Molecular, regulatory. and functional properties of alternative oxidases of non-angiosperm plants

生物电子传输链(ETC)为地球上的生命提供动力。所有植物细胞都含有线粒体，线粒体利用氧气，同时将碳分子(如糖)转化为能量。植物线粒体包含两条呼吸途径：细胞色素c氧化酶途径和交替氧化酶途径，前者存在于包括人类在内的大多数生物体中，后者的分布较为有限。尽管AOX的转录物、蛋白质水平和酶活性在各种各样的环境胁迫中都会增加，但AOX的生理作用尚不清楚。我的研究计划的长期目标是了解呼吸电子传递在新陈代谢和生理适应压力中所起的核心作用。这项建议描述了我的计划：(A)鉴定和检测非被子植物(非开花)植物中的AOX基因，并确认它们作为功能酶表达；(B)检验非被子植物AOX是单体(由一个亚基组成)并且受到不同于被子植物AOX的调控的假说；以及(C)检验由不同AOX基因编码的AOX蛋白能够形成异源二聚体的假说，这将影响酶的催化性质。回答这些问题将有助于阐明AOX的进化史，以及AOX酶的活性是如何调节的，AOX的结构，并确认AOX在所有植物中都存在。我们的结果将有助于全面了解植物线粒体的代谢灵活性如何使它们能够应对环境胁迫，从而有助于作物物种的改良。我的研究计划允许培养生物信息学、分子生物学、生物化学、生理学和进化论方面的高素质人员，并有助于说明比较和综合的生物学方法如何有助于提高知识。

Biological electron transport chains (ETCs) power life on this planet. All plant cells contain mitochondria which use oxygen while converting carbon molecules, such as sugars, into energy. Plant mitochondria contain two respiratory pathways: the cytochrome c oxidase pathway, which is found in most organisms, including humans, and the alternative oxidase (AOX) pathway, which has a more limited distribution. Despite the fact that AOX transcripts, protein levels, and enzyme activity increase during a wide variety of environmental stresses, the physiological role of AOX is unknown. The long term goal of my research program is to understand the central role that respiratory electron transport plays in metabolic and physiological adaptations to stress. This proposal describes my plans to: (A) identify and examine AOX genes in non-angiosperm (non-flowering) plants and confirm that they are expressed as functional enzymes, (B) test the hypothesis that non-angiosperm plant AOXs are monomeric (composed of one subunit) and are regulated differently than angiosperm AOXs, and (C) test the hypothesis that AOX proteins encoded by different AOX genes are capable of forming heterodimers and that this will influence the catalytic properties of the enzyme.The answers to these questions will help to shed light on the evolutionary history of AOX and, how AOX enzyme activity is regulated, the structure of AOX, and to confirm that AOX is present in all plants. Our results will contribute to an overall understanding of how metabolic flexibility in the mitochondria of plants allows them to cope with environmental stress and can, thereby, contribute to the improvement of crop species. My research program allows for the training of highly qualified personnel in bioinformatics, molecular biology, biochemistry, physiology, and evolution and serves to illustrate how a comparative and integrative approach to biology can contribute to advancing knowledge.