Abstract
The mitochondrion is a vital organelle in most eukaryotic cells. It contains its own DNA which differs from nuclear DNA, since it is often inherited from only one parent during sexual reproduction. In anisogamous mammals, this is largely due to the fact that the oocyte has over 1000 times more copies of mitochondrial DNA than the sperm. However, in the isogamous fungus Cryptococcus neoformans, uniparental mitochondrial inheritance (UMI) still occurs during sexual reproduction. It is proposed that UMI might have evolved in the last common ancestor of eukaryotes. Thus, understanding the fundamental process of UMI in lower eukaryotes may give insights into how the process might have evolved in eukaryotic ancestors. In this review, we discuss the current knowledge regarding the cellular features as well as the molecular underpinnings of UMI in Cryptococcus during the mating process, and open questions that need to be answered to solve the mystery of UMI in this eukaryotic microbe.
Highlights
Mitochondria, a characteristic organelle of eukaryotes, are thought to have evolved through an endosymbiotic relationship between an ancient archaeal cell and an alpha-proteobacterium [1].This symbiotic relationship is likely to have evolved in the last common ancestor of Eukaryota [2,3].In addition to being the powerhouse of the cell, the mitochondrion is responsible for diverse critical cellular events such as aerobic respiration, apoptosis, and calcium signaling [1]
In Cryptococcus during the mating process, and open questions that need to be answered to solve the mystery of uniparental mitochondrial inheritance (UMI) in this eukaryotic microbe
The mitochondrial genome is a fraction of the size of the nuclear genome: in humans, mtDNA consists of a circular DNA molecule containing approximately 16,000 base pairs, compared to the 3 × 109 base pairs of the nuclear genome arranged in linear chromosomes
Summary
Mitochondria, a characteristic organelle of eukaryotes, are thought to have evolved through an endosymbiotic relationship between an ancient archaeal cell and an alpha-proteobacterium [1] This symbiotic relationship is likely to have evolved in the last common ancestor of Eukaryota [2,3]. Evidence that Mendel’s laws of inheritance does not apply to organelle DNA was first shown in 1909 in independent studies by Carl Correns and Earl Bauer [5] They found that chloroplast plastids in different plant species were inherited maternally (Corren) or biparentally (Baur) [6]. The drastic difference in mtDNA copies can largely explain UMI in mammals, this cannot apply to UMI during sexual reproduction in isogamic lower eukaryotes like the green alga. We discuss controversies and challenges that need to be addressed to resolve the mechanism underpinning UMI in this eukaryotic microbe
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