拟南芥中一个新的constans等位基因及特性

植物开花是由内外信号途径共同调控的,CONSTANS是长日照途径上控制开花的基因.在筛选拟南芥滞绿突变体的过程中筛选到一个晚花突变体,工作名称为fnc25.后来证实为一个新的constans突变体co-9.在长日照条件下该突变体植株高大,叶片呈深绿色,莲座叶数目增多,开花延迟,寿限显著延长;春化处理和外源施加赤霉素对其开花时间几乎没有响应,在短日照条件下开花时间几乎不变.测序发现co-9中CO基因编码区中有10个碱基的缺失导致了CO蛋白C末端92个氨基酸没有被合成,这其中包含一个CCT结构域.CO基因的功能缺失很可能是导致co-9晚花的原因.RT-PCR实验表明co-9中CO直接调控的基因FT的mRNA水平显著下调,而另一个调控的基因SOC1的mRNA水平和野生型相比没有改变.说明CO通过不同的结构域作用于下游目的基因,一个结构域的改变只影响下游一个目的基因的表达,导致co-9的晚花表型.

Characterization of a New constans Allele in Arabidopsis thaliana

In plants,flowering was triggered by endogenous and environmental signals.CONSTANS (CO) promotes flowering of Arabidopsis in response to long-day conditions.In a screening for stay-green mutants in Arabidopsis thaliana,a late-flowering mutant in Columbia background was isolated and tentatively named fnc25.It was later testified a new constans allele,co-9.When grown in the long-day conditions,the mutant showed a tall stature and dark-green leaves,bearing more rosettes leaves,flowering late and extending its lifespan.As far as the flowering time is concerned,the co-9 was insensitive to vernalization,flowering slightly earlier under short days.The late-flowering phenotype was not resumed by applying exogenous gibberellin.A 10 nt fragment deletion was found in the coding region of CO gene,resulting in premature termination of CO protein and the absence of the 92 amino acids of C-terminal domain.These phenotypes were most likely caused by a reduction in the function of CONSTANS.It is remarkable that the mRNA level of FT,one of the direct target genes of CO,is dramatically reduced,whereas mRNA levels of SOC1,the other direct target gene of CO is almost not changed.CO maybe promotes the target genes through difference domains of its protein.One domain is altered but the other is intact maybe only influence promoting of one of the target genes,and thereby lead to a late-flowering phenotype.