Ethylene-Enhanced Latex Proteome Is Involved in Stimulation of Natural Rubber Production in the Hevea Rubber Tree

The Hevea brasiliensis is the only commercial source of natural rubber. In natural rubber production, exogenous ethylene is widely used as a stimulant for increasing rubber latex yield. To reveal the potential regulation mechanisms for ethylene stimulation of natural rubber production in H. brasiliensis, we performed an integrative analysis of transcriptomics and proteomics for ethylene-stimulated rubber latex. A total of 35,306 genes and 3620 proteins were successfully identified from the different latex samples upon ethylene stimulation. Gene Ontology analysis revealed that these genes are mainly involved in cytoplasm and cytoplasmic and catalytic activity. Kyoto Encyclopedia of Genes and Genomes analysis demonstrated that their pathways are mainly enriched in alanine and glutamate metabolism, carbon metabolism, and carbon fixation. Ethylene stimulation played a key regulatory role at the translational/post-translational modification level to promote natural rubber synthesis. Notably, 64 genes and 35 proteins are directly involved in natural rubber biosynthesis. Among them, several family members of 3-hydroxy-3-methylglutaryl coenzyme A reductase, small rubber particle protein, and cis-prenyl transferase (CPT) are ethylene-responsive ones. It is noteworthy that accumulation of CPT7 was significantly increased after ethylene application. Overexpression of HbCPT7 in a rubber-producing model plant, Taraxacum Kok-saghyz, resulted in a significant increase in rubber content in the transgenic Taraxacum Kok-saghyz roots.