21st Century Guidebook to Fungi

In Chapter 9 we showed how fungal hyphae are capable of a wide range of cell differentiation, and in other chapters (particularly Chapters 3 and 8) we have mentioned and illustrated some of the variety of multicellular fruiting structures (sexual and asexual) that fungi can produce. It must be evident, therefore, that a fungal mycelium has a number of alternative developmental pathways open to it:

• continuation of hyphal growth

• production of asexual structures

• progress into the sexual cycle.

These are not strict alternatives, because a mycelium of even modest size may express all of these possibilities at the same time, so we can deduce that whatever control of genetic expression is involved must be local.

In this chapter we explain the nature of development and morphogenesis in fungi and the formal terminology of developmental biology. Observations and experiments on fungal developmental biology lead to the conclusion that there are ten ways to make a mushroom, depending on different arrangements of competence and regional patterning. As specific examples we show how the Coprinopsis fruit body makes hymenia, and how Coprinopsis and Volvariella make gills (not forgetting how polypores make tubes). The Coprinopsis fruit body also provides examples of the construction of mushroom stems and the coordination of cell inflation throughout the maturing fruit body; which leads us to consider the mechanics of the mushroom fruit body.