Semidwarf (sd-1), "green revolution" rice, contains a defective gibberellin 20-oxidase gene

Wolfgang Spielmeyer, Marc H. Ellis, and Peter M. Chandler
Proceedings of the National Academy of Sciences, 2002, 99(13): 9043-9048     追溯原文......本站官方QQ群:62473826

The introduction of semidwarf rice (Oryza sativa L.) led to record yield increases throughout Asia in the 1960s. The major semidwarfing allele, sd-1, is still extensively used in modern rice cultivars. The phenotype of sd-1 is consistent with dwarfism that results from a deficiency in gibberellin (GA) plant growth hormones. We propose that the semidwarf (sd-1) phenotype is the result of a deficiency of active GAs in the elongating stem arising from a defective 20-oxidase GA biosynthetic enzyme. Sequence data from the rice genome was combined with previous mapping studies to locate a putative GA 20-oxidase gene (Os20ox2) at the predicted map location of sd-1 on chromosome 1. Two independent sd-1 alleles contained alterations within Os20ox2: a deletion of 280 bp within the coding region of Os20ox2 was predicted to encode a nonfunctional protein in an indica type semidwarf (Doongara), whereas a substitution in an amino acid residue (Leu-266) that is highly conserved among dioxygenases could explain loss of function of Os20ox2 in a japonica semidwarf (Calrose76). The quantification of GAs in elongating stems by GC-MS showed that the initial substrate of GA 20-oxidase activity (GA53) accumulated, whereas the content of the major product (GA20) and of bioactive GA1 was lower in semidwarf compared with tall lines. We propose that the Os20ox2 gene corresponds to the sd-1 locus.

绿色革命水稻Semidwarf (sd-1)中赤霉素20氧化酶基因发生突变

半矮水稻的推广引起了上世纪60年代亚洲水稻产量的新纪录。主效半矮基因sd-1在现代的水稻品种中仍然广泛使用。sd-1的半矮表型是由于植物生长激素赤霉素的缺乏引起的。我们认为sd-1的半矮表型是由于赤霉素生物合成酶赤霉素20氧化酶发生突变导致伸长的茎中活性GA的缺乏引起的。对水稻基因组序列进行分析以及结合之前的定位结果将1号染色体上的sd-1确定为赤霉素20氧化酶基因(Os20ox2)。两个独立的sd-1等位基因位点在Os20ox2基因上都发生了突变:籼稻半矮秆品种Doongara中Os20ox2基因的编码区中存在280bp的缺失,形成一个没有功能的蛋白,而粳稻半矮秆品种Calrose76中则在双加氧酶高度保守的氨基酸残基(第266位亮氨酸)上发生了氨基酸置换。气相色谱质谱联用仪测定了伸长的茎中GA含量,结果表明与高杆植株相比半矮秆植株中积累了赤霉素20氧化酶的起始底物GA53,而主要产物GA20和有活性的GA1的含量则降低。因此我们认为Os20ox2基因对应着sd-1位点。
结果:sd-1位点的遗传和物理分析;sd-1基因区中Os20ox2基因的鉴定;sd-1株系中Os20ox2基因突变的特征;伸长的茎中GA含量分析。


基因列表
  半矮秆基因 sd1; OsGA20ox2; qSD1-2