Removal of feedback inhibition of Δ1-pyrroline-5-carboxylate synthetase results in increased proline accumulation and protection of plants from osmotic stress
Removal of feedback inhibition of Δ1-pyrroline-5-carboxylate synthetase results in increased proline accumulation and protection of plants from osmotic stress
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DOI：
10.1104/pp.122.4.1129
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发表时间：
2000-04-01
期刊：
影响因子：
7.4
通讯作者：
Verma, DPS
中科院分区：
文献类型：
--
作者：
Hong, ZL;Lakkineni, K;Verma, DPS
δ（1）-吡咯啉-5-羧酸合成酶（P5CS; EC未指定）是植物脯氨酸（Pro）生物合成的限速酶，受Pro的反馈抑制。已经表明，在胁迫条件下，植物中P5CS的反馈调节丧失。我们比较了转基因烟草（烟草）植物表达的野生型形式的豇豆aconitifolia P5CS和突变形式的酶（P5CSF129A），其反馈抑制Pro的定点突变被删除的Pro水平。表达P5CSF129A的转基因植物比表达乌头叶野生型P5CS的植物积累约2倍的Pro。这种差异在用200 mM NaCl处理的植物中进一步增加。这些结果表明，在正常和胁迫条件下，P5CS的反馈调节在控制植物中Pro水平方面起作用。升高的Pro还降低了响应于渗透胁迫的自由基水平，如通过丙二醛产生所测量的，并且显著提高了转基因幼苗在含有高达200 mM NaCl的培养基中生长的能力。这些研究结果揭示了新的光在植物中的Pro生物合成的调节和Pro在减少渗透胁迫诱导的氧化胁迫的作用，除了其公认的作用作为渗透调节剂。
The Delta(1)-pyrroline-5-carboxylate synthetase (P5CS; EC not assigned) is the rate-limiting enzyme in proline (Pro) biosynthesis in plants and is subject to feedback inhibition by Pro. It has been suggested that the feedback regulation of P5CS is lost in plants under stress conditions. We compared Pro levels in transgenic tobacco (Nicotiana tabacum) plants expressing a wild-type form of Vigna aconitifolia P5CS and a mutated form of the enzyme (P5CSF129A) whose feedback inhibition by Pro was removed by site-directed mutagenesis. Transgenic plants expressing P5CSF129A accumulated about 2-fold more Pro than the plants expressing V. aconitifolia wild-type P5CS. This difference was further increased in plants treated with 200 mM NaCl. These results demonstrated that the feedback regulation of P5CS plays a role in controlling the level of Pro in plants under both normal and stress conditions. The elevated Pro also reduced free radical levels in response to osmotic stress, as measured by malondialdehyde production, and significantly improved the ability of the transgenic seedlings to grow in medium containing up to 200 mM NaCl. These findings shed new light on the regulation of Pro biosynthesis in plants and the role of Pro in reducing oxidative stress induced by osmotic stress, in addition to its accepted role as an osmolyte.