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Cochard H.,French National Institute for Agricultural Research | Cochard H.,University Blaise Pascal | Herbette S.,French National Institute for Agricultural Research | Herbette S.,University Blaise Pascal | And 6 more authors.
Plant, Cell and Environment | Year: 2010

The Cavitron spinning technique is used to construct xylem embolism vulnerability curves (VCs), but its reliability has been questioned for species with long vessels. This technique generates two types of VC: sigmoid 's'-shaped and exponential, levelling-off 'r'-shaped curves. We tested the hypothesis that 'r'-shaped VCs were anomalous and caused by the presence of vessels cut open during sample preparation. A Cavitron apparatus was used to construct VCs from samples of different lengths in species with contrasting vessel lengths. The results were compared with VCs obtained using other independent techniques. When vessel length exceeded sample length, VCs were 'r'-shaped and anomalous. Filling vessels cut open at both ends with air before measurement produced more typical 's'-shaped VCs. We also found that exposing segments of 11 woody species in a Cavitron at the pressure measured in planta before sampling considerably increased the degree of embolism above the native state level for species with long vessels. We concluded that open vessels were abnormally more vulnerable to cavitation than intact vessels. We recommend restricting this technique to species with short conduits. The relevance of our conclusions for other spinning techniques is discussed. © 2010 Blackwell Publishing Ltd.

Charfeddine M.,University of Sfax | Charfeddine M.,Laboratoire des Biotechnologies Vegetales | Bouaziz D.,Laboratoire des Biotechnologies Vegetales | Charfeddine S.,University of Sfax | And 7 more authors.
Plant Biotechnology Reports | Year: 2015

Plant growth and productivity are greatly affected by environmental stresses such as dehydration, high salinity, low temperature and pathogen infection. Plant adaptation to these environmental stresses is controlled by cascades of molecular networks. The dehydration-responsive element-binding (DREB) transcription factors play an important role in the response of plants to environmental stresses by controlling the expression of many stress-related genes. They specifically interact with C-repeat/DRE (A/GCCGAC) sequences present in the promoter regions of target genes. One of the DREB1 cDNA was previously cloned and overexpressed in transgenic potato plants. These transgenic plants displayed an improved tolerance to high salinity and drought stresses. The StDREB1 factor belongs to A-4 group that seem to be involved in biotic stress response. This report investigates the effect of Fusarium solani infection on the StDREB1 transgenic lines. Since a number of pathogenesis-related (PR) proteins are considered as DREB1 target genes, the expression of PR2, PR9 and PR3 genes were tested under biotic stress conditions. The β-1,3-glucanase (PR2) was specifically induced upon infection, whereas the chitinase and the peroxydase were expressed constitutively. The data also show that high levels of DREB1 transcripts accumulated rapidly when wild-type and transgenic plants were infected by F. solani. DREB1 transgenic potato plants accumulated higher levels of pathogenesis-related gene transcripts, such as PR2. These results showed that StDREB1 plays an important role in response to fungal attack in potato. © 2015, Korean Society for Plant Biotechnology and Springer Japan.

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