A REGULATORY SYSTEM CONTROLLING INHIBITION IN THE SEXUAL CYCLE OF NEUROSPORA

Abstract

A cross made by adding conidia to protoperithecia on a mycelium of opposite mating type inhibits a subsequent cross on the same mycelium, or on an adjacent mycelium connected either by hyphae or medium. The inhibitory activity reaches a steady rate of movement through the area of the second cross from the area of the first cross and brings about either total or partial inhibition of the second cross, depending upon certain controllable variables; translocation of the activity occurs primarily through the hyphae but to a lesser degree through the medium as well. Total inhibition is not a result of modification of the medium by the first cross, such as depletion of nutrients or change in pH. An uncrossed mycelium which received activity from a crossed mycelium becomes inhibited either irreversibly or, to a certain extent, reversibly, depending upon the degree of activity received; in either event, transmission of this passive activity may occur from this mycelium to an outgrowing mycelium on fresh medium. The experiments reported here were done primarily with N. tetrasperma, in which the inhibitory effect was first found, but the effect has also been observed in N. crassa.