Li Z H, Matthews P D, Burr B, Wurtzel E T
Department of Biological Sciences, Lehman College, The City University of New York, West Bronx, NY 10468, USA.
Plant Mol Biol. 1996 Jan;30(2):269-79. doi: 10.1007/BF00020113.
To study regulation of the plastid-localized maize carotenoid biosynthetic pathway, a cDNA encoding phytoene desaturase (PDS) was isolated and characterized. The DNA sequence of the maize Pds cDNA was determined and compared with available dicot Pds genes. The deduced PDS protein, estimated at 64.1 kDa (unprocessed), had a dinucleotide binding domain and conserved regions characteristic of other carotene desaturases. Alignment of available PDS sequences from distantly related organisms suggests that Pds has potential as a phylogenetic tool. By use of heterologous complementation in Escherichia coli, maize PDS was shown to catalyze two desaturation steps converting phytoene to zeta-carotene. RFLP (restriction fragment length polymorphism) mapping was used to place Pds on chromosome 1S near viviparous5 (vp5), and RT-PCR (reverse-transcriptase polymerase chain reaction) analysis indicated reduced Pds transcript in vp5 mutant relative to normal endosperm. Other phytoene-accumulating mutant endosperms, vp2 and white3 (w3), showed no difference in Pds transcript accumulation as compared with normal endosperm counterparts. RT-PCR analysis of Pds transcript accumulation in developing endosperm showed Pds was constitutively expressed. Therefore, endosperm carotenogensis is not regulated by increasing the level of Pds transcripts.
为了研究质体定位的玉米类胡萝卜素生物合成途径的调控，分离并鉴定了一个编码八氢番茄红素去饱和酶（PDS）的cDNA。测定了玉米Pds cDNA的DNA序列，并与现有的双子叶植物Pds基因进行了比较。推导的PDS蛋白估计为64.1 kDa（未加工），具有一个二核苷酸结合结构域和其他类胡萝卜素去饱和酶特有的保守区域。来自远缘生物的现有PDS序列比对表明，Pds有作为系统发育工具的潜力。通过在大肠杆菌中使用异源互补，表明玉米PDS催化将八氢番茄红素转化为ζ-胡萝卜素的两个去饱和步骤。利用限制性片段长度多态性（RFLP）作图将Pds定位在第1S染色体上靠近类产糊粉层5（vp5）的位置，逆转录-聚合酶链反应（RT-PCR）分析表明，与正常胚乳相比，vp5突变体中Pds转录本减少。其他积累八氢番茄红素的突变胚乳，vp2和白色3（w3），与正常胚乳对应物相比，Pds转录本积累没有差异。对发育中的胚乳中Pds转录本积累的RT-PCR分析表明，Pds是组成型表达的。因此，胚乳类胡萝卜素的生成不受Pds转录本水平增加的调控。
