CONFIGURATION OF ACTIN MICROFILAMENTS DURING SPORANGIUM DEVELOPMENT IN ACHLYA-BISEXUALIS - COMPARISON OF 2 STAINING PROTOCOLS

The spatial organization of actin microfilaments during the asexual life cycle of Achlya bisexualis has been examined by two methods. One is the standard procedure described by Heath [Eur J Cell Biol (1987) 44: [0-16], in which specimens are fixed with formaldehyde and then stained with rhodamine-phalloidin. In the other, introduced by Sonobe and Shibaoka [Protoplasma (1989) 148: 8086], specimens are treated with the protein crosslinking agent MBS (m-maleimidobenzoyl-N-hydroxysuccinimide) before fixation and staining. Both methods display the actin-rich cleavage zones that outline the developing zoospores. However, in extending hyphae and young sporangia the images are significantly different. Specimens pretreated with MBS display more prominent axial microfilament cables than do standard specimens, while peripheral actin plaques are sparse or absent. The results suggest that actin microfilaments occur in several configurations, some of which may be obscured by the standard fixation procedure. Pretreatment with MBS, though probably subject to artefacts of its own, may help preserve some features that would otherwise be missed.