Purification and the mode of actions of differentiation inducing factors in a cellular slime mold

细胞黏菌Dectyostelium discoideum的发育主要依赖于多细胞复合体的形成。使用这种生物体，我们已经着手澄清由细胞分泌并诱导分化的物质的性质。结果如下：（1）在高细胞密度的振荡培养中，饥饿0 h（t_0）或5 h（t_5）的细胞在作为分离的单细胞孵育时不经历前孢子分化。然而，<10>在cAMP和BSA存在下，在相同条件下饥饿10 h（t_）的细胞也是如此。这表明t5和t10之间的细胞相互作用对于提供细胞在分离条件下分化的能力是必要的。(2)分离的t_5细胞在培养条件下能进行前孢子分化<11>，表明存在使t_5细胞具有分化能力的物质。该物质具有热稳定性、链霉蛋白酶抗性和水溶性。Amicon分馏证明存在两种以上具有不同分子量的组分。这些物质仅对饥饿5小时以上的细胞起作用。(3)细胞在隔离条件下分化的能力在饥饿11小时后降低。然而，通过添加从发育后期的细胞或培养基中获得的另一种因子，这种降低得以恢复。后一种因子是耐热的，可溶于酸性有机溶剂，并可通过HPLC分离成两种不同的组分，这两种组分的分子量均为约300。这两个过程似乎处于不同的发展阶段。盘状突通过细胞在不同阶段分泌的多种物质的作用而进行。

Development of the cellular slime mold Dectyostelium discoideum greagly depends on the formation of multicellular complexes. Using this organism, we have undertaken to clarify the nature of the substance(s) which is secreted by cells and induces differentiation. The results are summarised as follows:(1) Cells starved for 0 h (t_0) or 5 h (t_5) in the shake culture at a high cell density do not undergo prespore differentiation when incubated as an isolated, single cell. However, 10 h (t_<10>) starved cells under the same conditions do so in the presence of cAMP and BSA. This indicated that the cellular interactions between t5 and t10 is essential to provide cells an ability to differentiate under isolated conditions.(2) Isolated t_5-cells can undergo prespore differentiation in the conditioned medium obtained from the t_<11>-cell culture, indicating the presence of a substance(s) which renders the t_5-cells competent for differentiation. This substance(s) is heat stable, pronase resistant and water soluble. Amicon fractionation demonstrates the presence of more than two components having different molecular masses. The substances exert thier effects only on the cells starved for more than 5 h.(3) The ability of cells to differentiate under isolated conditions decreases after 11 h of starvation. However, this decrease is restored by addition of another factor(s) obtained from the cells or medium of the late stages of development. This latter factor(s) is heat resistant, soluble in acidic organic solvents and separable into two distinct components by HPLC, both of which have a molecular mass of about 300. These two appear to work at different stages.From these results, it is concluded that the development of D. discoideum proceeds through the action of multiple substances which are secreted by cells at different stages.