Meiosis in Coprinus. III. Timing of meiotic events in C. lagopus (sensu Buller)

Abstract

The close synchrony of meiotic events within the basidiocarp of Coprinus lagopus permits the time sequence study of division stages. It takes about 16 h from the beginning of karyogamy to the completion of meiosis (zygotene to tetrad formation). Nuclear fusion and chromosome pairing occupy about 4 h, pachytene 5 h, diplotene 4 h, and all the other stages including the second meiotic division appear to be very transitory and together occupy less than 3 h. The centrosome divides at late diplotene. The entire second meiotic division takes about 1 hour and different stages overlap a great deal. The four sterigmata are formed after the completion of second division. The basidiospores mature in 8–10 h after the tetrad formation.

Life History and Developmental Processes in the BasidiomyceteCoprinus cinereus

“…During this time, stage 1 primordia grow from about 2-3 mm to 7-9 mm in diameter. They are characterized by well-developed gills containing basidia of about 12 m and cystidia (large sterile cells sized between 20 and 25 m) at their surface (263,344,402,450). Gills are essentially vertical plates arranged radially around the stipe.…”

“…As the gill cavity moves outward, it expands tangentially, making room for a new gill organizer to appear, which initiates further gill splitting (89,333,414,422,424 (277,344). During further development of stage 1 primordia, the basidia change from a cylindrical to a club-shaped structure (402). Glycogen accumulates in the subhymenium and cystidia and in the basal plectenchyma of the stipe (263,344,450).…”

“…A pore cap develops at the spore apex and covers the germ pore, and the walls thicken extensively; within 2 h, the spores become pigmented (184,193,313,314). Nuclei migrate into the spores at stage 4 (239,313), although other authors report earlier nuclear migration (402). The cytoplasma of stage 4 spores resembles that of mature, ungerminated spores.…”

“…A remarkable feature of C. cinereus is the natural synchrony of karyogamy and meiosis-60 to 85% of all basidia within a given cap will always be in the same developmental phase during all stages of meiosis. In general, the basidia at the bottom of the gills are slightly more advanced in their development than are those at the apex (53,55,155,271,402). Synchronization of karyogamy and meiosis occurs through light impulses (286,324) and is thought to be a consequence of spore liberation by autodigestion of the cap, since this limits the time during which mature basidiospores can be produced on the gills (53,55).…”

“…When carefully prepared, a few gills can be removed at successive time points from a single developing mushroom without resulting in any apparent effects on development, and progeny will still be left for genetic analysis (239,271,283). Moreover, because of the control by environmental signals (275,278,286) meiosis can be monitored in a regular and predictable manner (402). C. cinereus has a total genome size of 37,500 kb (115, 539) distributed over 13 chromosomes (176,371,391,392,535), although only 10 linkage groups have been defined genetically so far (71,366).…”