拟南芥At1g10300基因调节叶形和开花时间

Arabidopsis At1g10300 gene regulates leaf morphology and flowering time

关键词:  拟南芥, 核仁G蛋白1, At1g10300基因, 开花时间, 叶形

Key words:  Arabidopsis, nucleolar G protein 1(NOG1), At1g10300 gene, flowering time, leaf morphology

摘要:

核仁G蛋白1(Nucleolar G protein 1, NOG1)是一种高度保守的核仁GTP酶,在真核生物中广泛存在,参与60 S核糖体亚基前体的组装。在线虫中敲减NOG1的表达造成生长缓慢、虫体变小和寿命延长的表型,而过量表达NOG1则使线虫的寿命缩短。拟南芥的At1g10300基因注释为NOG1-2,但是其生物学功能还有待研究。该研究对其功能进行了初步研究,首先检测了该基因在拟南芥各个器官的表达情况。结果表明:该基因在7 d龄幼苗、茎生叶和花中均有表达,其中在花中表达量最高。获得了At1g10300基因的T-DNA插入突变体,发现在长日照条件下,At1g10300突变体植株的莲座紧凑,莲座叶片长宽比降低,但叶面积和植株高度与野生型相比无显著差异,表明其叶形发生改变; 突变体植株的抽薹时间晚于野生型。荧光定量RT-PCR结果表明,突变体植株中开花促进因子FT、CO和GI的表达水平下调,而开花抑制因子FLC的表达水平上调。以上结果揭示At1g10300基因的突变影响了FT、CO、GI及FLC基因的表达,使植株出现晚花表型。

Abstract:

Nucleolar G protein 1(NOG1)is a highly conserved eukaryotic GTPase. NOG1 plays a significant role in the assembly of pre-60S ribosomal subunits. In yeast and animals, depletion of NOG1 results in reduced levels of 60S ribosomal subunits, aberrant pre-rRNA processing, and blockage of 60S ribosomal subunit export. A recent study in Caenorhabditis elegans found that knock-down NOG1 expression causes slower growth, smaller body size and increased life span, whereas over-expression of NOG1 results in decreased lifespan. However, the plant NOG1 has not been characterized. The Arabidopsis At1g10300 gene was annotated as NOG1-2. However, its role in Arabidopsis growth and development is still unknown. In this study, we used physiological, genetics and molecular tools to analyze the biological roles of the Arabidopsis At1g10300 gene. We firstly used semi-quantitative RT-PCR to investigate the transcriptional levels of At1g10300 gene in various tissues of Arabidopsis, including 7-day-old seedling, rosette leaf, cauline leaf, stem, bud and flower. The transcription of the At1g10300 gene was detected in seedlings, cauline leaves and blooming flowers. Among them, the highest transcriptional level was detected in blooming flowers. We then isolated a T-DNA insertion mutant allele of the At1g10300 gene. Phenotypic analysis found that the At1g10300 mutant had compact rosette and reduced ratio of leaf length/width compared to wild type. However, there was no significant difference in leaf area or plant height between the At1g10300 mutant and wild type. These data indicated that leaf morphology of At1g10300 mutant was altered. The At1g10300 mutant also displayed a late bolting phenotype under the condition of long-day photoperiod. To determine the molecular mechanism of this late flowering phenotype, we used quantitative RT-PCR to analyze the transcriptional levels of key genes of the flowering time pathway, including FLOWERING LOCUS T(FT), CONSTANS(CO), GIGANTEA(GI)and FLOWERING LOCUS C(FLC). The results showed that the transcriptional levels of the flowering promoting factors FT, CO and GI were down-regulated in the mutant plants compared with the wild type, whereas the transcription levels of the flowering inhibiting factor FLC was up-regulated. Taken together, these results suggest that mutation of At1g10300 gene delays flowering time by regulating the expressions of FT, CO, GI and FLC genes in Arabidopsis. Our data indicate that like its ortholog in worms, loss-of-function of At1g10300 gene also affects Arabidopsis rosette size and lifespan.