State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou, China; Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China.
J Integr Plant Biol. 2014 Feb;56(2):170-80. doi: 10.1111/jipb.12125. Epub 2014 Jan 8.
Mutations in the photorespiration pathway display a lethal phenotype in atmospheric air, which can be fully recovered by elevated CO2 . An exception is that mutants of peroxisomal hydroxypyruvate reductase (HPR1) do not have this phenotype, indicating the presence of cytosolic bypass in the photorespiration pathway. In this study, we constructed overexpression of the OsHPR1 gene and RNA interference plants of OsHPR1 and OsHPR2 genes in rice (Oryza sativa L. cv. Zhonghua 11). Results from reverse transcription-polymerase chain reaction (RT-PCR), Western blot, and enzyme assays showed that HPR1 activity changed significantly in corresponding transgenic lines without any effect on HPR2 activity, which is the same for HPR2. However, metabolite analysis and the serine glyoxylate aminotransferase (SGAT) activity assay showed that the metabolite flux of photorespiration was disturbed in RNAi lines of both HPR genes. Furthermore, HPR1 and HPR2 proteins were located to the peroxisome and cytosol, respectively, by transient expression experiment. Double mutant hpr1 × hpr2 was generated by crossing individual mutant of hpr1 and hpr2. The phenotypes of all transgenic lines were determined in ambient air and CO2 -elevated air. The phenotype typical of photorespiration mutants was observed only where activity of both HPR1 and HPR2 were downregulated in the same line. These findings demonstrate that two hydroxypyruvate reductases encoded by OsHPR1 and OsHPR2 are involved in photorespiratory metabolism in rice.
突变体在大气空气中表现出致死表型，这种表型可以通过升高的 CO2 完全恢复。例外的是过氧化物酶体羟丙酮酸还原酶（HPR1）的突变体没有这种表型，这表明光合作用途径中存在细胞质旁路。在这项研究中，我们构建了水稻（Oryza sativa L. cv. Zhonghua 11）中 OsHPR1 基因的过表达和 OsHPR1 和 OsHPR2 基因的 RNA 干扰植株。反转录聚合酶链反应（RT-PCR）、Western blot 和酶测定结果表明，相应的转基因系中 HPR1 活性发生了显著变化，而 HPR2 活性没有任何影响，HPR2 也是如此。然而，代谢物分析和丝氨酸乙醛酸氨基转移酶（SGAT）活性测定表明，两种 HPR 基因的 RNAi 系中光合作用途径的代谢通量受到干扰。此外，通过瞬时表达实验表明，HPR1 和 HPR2 蛋白分别定位于过氧化物酶体和细胞质。通过杂交个体突变体 hpr1 和 hpr2 生成双突变体 hpr1 × hpr2。在大气空气中和 CO2 升高的空气中确定了所有转基因系的表型。只有当同一系中 HPR1 和 HPR2 的活性都下调时，才观察到光合作用突变体的典型表型。这些发现表明，由 OsHPR1 和 OsHPR2 编码的两种羟丙酮酸还原酶参与了水稻的光合作用代谢。
