Radhouane Ellouz

Transformation of two potato cultivars ‘Spunta’ and ‘Claustar’ (Solanum tuberosum) with lettuce mosaic virus coat protein gene and heterologous immunity to potato virus Y

Abstract The coat protein (CP) gene of the lettuce mosaic potyvirus (LMV) was introduced into two potato cultivars—Spunta and Claustar—via Agrobacterium tumefaciens -mediated transformation. Gene expression was verified by Southern. Northern and Western blot. The regenerated plants have been tested for resistance against potato virus Y (PVY-0) in greenhouse. We observed an immune phenotype in four transgenic lines expressing the CP-LMV protein at different detectable levels. However, in two other transgenic plant lines, symptoms were developed at a frequency of 25 and 60% with a delay in their appearance. Transgene transcripts of the CP-LMV gene were detected by Northern blot in these two lines, but the protein could not be detected by Western blot. The correlation between the presence of the CP protein at a detectable level and the expression of an immune phenotype is discussed.

Marker-free transgenic durum wheat cv. Karim expressing the AlSAP gene exhibits a high level of tolerance to salinity and dehydration stresses

We have recently isolated the AlSAP (stress-associated protein) gene from the halophyte grass Aeluropus littoralis and demonstrated that AlSAP expression improves tolerance to continuous salt and drought stresses in transgenic tobacco. To extend these findings to an important crop, we generated marker-free transgenic durum wheat plants of the commercial cv. Karim expressing the AlSAP gene. The integration and expression of AlSAP in T3 homozygous plants were ascertained by Southern, Northern and Western blotting respectively. AlSAP wheat lines exhibited improved germination rates and biomass production under severe salinity and osmotic stress conditions. Following a long-term salt or drought stress greenhouse trial, AlSAP lines produced normally filled grains whereas wild-type (WT) plants either died at the vegetative stage under salt stress or showed markedly reduced grain filling under drought stress. Measurements of the RWC (relative water content) and endogenous Na+ and K+ levels in leaves of AlSAP plants, showed a lower water loss rate and a higher Na+ accumulation in senescent-basal leaves, respectively, compared to those of WT plants. Taken together, these results extend to cereals the high potential of the AlSAP gene for engineering effective drought and salt tolerance.

Tobacco plants transformed with an untranslatable form of the coat protein gene of the Potato virus Y are resistant to viral infection

The coat protein (CP) gene of the Potato virus Y common strain (PVYo), rendered untranslatable by introduction of a stop codon immediately after the initiation codon, was cloned into an Agrobacterium tumefaciens transformation vector. The regenerated transgenic tobacco plants were analyzed for the presence of the CP gene. Although transgene transcripts were observed in all transgenic lines tested, three different phenotypes of resistance were observed, including high resistance, partial resistance, and susceptibility. An inverse correlation between the transgene transcript steady-state levels and resistance of transgenic plants to PVYo was observed. The results obtained suggest that the resistance observed in the transgenic plants is essentially due to the presence of multiple PVY transgenes that accumulate low levels of the transgene transcript. A post-transcriptional RNA degradation process appears to support the transgene transcript reduction within the RNA-mediated resistance mechanism.

AFLP and SSR fingerprinting to evaluate genetic diversity among bread wheat cultivars in Tunisia

Bread wheat ( Triticum aestivum L.) is an economically and nutritionally important cereal crop in the Mediterranean region. Characterization of wheat germplasm by means of DNA fingerprinting techniques provides a tool to assess genetic diversity and to identify varieties. In this study, six Tunisian bread wheat cultivars were characterized by AFLP and SSR markers. Five AFLP primer pairs showed clear different patterns and seems to be the most suitable for analysis of the bread wheat varieties. Three SSR primers were polymorphic with more than two alleles. The pairwise genetic similarities (GS) based on these molecular markers were calculated and used to construct a dendrogram that allowed the discrimination of the six cultivars. The GS among the six varieties ranged from 0.79 to 0.36. The six varieties used in this work clustered into four groups using either AFLP or SSR markers. A high GS was found between Tebecca and Vaga Varieties which have a similar pedigree.

Role of Lignin Peroxidase and Manganese Peroxidase of Phanerochaete Chrysosporium in the Decolorization of Olive Mill Wastewaters

The relative contributions of lignin peroxidase (LiP) and manganese peroxidase (MnP) to the decolorization of olive mill wastewaters (OMW) by Phanerochaete chrysosporium were investigated. A relatively low level (25%) of OMW decolorization was found with P. chrysosporium which was grown in a medium with a high Mn(II) concentration and in which a high level of MnP (0.65 (mu)M) was produced. In contrast, a high degree of OMW decolorization (more than 70%) was observed with P. chrysosporium which was grown in a medium with a low Mn(II) concentration but which resulted in a high level of LiP activity (0.3 (mu)M). In this culture medium, increasing the Mn(II) concentration resulted in decreased levels of OMW decolorization and LiP activity. Decolorization by reconstituted cultures of P. chrysosporium was found to be more enhanced by the addition of isolated LiP than by the addition of isolated MnP. The highest OMW decolorization levels were obtained at low initial chemical oxygen demands combined with high levels of extracellular LiP. These data, plus the positive effect of veratryl alcohol on OMW decolorization and LiP activity, indicate that culture conditions which yield high levels of LiP activity lead to high levels of OMW decolorization.