# Molecular Genetic Research and Genetic Engineering of _Taraxaxacum kok-saghyz_ [PERSON]
## 3 Rubber Biosynthesis Genes
Phylogenetic analysis showed that all four _CPT_ genes of type I in the assembled TKS genome were located in the group 1, which also contains genes for three _T. brevicorniculatum CPTs_, two _L. sativa CPTs_, and two _H. brasiliensisis CPTs_, suggesting the importance of this group for rubber biosynthesis. It has been shown that the _TKCPT1_ and _TKCPT2_ genes are predominantly expressed in latex. One _TkREF_ gene and nine _TKSRPP_ genes have also been found in the TKS genome. The next genome-wide analysis also showed that TKS has nine SRPP genes (_TKSRPP1-9_) and one REF gene (_TKREF1_) [55]. All proteins of the TkSRPP family were predicted to have a cytoplasmic location, while the TkREF1 protein was predicted to have a transmembrane domain. Based on the results of phylogenetic analysis of the _SRPP_/_REF_ genes of TKS and other plants, five subgroups were identified. Proteins of the TkSRPP/REF family were distributed into four of five subgroups, with most of them belonging to subgroups III and IV, as well as in _L. sativa_, while in _H. brasiliensis_ only a few proteins of this family belonged to subgroups III and IV. The promoters of the _TKSRPP_/_REF_ genes have been predicted to contain many _cis_-elements sensitive to hormones and abiotic stress. The authors also experimentally proved that treatment with methyl jasmonate (MeJA) increases the expression levels of the _TKSRPP3-4_ and _TKREF1_ genes. It was previously reported that the _TKSRPP2_ gene was cloned, its localization in the cytoplasm was shown, and its high expression was found in 6-month-old TKS roots [56]. The ontogenesis of rubber particles most likely proceeds similarly to secretory protein pathways, including the rough endoplasmic reticulum and the Golgi apparatus. Indeed, using _H. brasiliensis_ as an example, it has been shown that REFs, SRPPs, soluble CPTs, and bridging proteins (HRBP or CBP) are associated with the endoplasmic reticulum. The biosynthesis of NR occurs in the latex (the cytoplasm of highly specialized cells, laticifers) [57]. The vacuoles appear to be the storage for mature rubber particles, but rubber biosynthesis and true particle growth take place in the cytosol. The biosynthesis of rubber is catalyzed by the rubber polymerization complex embedded in the rubber particle membrane and cannot take place inside the vacuole [9]. Another way to elucidate the biological functions of rubber biosynthesis genes can be to study the tissue-specific and inducible expression of their promoters. For this purpose, the promoter sequence of the geranylgeranyl pyrophosphate synthase (GGPPS) gene was cloned from TKS in the pCAMBIA1304 binary vector with the _GFP_ reporter gene. The functionality of the resulting vector was proven on cells of the onion epidermis. It was planned to use this construct to study tissue-specific and inducible expression of the _GGPPS_ gene and hence the biosynthesis of rubber [58]. For an analysis of the _TKSRPP_ gene promoter, it was fused in various deletion variants with the _GUS_ reporter gene [59]. Then, it was shown on transgenic tobacco plants that the full-length promoter is not tissue specific, but that the core part of the promoter induced reporter gene expression under the action of MeJA, abscisic acid (ABA), and salicylic acid (SA), as well as wounds. Figure 2: The pathway of natural rubber, 2-C-methyl-D-erythritol-4 phosphate (MEP) and mevalonate (MVA) in _Taraxacum kok-saghyz_.