一氧化氮:植物体内一种新的生长调控因子

一氧化氮是具有生物活性,自然界存在的10种最小分子之一。越来越多的证据显示,一氧化氮是生物体内一种广泛分布的信号传导分子。一氧化氮参与植物生长发育调控和对生物与非生物环境胁迫的应答反应。该文重点讨论一氧化氮在植物体内的产生,基本功能以及在信号传导网络系统中与Ca^2 的相互作用。     

Root Hair Development

Root hairs are projections from the epidermal cells of the root that are thought to increase its effective surface area for nutrient and water uptake, enlarge the volume of exploited soil, and aid in anchoring the plant to the soil. Their formation occurs as a series of developmental processes starting with cell fate specification in the meristem. The root-hair-forming epidermal cell, or trichoblast, then participates in the diffuse growth phase associated with the elongation of the main root axis. After the fully elongated trichoblast exits the elongation zone, growth is reorganized and localized to the side in the process of root hair initiation. Initiation is then followed by a sustained phase of tip growth until the hair reaches its mature length. Thus, root hairs provide insight into a range of developmental processes from cell fate determination to growth control. The theme emerging from the molecular analysis of the control of root hair formation is that many regulators act at several stages of development. Root hair formation is also responsive to a multitude of nutrient and other environmental stimuli. Therefore, one explanation for the presence of the complex networks that regulate root hair morphogenesis may lie in the need to coordinate their highly plastic developmental program and entrain it to the current soil microenvironment being explored by the root.     

Root Hair Development

Root hairs are projections from the epidermal cells of the root that are thought to increase its effective surface area for nutrient and water uptake, enlarge the volume of exploited soil, and aid in anchoring the plant to the soil. Their formation occurs as a series of developmental processes starting with cell fate specification in the meristem. The root-hair-forming epidermal cell, or trichoblast, then participates in the diffuse growth phase associated with the elongation of the main root axis. After the fully elongated trichoblast exits the elongation zone, growth is reorganized and localized to the side in the process of root hair initiation. Initiation is then followed by a sustained phase of tip growth until the hair reaches its mature length. Thus, root hairs provide insight into a range of developmental processes from cell fate determination to growth control. The theme emerging from the molecular analysis of the control of root hair formation is that many regulators act at several stages of development. Root hair formation is also responsive to a multitude of nutrient and other environmental stimuli. Therefore, one explanation for the presence of the complex networks that regulate root hair morphogenesis may lie in the need to coordinate their highly plastic developmental program and entrain it to the current soil microenvironment being explored by the root.     

一氧化氮在植物体内的信号分子作用

一氧化氮 (ｎｉｔｒｉｃｏｘｉｄｅ ,ＮＯ)是一种广泛分布于生物体的气体活性分子 ,它具有多种生理功能。动物体研究结果揭示 ,ＮＯ在血管松驰、神经转导及先天性免疫反应等一系列生理代谢过程均可作为一种关键的信号和效应分子。有关ＮＯ作为信使物质参与植物抗病及其他生理代谢调节的报道也日益增多。1 .植物内源ＮＯ的产生途径植物体内氮代谢的关键酶硝酸还原酶(ｎｉｔｒａｔｅｒｅｄｕｃｔａｓｅ,ＮＲ)也可以ＮＡＤＨ/ＮＡＤＰＨ作为电子供体 ,催化硝酸盐和亚硝酸盐的单电子还原反应来合成ＮＯ。如在含有ＮＯ-2 和ＮＡＤＨ的缓冲液 (ｐ…     

一氧化氮（NO）对植物的生理和病理功能

介绍了NO在植物抑御病害及种子萌发、叶片生长、果实成熟、胁迫响应等过程中的作用及其机制。     

Cyclin G Functions as a Positive Regulator of Growth and Metabolism in Drosophila

In multicellular organisms, growth and proliferation is adjusted to nutritional conditions by a complex signaling network. The Insulin receptor/target of rapamycin (InR/TOR) signaling cascade plays a pivotal role in nutrient dependent growth regulation in Drosophila and mammals alike. Here we identify Cyclin G (CycG) as a regulator of growth and metabolism in Drosophila. CycG mutants have a reduced body size and weight and show signs of starvation accompanied by a disturbed fat metabolism. InR/TOR signaling activity is impaired in cycG mutants, combined with a reduced phosphorylation status of the kinase Akt1 and the downstream factors S6-kinase and eukaryotic translation initiation factor 4E binding protein (4E-BP). Moreover, the expression and accumulation of Drosophila insulin like peptides (dILPs) is disturbed in cycG mutant brains. Using a reporter assay, we show that the activity of one of the first effectors of InR signaling, Phosphoinositide 3-kinase (PI3K92E), is unaffected in cycG mutants. However, the metabolic defects and weight loss in cycG mutants were rescued by overexpression of Akt1 specifically in the fat body and by mutants in widerborst (wdb), the B''-subunit of the phosphatase PP2A, known to downregulate Akt1 by dephosphorylation. Together, our data suggest that CycG acts at the level of Akt1 to regulate growth and metabolism via PP2A in Drosophila.     

根毛的生长发育及其遗传基础

根毛是根系特异化表皮细胞外伸形成的管状凸起物,是植物吸收矿质养分和水分的重要器官。根毛的发育可分为根毛细胞命运决定、根毛起始、根毛顶端生长和根毛成熟等阶段。本文对根毛发育生长过程中的细胞形态及其生理生化变化进行了综述,并从根表皮细胞命运决定分子机理, EXPANSIN、bHLH和MYB等转录因子以及小G蛋白和生长素/乙烯等方面简要说明了根毛生长发育的遗传基础。     

Nitric Oxide Alleviates Submergence-Induced Maize Seedling Root Tip Cell Death

Journal of Plant Growth Regulation - Submergence results in submergence-induced hypoxia in plants. Hypoxia sensing and signaling in the root, as a main organ sensing hypoxic stress, play critical...     

ASM-3 Acid Sphingomyelinase Functions as a Positive Regulator of the DAF-2/AGE-1 Signaling Pathway and Serves as a Novel Anti-Aging Target

In C. elegans, the highly conserved DAF-2/insulin/insulin-like growth factor 1 receptor signaling (IIS) pathway regulates longevity, metabolism, reproduction and development. In mammals, acid sphingomyelinase (ASM) is an enzyme that hydrolyzes sphingomyelin to produce ceramide. ASM has been implicated in CD95 death receptor signaling under certain stress conditions. However, the involvement of ASM in growth factor receptor signaling under physiological conditions is not known. Here, we report that in vivo ASM functions as a positive regulator of the DAF-2/IIS pathway in C. elegans. We have shown that inactivation of asm-3 extends animal lifespan and promotes dauer arrest, an alternative developmental process. A significant cooperative effect on lifespan is observed between asm-3 deficiency and loss-of-function alleles of the age-1/PI 3-kinase, with the asm-3; age-1 double mutant animals having a mean lifespan 259% greater than that of the wild-type animals. The lifespan extension phenotypes caused by the loss of asm-3 are dependent on the functions of daf-16/FOXO and daf-18/PTEN. We have demonstrated that inactivation of asm-3 causes nuclear translocation of DAF-16::GFP protein, up-regulates endogenous DAF-16 protein levels and activates the downstream targeting genes of DAF-16. Together, our findings reveal a novel role of asm-3 in regulation of lifespan and diapause by modulating IIS pathway. Importantly, we have found that two drugs known to inhibit mammalian ASM activities, desipramine and clomipramine, markedly extend the lifespan of wild-type animals, in a manner similar to that achieved by genetic inactivation of the asm genes. Our studies illustrate a novel strategy of anti-aging by targeting ASM, which may potentially be extended to mammals.     

Nitric Oxide Donors as Potential Antitumor Agents

Biophysics - The role of nitric oxide as one of the universal regulators of metabolic processes in living organisms is considered. The results of experimental studies of NO association with cancer...