# Advances in Genome Sequencing and Natural Rubber Biosynthesis in Rubber-Producing Plants
## 5 Conclusions and Perspectives  
Although rubber trees face various challenges, such as long breeding cycles, narrow genetic diversity, limited planting areas, rising labor costs of harvesting, and the threat of South American leaf blight, they remain presently almost the sole commercial source of natural rubber [10; 11; 12; 70; 71]. In recent years, there has been a significant acceleration in the genome sequencing of rubber trees, resulting in the release of high-quality genome assemblies from a number of cultivars and wild germplasm [23; 24; 25; 26]. As a result, genome sequencing research in rubber trees has reached a cutting-edge level. Meanwhile, genome research has advanced the studies of population genetics in rubber trees, such as parental mapping populations and genome-wide association study (GWAS) populations, and led to notable research breakthroughs. The complete genome sequences also provide a solid foundation for identifying various genes associated with rubber biosynthesis. Subsequently, a series of core catalytic enzymes and regulatory genes related to rubber biosynthesis were identified in latex and thereby enhanced our understanding of the rubber biosynthesis process. However, the genetic transformation of the rubber tree remains a significant challenge, rendering it a less-than-ideal candidate for investigating the underlying regulatory mechanisms of rubber production.  
Several alternative rubber-producing plants, including _T. koksaghyz, L. sativa_, and _P. argentatum_, are being developed to address the problems faced by rubber trees and to expand sources of natural rubber. Genetic transformation systems have been established in these plants, with each having its own advantages in natural rubber production. Interestingly, these plants share nearly identical rubber-producing pathways as rubber trees and retain the homologs of reported rubber transferase complex components, such as _CPT_, _CPTL_, _REF_, and _SRPP_. The overexpression and knock-out of these genes in alternative rubber-producing plants have demonstrated their critical roles in rubber transferase activity and rubber biosynthesis. However, in vitro rubber biosynthesis experiments have shown that the combination of all these proteins lacks rubber transferase activity, suggesting that unknown essential components of the rubber transferase complex remain to be identified. Therefore, the identification of new components of the rubber transferase complex is crucial to gaining deeper insight into the process of rubber biosynthesis. In addition, rubber transferase complex members tend to exhibit specific high expression levels. Furthermore, the transcription factors and other regulatory components responsible for the predominant expression of the rubber transferase complex in rubber-producing laticifer cells or parenchyma cells have been poorly understood. We believe that identifying new components of the rubber transferase complex and their regulatory factors will contribute to both the understating of rubber production in alternative rubber-producing plants and the molecular breeding of high-yielding rubber clones.  
[PERSON] and [PERSON] wrote the manuscript; [PERSON] and [PERSON] drew the figures; [PERSON] revised the manuscript. All authors have reviewed and approved the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China (Grant Nos. 32101543, 32160383, 32201450, and 31825007), the Yunnan Academician and Expert Workstation Project (202105 AF150017), and the Starting Research Fund of Hainan University.  
Not applicable.  
We would like to thank the staff in the Laboratory of Rubber Production Biology at Hainan University for their technical assistance.