SYNCHRONOUS MITOCHONDRIAL DIVISION IN NEUROSPORA CRASSA

Abstract

Samples of mycelium of Neurospora crassa of known age were harvested from agar plates and examined with the electron microscope. The relative volume of the mitochondria was determined for mycelium of different ages. The volume measurements indicated that the mitochondria were dividing synchronously in fronts 6, 13, and 22k• hr behind the growing hyphal tips. The sequence of mitochondrial division is hypothesized to include mitochondrial cupping followed by division which results in closely associated daughter mitochondria. On the basis of percentages of mitochondrial cupping and association, mitochondrial division was postulated to be occurring at 6, 14, and 26 hr. Close agreement between the mycelial mass doubling time and the calculated mitochondrial mass doubling time indicates that synchronous mitochondrial division is sufficient to maintain growth. The possibility that mitochondrial division is due to intercellular regulation of a mitochondrial genetic system is advanced.

Studies on mitochondrial structure and function in Physarum polycephalum. IV. Mitochondrial division cycle.

“…These observations support previous results (Lewitsky 1924, Lehninger 1964, Diers 1966, Hawley and Wagner 1967, and Oosumi and Sando 1969 suggesting that dumbbell-shaped mitochondria may be dividing mitochondria and that new mitochondria are formed by the division of preexisting mitochondria.…”

“…14 h. This is very similar to the duration of the mitotic cycle, sug gesting that there is a mechanism which correlates the nuclear and mitochondrial division cycles in multinucleated cells. The duration of the mitochondrial division cycle of P. polycephalum is slightly longer than that of Neurospora crassa which lasts only 8.5h (Hawley and Wagner 1967).…”

Biogenesis of Mitochondria in Trichoderma viride: Structural Changes in Mitochondria and Other Spore Constituents during Conidium Maturation and Germination

“…A striking structural change in the mitochondria during conidium maturation and germination was the disappearance of the dumb-bell and ring-shaped configurations at the resting conidium stage and their reappearance during conidial swelling. Similar mitochondrial shapes have been found in a number of other organisms under various physiological conditions (Christensen & Chapman, 1959 (Hawley & Wagner, 1967;Mitchell & McKeen, 1970). Examination of serial sections of such configurations in T. viride, however, revealed that the dumb-bell and ring shapes were derived from slicing a three-dimensional cup-shaped organelle (Fig.…”

SEPARATION OF MITOCHONDRIAL MEMBRANES OF NEUROSPORA CRASSA

“…Samples were rinsed in three 10-min changes of buffer, fixed 1 hr in 1 % osmium tetroxide, rinsed twice in distilled water, and stained in 0 .5% uranyl acetate for 16-20 hr. Further processing was accomplished according to the procedure of Hawley and Wagner (14) . Thin sections were cut on a Porter-Blum MT-I ultramicrotome equipped with a diamond knife .…”