Abstract
Ethylene is a stimulant to increase natural rubber latex. After ethylene application, both fresh yield and dry matter of latex are substantially improved. Moreover, we found that ethylene improves the generation of small rubber particles. However, most genes involved in rubber biosynthesis are inhibited by exogenous ethylene. Therefore, we conducted a proteomics analysis of ethylene-stimulated rubber latex, and identified 287 abundant proteins as well as 143 ethylene responsive latex proteins (ERLPs) with mass spectrometry from the 2-DE and DIGE gels, respectively. In addition, more than 1,600 proteins, including 404 ERLPs, were identified by iTRAQ. Functional classification of ERLPs revealed that enzymes involved in post-translational modification, carbohydrate metabolism, hydrolase activity, and kinase activity were overrepresented. Some enzymes for rubber particle aggregation were inhibited to prolong latex flow, and thus finally improved latex production. Phosphoproteomics analysis identified 59 differential phosphoproteins; notably, specific isoforms of rubber elongation factor and small rubber particle protein that were phosphorylated mainly at serine residues. This post-translational modification and isoform-specific phosphorylation might be important for ethylene-stimulated latex production. These results not only deepen our understanding of the rubber latex proteome but also provide new insights into the use of ethylene to stimulate rubber latex production.
Highlights
It has long been known that ethylene stimulates natural rubber production, many genes involved in natural rubber biosynthesis are not induced upon treatment with ethephon[1]
We considered whether the regulation of rubber latex production by ethylene stimulation might occur not solely at the gene level and at the protein level, with post-translational modifications (PTMs) playing crucial roles in controlling the final function of enzymes involved in rubber biosynthesis
DdH2O-treated plants exhibited a significant increase in latex (Fig. 1a), which were attributed to the mechanical effects of wounding caused by tapping[15]
Summary
It has long been known that ethylene stimulates natural rubber production, many genes involved in natural rubber biosynthesis are not induced upon treatment with ethephon[1]. The treatment of rubber tree bark with ethephon induces fresh latex production and stimulates latex regeneration between tappings[3,6]. This stimulation is associated with obvious changes in both the physiology and metabolism of laticifers[6]. In the first reported accelerative effect of ethephon on rubber biosynthesis, HMGS gene expression and enzyme activity were significantly enhanced upon the addition of ethylene[11]
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