were strongly induced by cold (Fig. 3A) and exhibited quite similar expression profiles with contrasting relative transcript abundances. While the maximum induction was observed between 2 h and 5 h for the EguCBF1a gene (1760-fold and 1690-fold, respectively), there was a less impressive induction peak at 5 h for the EguCBF1d/b/c genes (436-, 131- and 91-fold, respectively). In addition, Fig. 3A shows that the EguCBF1 gene cold response was early and durable: the induction was already detectable at 15 min and remained high at 24 h, but much lower than at 5 h. This profile is in agreement with the data previously published for EguCBF1a/b genes (El Kayal et al., 2006), except for slight differences in induction levels due to the use here of mean control values that were more representative (basal level in Table 1) instead of the specific control value.


Complementary regulation of four Eucalyptus CBF genes under various cold conditions.

Navarro M, Marque G, Ayax C, Keller G, Borges JP, Marque C, Teulières C - J. Exp. Bot. (2009)

Time-course of EguCBF1 gene expression at 4 °C in the dark. Total RNA was extracted from a pool of leaves harvested before cold exposure (control), after 15 min, 30 min, 2 h, 5 h, and 24 h. (A) The relative EguCBF1 transcript abundance was determined as described in the legend of Fig. 2. (B) Copy number ng−1 of cDNA of EguCBF1 genes was calculated using a standard curve (see the Materials and methods for details). For transcript copy number ng−1 of cDNA values, closed circles, open triangles, open circles, closed triangles, and closed squares correspond to EguCBF1a, EguCBF1b, EguCBF1c, EguCBF1d genes, and the total amount of the EguCBF1 genes, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2692017&req=5

fig3: Time-course of EguCBF1 gene expression at 4 °C in the dark. Total RNA was extracted from a pool of leaves harvested before cold exposure (control), after 15 min, 30 min, 2 h, 5 h, and 24 h. (A) The relative EguCBF1 transcript abundance was determined as described in the legend of Fig. 2. (B) Copy number ng−1 of cDNA of EguCBF1 genes was calculated using a standard curve (see the Materials and methods for details). For transcript copy number ng−1 of cDNA values, closed circles, open triangles, open circles, closed triangles, and closed squares correspond to EguCBF1a, EguCBF1b, EguCBF1c, EguCBF1d genes, and the total amount of the EguCBF1 genes, respectively.
Mentions: The expression of the four EguCBF1 genes was then quantified in plantlets during a 24 h cold exposure in the dark, after a direct transfer from 22 °C to 4 °C. The four EguCBF1 genes were strongly induced by cold (Fig. 3A) and exhibited quite similar expression profiles with contrasting relative transcript abundances. While the maximum induction was observed between 2 h and 5 h for the EguCBF1a gene (1760-fold and 1690-fold, respectively), there was a less impressive induction peak at 5 h for the EguCBF1d/b/c genes (436-, 131- and 91-fold, respectively). In addition, Fig. 3A shows that the EguCBF1 gene cold response was early and durable: the induction was already detectable at 15 min and remained high at 24 h, but much lower than at 5 h. This profile is in agreement with the data previously published for EguCBF1a/b genes (El Kayal et al., 2006), except for slight differences in induction levels due to the use here of mean control values that were more representative (basal level in Table 1) instead of the specific control value.

Bottom Line: This basal level, significant for the four genes, greatly influences the final EguCBF1 transcript level in the cold.The differential expression of the four EguCBF1 genes under these cold regimes suggests that there is a complementary regulation.The high accumulation of the CBF transcript, observed in response to the different types of cold conditions, might be a key for the winter survival of this evergreen broad-leaved tree.

View Article: PubMed Central - PubMed

Affiliation: Université de Toulouse (UT3): ERT1045-UMR5546, Pôle de Biotechnologie Végétale, 24 Chemin de Borde Rouge BP 42617 Auzeville, 31326 Castanet-Tolosan, France.

ABSTRACT
CBF transcription factors play central roles in the control of freezing tolerance in plants. The isolation of two additional CBF genes, EguCBF1c and EguCBF1d, from E. gunnii, one of the cold-hardiest Eucalyptus species, is described. While the EguCBF1D protein sequence is very similar to the previously characterized EguCBF1A and EguCBF1B sequences, EguCBF1C is more distinctive, in particular in the AP2-DBD (AP2-DNA binding domain). The expression analysis of the four genes by RT-qPCR reveals that none of them is specific to one stress but they are all preferentially induced by cold, except for the EguCBF1c gene which is more responsive to salt. The calculation of the transcript copy number enables the quantification of constitutive CBF gene expression. This basal level, significant for the four genes, greatly influences the final EguCBF1 transcript level in the cold. A cold shock at 4 degrees C, as well as a progressive freezing which mimics a natural frost episode, trigger a fast and strong response of the EguCBF1 genes, while growth at acclimating temperatures results in a lower but more durable induction. The differential expression of the four EguCBF1 genes under these cold regimes suggests that there is a complementary regulation. The high accumulation of the CBF transcript, observed in response to the different types of cold conditions, might be a key for the winter survival of this evergreen broad-leaved tree.

Show MeSH
Related in: MedlinePlus