Abstract
Rubber tree is a major commercial source of natural rubber. Latex coagulation is delayed by thiols, which belong to the important type of antioxidants in laticifer submembrane, and is composed of glutathione (GSH), cysteine, and methionine. The rate-limiting enzyme, γ-ECS, plays an important role in regulating the biosynthesis of glutathione under any environment conditions. To understand the relation between γ-ECS and thiols and to correlate latex flow with one-time tapping and continuous tapping, we cloned and derived the full length of one γ-ECS from rubber tree latex (Hbγ-ECS1). According to qPCR analysis, the expression levels of Hbγ-ECS1 were induced by tapping and Ethrel stimulation, and the expression was related to thiols content in the latex. Continuous tapping induced injury, and the expression of HbγECS1 increased with routine tapping and Ethrel-stimulation tapping (more intensive tapping). According to expression in long-term flowing latex, the gene was related to the duration of latex flow. HbγECS1 was expressed in E. coli Rosetta using pET-sumo as an expression vector and the recombinant enzyme was purified; then we achieved 0.827 U/mg specific activity and about 66 kDa molecular weight. The present study can help us understand the complex role of Hbγ-ECS in thiols biosynthesis, which is influenced by tapping.
Highlights
Rubber tree (Hevea brasiliensis) is a major commercial source of natural rubber [1]
Thiols are primarily associated with the redox potential of latex; GSH accounts for a major proportion of thiols in latex of rubber tree
The TargetP and the ChloroP software predicted the presence of a putative transit peptide of 74 amino acids in the Hbγ-ECS1 putative protein sequence of chloroplast
Summary
Rubber tree (Hevea brasiliensis) is a major commercial source of natural rubber [1]. The duration of the latex flow must be restricted to control the latex yield. Thiols, which can delay coagulation of latex, belong to the important type of antioxidants which act in the laticifer submembrane; thiols are closely related to the duration of latex flow. Glutathione (GSH), cysteine, and methionine form thiols in the latex of Hevea brasiliensis [4]. The total thiol groups expressed in cytosol amounted to 2.2 ± 0.5 mM [6]; in the latex, the concentration of thiol-related cytosol is about 0.5–0.9 mM [4]. Thiols are primarily associated with the redox potential of latex; GSH accounts for a major proportion of thiols in latex of rubber tree
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