CRISPR-Cas Genome Editing for Horticultural Crops Improvement: Advantages and Prospects

Horticultural plants, in particular fruit trees, berry crops, and ornamentals, are valuable objects for studying their genetic and biochemical properties. Along with traditional methods of studying these plants, modern molecular genetic technologies are emerging, in particular genome editing using CRISPR/Cas9 nucleases. In this review, we have analyzed modern advances in genome editing of horticultural plants. To date, it has become possible to improve many plant characteristics using this technology, e.g., making plants resistant to biotic and abiotic stress factors, changing the time of flowering and fruit ripening, changing the growth characteristics of plants, as well as the taste properties of their fruits. CRISPR/Cas9 genome editing has been successfully carried out for many horticultural plants. Dozens of genes from these plants have been modified by means of genome editing technology. We have considered the main ways of delivering genetic constructs to plants as well as limitations that complicate the editing of target genes. The article reviews the prospects of using genome editing to improve the valuable properties of plants important to humans

Auxin synthesis gene tms1 driven by tuber-specific promoter alters hormonal status of transgenic potato plants and their responses to exogenous phytohormones

Key message: Ectopic auxin overproduction in transgenic potato leads to enhanced productivity accompanied with concerted and occasional changes in hormonal status, and causing altered response of transformants to exogenous auxin or cytokinin.Abstract: Previously, we generated potato transformants expressing Agrobacterium-derived auxin synthesis gene tms1 driven by tuber-specific patatin gene promoter (B33-promoter). Here, we studied the endogenous hormonal status and the response to exogenous phytohormones in tms1 transformants cultured in vitro. Adding indole-3-acetic acid (IAA) or kinetin to culture medium affected differently tuberization of tms1-transformed and control plants, depending also on sucrose content in the medium. Exogenous phytohormones ceased to stimulate the tuber initiation in transformants at high (5–8%) sucrose concentration, while in control plants the stimulation was observed in all experimental settings. Furthermore, exogenous auxin partly inhibited the tuber initiation, and exogenous cytokinin reduced the average tuber weight in most transformants at high sucrose content. The elevated auxin level in tubers of the transformants was accompanied with a decrease in content of cytokinin bases and their ribosides in tubers and most shoots. No concerted changes in contents of abscisic, jasmonic, salicylic acids and gibberellins in tubers were detected. The data on hormonal status indicated that the enhanced productivity of tms1 transformants was due to auxin and not mediated by other phytohormones. In addition, exogenous cytokinin was shown to upregulate the expression of genes encoding orthologs of auxin receptors. Overall, the results showed that tms1 expression and local increase in IAA level in transformants affect both the balance of endogenous cytokinins and the dynamics of tuberization in response to exogenous hormones (auxin, cytokinin), the latter reaction depending also on the carbohydrate supply. We introduce a basic model for the hormonal network controlling tuberization

Expression of a Stilbene Synthase Gene from the Vitis labrusca x Vitis vinifera L. Hybrid Increases the Resistance of Transgenic Nicotiana tabacum L. Plants to Erwinia carotovora

‘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