# Molecular Genetic Research and Genetic Engineering of _Taraxaxacum kok-saghyz_ [PERSON]
## 4 Genes for Inulin Biosynthesis and Other Genes  
In addition to rubber, inulin (Figure 1B) is also a valuable metabolite of TKS. Therefore, it is not surprising that the genes of the biosynthesis of this polymer in TKS are also already well known. Inulin synthesis in plants is regulated by several fructosyltransferases, of which the most important are sucrose:sucrose-1-fructosyltransferase (1-SST) and fructan:fructan-1-fructosyltransferase (1-FFT) (Figure 3). Inulin cleavage is catalyzed by fructan-1-exohydrolase (1-FEH1), which sequentially hydrolyzes terminal fructose residues from fructan molecules (Figure 3). The highest level of expression of the three main inulin biosynthesis genes (_1-SST_, _1-FFT_, and _1-FEH1_) is found in the roots of TKS, compared with other organs. The addition of low concentrations of naphthalene acid to the nutrient medium stimulates inulin biosynthesis in suspension cultures of TKS due to a positive effect on the expression level of the _1-SST_ and _1-FFT_ genes [61]. It is known that, in dandelions, excess free sugars (fructose and sucrose), which are formed during the degradation of inulin, can be used to synthesize IPP, which increases the production of polyisoprene. Even Soviet researchers have shown that wild-growing TKS is able to accumulate rubber in greater quantities when the level of inulin decreases [62]. Similar data, on the other hand, were shown in studies by [PERSON] et al. [52] using the example of TB, which accumulated more inulin due to inhibition of the activity of the enzyme CPT (which catalyzes polyisoprene chain elongation), which ultimately led to a decrease in rubber content. It was also shown that overexpression of the _1-FEH1_ gene in transgenic TKS and TB led to a twofold increase in the rubber content in the roots of these plants [63]. CRISPR/Cas9 editing of the TKS genome, during which the _1-FFT_ gene is knocked out, may also lead to an increase in rubber content [39]. Obviously, the pathways of rubber and inulin biosynthesis in dandelion roots are in antagonistic relationships, primarily due to competition for the same photoaessimates. Moreover, the degradation of inulin is considered the main source of the formation of new acetyl-CoA, which, in turn, is used to produce MVA and polyisoprene [63]. That is why many studies of inulin biosynthesis genes are carried out in the context of their influence on rubber biosynthesis. For example, a comparative analysis of the transcriptomes of TKS lines with increased (HR) and decreased (LR) rubber accumulation showed that there was no difference between these lines in the level of expression of the _1-FEH1_ gene. However, in HR lines, an increase in the content of transcripts of the gene encoding sucrose-1-fructosyltransferase (_1-SST_) was found, while the expression level of the fructan-1-fructosyltransferase (_1-FFT_) gene in these plants was suppressed [31]. Figure 3: Biosynthesis of inulin in _Taraxacum kok-saghyz_. 1-SST—sucrose:sucrose-1-fructosyltransferase; 1-FFT—fructan:fructan-1-fructosyltransferase; 1-FEH1—fructan-1-exohydrolase. Taken from [61]. After the full genome annotation of TKS, genome-wide studies of entire gene families were begun, which are very useful for future work on the genetic engineering of this plant. For example, in _T. kok-saghyz_, _22 TKSWEET_ genes coding for sugar transporter proteins were identified by a search for homologues using bioinformatic approaches. Using RNA-seq and qRT-PCR methods, it was shown that all these genes have overlapping yet still different expression patterns in different plant tissues. In the latex of rubber-bearing dandelions, the _TKSWEET1_ and _TKSWEET12_ genes were primarily expressed and their protein products were localized on the plasma membrane [64]. On yeast mutants, when studying heterologous expression, it was proven that only TkSWEET1 exhibited sugar transporter activity, with a preference for monosaccharides. Studies on the transcription factor _WRKY_ genes were also started and, in TKS, _72 WRKY_ genes were identified.