Evolutionary Assembly of C4 Leaf Structure

C4叶结构的进化组装

基本信息

批准号：
RGPIN-2020-05925
负责人：
Sage, Tammy
金额：
$ 2.91万
依托单位：
University of Toronto
依托单位国家：
加拿大
项目类别：
Discovery Grants Program - Individual
财政年份：
2022
资助国家：
加拿大
起止时间：
2022-01-01 至 2023-12-31
项目状态：
已结题

来源：
https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751456
关键词：
Evolutionary Assembly C4 Leaf Structure

项目摘要

Ribulose bisphosphate carboxylase-oxygenase (Rubisco), is the primary autotrophic carboxylase in oxygenic photosynthetic organisms. Oxygenase activity of Rubisco results in production of cytotoxic phosphoglycolate that is removed by photorespiration. Photorespiration releases previously fixed CO2 resulting in a net loss of carbon for growth. C4 photosynthesis concentrates CO2 around Rubisco relative to O2 eliminating Rubisco oxygenase activity. An essential feature of the C4 carbon concentrating mechanism is the spatial separation of the initial fixation of CO2 by phosphoenolpyruvate carboxylase in mesopyhyll cells from secondary refixation of CO2 by Rubisco in bundle sheath (BS) cells surrounding vascular tissue. Initial fixation produces a C4-acid that is transported to BS cells where it is decarboxylated enhancing CO2 around Rubisco 15-fold. The purpose of this research is to test our hypothesis that evolution of C4 photosynthetic leaf structure from C3 photosynthetic ancestors arises from cis- and trans-regulatory divergence of genes involved in tissue patterning, cell and plastid division/expansion, plasmodesmata and VT formation, and auxin biosynthesis, signalling and transport. We will determine the spatial-temporal series of events giving rise to the cellular/tissue architecture of a C4 photosynthetic leaf that is essential for photosynthetic function. Comparative studies on leaf development in Atriplex prostrata (C3), A. rosea (C4) and their C3xC4 F1 hybrid will be conducted and analyzed in the context of RNA-seq/genomic data already obtained by our laboratory. We will confirm 3-D patterns of cell division/expansion, as well as chloroplast/plasmodesmata development in M and BS cells. These features will be obtained using confocal microscopy, serial block-face scanning electron microscopy, high resolution transmission electron microscopy of thin sections and immunodetection of proteins and localization of the reactive oxygen species H2O2 with transmission electron microscopy. Immunohistochemistry will be performed using antibodies to detect auxin and proteins involved in tissue patterning, cell and plastid division/expansion, and plasmodesmata formation. C4 photosynthesis has evolved independently over 60 times making it one of the best examples of evolutionary convergence in the living world. C4 photosynthesis accounts for 23% of terrestrial gross primary productivity although it only occurs in 3% of plant species. In spite of the importance of C4 photosynthesis, our understanding of the cellular and molecular control of C4 evolution is in its infancy. Results from our study will enable identification of key genes essential for C4 leaf structure/function and regulation of those genes. To maintain global food security, cereal production will have to increase 70% by 2050. Our study will provide information to assist in maintaining global food security by engineering the C4 pathway into C3 crops, as is now being done in rice.

核酮糖二磷酸羧化酶加氧酶 (Rubisco) 是含氧光合生物中的主要自养羧化酶，Rubisco 的加氧酶活性会产生细胞毒性的磷酸乙醇酸，光呼吸会释放先前固定的二氧化碳，导致生长所需的碳净损失。 C4 光合作用将 CO2 集中在 Rubisco 周围，相对于 O2，消除了 Rubisco 加氧酶活性 C4 碳的基本特征。浓缩机制是叶皮细胞中磷酸烯醇丙酮酸羧化酶对 CO2 的初始固定与维管组织周围束鞘 (BS) 细胞中 Rubisco 对 CO2 的二次再固定之间的空间分离。它脱羧使 Rubisco 周围的 CO2 增强 15 倍。这项研究的目的是检验我们的假设，即 C4 光合作用的进化。 C3 光合祖先的叶子结构源于参与组织模式、细胞和质体分裂/扩展、胞间连丝和 VT 形成以及生长素生物合成、信号传导和运输的基因的顺式和反式调节差异。产生 C4 光合叶细胞/组织结构的事件，这对于叶发育的比较研究至关重要。 Atriplex prostrata (C3)、A.rosea (C4) 及其 C3xC4 F1 杂交体将在我们实验室已获得的 RNA-seq/基因组数据的背景下进行和分析，我们将确认细胞分裂/扩张的 3-D 模式。，以及 M 和 BS 细胞中叶绿体/胞间连丝的发育，这些特征将通过共聚焦显微镜、串行块面扫描电子显微镜、高分辨率透射电子显微镜获得。薄切片显微镜检查和蛋白质免疫检测以及活性氧 H2O2 的透射电子显微镜定位将使用抗体进行，以检测参与组织模式、细胞和质体分裂/扩张以及胞间连丝形成的生长素和蛋白质。已经独立进化了 60 多次，使其成为生物世界中进化趋同的最佳例子之一。光合作用占陆地总初级生产力的 23%，尽管它只发生在 3% 的植物物种中。尽管 C4 光合作用很重要，但我们对 C4 进化的细胞和分子控制的理解还处于起步阶段。将能够鉴定对 C4 叶片结构/功能和这些基因的调节至关重要的关键基因。为了维护全球粮食安全，到 2050 年谷物产量必须增加 70%。我们的研究将提供信息来协助实现这一目标。通过将 C4 途径设计到 C3 作物中来维护全球粮食安全，就像现在在水稻中所做的那样。