ROLE OF ASCORBATE IN COORDINATING GROWTH & SENESCENCE IN ARABIDOPSIS THALIANA

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。衰老的氧化应激假说认为，与衰老相关的生理功能衰减是由活性氧（ROS）诱导的分子氧化损伤引起的。虽然有相当多的证据表明氧化应激与衰老有关，但需要更多的数据来清楚地定义这种参与的性质。抗坏血酸（AsA）是抗氧化能力的主要贡献者，细胞必须抵消活性氧的作用。初步研究表明，拟南芥植物的高asa品系具有显著的延长寿命、延长生育期和增强活力的迹象。这些表达肌醇（MI）通往AsA途径（类似于动物通往AsA途径的最后几个步骤）的转基因基因，以及拟南芥的遗传和基因组资源，构成了一个强大的系统，可以探索AsA介导的抗衰老机制和生物学基础，这是生物医学研究中一个重要的课题。目的1-3将验证一个假设，即抗坏血酸为高asa拟南芥提供额外的抗氧化应激保护，这种保护对这些植物延长寿命和延长生殖活性至关重要。在Aim 1中，AsA在调节生活史性状（生长、寿命、生殖活动长度和衰老）的时间控制中的作用将被描述。在Aim 2中，将确定导致AsA形成与长寿表型相关的途径。我们建议利用我们为特定的AsA生物合成酶开发的敲除突变体来了解是否存在与这种表型相关的途径。众所周知，在拟南芥中，体细胞组织寿命不受生殖发育的支配。在Aim 3中，将确定导致AsA形成与延长开花表型相关的途径。生殖和活跃生长的组织具有更高的代谢率，因此对抗氧化剂的需求更高。在Aim 4中，将确定MI途径的酶（MI加氧酶[MIOX]，葡萄糖醛酸还原酶，葡萄糖醛酸内酯酶和古罗酮-1,4-内酯氧化酶[GLOase]）的细胞和亚细胞定位，以了解不同异构体对不同组织和细胞器中AsA库的贡献。对细胞中抗氧化活性的更深入和更好的了解将有助于开发对抗/延缓与衰老相关的一些破坏性过程的疗法，这些过程对植物、动物和人类都是常见的。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The oxidative stress hypothesis of aging postulates that senescence-associated attenuations in physiological function are caused by molecular oxidative damage induced by reactive oxygen species (ROS). Although there is considerable evidence implicating oxidative stress in aging, additional data are needed to clearly define the nature of this involvement. Ascorbate (AsA) is a major contributor to the antioxidant capacity cells have to counteract the action of ROS. Preliminary studies have shown significant signs of enhanced longevity, expanded reproductive period, and increased vigor in high-AsA lines of the Arabidopsis thaliana plant. These transgenics expressing genes of the myo-inositol (MI) pathway to AsA (a route that resembles the last steps of the animal pathway to AsA), and the genetic and genomic resources of Arabidopsis constitute a powerful system to explore the mechanisms and biological basis of an AsA-mediated resistance to aging, a subject of significant importance in biomedical research. Aims 1-3 will test the hypothesis that ascorbate is providing high-AsA Arabidopsis lines additional protection against oxidative stress, and that this protection is critical for the increased lifespan and extended reproductive activity displayed by those plants. In Aim 1, the role of AsA in modulating the temporal control of life-history traits [growth, lifespan, length of reproductive activity, and senescence] will be characterized. In Aim 2, the route(s) leading to AsA formation linked to the extended longevity phenotype will be determined. We propose leveraging the repertoire of knockout mutants we have developed for specific AsA biosynthetic enzymes to learn if there is a pathway linked to this phenotype. It is known that in Arabidopsis, somatic tissue longevity is not governed by reproductive development. In Aim 3, the route(s) leading to AsA formation linked to the extended flowering phenotype will be determined. Reproductive and actively growing tissues have higher metabolic rates and, therefore, a higher demand for antioxidants. In Aim 4, the cellular and subcellular localization of enzymes of the MI pathway to AsA (MI oxygenase [MIOX], glucuronate reductase, glucuronolactonase and gulono-1,4-lactone oxidase [GLOase]) will be determined in order to learn about the contribution of the different isoforms to the AsA pool in various tissues and organelles. A deeper and better understanding of the antioxidant activities in cells will contribute to developing therapies to combat/retard some of the destructive processes associated with aging, processes common to plants, animals, and humans.