Crystalloids of Phycomyces Sporangiophores: Nature and Photosensitive Accumulation

Abstract

(4,10). Kinetic analyses have likewise pointed to the possibility that adaptation of the growth rate involves relatively large changes in metabolic pool levels (3, 7). Thus it seems that a study of constitutional changes in response to light may yXield insights into the still elusive earlx steps in the photores-ponses of this fungus. Toward that end, the present report descrilbes light-induced changes in the accumulation of crv-stalloids in the sporangiophore.The occurrence of octahedral cry-stalloids in the sl)orangiophores of mucoraceous fungi has been kinowni since 1872 (12,18). The crystalloids of P. blakeslceanus have been found by electron microscopic examination to consist of approximately isodiamiietric subunits in a cubic space lattice with spacings in the vicinity of 120A (18, 23). In the same studies, crystalloids were found in s,porangiophores that were as small as 1 % of the terminal size, but not in vegetative hyphae or storage vesicles.

The sporangiophore of Phycomyces blakesleeanus: a tool to investigate fungal gravireception and graviresponses

“…). The octahedral crystals, which had been known for several decades (Thornton ; Wolken , ; Ootaki & Wolken ), are made up of three proteins that are associated with pterin‐ and flavin‐like pigments (Eibel et al . ; Fries et al .…”

“…The central vacuoles of Phycomyces contain octahedral protein crystals of high density (1.27 gÁcm À3 ) that rapidly sediment upon reorientation of the sporangiophore, and must participate in gravisusception because mutants lacking these crystals are gravitropically moderately defective (Schimek et al 1999a,b) and display an elevated threshold ). The octahedral crystals, which had been known for several decades (Thornton 1969;Wolken 1969Wolken , 1972Ootaki & Wolken 1973), are made up of three proteins that are associated with pterin-and flavinlike pigments Fries et al 2002). There is strong circumstantial evidence that the vacuolar crystals also operate as gravisusceptors in other zygomycete fungi.…”

Statoliths in Phycomyces: Characterization of Octahedral Protein Crystals

“…In previous studies we showed that paracrystalline protein bodies, so-called octahedral crystals, occurring in sporangiophores of Phycomyces blakesleeanus function as statoliths (Horie et al, 1998a;Schimek et al, 1999a,b). These octahedral crystals had been known before, but had never been associated with gravitropism (Thornton, 1968(Thornton, , 1969Thornton and Thimann, 1964;Wolken, 1969Wolken, , 1970Ootaki and Wolken, 1973), even though their purported high specific mass (Zalokar, 1969) would have let them appear ideal contenders as statoliths. Octahedral crystals occur in the central vacuoles of the sporangiophore, in which they can move freely.…”

OCTAHEDRAL CRYSTALS IN PHYCOMYCES. II

“…Crystals in Phycomyces sporangiophores were first observed by van Tieghem (1875) . More recently, they have been investigated by Thornton and Thimann (1964), Thornton (1969), Wolken (1969), and Zalokar (1969) . However, the function of these crystals in Phycomyces is not known .…”