T. Denny, P. S. Matthews, H. Vanetten
1987
Citations
0
Influential Citations
32
Citations
Journal
Physiological and Molecular Plant Pathology
Abstract
Abstract Nectria haematococca MP VI, a pathogen of pea, is tolerant of pisatin, the major phytoalexin that accumulates in pea during pathogenesis. One mode of pisatin tolerance is the detoxification of this phytoalexin. In previous research, we identified and partially characterized a second mode of tolerance that occurs independently of detoxification (“nondegradative” tolerance). In the current study, we attempted to determine a likely mechanism for nondegradative pisatin tolerance. Pisatin was taken up and retained by mycelium of isolate 126-80 during the time that growth was inhibited by the phytoalexin, but a decrease in the amount of pisatin retained was associated with development of nondegradative tolerance. The evidence was consistent with nondegradative tolerance being the result of a mechanism that excludes pisatin from its site of action, although other mechanisms could not be ruled out. The initial accumulation of pisatin did not appear to require metabolic energy, but energy and protein synthesis were needed for the expression of reduced pisatin retention. However, it was unclear whether metabolic energy was necessary for the maintenance of reduced levels of pisatin. In the absence of any significant changes in pisatin efflux, we deduced that reduced pisatin retention probably occurs when the rate of pisatin influx decreases, and that membrane modifications may be occurring simultaneously.