AbhemC encoding porphobilinogen deaminase plays an important role in chlorophyll biosynthesis and function in albino Ananas comosus var. bracteatus leaves.
AbhemC encoding porphobilinogen deaminase plays an important role in chlorophyll biosynthesis and function in albino Ananas comosus var. bracteatus leaves.
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AbhemC 编码胆色素原脱氨酶，在白化 Ananas comosus var. 的叶绿素生物合成和功能中发挥重要作用。
作者：
Xue Y;Li X;Mao M;He Y;Owusu Adjei M;Zhou X;Hu H;Liu J;Li X;Ma J
背景 Ananas comosus var. 的嵌合叶。 bracteatus 由正常绿色部分 (Grs) 和白化白色部分 (Whs) 组成。尽管 A. comosus var. 白化病的潜在机制。 Bracteatus 叶子尚未完全了解，它可能与叶绿素 (Chl) 生物合成有关。在此生物合成过程中，胆色素原脱氨酶 (PBGD) 通过催化胆色素原 (PBG) 转化为尿卟啉原 III (Urogen III) 发挥着至关重要的作用。因此，本文研究了其编码基因 AbhemC 与嵌合 A. comosus var. 中叶绿素生物合成和白化病的关系。苞叶。方法测定并比较白苋菜Whs和Grs的叶绿素含量、主要叶绿素生物合成前体含量和主要酶活性。苞叶。此外，还克隆了AbhemC并分析了其转录表达和原核蛋白表达。此外，在烟草植物中产生并评估了 RNAi 介导的 AbhemC 沉默。结果Grs中的Chl a和Chl b浓度分别显着高于Whs。此外，与Grs相比，Whs中叶绿素生物合成前体尿原III的含量显着降低。因此，PBG 向 Urogen III 的转变可能是导致 A. comosus var. 嵌合叶白化病的第一个限速步骤。苞片。 AbhemC基因全长1,135 bp，编码为371个氨基酸的蛋白质；从系统发育上看，AbhemC 与菠萝的 hemC 关系最密切。原核表达及体外酶活性分析表明，克隆的AbhemC mRNA序列成功整合，并具有PBGD活性。与对照植物相比，带有pFGC5941-AbhemC-RNAi载体的转基因烟叶的绿色明显降低，hemC表达和叶绿素含量显着降低，PBGD酶活性降低，从Urogen III开始显着降低叶绿素生物合成前体的含量。我们的结果表明，hemC 表达的缺失会降低 PBGD 的酶活性，从而阻止 PBG 向 Urogen III 的转变，进而抑制叶绿素合成，导致淡绿色叶子颜色。因此，我们认为AbhemC在叶绿素合成中发挥着重要作用，并且可能是A. comosus var.白化病的重要因素。苞叶。
Background The chimeric leaves of Ananas comosus var. bracteatus are composed of normal green parts (Grs) and albino white parts (Whs). Although the underlying mechanism of albinism in A. comosus var. bracteatus leaves is not fully understood, it is likely associated with the chlorophyll (Chl) biosynthesis. In this biosynthetic process, porphobilinogen deaminase (PBGD) plays a crucial role by catalyzing the conversion of porphobilinogen (PBG) to uroporphyrinogen III (Urogen III). Therefore, its encoding gene AbhemC was investigated here in association with Chl biosynthesis and albinism in chimeric A. comosus var. bracteatus leaves. Methods The Chl content, main Chl biosynthesis precursor content, and main enzyme activity were determined and compared between the Whs and Grs of A. comosus var. bracteatus leaves. In addition, AbhemC was cloned and its transcriptional expression and prokaryotic protein expression were analyzed. Furthermore, RNAi-mediated silencing of AbhemC was produced and assessed in tobacco plants. Results The concentration of Chl a and Chl b in the Grs was significantly higher than that in the Whs, respectively. Additionally, the content of the Chl biosynthesis precursor Urogen III decreased significantly in the Whs compared with the Grs. Thus, the transition of PBG to Urogen III may be the first rate-limiting step leading to albinism in the chimeric leaves of A. comosus var. bracteatus. The gene AbhemC comprised 1,135 bp and was encoded into a protein with 371 amino acids; phylogenetically, AbhemC was most closely related to hemC of pineapple. Prokaryotic expression and in vitro enzyme activity analysis showed that the cloned mRNA sequence of AbhemC was successfully integrated and had PBGD activity. Compared with control plants, transgenic tobacco leaves with pFGC5941-AbhemC-RNAi vector were substantially less green with significantly reduced hemC expression and Chl content, as well as reduced PBGD enzyme activity and significantly decreased content of Chl biosynthesis precursors from Urogen III onwards. Our results suggest that the absence of hemC expression reduces the enzyme activity of PBGD, which blocks the transition of PBG to Urogen III, and in turn suppresses Chl synthesis leading to the pale-green leaf color. Therefore, we suggest that AbhemC plays an important role in Chl synthesis and may be an important factor in the albinism of A. comosus var. bracteatus leaves.