Plant hormones: a fungal point of view

Abstract

Most classical plant hormones are also produced by pathogenic and symbiotic fungi. The way in which these molecules favour the invasion of plant tissues and the development of fungi inside plant tissues is still largely unknown. In this review, we examine the different roles of such hormone production by pathogenic fungi. Converging evidence suggests that these fungal-derived molecules have potentially two modes of action: (i) they may perturb plant processes, either positively or negatively, to favour invasion and nutrient uptake; and (ii) they may also act as signals for the fungi themselves to engage appropriate developmental and physiological processes adapted to their environment. Indirect evidence suggests that abscisic acid, gibberellic acid and ethylene produced by fungi participate in pathogenicity. There is now evidence that auxin and cytokinins could be positive regulators required for virulence. Further research should establish whether or not fungal-derived hormones act like other fungal effectors.

Keywords: fungi; plant hormones; virulence.

Figure 1

Schematic representation of the effects of hormones on fungal biology. A schematic view of yeast‐like (light grey background), infecting and sporulating filamentous fungi is given. This model summarizes the effects of hormones on fungal biological processes reported to date; the effects caused by the dose, the molecule tested, other environmental factors and the species studied are provided in the text and could differ among fungi. Arrows and ‘T’ bars represent positive and negative effects, respectively. ABA, abscisic acid; AUX, auxins; ET, ethylene; CKs, cytokinins; GAs, gibberellic acids; JA, jasmonic acid; SA, salicylic acid.