Variable properties of transgenic cucumber plants containing the thaumatin II gene from Thaumatococcus daniellii

Abstract

Thaumatin represents a unique class of the sweet-tasting plant proteins. Transgenic cucumber (Cucumis sativus L.) plants with stable integrated constructs consisting of the cauliflower mosaic virus 35S promoter and thaumatin II cDNA were produced. Transformed cucumber plants were obtained using Agrobacterium tumefaciens, with one, two or five integration sites in diploid cucumber and with inheritance confirmed by a 3:1 Mendelian ratio and normal morphologies and viable seeds. Inter-and intra-transformant variabilities in the expression of the thaumatin II gene were observed. The variability was independent of integrated copy number of the T-DNA. Variation in thaumatin II protein accumulation levels in the ripe fruits and the lack of correlation between protein and mRNA levels were observed, suggesting that thaumatin may be controlled at the levels of both transcription and translation. Transgenic fruits accumulating thaumatin II protein exhibited sweet phenotype and positive correlation between thaumatin accumulation levels and sweet taste intensity was noticed. Thaumatin II belongs to the pathogenesis-related (PR) proteins family. Some of the T2 progeny plants expressing thaumatin II protein did not exhibit tolerance for pathogenic fungus Pseudoperonospora cubensis. These results, together with previously reported results, suggest no relationship between transgenic protein levels and the increased tolerance phenotype.

Cucurbits (Cucurbitaceae; Cucumis spp., Cucurbita spp., Citrullus spp.)

“…These transgenic cucumber strains have been further characterized by Ishimoto et al (2002), Koga-Ban et al (2004). Szwacka et al (2002) produced transgenic cucumber plants with stable integrated constructs consisting of the cauliflower mosaic virus 35S promoter and thaumatin II cDNA, which codes for a unique protein with a sweet flavor. Inter-and intra-transformant variability in the expression of the thaumatin II gene was observed.…”

The effect of transgenic cucumbers expressing thaumatin on selected immunity parameters in rats

“…Introduction of the gene controlling the synthesis of a sweet protein, thaumatin (Szwacka et al, 2000), may considerably affect the diversification and feed use of plants. Synthesis of new protein may reveal allergenic or immunogenic activity and have unknown biological activities.…”

Evaluation of the possibility of horizontal gene transfer and accumulation of transgenic DNA from the diet in the bodies of rats

“…Transgenic plants (generation T2 of the independent transgenic line 224 09), the fruits of which were used, possessed insert T-DNA with 2 chimerical genes: 35S-cDNA of the preprothaumatin gene (gene of sweet protein derived from Thaumatococccus daniellii Benth.) and nos-nptII, expressing resistance to antibiotics from the neomycin group (expression of neomycin phosphotransferase) (Szwacka et al, 2002). Transformation of cucumber using Agrobacterium tumefaciens was conducted at the Department of Plant Genetics, Breeding and Biotechnology of Warsaw University of Life Sciences (Szwacka et al, 1996).…”

“…Protein extraction from cucumber fruit probes and animal material as well as immuno-analysis were performed as described by Szwacka et al (2002). Protein extracts were fractionated on SDS-PAGE and subjected to immunoblot analysis using specific anti-thaumatin rabbit polyclonal antibodies (Kucharczyk) and anti-rabbit IgG goat antibodies conjugated with alkaline phosphatase (Roche).…”