Siebert M, Sommer S, Li S M, Wang Z X, Severin K, Heide L
Pharmazeutisches Institut, Universität Tübingen, Germany.
Plant Physiol. 1996 Oct;112(2):811-9. doi: 10.1104/pp.112.2.811.
The ubiC gene of Escherichia coli encodes chorismate pyruvatelyase, an enzyme that converts chorismate into 4-hydroxybenzoate (4HB) and is not normally present in plants. The ubiC gene was expressed in Nicotiana tabacum L. plants under control of a constitutive plant promoter. The gene product was targeted into the plastid by fusing it to the sequence for the chloroplast transit peptide of the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Transgenic plants showed high chorismate pyruvate-lyase activity and accumulated 4HB as beta-glucosides, with the glucose attached to either the hydroxy or the carboxyl function of 4HB. The total content of 4HB glucosides was approximately 0.52% of dry weight, which exceeded the content of untransformed plants by at least a factor of 1000. Feeding experiments with [1,7-13C2]shikimic acid unequivocally proved that the 4HB that was formed in the transgenic plants was not derived from the conventional phenylpropanoid pathway but from the newly introduced chorismate pyruvate-lyase reaction.
大肠杆菌的ubiC基因编码分支酸丙酮酸裂解酶，该酶可将分支酸转化为4-羟基苯甲酸（4HB），而植物中通常不存在这种酶。ubiC基因在组成型植物启动子的控制下在烟草植株中表达。通过将该基因产物与1,5-二磷酸核酮糖羧化酶/加氧酶小亚基的叶绿体转运肽序列融合，将其靶向导入质体。转基因植物表现出较高的分支酸丙酮酸裂解酶活性，并积累了4HB的β-葡萄糖苷，葡萄糖连接在4HB的羟基或羧基上。4HB葡萄糖苷的总含量约为干重的0.52%，比未转化植株的含量至少高出1000倍。用[1,7-13C2]莽草酸进行的饲喂实验明确证明，转基因植物中形成的4HB并非来自传统的苯丙烷途径，而是来自新引入的分支酸丙酮酸裂解酶反应。
