Two EguCBF1 genes overexpressed in Eucalyptus display a different impact on stress tolerance and plant development.
Two C-repeat binding factor genes (EguCBF1a/b), isolated from E. gunnii and differentially cold-regulated, were constitutively overexpressed in a cold-sensitive Eucalyptus hybrid. In addition to the expected improvement on freezing tolerance, some resulting transgenic lines (EguCBF1a-OE and EguCBF1b-OE) exhibited a decrease in stomata density and an over-accumulation of anthocyanins also observed to a lesser extent in a cold-acclimated control plant. Given that the induction of five putative CBF target genes was observed in CBF-overexpressing lines as well as in the cold-acclimated control line, these phenotypes might be related to cold acclimation. In comparison with the control plant, the most altered transgenic line (EguCBF1a-OE A1 line), exhibited reduced growth and better water retention capacity. This modified phenotype includes reduced leaf area and thickness associated with a decrease in cell size, as well as a higher oil gland density and a wax deposition on the cuticle. Surprisingly, the EguCBF1b-OE B9 line, with a level of transgene expression equivalent to the A1 line, showed a less marked phenotype, suggesting a difference in transactivation efficiency between EguCBF1A and B factors. The features of these transgenic lines provide the first signs of adaptive mechanisms controlled by CBF transcription factors in an evergreen broad-leaved tree. These data also open new prospects towards genetic improvement on Eucalyptus for freezing tolerance.
Navarro
Marie
M
Université de Toulouse (UT3): ERT 1045, Pôle de Biotechnologie Végétale, Castanet-Tolosan, France.
Ayax
Céline
C
Martinez
Yves
Y
Laur
Joan
J
El Kayal
Walid
W
Marque
Christiane
C
Teulières
Chantal
C
D003080:Cold Temperature; D005052:Eucalyptus / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D005615:Freezing; D018506:Gene Expression Regulation, Plant; D013312:Stress, Physiological; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D019076:Transgenes / Q000502:physiology; D015854:Up-Regulation
D015534:Trans-Activators