Taraxacum kok-saghyz Rodin (TKS) is a promising alternative crop source for producing high-quality natural rubber (NR) and has become an ideal model plant for studying NR biosynthesis, regulation mechanisms, and production. So far, only a very limited number of functional genes related to NR biosynthesis have been identified in TKS. To achieve a systematic identification of its novel functional genes, we developed a mutant system denoted Sense/Antisense RNA Expression (SARE) and have generated more than 8,000 transgenic TKS plants. A series of mutants with altered phenotypes, particularly changes in NR contents, were identified. To evaluate the efficiency of this library, we chose one mutant, c112, which exhibits a significant increase in NR content, for in-depth characterization. Thec112mutant arose from the sense insertion of adormancy-associated gene1(DRM1)/auxin repressed protein(ARP) gene, which we namedHigh natural Rubber Content1(HRC1). In the c112 mutant, the concentrations of NR precursors isopentenyl pyrophosphate (IPP) and dimethylallyl diphosphate (DMAPP) decreased, while geranylgeranyl diphosphate (GGPP) increased, suggesting that HRC1 regulates metabolic flux in NR biosynthesis. In summary, the developed TKS SARE mutant library provides valuable genetic resources for identifying key functional genes to accelerate the domestication of TKS from wild species to economic crops through molecular breeding.