Photoreceptor pigment that induces differentiation in the slime mold Physarum polycephalum.

An extract of small molecules (molecular weight less than 500) of the slime mold Physarum polycephalum undergoes a shift in ultraviolet-visible absorption spectrum upon illumination. This illumination also confers on the extract the ability to induce sporulation when injected into a starved, unilluminated slime mold. The spectral shift and appearance of the sporulation-inducing activity both occur regardless of whether the illumination is carried out on an intact slime mold or on the plasmodium-free extract itself. Thin-layer chromatography resolves the slime mold extract into four major visible fractions. One of these has high sporulation-inducing activity after illumination in vitro.