Réponse aux stress abiotiques chez Eucalyptus gunii (analyse globale du transcriptome sur filtres haute densité et caractérisation moléculaire du gène Sxd1 (synthèse de la vitamine E))

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Etude fonctionnelle de gènes de facteurs de transcription CBFs impliqués dans la tolérance au froid chez l'eucalyptus

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Isolement et caractérisation chez l'Eucalyptus de gènes codant les facteurs de transcription CBF impliqués dans la réponse au froid

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Expression profile of CBF-like transcriptional factor genes from Eucalyptus in response to cold

Two CBF (CRT/DRE-binding factor) homologues isolated from Eucalyptus gunnii were designated EguCBF1a and EguCBF1b and belong to a gene family which includes at least five members. Both promoter and coding sequences were found to exhibit the main characteristics of a CBF transcription activator gene and, as expected, the corresponding protein targeted the nucleus. Gene expression was quantitatively analysed using real-time reverse transcription-polymerase chain reaction (RT-PCR) after a short exposure to different environmental conditions or along a two-step cold acclimation programme with either short or long daylengths. A very strong and fast response to cold was observed, with dark conditions and cold intensity (down to 0°C) having a positive effect on the magnitude of induction. The two genes under study exhibited several similar features such as light response. However, interestingly, their regulation by cold proved differential and complementary as EguCBF1a was more transiently induced by a direct and intense exposure while EguCBF1b responded to milder treatments and exhibited a longer (i.e. which started earlier and finished later) time course. During acclimation, the short daylength positively affected the freezing tolerance in the same way as it positively affected the CBF transcript accumulation, suggesting a potential involvement of these genes in the adaptive response. Although very quick after the first signal, the up-regulation of the two EguCBF1 genes unexpectedly lasted throughout the chilling culture, and new inductions were seen during the thermoperiod transitions. Using a quantitative and highly sensitive measurement of gene expression combined with the application of a cold treatment consistent with natural environmental conditions, this study provides new information on the regulation of CBF-like genes by cold in planta. © 2006 The Author(s)

Wood architecture and composition are deeply remodeled in frost sensitive eucalyptus overexpressing CBF/DREB1 transcription factors

Eucalypts are the most planted trees worldwide, but most of them are frost sensitive. Overexpressing transcription factors for CRT-repeat binding factors (CBFs) in transgenic Eucalyptus confer cold resistance both in leaves and stems. While wood plays crucial roles in trees and is affected by environmental cues, its potential role in adaptation to cold stress has been neglected. Here, we addressed this question by investigating the changes occurring in wood in response to the overexpression of two CBFs, taking advantage of available transgenic Eucalyptus lines. We performed histological, biochemical, and transcriptomic analyses on xylem samples. CBF ectopic expression led to a reduction of both primary and secondary growth, and triggered changes in xylem architecture with smaller and more frequent vessels and fibers exhibiting reduced lumens. In addition, lignin content and syringyl/guaiacyl (S/G) ratio increased. Consistently, many genes of the phenylpropanoid and lignin branch pathway were upregulated. Most of the features of xylem remodeling induced by CBF overexpression are reminiscent of those observed after long exposure of Eucalyptus trees to chilling temperatures. Altogether, these results suggest that CBF plays a central role in the cross-talk between response to cold and wood formation and that the remodeling of wood is part of the adaptive strategies to face cold stress.The Centre National pour la Recherche Scientifique (CNRS), the University Paul Sabatier Toulouse III (UPS), the French MERI (Ministry of Education, Research and Innovation), and the French Laboratory of Excellence project ‘TULIP’(ANR-10-LABX-41; ANR-11-IDEX-0002-02). This research was also financially supported by the Vietnamese government for PhD grants (P.B. Cao and C. Nguyen).http://www.mdpi.com/journal/ijmshj2020BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog