Functional Plant Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Japan.
Plant Signal Behav. 2011 Dec;6(12):1932-6. doi: 10.4161/psb.6.12.18207.
We have recently isolated a rice circadian clock-related mutant carrying a null mutation in Os-GIGANTEA(GI) gene, the solo ortholog of Arabidopsis GI. Time-course global transcriptome analyses of leaves from wild-type and osgi mutant grown in the field have revealed that Os-GI affects gene expression of more than half of genes on rice 44k microarray. To better understand the biological significance of circadian clock function in growth and development of rice, we here investigated the gene expression involved in phytohormone biosynthesis. Here we found that mRNA levels of a few major genes encoding GA2-oxidase which can inactivate bioactive gibberellins (GAs) were remarkably increased in osgi-1 plants. This suggests that Os-GI functions to maintain bioactive GA level through the regulation of the GA-deactivating enzyme genes in rice. Consistently, osgi-1 plants showed semi-dwarf phenotype with reduced internode and leaf sheath elongation.
我们最近分离到一个携带 Os-GIGANTEA(GI) 基因 null 突变的水稻生物钟相关突变体，该基因是拟南芥 GI 的独同源基因。对在田间生长的野生型和 osgi 突变体叶片进行的时间进程全基因组转录组分析表明，Os-GI 影响水稻 44k 微阵列上超过一半基因的表达。为了更好地理解生物钟功能在水稻生长和发育中的生物学意义，我们研究了参与植物激素生物合成的基因表达。在这里，我们发现编码 GA2-氧化酶的几个主要基因的 mRNA 水平在 osgi-1 植株中显著升高，GA2-氧化酶可以使有生物活性的赤霉素（GAs）失活。这表明 Os-GI 通过调节水稻中 GA 失活酶基因来维持生物活性 GA 水平。一致地，osgi-1 植物表现出半矮化表型，节间和叶鞘伸长减少。
