An improved tolerance to cadmium by overexpression of two genes for cysteine synthesis in tobacco
An improved tolerance to cadmium by overexpression of two genes for cysteine synthesis in tobacco
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DOI：
10.5511/plantbiotechnology.14.0130a
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发表时间：
2014-06
影响因子：
1.6
通讯作者：
Michimi Nakamura;T. Ochiai;M. Noji;Y. Ogura;Kazuo T. Suzuki;N. Yoshimoto;M. Yamazaki;K. Saito
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文献类型：
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作者：
Michimi Nakamura;T. Ochiai;M. Noji;Y. Ogura;Kazuo T. Suzuki;N. Yoshimoto;M. Yamazaki;K. Saito
镉等重金属对土壤的污染对农业生产和人类健康造成了严重的负面影响。因此，提高对Cd的耐受性是植物生物技术面临的主要挑战之一。在本研究中，我们通过与各自的单基因转基因烟草杂交，获得了高表达丝氨酸乙酰转移酶(SAT)和半胱氨酸合成酶(CS)[O-乙酰丝氨酸(硫醇)裂解酶]的烟草转基因植株，这两种酶是半胱氨酸(Cys)生物合成的最后两步。两种酶活性均较高，表现出比野生型和单基因转基因植株更强的抗Cd胁迫能力。双基因转基因植株在Cd胁迫诱导下也表现出较高的植物螯合素(PC)产量。双基因转基因植株的游离非螯合镉含量低于野生型和单基因转基因植株。在双转基因植物中，半胱氨酸和谷氨酰半胱氨酸(γ-Glamylcysteine，γ-EC)的水平也增加了，推测这可能增强了半胱氨酸生物合成的代谢流，导致最终合成PC，通过螯合来解毒Cd。这些结果表明，SAT和CS两个基因的过表达可能是一种很有前途的抗Cd植物工程策略。
Contamination of soil by heavy metals such as Cd causes a serious negative impact on agricultural production and human health. Thus, improvement of tolerance to Cd is one of the major challenges in plant biotechnology. In the present study, we have generated transgenic Nicotiana tabacum (tobacco) plants overexpressing both serine acetyltransferase (SAT) and cysteine synthase (CS) [O-acetylserine (thiol)-lyase], which are committed in the last two steps of cysteine (Cys) biosynthesis, by crossing the respective single-gene transgenic plants. Two enzymatic activities were high in these two-gene overexpressing plants, and these plants exhibited more resistance to Cd stress than wild-type and single-gene transgenic plants. The two-gene transgenic plants also exhibited a higher production of phytochelatins (PCs) in an inducible manner by the Cd stress. The levels of free non-chelated Cd were lower in the two-gene transgenic plants than the wild-type and single-gene transformants. The levels of Cys and γ-glutamylcysteine (γ-EC) were also increased in the dual transgenic plants, presumably enhancing the metabolic flow of Cys biosynthesis leading to the ultimate synthesis of PCs which detoxify Cd by chelating. These results suggested that the overexpression of two genes, SAT and CS, could be a promising strategy for engineering Cd resistant plants.