Hormones in Mycelial Fungi
The major means that a fungus has to monitor the environment is through its chemosensory system. Thus, it is not surprising that specific chemicals are used as signalling molecules in a range of activities of fungal cells. These chemicals are diverse in t
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CONTENTS I. II. A. B. C.
D. E. III. A. B. C.
D. IV.
Introduction ............................. . Sex Hormones ............................ Oomycota .............................. . Chytridiomycota ......................... . Zygomycota ............................. . Dikaryomycota: Ascomycetes ............. . Dikaryomycota: Basidiomycetes ........... . Hormones of Growth and Development ..... . Hormones Resembling Those of Animals .... . Hormones Resembling Those of Plants ...... . Hormones of Basidiomycetes Fruit Bodies ... . Hormones Involved in Autotropisms? ...... . Conclusions ............................. . References .............................. .
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I. Introduction The major means that a fungus has to monitor the environment is through its chemosensory system. Thus, it is not surprising that specific chemicals are used as signalling molecules in a range of activities of fungal cells. These chemicals are diverse in their chemical structures, in their effective concentrations, in their specificities and in their types of action. This chapter discusses nonnutritional chemical control of growth and development of fungi, concentrating on hormones, but also considering other chemicals with effects that are apparently specific. The term "hormone" will be used in its broadest sense as defined by Huxley (1935) as "a chemical substance produced by one tissue with the primary function of exerting a specific effect of functional value on another tissue". Raper (1952) adapted this definition to cover "the regulation of sex processes (in fungi) by substances produced by the affected plant or by others of the same species ... performing indispensible regulatory roles in the sexual process". Other terms to be found in the fungal literature i. Department of Microbiology, Marchial College, UniverSity of Aberdeen, Aberdeen AB9 lAS, UK
are "pheromone" for a chemical acting at a distance (cf. insect sex attractants), "growth substance" for a chemical regulating development by its overall concentration (cf. plant auxins), "morphogen" for a chemical triggering localised differentiation (cf. retinoic acid in animal embryogenesis) and "sex factor" as a general term for a chemical controlling sexual morphogenesis (Dyer et al. 1992). Reviews of various aspects of fungal hormones include those of Dyer et al. (1992), Gooday (1974, 1983), Gooday and Adams (1992). Machlis (1972), Raper (1952) and Van den Ende (1984) .
II. Sex Hormones A. Oomycota
Antheridiol and oogoniol are sterol sex hormones ~roduced by female and male hyphae, respectIvely, of Achlya species which under conditions of sta~~tion cause male hyphae to develop an~hendla and female hyphae to develop oogonia (Fig. 1, Table 1; McMorris 1978). Details of these systems are discussed Chapter 25. There are certainly other equivalent hormone systems in other oomycete species, but these remain to be characterised (Gooday and Adams 1992). There has been much interest in the possible occurrence of sterol hormones as regul
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