# Biosynthesis of Natural Rubber: Current State and Perspectives
## 3 Omics Analyses Provide New Insights into Natural Rubber Biosynthesis
### Genome Analysis
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Species** & **Chromosome** & **Assembly Length/** & **Predicted Gene Number** & **BioProject/Accession No.** & **Ref.** \\ \hline _Héeu brasiliensis_ & & & 68955 & GenBank: & \\ RRIM 600 & 2N = 2X = 36 & 1.1 Gb/2.15 Gb & 8 CPTs, 10 SERPs, 12 REFs & AlJZ01000000 & [91] \\ \hline _Héeu brasiliensis_ & & & 43792 & & \\ Reyan 7-3-97 & & & 11 CPHs, 8 REFs, 10 SERPs & \begin{tabular}{c}GenBank: \\ LVX001000000 \\ \end{tabular} & [92] \\ \hline _Héeu brasiliensis_ & & & 84440 & GenBank: & \\ RRIM 600 & 2N = 2X = 36 & 1.55 Gb/2.15 Gb & 7 CPTs, 1 CPTL, 9 REFs, 8 SRPs & PRJB4387 & [22] \\ \hline _Tanaxecum kok-seqhyz_ & & & 46731 & & \\ line 1151 & & & 9 CPTs, 2 CPTLs, 1 REF, 9 SRPs & \begin{tabular}{c} Genome Warehouse: \\ PBICA000437 \\ GWHAAAA0000000 \\ \end{tabular} & [11] \\ \hline _Euacomnia ulmoides_ & & & & 26723 & & \\ a wild _E. ulmoides_ & 2N = 2X = 34 & 1.2 Gb/1.1 Gb & 26723 & \
\begin{tabular}{c} Genome Warehouse: \\ PBICA000677 \\ GWHAAAL0000000 \\ \end{tabular} & [5] \\ tree in Shennongia & & & 5 FPSs, 5 REFs, 7 SRPs &
\begin{tabular}{c} GWHAAAL0000000 \\ \end{tabular} & [5] \\ \hline CPT, _cis_-preynyltransferase; CPTL, CPT-Like protein; FPS, Famesyl diphosphate synthase; REF, rubber elongation factor; SRPP, small rubber particle protein. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of genome assembly of the main rubber-producing plants. genes involved in stress responses and biosynthesis of secondary metabolites which were supposed to account for disease resistance and environmental adaptability. Five _EuFPSs_ were identified in the genome. Conserved domain and phylogenetic analysis, gene expression patterns and heterogenous overexpression suggested EuFPS1, 3, and 5 may be responsible for _trans_-polyisoprene biosynthesis in _E. ulmoides_. The coordinated expression patterns of _EuSRPP1_, 2, and 7 with the accumulation of Eu-rubber implied that they might play critical roles in Eu-rubber biosynthesis and stabilizing the rubber particle membrane in _E. ulmoides_[5]. Their results also showed that _EuFPS_ and _EuREF_/_EuSRPP_ gene families were expanded independently from the _H. brasiliensis_ lineage, indicating the polyphyletic origin of polyisoprene biosynthesis in eudicots [5; 89]. [PERSON] et al. reported the genome sequencing and assembly for _T. kok-saghyz_ [PERSON] which has a length of 1.29 Gb and contains 46,731 predicted genes [11]. The comparative studies of _T. kok-saghyz_ with the non-rubber-producing plant Globe artichoke and the rubber-producing plant _H. brasiliensis_ showed that the gene number is similar for enzymes in the MEP pathway and rubber initiator synthesis, but differs in the MVA pathway and rubber elongation, suggesting the MVA pathway and rubber elongation-related genes might be more important for rubber biosynthesis in _T. kok-saghyz_[11]. Only one _TkREF_ was found in the _T. kok-saghyz_ genome and TkREF/TkRPPs clustered into a clade that were different from the HbREFs/HbSRPPs clade, implying genetic divergence and different mechanisms were involved in rubber biosynthesis between the two species. So far, there has been no draft genome report about _P. argentatum_, due to its complex natural ploidy series [103; 104].