Division of Applied Bioscience, Research Faculty of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo, 060-8589, Japan.
Division of Life Science, Graduate School of Life Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo, 060-0810, Japan.
Sci Rep. 2019 Mar 18;9(1):4751. doi: 10.1038/s41598-019-39647-8.
Coralloid roots are specialized tissues of cycads (Cycas revoluta) that are involved in symbioses with nitrogen-fixing Nostoc cyanobacteria. We found that a crude methanolic extract of coralloid roots induced differentiation of the filamentous cell aggregates of Nostoc species into motile hormogonia. Hence, the hormogonium-inducing factor (HIF) was chased using bioassay-based isolation, and the active principle was characterized as a mixture of diacylglycerols (DAGs), mainly composed of 1-palmitoyl-2-linoleoyl-sn-glycerol (1), 1-palmitoyl-2-oleoyl-sn-glycerol (2), 1-stearoyl-2-linolenoyl-sn-glycerol (3), and 1-stearoyl-2-linoleoyl-sn-glycerol (4). Enantioselectively synthesised compound 1 showed a clear HIF activity at 1 nmol (0.6 µg) disc for the filamentous cells, whereas synthesised 2-linoleoyl-3-palmitoyl-sn-glycerol (1') and 1-palmitoyl-2-linoleoyl-rac-glycerol (1/1') were less active than 1. Conversely, synthesised 1-linoleoyl-2-palmitoyl-rac-glycerol (8/8') which is an acyl positional isomer of compound 1 was inactive. In addition, neither 1-monoacylglycerols nor phospholipids structurally related to 1 showed HIF-like activities. As DAGs are protein kinase C (PKC) activators, 12-O-tetradecanoylphorbol-13-acetate (12), urushiol C15:3-Δ (13), and a skin irritant anacardic acid C15:1-Δ (14) were also examined for HIF-like activities toward the Nostoc cells. Neither 12 nor 13 showed HIF-like activities, whereas 14 showed an HIF-like activity at 1 nmol/disc. These findings appear to indicate that some DAGs act as hormogonium-inducing signal molecules for filamentous Nostoc cyanobacteria.
珊瑚根是苏铁（苏铁 revoluta）的特化组织，参与与固氮蓝藻（ Nostoc ）的共生。我们发现珊瑚根的粗甲醇提取物诱导蓝藻属丝状细胞聚集体分化为游动的藻殖段。因此，使用基于生物测定的分离法追踪藻殖段诱导因子（HIF），并将活性物质表征为二酰基甘油（DAG）混合物，主要由 1-棕榈酰-2-亚油酰-sn-甘油（1）、1-棕榈酰-2-油酰-sn-甘油（2）、1-硬脂酰-2-亚麻酰-sn-甘油（3）和 1-硬脂酰-2-亚油酰-sn-甘油（4）组成。对映选择性合成的化合物 1 在 1 nmol（0.6 µg）盘上对丝状细胞表现出明显的 HIF 活性，而合成的 2-亚油酰-3-棕榈酰-sn-甘油（1'）和 1-棕榈酰-2-亚油酰-rac-甘油（1/1'）的活性低于 1。相反，化合物 1 的酰基位置异构体 1-亚麻酰-2-棕榈酰-rac-甘油（8/8'）没有活性。此外，与 1 结构相关的 1-单酰基甘油或磷脂均没有表现出 HIF 样活性。由于 DAG 是蛋白激酶 C（PKC）激活剂，因此还检查了 12-O-十四烷酰佛波醇-13-乙酸酯（12）、漆酚 C15:3-Δ（13）和皮肤刺激剂漆酚 C15:1-Δ（14）对 Nostoc 细胞的 HIF 样活性。12 和 13 均没有表现出 HIF 样活性，而 14 在 1 nmol/disc 时表现出 HIF 样活性。这些发现似乎表明，某些 DAG 作为丝状 Nostoc 蓝藻的藻殖段诱导信号分子发挥作用。
