Insight into missing genetic links between two evening-expressed pseudo-response regulator genes TOC1 and PRR5 in the circadian clock-controlled circuitry in Arabidopsis thaliana
Insight into missing genetic links between two evening-expressed pseudo-response regulator genes TOC1 and PRR5 in the circadian clock-controlled circuitry in Arabidopsis thaliana
复制标题
DOI：
10.1093/pcp/pcm178
复制
发表时间：
2008-02-01
影响因子：
4.9
通讯作者：
Mizuno, Takeshi
中科院分区：
文献类型：
--
作者：
Ito, Shogo;Niwa, Yusuke;Mizuno, Takeshi
在拟南芥中，已鉴定出许多与生物钟相关的基因。其中，晚上表达的TOC1（TIMING OF CAB EXPRESSION 1）基因通过与早上表达的CCA1（CIRCADIAN CLOCK-ASSOCIATED 1）基因及其同源LHY（LATE ELONGATED HYPOCOTYL）基因一起形成转录反馈核心环而发挥作用。 TOC1 编码伪响应调节器 (PRR) 家族的成员，包括 PRR9、PRR7、PRR5、PRR3 和 PRR1/TOC1。除 TOC1（或 PRR1）之外的 PRR 基因似乎对某些昼夜节律相关事件也至关重要。为了澄清这些 PRR 基因之间缺失的遗传联系，我们构建了一个 toc1 prr5 双敲低突变体。在自由运行的昼夜节律中，所得的toc1-2 prr5-11突变体植物表现出极短的周期和降低的幅度表型，这比toc1-2单突变体植物更严重，表明TOC1和PRR5之间存在非线性遗传相互作用。令人惊讶的是，当与 prr5-11 等位基因结合时，短日照条件下 toc1-2 标志性的早花表型已转变为长日照条件下明显晚花的表型，而 prr5-11 等位基因本身显示出微妙的开花表型。这种意想不到的遗传结果（即表型符号转换）表明 TOC1 和 PRR5 基因协同参与非线性和封闭的遗传电路。在 toc1-2 prr5-11 双突变体中，CDF1（循环自由因子 1）的昼夜表达谱在长日照条件下的晚上显着去抑制。这项研究的这些结果和其他结果使我们提出了一个新颖的观点，即 TOC1 可能在闭合电路内控制开花时间方面发挥双重作用；一种是通过CCA1/LHY依赖GI（GIGANTEA）的负作用，另一种是通过与PRR5密切合作依赖CDF1的正作用。
In Arabidopsis thaliana, many circadian clock-associated genes have been identified. Among them, the evening-expressed TOC1 (TIMING OF CAB EXPRESSION 1) gene plays a role by forming a transcriptional feedback core loop together with the morning-expressed CCA1 (CIRCADIAN CLOCK-ASSOCIATED 1) gene and its homologous LHY (LATE ELONGATED HYPOCOTYL) gene. TOC1 encodes a member of the PSEUDO-RESPONSE REGULATOR (PRR) family, including PRR9, PRR7, PRR5, PRR3,and PRR1/TOC1. The PRR genes other than TOC1 (or PRR1) also appear to be crucial for certain circadian-associated events. To clarify missing genetic linkages amongst these PRR genes, here we constructed a toc1 prr5 double knockdown mutant. In free-running circadian rhythms, the resulting toc1-2 prr5-11 mutant plants showed an extremely short period and reduced amplitude phenotype, which was more severe than that of the toc1-2 single mutant plant, suggesting a non-linear genetic interaction between TOC1 and PRR5. Surprisingly, the hallmark early flowering phenotype of toc1-2 in the short-day conditions had been converted to a markedly late flowering phenotype in the long-day conditions, when combined with the prr5-11 allele, which itself showed a subtle flowering phenotype. This unexpected genetic result (i.e. phenotypic sign conversion) suggested that the TOC1 and PRR5 genes are coordinately implicated in a non-linear and closed genetic circuitry. In the toc1-2 prr5-11 double mutant, the diurnal expression profile of CDF1 (CYCLING DOF FACTOR 1) was markedly de-repressed in the evening in the long-day conditions. These and other results of this study led us to propose the novel view that TOC1 might play bipartite roles in the control of flowering time within a closed circuitry; the one is a GI (GIGANTEA)-dependent negative role through CCA1/LHY, and the other is a CDF1-dependent positive role through cooperating closely with PRR5.