The Arabidopsis-accelerated cell death gene ACD1 is involved in oxygenation of pheophorbide a:: Inhibition of the pheophorbide a oxygenase activity does not lead to the "Stay-Green" phenotype in Arabidopsis
The Arabidopsis-accelerated cell death gene ACD1 is involved in oxygenation of pheophorbide a:: Inhibition of the pheophorbide a oxygenase activity does not lead to the "Stay-Green" phenotype in Arabidopsis
复制标题
DOI：
10.1093/pcp/pcg172
复制
发表时间：
2003-12-01
影响因子：
4.9
通讯作者：
Tanaka, A
中科院分区：
文献类型：
--
作者：
Tanaka, R;Hirashima, M;Tanaka, A
脱镁叶绿酸a的氧化是叶绿素分解的关键步骤。一些生化研究表明，这一步骤是由含铁和铁氧还蛋白依赖性单加氧酶，脱镁叶绿酸a加氧酶（PaO）催化的。已经提出，抑制其活性阻止叶绿素分解并导致“持绿”表型。我们搜索了拟南芥基因组中可能的PaO编码基因，并假设它与已知的含铁Rieske型单加氧酶序列具有同源性。我们鉴定了三个这样的开放阅读框架，Tic 55，ACD 1和ACD 1-Like。我们生产了表达反义RNA的转基因拟南芥植物作为抑制这些基因表达的方法。在光照下，这些反义植物的外观与野生型的外观无法区分。然而，在黑暗下保持5 d并再次光照后，反义ACD 1植物（AsACD 1）的叶片变白。AsACD 1的叶片积累了387 nmol（g FW）（-1）脱镁叶绿酸a，相当于叶绿素a降解的60%。衰老AsACD 1叶片中叶绿素a的下降速率不受影响。这些结果表明，ACD 1参与PaO活性，其抑制导致细胞的光氧化破坏，而不是“保持绿色”表型。
Oxygenation of pheophorbide a is a key step in chlorophyll breakdown. Several biochemical studies have implicated that this step was catalyzed by an iron-containing and ferredoxin-dependent monooxygenase, pheophorbide a oxygenase (PaO). It has been proposed that inhibition of its activity arrests the chlorophyll breakdown and leads to the "stay-green" phenotype. We searched the Arabidopsis genome for a possible PaO-encoding gene and hypothesized that it has homology to known iron-containing Rieske-type monooxygenase sequences. We identified three such open reading frames, Tic55, ACD1 and ACD1-Iike. We produced transgenic Arabidopsis plants which expressed antisense RNA as a method to inhibit the expression of these genes. The appearance of these antisense plants were indistinguishable from that of the wild type under illumination. However, after they were kept under darkness for 5 d and again illuminated, the leaves of the antisense ACD1 plants (AsACD1) were bleached. Leaves of AsACD1 accumulated 387 nmol (g FW)(-1) pheophorbide a which corresponded to 60% of chlorophyll a degraded. The rate of decrease in chlorophyll a was not influenced in senesced AsACD1 leaves. These results demonstrated that ACD1 is involved in PaO activity, and its inhibition led to photooxidative destruction of the cell instead of the "stay-green" phenotype.