Metabolic alterations in bean rust germlings during differentiation induced by the potassium ion

Abstract

Induction of differentiation of uredospore germlings of the bean rust fungus ( Uromyces phaseoli) by K + offers a new approach to the study of the differentiation process. Plastic membranes, required to induce infection structures thigmotropically, often interfere with biochemical analyses, and these may now be omitted from experimental protocols when this is advantageous. In this study, germling metabolism was surveyed for changes which occur in response to potassium salts. It was found that K + induced a small but significant shift in metabolism toward an increased rate of protein synthesis at the expense of sugars. Studies on respiration showed that a shift occurred about the time of appressoria development. An increased ionic flux was not a part of the inductive effect. Continued synthesis of protein was required for appearance of the appressoria. DNA replication and mitosis were also induced by the K + ion. Although the induction of infection structures by either chemicals or contact stimuli starts mitosis, the two processes may be different.