Metabolism of the Phytoalexin Rishitin by Gibberella pulicaris Is Highly Reduced in Liquid Culture

Abstract

Gibberella pulicaris is a causal agent of potato dry rot. The fungus is able to metabolize the potato phytoalexin rishitin, a trait which is possibly associated with virulence against potato tubers. Metabolism of the plant defence compound on agar medium is completed within 24 h. In contrast, incubations in various liquid media and buffers highly reduced degradation of rishitin with a maximal reduction of substrate down to 30% of the initial concentration within five days. The structurally related sesquiterpene lubimin was degraded completely within 12 hr in all tested liquid media. Our data suggest that rishitin metabolism is under an unusual genetic control requiring growth on a solid surface for efficient metabolism.

Degradation of the benzoxazolinone class of phytoalexins by Fusarium pseudograminearum, a pathogenic fungus of wheat

“…'pisi' uses a demethylase to render the pea defence compound pisatin ineffective (Milani et al, 2012). Similarly, F. sambucinum deals with the potato phytoalexin rishitin by exporting the phytoalexin using an ABC transporter (Fleissner et al, 2002), as well as full degradative metabolism (Weltring & Altenburger, 1998). Defeating the saponin tomatine, a defense compound produced by tomato, is achieved by the detoxification enzyme, tomatinase produced by the tomato wilt pathogen F. oxysporum f. sp.…”