The band mutation in Neurospora crassa is a dominant allele of ras-1 implicating RAS signaling in circadian output
The band mutation in Neurospora crassa is a dominant allele of ras-1 implicating RAS signaling in circadian output
复制标题
DOI：
10.1101/gad.1551707
复制
发表时间：
2007-06-15
影响因子：
10.5
通讯作者：
Dunlap, Jay C.
中科院分区：
文献类型：
--
作者：
Belden, William J.;Larrondo, Luis F.;Dunlap, Jay C.
条带是一种等位基因，可以清晰地显示昼夜节律调节的孢子形成（分生孢子条带），40年来一直是昼夜节律研究中不可或缺的工具。利用单核苷酸多态性（snp）对bd进行定位，克隆并确定其为ras-1的T79I点突变。RAS -1（bd）突变体中光调控基因表达的改变表明，神经孢子虫光感受器WHITE COLLAR-1是RAS信号转导的靶标，而wc-1和fluffy转录的增加表明，RAS -1（bd）的分生调控基因升高。RAS- 1bd与显性活性和显性阴性RAS-1突变体的比较以及RAS功能的生化分析表明，RAS-1（bd）表现出GDP/GTP交换的适度增强，而GTP酶活性没有变化。由于ras-1（bd）中的生物钟似乎是正常的，因此在标准检测条件下，ras-1（bd）显然放大了一个微妙的内源性时钟输出信号。活性氧（Reactive oxygen species， ROS）可以影响RAS信号传导，也可以受RAS信号传导的影响，它增加了条件，表明ROS的产生与RAS-1信号传导之间存在联系；然而，令人惊讶的是，ras-1中的ROS水平并未升高（bd）。这些数据表明，神经孢子虫中相互关联的RAS和ros应答信号通路调节了昼夜节律和光调节基因表达的幅度。
Band, an allele enabling clear visualization of circadianly regulated spore formation (conidial banding), has remained an integral tool in the study of circadian rhythms for 40 years. bd was mapped using single-nucleotide polymorphisms (SNPs), cloned, and determined to be a T79I point mutation in ras-1. Alterations in light-regulated gene expression in the ras-1(bd) mutant suggests that the Neurospora photoreceptor WHITE COLLAR-1 is a target of RAS signaling, and increases in transcription of both wc-1 and fluffy show that regulators of conidiation are elevated in ras-1(bd). Comparison of ras-1bd with dominant active and dominant-negative ras-1 mutants and biochemical assays of RAS function indicate that RAS-1(bd) displays a modest enhancement of GDP/GTP exchange and no change in GTPase activity. Because the circadian clock in ras-1(bd) appears to be normal, ras-1(bd) apparently acts to amplify a subtle endogenous clock output signal under standard assay conditions. Reactive oxygen species (ROS), which can affect and be affected by RAS signaling, increase conidiation, suggesting a link between generation of ROS and RAS-1 signaling; surprisingly, however, ROS levels are not elevated in ras-1(bd). The data suggest that interconnected RAS- and ROS-responsive signaling pathways regulate the amplitude of circadian- and light-regulated gene expression in Neurospora.