Kishor PBK., Hong Z., Miao G. H., Hu CAA., Verma DPS.
Department of Molecular Genetics and Plant Biotechnology Center, The Ohio State University, 1060 Carmack Road, Columbus, Ohio 43210-1002.
Plant Physiol. 1995 Aug;108(4):1387-1394. doi: 10.1104/pp.108.4.1387.
Proline (Pro) accumulation has been correlated with tolerance to drought and salinity stresses in plants. Therefore, overproduction of Pro in plants may lead to increased tolerance against these abiotic stresses. To test this possibility, we overexpressed in tobacco the mothbean [delta]-pyrroline-5-carboxylate synthetase, a bifunctional enzyme able to catalyze the conversion of glutamate to [delta]-pyrroline-5-carboxylate, which is then reduced to Pro. The transgenic plants produced a high level of the enzyme and synthesized 10- to 18-fold more Pro than control plants. These results suggest that activity of the first enzyme of the pathway is the rate-limiting factor in Pro synthesis. Exogenous supply of nitrogen further enhanced Pro production. The osmotic potentials of leaf sap from transgenic plants were less decreased under water-stress conditions compared to those of control plants. Overproduction of Pro also enhanced root biomass and flower development in transgenic plants under drought-stress conditions. These data demonstrated that Pro acts as an osmoprotectant and that overproduction of Pro results in the increased tolerance to osmotic stress in plants.
脯氨酸（Pro）积累与植物对干旱和盐胁迫的耐受性相关。因此，植物中脯氨酸的过量产生可能导致对这些非生物胁迫的耐受性增强。为了验证这种可能性，我们在烟草中过表达了蛾豆Δ-吡咯啉-5-羧酸合成酶，这是一种双功能酶，能够催化谷氨酸转化为Δ-吡咯啉-5-羧酸，然后再还原为脯氨酸。转基因植物产生了高水平的该酶，并且合成的脯氨酸比对照植物多10至18倍。这些结果表明该途径中第一种酶的活性是脯氨酸合成的限速因子。外源供应氮进一步提高了脯氨酸的产量。与对照植物相比，在水分胁迫条件下转基因植物叶汁的渗透势降低得较少。脯氨酸的过量产生还增强了干旱胁迫条件下转基因植物的根生物量和花发育。这些数据表明脯氨酸作为一种渗透保护剂，脯氨酸的过量产生导致植物对渗透胁迫的耐受性增强。
