Elevated Riboflavin Requirement for Postphotoinductive Events in Sporulation of a Trichoderma Auxotroph

A riboflavin auxotroph of Trichoderma required more riboflavin for blue-light-induced conidiation than for growth. Colonies transferred after illumination from 0.2 micromolar (limiting conidiation, not growth) to 3.5 micromolar riboflavin (nonlimiting), responded the same as those grown at 3.5 micromolar. The additional riboflavin is therefore not required as a photoreceptor. The data do not rule out the hypothesis that cryptochrome(s) is/are flavin(s).