Kodama H, Akagi H, Kusumi K, Fujimura T, Iba K
Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
Plant Mol Biol. 1997 Feb;33(3):493-502. doi: 10.1023/a:1005726210977.
The omega-3 fatty acid desaturases are membrane-bound enzymes catalyzing the conversion of linoleic acid to linolenic acid in lipids, and are located both in the microsome and plastid envelopes as two different isoforms. A cDNA encoding the microsome omega-3 fatty acid desaturase (OsFAD3) and the corresponding genomic clone were isolated from rice (Oryza sativa L.). The OsFAD3 gene was composed of 8 exons and 7 introns. A microsatellite was present in the second exon of the OsFAD3 gene, showing polymorphism between Indica and Japonica rice varieties. The mapping of this microsatellite showed that the OsFAD3 gene was located on chromosome 11. Expression of the OsFAD3 cDNA in tobacco hairy root tissues and subsequent analysis of fatty acid compositions demonstrated the activity of the microsome omega-3 fatty acid desaturase. The OsFAD3 mRNA was abundant in root tissues, but was hardly detectable in leaves. In root tissues, a high level of the OsFAD3 mRNA was observed at 15 degrees C and 20 degrees C, with its level decreasing markedly at temperatures below 10 degrees C. The accumulation of the OsFAD3 mRNA in leaf tissues remained at quite low levels, both at normal growth temperatures and at chilling temperatures. Similar temperature responses of the OsFAD3 gene were observed both in chilling- tolerant and in chilling-intolerant rice cultivars.
ω-3脂肪酸去饱和酶是膜结合酶，可催化脂质中亚油酸向亚麻酸的转化，以两种不同的同工型存在于微粒体和质体包膜中。从水稻（Oryza sativa L.）中分离出了编码微粒体ω-3脂肪酸去饱和酶（OsFAD3）的cDNA及相应的基因组克隆。OsFAD3基因由8个外显子和7个内含子组成。在OsFAD3基因的第二个外显子中存在一个微卫星，在籼稻和粳稻品种间表现出多态性。该微卫星的定位显示OsFAD3基因位于第11号染色体上。OsFAD3 cDNA在烟草毛状根组织中的表达及随后对脂肪酸组成的分析证明了微粒体ω-3脂肪酸去饱和酶的活性。OsFAD3 mRNA在根组织中丰富，但在叶中几乎检测不到。在根组织中，15℃和20℃时观察到高水平的OsFAD3 mRNA，在低于10℃时其水平显著下降。在正常生长温度和低温条件下，OsFAD3 mRNA在叶组织中的积累水平都很低。在耐冷和不耐冷的水稻品种中都观察到了OsFAD3基因类似的温度响应。
