THE PLANT CELL, Vol 6, Issue 10 1477-1484, Copyright © 1994 by American Society of Plant Biologists
Occurrence of Mitochondria in the Nuclei of Tobacco Sperm Cells
H. S. Yu and S. D. Russell
Department of Botany and Microbiology, University of Oklahoma, Norman, Oklahoma 73019-0245
Tobacco sperm cells contain intact mitochondria within their nuclei with a
frequency of 0.35 [plusmn] 0.13 per cell. These inclusions appear to
originate from mitochondria found among chromatids in the highly elongated
metaphase plate of the dividing generative cell. These organelles are
apparently captured during the reconstitution of the nuclear envelope. Only
sperm cells were observed to contain these nuclear mitochondria; generative
cells, vegetative pollen cells, transmitting tissue cells, unfertilized egg
cells, and central cells lacked them. Nuclear mitochondria were also seen
in the nuclei of the egg and central cell after fusion with sperm nuclei,
suggesting that nuclear mitochondria are transmitted into the zygote and
primary endosperm cells during double fertilization. Organellar inclusions
in the sperm nucleus provide a potential mechanism for transmitting
organellar DNA into the next generation and could potentially facilitate
the transfer of genetic material between the nucleus and other organelles.