Molecular basis of late-flowering phenotype caused by dominant epi-alleles of the FWA locus in Arabidopsis
Molecular basis of late-flowering phenotype caused by dominant epi-alleles of the FWA locus in Arabidopsis
复制标题
DOI：
10.1093/pcp/pcl061
复制
发表时间：
2007-02-01
影响因子：
4.9
通讯作者：
Araki, Takashi
中科院分区：
文献类型：
--
作者：
Ikeda, Yoko;Kobayashi, Yasushi;Araki, Takashi
fwa显性突变体的晚花表型是由fwa位点的低甲基化引起的，导致同源结构域亮氨酸拉链（HD-ZIP）蛋白的异位表达。然而，关于FWA是否在开花调控中起作用以及异位表达的FWA如何延迟开花，人们知之甚少。通过分析野生型幼苗中FWA的表达，发现FWA在营养期不表达。这表明FWA在开花过程中没有作用。先前有报道称，fwa抑制过表达开花位点T（开花位点T）的植物的早熟开花表型，这表明fwa阻断了FT上或FT下游的开花途径。比较三种异位表达FWA的遗传背景及其各自的野生型的基因表达谱未能发现共同的变化，排除了FWA通过转录失调起作用的可能性。酵母双杂交分析和体外拉下实验表明，FWA蛋白与FT蛋白具有特异性相互作用。有关FWA n端和c端截断的研究支持了蛋白质与FT相互作用在延迟开花中的重要性。互作终止的c端截断在过表达时不会延迟开花，而保留互作的n端截断则会延迟开花。FWA与FT的特异性相互作用使我们能够使用FWA蛋白作为FT蛋白功能的特异性抑制剂。通过组织特异性异位表达FWA，进一步支持了茎尖是FT蛋白的作用位点。
The late-flowering phenotype of dominant fwa mutants is caused by hypomethylation in the FWA locus leading to ectopic expression of a homeodomain leucine zipper (HD-ZIP) protein. However, little is known about whether FWA has any role in regulation of flowering and how ectopically expressed FWA delays flowering. Through analysis of FWA expression in wild-type seedlings, it was shown that FWA is not expressed during the vegetative phase. This suggests that FWA has no role in flowering. The previous reports that fwa suppressed the precocious-flowering phenotype of plants overexpressing FLOWERING LOCUS T (FT) suggest that the flowering pathway(s) either at and/or downstream of FT is blocked by FWA. Comparison of gene expression profiles in three genetic backgrounds ectopically expressing FWA and their respective wild types failed to detect common changes, ruling out the possibility that FWA acts through transcriptional misregulation. Yeast two-hybrid analysis and in vitro pull-down assay showed that FWA protein can specifically interact with FT protein. The importance of protein interaction with FT in delaying flowering was supported by studies involving N-terminal and C-terminal truncations of FWA. The C-terminal truncation with abolished interaction did not delay flowering when overexpressed, while the N-terminal truncation, which retains interaction, did. Specific interaction of FWA with FT enabled us to use FWA protein as a specific inhibitor of FT protein function. Through tissue-specific ectopic expression of FWA, further support for the shoot apex being the site of action of FT protein was provided.