Cloning and Expression Analysis of One Gamma-Glutamylcysteine Synthetase Gene (Hbγ-ECS1) in Latex Production in Hevea brasiliensis

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 betweenγ-ECS and thiols and to correlate latex flow with one-time tapping and continuous tapping, we cloned and derived the full length of oneγ-ECS from rubber tree latex (Hbγ-ECS1). According to qPCR analysis, the expression levels ofHbγ-ECS1were induced by tapping and Ethrel stimulation, and the expression was related to thiols content in the latex. Continuous tapping induced injury, and the expression ofHbγECS1increased 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.HbγECS1was expressed inE. coliRosetta 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 ofHbγ-ECSin thiols biosynthesis, which is influenced by tapping.