Tao Fang, Zhu Su-Wen, Fan Jun, Cheng Bei-Jiu
Laboratory of Biophysics, Department of Life Sciences, Anhui Agricultural University, Hefei 230036, China.
Zhi Wu Sheng Li Yu Fen Zi Sheng Wu Xue Xue Bao. 2006 Dec;32(6):649-56.
Delta-12 desaturases are involved in the conversion of oleic acid to linoleic acid in plant. Based on the conserved oligo amino acid residues of the published delta-12 desaturase genes from other higher plant species, a cDNA fragment was amplified by RT-PCR (reverse transcriptase-polymerase chain reaction) from the total RNA of immature maize embryos. According to bioinformation analysis of the cDNA sequence, a specific fragment of FAD2 gene was isolated by RT-PCR from immature maize embryos, and DNA of the same length was amplified from maize genome. Results of sequence analysis indicate that they are all 1 164 bp long, and have just an open reading frame (ORF) coding for 387 amino acids, and there is no intron in the FAD2 ORF (GenBank accession DQ496227). The deduced amino acid sequence of the cloned FAD2 showed high identity to those of other plant delta-12 fatty acid desaturases. It contains three histidine motifs and two long stretches of hydrophobic residues, indicative of an integral membrane protein spanning membrane four times. Analysis by semi-quantitive RT-PCR showed that FAD2 was strongly expressed in maize immature embryos than in leaves, stems and roots.
Δ-12去饱和酶参与植物中油酸向亚油酸的转化。基于已发表的其他高等植物物种的Δ-12去饱和酶基因的保守寡氨基酸残基，通过逆转录聚合酶链反应（RT-PCR）从未成熟玉米胚的总RNA中扩增出一个cDNA片段。根据该cDNA序列的生物信息学分析，通过RT-PCR从未成熟玉米胚中分离出FAD2基因的一个特异性片段，并从玉米基因组中扩增出相同长度的DNA。序列分析结果表明，它们均长1164 bp，仅有一个编码387个氨基酸的开放阅读框（ORF），且FAD2的ORF中无内含子（GenBank登录号DQ496227）。克隆的FAD2推导氨基酸序列与其他植物的Δ-12脂肪酸去饱和酶具有高度同源性。它包含三个组氨酸基序和两段长的疏水残基，表明是一种跨膜四次的整合膜蛋白。半定量RT-PCR分析表明，FAD2在玉米未成熟胚中的表达强于叶、茎和根。
