Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
Departments of Biochemistry and Molecular Biology, Plant Biology, and Plant, Soil, and Microbial Sciences, Plant Resilience Institute, Michigan State University, East Lansing, Michigan, USA.
Plant Cell Environ. 2024 Sep;47(9):3541-3560. doi: 10.1111/pce.15069. Epub 2024 Aug 12.
C photosynthesis is a photosynthetic pathway in which photorespiratory CO release and refixation are enhanced in leaf bundle sheath (BS) tissues. The evolution of C photosynthesis has been hypothesized to be a major step in the origin of C photosynthesis, highlighting the importance of studying C evolution. In this study, physiological, anatomical, ultrastructural, and immunohistochemical properties of leaf photosynthetic tissues were investigated in six non-C Tribulus species and four C Tribulus species. At 42°C, T. cristatus exhibited a photosynthetic CO compensation point in the absence of respiration (C) of 21 µmol mol, below the C mean C of 73 µmol mol. Tribulus astrocarpus had a C value at 42°C of 55 µmol mol, intermediate between the C species and the C T. cristatus. Glycine decarboxylase (GDC) allocation to BS tissues was associated with lower C. Tribulus cristatus and T. astrocarpus allocated 86% and 30% of their GDC to the BS tissues, respectively, well above the C mean of 11%. Tribulus astrocarpus thus exhibits a weaker C (termed sub-C) phenotype. Increased allocation of mitochondria to the BS and decreased length-to-width ratios of BS cells, were present in non-C species, indicating a potential role in C and C evolution.
C 光合作用是一种光合作用途径，其中光呼吸 CO 释放和再固定在叶片束鞘（BS）组织中得到增强。C 光合作用的进化被假设为 C 光合作用起源的主要步骤，突出了研究 C 进化的重要性。在这项研究中，研究了六种非 C 蒺藜物种和四种 C 蒺藜物种的叶片光合组织的生理、解剖、超微结构和免疫组织化学特性。在 42°C 下，T. cristatus 在没有呼吸（C）的情况下表现出 21 μmol/mol 的光合 CO 补偿点，低于 C 均值 73 μmol/mol。Tribulus astrocarpus 在 42°C 时的 C 值为 55 μmol/mol，介于 C 种和 C T. cristatus 之间。甘氨酸脱羧酶（GDC）在 BS 组织中的分配与较低的 C 有关。T. cristatus 和 T. astrocarpus 分别将其 GDC 的 86%和 30%分配到 BS 组织中，远高于 C 的均值 11%。因此，Tribulus astrocarpus 表现出较弱的 C（称为亚 C）表型。非 C 物种中存在更多的线粒体分配到 BS 和 BS 细胞长度与宽度比降低，这表明其在 C 和 C 进化中可能具有作用。
