MORPHOGENENSIS OF THE CARPOPHORE OF COPRINUS CINEREUS

Abstract

An interpretation of carpophore morphogenesis is presented which is derived both from the literature and from original observations. Cultured material of Coprinus cinereus (also called C. macrorhizus and C. lagopus) has been studied using biochemical assays together with light‐, scanning‐ and transmission electron microscopy to provide details of histology and the levels and distribution of protein, glycogen and NADP‐linked glutamate dehydrogenase during the course of development of stipe and cap. Initially, aggregates of hyphae form primordia which subsequently develop into mature carpophores. During stipe development glycogen deposition is at first restricted to cells forming a cup‐shaped mass in the stipe base, but very early in primordium development this deposit is depleted and glycogen accumulates in the gills, particularly the subhymenium, where it probably serves as a reserve material for the later stages of cap development. The distribution of cytochemically detectable protein differs from that of glycogen in that the former initially accumulates in the upper regions of the primordial stipe and in the gill hymenium. The stipe showed no conspicuous change in its content of protein during development although in the cap the fraction of the dry wt represented by protein increased substantially. Primordial stipes are composed of overlapping cells of hyphal dimensions with dense cytoplasm and small vacuoles. Stipe development depends on cell enlargement, this seeming to be biphasic; an initial increase in volume being attributable to an increase in cell diameter to give an undifferentiated dikaryotic central region and a differentiated multi‐nucleate cortex. Stipe growth depends on reallocation of cellular components, no one reserve material being identifiable as of prime importance although a few simple sugars do appear to be correlated with the osmoregulatory activity connected with the large scale uptake of water involved in stipe elongation. In the primordium cap the subhymenium is an open tissue of interwoven hyphae, the cells containing large accumulations of glycogen. The hymenium is formed from dikaryotic branches of the subhymenial hyphae to become an organised layer of hyphal tips. Subsequently, although the subhymenial hyphae remain as such, the hymenial cells become inflated. The paraphyses come to form a pavement of appressed and interlocked cells each containing a large central vacuole. Basidia are only slightly enlarged and contain dense cytoplasm with few vacuoles; they contrast with the much extended and inflated cystidia. Despite their inflation, all three cell types still show continuity with the subhymenial hyphae. During cap expansion the major inflationary force is paraphyseal enlargement but as the gill lamellae are removed by autodigestion fürther cell inflation in the pileal flesh enables it to assume a supportive role. In the earlier stages there is some correlation between declining glycogen content of the cap and increasing activity of NADP‐linked glutamate dehydrogenase. It is suggested that cap expansion is driven osmotically and that at least some of the osmotically active materials are synthesised through the urea cycle. At first this activity could be supported by glycogenolysis and amination but later on substrates may be provided by autodigestion of spent gill tissues. It is concluded that cap development is regulated by a metabolism quite distinct from those of either the parental mycelium or the stipe, and that the fundamental metabolic changes occurring throughout carpophore development are orchestrated by light. As carbohydrate nutrients in the medium approach exhaustion suppression of mycelial morphogenesis into hyphal aggregates is lifted, but the subsequent switch from the vegetative pathway of sclerotium development to carpophore formation is normally dependent on illumination with low intensity blue light. Growth then becomes polarized to form a presumptive pileus and glycogen is mobilized from the surrounding mycelium to accumulate at the base of the stipe. Receipt of a second illumination inhibits fürther growth of the stipe base and causes glycogen reserves to be translocated to the cap. Glycogen is utilized in the cap to produce glycolytic intermediates, allowing regulation of many aspects of metabolism by catabolite concentration and contributiong to the diverse syntheses required for spore formation and dissemination. Copyright © 1979, Wiley Blackwell. All rights reserved