The Role of Chloroplast Gene Expression in Plant Growth and Development

叶绿体在植物新陈代谢和支持植物细胞的生长和分化中起着核心作用。虽然大多数叶绿体蛋白在细胞核中编码，在胞质中产生，然后输入到叶绿体中，但很少有蛋白质是由叶绿体基因组编码的。通常，干扰叶绿体基因功能会导致光合作用的缺陷，但在一些物种中，这种干扰的影响更严重，并导致早期死亡。例如，在拟南芥中，扰乱叶绿体的翻译通常会导致胚胎死亡，但在其他物种中，会导致幼苗白化，但可以存活。最近的工作表明，一个单一的叶绿体基因(ACCD)编码脂肪酸生物合成所需的异构体乙酰-辅酶A羧基酶的一个亚基，可能是导致不同植物阻止叶绿体翻译的显著不同后果的原因--致命性和活性白化。这个项目将评估这个模型，探索它对植物生物学的影响，并对植物发育的基本细胞和新陈代谢过程提供有价值的见解。将采取几种不同的策略：(1)确定叶绿体翻译缺陷突变体的胚胎致死性是否可以通过编码正常胞质同源羧基酶的叶绿体定位版本的核转基因来挽救；(2)比较不同拟南芥材料中叶绿体翻译中断的后果；以及(3)评估ACCD从叶绿体基因组中缺失的植物谱系。这项工作将有助于说明在不同植物物种中编码相同新陈代谢功能的干扰基因如何产生不同的发育影响。研究结果将发表在科学期刊和分发给拟南芥库存中心的生物材料上。基于这项研究的暑期实验室课程将结合植物遗传学、生物化学和进化论的原理，为生物学专业的学生提供一种替代方法，通过加强研究、分析和写作技能来满足实验室要求。

Chloroplasts play a central role in plant metabolism and in supporting the growth and differentiation of plant cells. Although most chloroplast proteins are encoded in the nucleus, produced in the cytosol, and imported into the chloroplast, few are encoded by the chloroplast genome. Typically, interfering with chloroplast gene function causes defects in photosynthesis, but in some species the effects of such disruptions are more severe and result in early lethality. For example, disrupting chloroplast translation in Arabidopsis often causes embryo lethality, but in other species results in seedlings that are albino, but viable. Recent work suggests that a single chloroplast gene (accD), encoding one subunit of a heteromeric acetyl-CoA carboxylase required for fatty acid biosynthesis, may be responsible for the strikingly different consequences - lethality vs. viable albino - of blocking chloroplast translation in different plant species. This project will evaluate this model, explore its implications for plant biology, and provide valuable insights into basic cellular and metabolic processes that underlie plant development. Several different strategies will be pursued: (1) Determine whether embryo lethality in Arabidopsis mutants defective in chloroplast translation can be rescued by a nuclear transgene encoding a chloroplast-localized version of the normally cytosolic, homomeric carboxylase; (2) Compare the consequences of disrupting chloroplast translation in different accessions of Arabidopsis; and (3) Evaluate plant lineages where accD has been lost from the chloroplast genome. This work will help to illustrate how disrupting genes encoding the same metabolic function in different plant species can have divergent developmental impacts. Results will be published in scientific journals and biological materials distributed to Arabidopsis stock centers. A summer lab course based on this research will be developed to incorporate principles of plant genetics, biochemistry, and evolution, offering biology majors an alternative way to meet lab requirements by focusing on enhanced research, analytical, and writing skills.