Dynamic rearrangement and autophagic degradation of the mitochondria during plant spermiogenesis
A collaborative team of researchers from the National Institute for Basic Biology, the University of Tokyo, and Gunma University in Japan reported that in the liverwort Marchantia polymorpha, the number of mitochondria in ...
Most eukaryotic cells possess mitochondria in greatly varying numbers and shapes depending on the cell type and cellular conditions. Compared with other cell types, eukaryotic sperm cells generally exhibit a characteristic mitochondrial morphology and distribution, while also exhibiting a remarkable diversity among species.
Though the word "sperm" brings to the mind images of the mammalian sperms that "swim," certain groups of plants also use sperms for sexual reproduction. One such group is the Bryophytes that are commonly found in city parks and backyards of homes.
A single bryophyte somatic cell possesses anywhere from tens to hundreds of mitochondria. By contrast, the spermatozoid cell possesses a fixed number of two mitochondria: one in the head and the other in the tail of the cell body. However, the mechanism by which these two mitochondria are formed during spermiogenesis remains unclear.
In an article published in Cell Reports, this research team examined in detail how the number and shape of mitochondria change during the transformation of spermatids into spermatozoids (spermiogenesis) in liverworts.
During spermiogenesis, the mitochondrial number is reduced to one through fission and autophagic degradation, and subsequently increased to two through fission of the anterior mitochondrion. Other cytoplasmic components are later degraded through autophagic (and non-autophagic) degradation. Credit: NIBB
The wild-type spermatozoids possess two mitochondria, whereas, most defective spermatozoids in mitochondrial fission possess only one anterior mitochondrion. The mitochondria are shown in green. Credit: NIBB
Autophagy-defective spermatozoids possess a larger number of mitochondria, as opposed to two mitochondria in wild-type spermatozoids. Mitochondria and nuclei are colored green and blue, respectively. Credit: NIBB