Nakano Michiharu, Yamada Tetsuya, Masuda Yu, Sato Yutaka, Kobayashi Hideki, Ueda Hiroaki, Morita Ryouhei, Nishimura Minoru, Kitamura Keisuke, Kusaba Makoto
Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8526 Japan These authors contributed equally to this work.
Graduate School of Agriculture, Hokkaido University, Kita, Sapporo, Hokkaido, 060-8589 Japan These authors contributed equally to this work.
Plant Cell Physiol. 2014 Oct;55(10):1763-71. doi: 10.1093/pcp/pcu107. Epub 2014 Aug 9.
The recent whole-genome sequencing of soybean (Glycine max) revealed that soybean experienced whole-genome duplications 59 million and 13 million years ago, and it has an octoploid-like genome in spite of its diploid nature. We analyzed a natural green-cotyledon mutant line, Tenshin-daiseitou. The physiological analysis revealed that Tenshin-daiseitou shows a non-functional stay-green phenotype in senescent leaves, which is similar to that of the mutant of Mendel's green-cotyledon gene I, the ortholog of SGR in pea. The identification of gene mutations and genetic segregation analysis suggested that defects in GmSGR1 and GmSGR2 were responsible for the green-cotyledon/stay-green phenotype of Tenshin-daiseitou, which was confirmed by RNA interference (RNAi) transgenic soybean experiments using GmSGR genes. The characterized green-cotyledon double mutant d1d2 was found to have the same mutations, suggesting that GmSGR1 and GmSGR2 are D1 and D2. Among the examined d1d2 strains, the d1d2 strain K144a showed a lower Chl a/b ratio in mature seeds than other strains but not in senescent leaves, suggesting a seed-specific genetic factor of the Chl composition in K144a. Analysis of the soybean genome sequence revealed four genomic regions with microsynteny to the Arabidopsis SGR1 region, which included the GmSGR1 and GmSGR2 regions. The other two regions contained GmSGR3a/GmSGR3b and GmSGR4, respectively, which might be pseudogenes or genes with a function that is unrelated to Chl degradation during seed maturation and leaf senescence. These GmSGR genes were thought to be produced by the two whole-genome duplications, and they provide a good example of such whole-genome duplication events in the evolution of the soybean genome.
最近对大豆（Glycine max）进行的全基因组测序显示，大豆在5900万年前和1300万年前经历了全基因组复制，尽管其为二倍体性质，但却拥有类似八倍体的基因组。我们分析了一个天然的绿色子叶突变系——“天 Shin - 大紫豆”。生理分析表明，“天 Shin - 大紫豆”在衰老叶片中呈现出无功能的持绿表型，这与孟德尔绿色子叶基因I的突变体类似，该基因是豌豆中SGR的直系同源基因。基因突变鉴定和遗传分离分析表明，GmSGR1和GmSGR2的缺陷导致了“天 Shin - 大紫豆”的绿色子叶/持绿表型，这通过使用GmSGR基因的RNA干扰（RNAi）转基因大豆实验得到了证实。已鉴定的绿色子叶双突变体d1d2被发现具有相同的突变，这表明GmSGR1和GmSGR2就是D1和D2。在所检测的d1d2菌株中，d1d2菌株K144a在成熟种子中的叶绿素a/b比值低于其他菌株，但在衰老叶片中并非如此，这表明K144a中存在种子特异性的叶绿素组成遗传因子。对大豆基因组序列的分析揭示了四个与拟南芥SGR1区域存在微共线性的基因组区域，其中包括GmSGR1和GmSGR2区域。另外两个区域分别包含GmSGR3a/GmSGR3b和GmSGR4，它们可能是假基因或在种子成熟和叶片衰老过程中与叶绿素降解无关的功能基因。这些GmSGR基因被认为是由两次全基因组复制产生的，它们为大豆基因组进化中的此类全基因组复制事件提供了一个很好的例子。
