MUSHROOMS UPRIGHT, SIDEWAYS AND INSIDE-OUT

Morphogenesis is not simply a matter of playing out a predefined genet ic programme. Expression of developmentally important genes is epigene tic and place- and time-dependent relying on previously-formed tissue structures. Most differentiated hyphal cells require reinforcement of their differentiation 'instructions'. This reinforcement is part of th e context (chemical, electrical and structural/mechanical environment) within which they normally develop. Key words at each stage of develo pment in fungi are: competence, induction and change. Fungal morphogen esis is compartmentalized into a collection of 'sub-routines' which ar e distinct genetically and physiologically. Flexibility in expression of developmental sub-routines illustrates that tolerance of imprecisio n is an important attribute of fungal morphogenesis.