Abstract
‘Isabel’ grape (Vitis labrusca x V. vinifera L. hybrid) is one of the main grape cultivars in Russia and some other countries for processing, due to its vigor, tolerance to the main fungal diseases, high yield and potential for sugar accumulation. The stilbene synthase gene VlvSTS was isolated from the hybrid grape cv. Isabel and cloned into a pSS plant transformation vector under the control of a constitutive 35S RNA double promoter of the cauliflower mosaic virus, CaMV 35SS. VlvSTS-gene containing transgenic tobacco lines were obtained and analyzed. For the first time plants expressing the VlvSTS gene were shown to have an enhanced resistance to the bacterial pathogen Erwinia carotovora subsp. carotovora B15. Transgenic plants were tested for resistance to a number of fungal pathogens. The plants were resistant to the grey mould fungus Botrytis cinerea, but not to the fungi Fusarium oxysporum, F. sporotrichioides, or F. culmorum. According to the results of a high performance liquid chromatography-mass spectrometry analysis, the amount of trans-resveratrol in leaves of transgenic plants with the highest expression of the VlvSTS gene was in a range from 150 to 170 μg/g of raw biomass. Change in the color and a decreased anthocyanin content in the flower corollas of transgenic plants were observed in transgenic lines with the highest expression of VlvSTS. A decrease in total flavonoid content was found in the flower petals but not the leaves of these tobacco lines. High expression of the VlvSTS gene influenced pollen development and seed productivity in transgenic plants. The size of pollen grains increased, while their total number per anther decreased. A decrease in the number of fertile pollen grains resulted in a decreased average weight of a seed boll in transgenic plants.
Highlights
Creation of pathogen-resistant plants relies on a number of strategies
We were the first to show that transgenic tobacco plants carrying the VlvSTS gene had a significantly larger pollen grain size and a smaller number of pollen grains per anther
The number of fertile pollen grains decreased, especially in the plant line with the highest expression of the VlvSTS gene. These changes resulted in a decreased weight of seed bolls in the transgenic tobacco lines
Summary
Creation of pathogen-resistant plants relies on a number of strategies. One of them is to develop plants capable of synthesizing low-molecular antimicrobial compounds, phytoalexins, e.g., stilbenes. It was shown that transgenic plants expressing stilbene synthase genes may have a higher resistance to pathogens. Transgenic rice plants with the grape stilbene synthase Vst gene were partially resistant to the fungus Pyricularia oryzae [2]. Transgenic tomato plants with grape stilbene synthase genes were less susceptible to the fungus Phytophthora infestans, but lacked resistance to B. cinerea and Alternaria solani [5]. The use of stilbene synthase genes from wild-type grapes V. quinquangularis and V. amurensis for Arabidopsis transformation yielded conflicting data on plant resistance to biotrophic and necrotrophic pathogens [9,10]. The dependence of the expression of genes of stilbene synthases of ‘Isabel’ grapes on infection with downey mildew Plasmopara viticola was shown [14]. The aim of our investigation was to isolate a VlvSTS stilbene synthase gene from the hybrid grape V. labrusca x V. vinifera L. and obtain transgenic tobacco plants overex-. We tested the TL lines for resistance to the funga
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