Transgenic Grapes (Vitis Species). In: Bajaj YPS, editor. Transgenic Crops II. Berlin: Springer Berlin Heidelberg; 2001. pp. 325-38. [DOI: 10.1007/978-3-642-56901-2_21]

Differential regulation of SERK, LEC1-like and pathogenesis-related genes during indirect secondary somatic embryogenesis in grapevine

A culture model was developed in Vitis vinifera L., cultivar 'Chardonnay' for studying SE (Somatic Embryogenesis). The auxin 2,4-D (2,4-Dichlorophenoxyacetic acid) was used to induce indirect secondary embryogenesis at a high rate, starting from embryos derived from embryogenic cultures previously obtained. Cotyledonary embryos were shown to be more responsive to SE induction than embryos at the torpedo-stage and were used for molecular analyses. The expression of SERK (Somatic Embryogenesis Receptor Kinase), L1L (Leafy Cotyledon1 Like) and a set of PR (Pathogenesis-Related) genes was monitored during the whole SE process. VvSERK1, VvSERK2 and VvL1L were down-regulated by the 2,4-D treatment but expressed in embryonic tissues. On the contrary, VvPR1, VvPR8, VvPR10.1 and VvPR10.3 were strongly up-regulated by the 2,4-D treatment, and their transcripts were not or only weakly detected in clusters of secondary embryos. VvSERK3, VvPR3 and VvPR10.2 were more stably expressed in all tissues examined. The discussion deals with the putative role of the different genes in grapevine SE.

Elaboration of a reliable strategy based on real-time PCR to characterize genetically modified plantlets and to evaluate the efficiency of a marker gene removal in grape (Vitis spp.)

We have developed an effective strategy based on real-time PCR assay for the molecular characterization of genetically modified grape and to quantify the efficiency of a marker gene removal. This research has been implemented in Vitis vinifera cv. Brachetto plantlets where exogenes were inserted during cocultures of embryogenic calli with Agrobacterium tumefaciens carrying the chemically inducible site-specific cre/loxP pX6 vector where the expression of the cre recombinase is regulated by 17-beta-estradiol. The neomycin phosphotransferase gene (nptII) for the kanamycin resistance trait was inserted as part of the gene transfer protocol, and this exogene was employed as a case study for carrying out our research. The 9-cis-epoxycarotenoid dioxygenase (nced2) and chalcone isomerase (chi) genes coding for two enzymes, involved respectively in abscisic acid and flavonoid biosynthesis, proved to be valuable reference endogenes for real-time PCR assays. Two types of duplo-target plasmids were exploited for building the standard curves: in one type (p-nptII/nced2) the nptII sequence is linked to the nced2 sequence; in the other (p-nptII/chi) it is linked to the chi. These calibrators were intended to simulate an ideal genetically modified plant carrying a homozygous single-copy exogene insertion. The repeatability test confirmed the suitability of both plasmid calibrators. Foreign gene stability can be monitored during long-term plant preservation, and the method proved to be suitable for quantifying the efficiency of nptII gene removal induced by 17-beta-estradiol.

Genetic chimerism of Vitis vinifera cv. Chardonnay 96 is maintained through organogenesis but not somatic embryogenesis

BACKGROUND

Grapevine can be a periclinal chimera plant which is composed at least of two distinct cell layers (L1, L2). When the cell layers of this plant are separated by passage through somatic embryogenesis, regenerated plants could show distinct DNA profiles and a novel phenotype which proved different from that of the parent plant.

RESULTS

Genetically Chardonnay clone 96 is a periclinal chimera plant in which is L1 and L2 cell layers are distinct. Plants obtained via organogenesis through meristematic bulks are shown to be composed of both cell layers. However, plants regenerated through somatic embryogenesis starting from anthers or nodal explants are composed only of L1 cells. These somaclones do not show phenotypic differences to the parental clone up to three years after regeneration. Interestingly, the only somaclone showing an atypical phenotype (asymmetric leave) shows a genotypic modification.

CONCLUSION

These results suggest that the phenotype of Chardonnay 96 does not result from an interaction between the two distinct cell layers L1 and L2. If phenotype conformity is further confirmed, somatic embryogenesis will result in true-to-type somaclones of Chardonnay 96 and would be well suitable for gene transfer.