Graduate School of Arts and Sciences, Iwate University, Morioka, Japan.
Faculty of Agriculture, Iwate University, Morioka, Japan.
J Plant Res. 2024 Mar;137(2):255-264. doi: 10.1007/s10265-023-01514-z. Epub 2023 Dec 19.
The kinetic properties of Rubisco, a key enzyme for photosynthesis, have been examined in numerous plant species. However, this information on some plant groups, such as ferns, is scarce. This study examined Rubisco carboxylase activity and leaf Rubisco levels in seven ferns, including four Equisetum plants (E. arvense, E. hyemale, E. praealtum, and E. variegatum), considered living fossils. The turnover rates of Rubisco carboxylation (k) in E. praealtum and E. hyemale were comparable to those in the C plants maize (Zea mays) and sorghum (Sorghum bicolor), whose k values are high. Rubisco CO affinity, estimated from the percentage of Rubisco carboxylase activity under CO unsaturated conditions in k in these Equisetum plants, was low and also comparable to that in maize and sorghum. In contrast, k and CO affinities of Rubisco in other ferns, including E. arvense and E. variegatum were comparable with those in C plants. The N allocation to Rubisco in the ferns examined was comparable to that in the C plants. These results indicate that E. praealtum and E. hyemale have abundant Rubisco with high k and low CO affinity, whereas the carboxylase activity and abundance of Rubisco in other ferns were similar to those in C plants. Herein, the Rubisco properties of E. praealtum and E. hyemale were discussed regarding their evolution and physiological implications.
Rubisco 是光合作用的关键酶，其动力学特性已在众多植物物种中进行了研究。然而，关于某些植物群体（如蕨类植物）的信息却很少。本研究检测了七种蕨类植物（包括四个木贼属植物，即 E. arvense、E. hyemale、E. praealtum 和 E. variegatum）的 Rubisco 羧化酶活性和叶片 Rubisco 水平，这些植物被认为是活化石。E. praealtum 和 E. hyemale 的 Rubisco 羧化周转率（k）与 C 植物玉米（Zea mays）和高粱（Sorghum bicolor）的 k 值相当，这两种植物的 k 值较高。从 Rubisco 羧化酶活性在 CO 不饱和条件下的百分比以及这些木贼属植物中的 k 值来估计 Rubisco 的 CO 亲和力，其值较低，与玉米和高粱的 CO 亲和力相当。相比之下，其他蕨类植物（包括 E. arvense 和 E. variegatum）中的 Rubisco 的 k 和 CO 亲和力与 C 植物相当。研究中检查的蕨类植物的 Rubisco 向 N 的分配与 C 植物相当。这些结果表明，E. praealtum 和 E. hyemale 具有丰富的 Rubisco，其 k 值高，CO 亲和力低，而其他蕨类植物的羧化酶活性和 Rubisco 丰度与 C 植物相似。在此，讨论了 E. praealtum 和 E. hyemale 的 Rubisco 特性，及其进化和生理意义。
