Figure 4.

Model of mito-UPI regulation in Cryptococcus species. The mito-UPI process starts when compatible mating partners sense pheromones from each other [(A) and (B)]. The asymmetric nature of this process could lead to activation of transcription factors (e.g., MAT2) and target genes whose products differentially tag the mitochondria in the two mating partners so that they would be targeted for or protected from degradation by mitophagy, or other processes yet to be defined. (C) Successful pheromone and pheromone receptor interaction induces the formation of a conjugation tube from the MATα parent, through which the MATα nucleus migrates into the MATa parent to form the zygote. It is possible that the mitochondria remaining in the MATα parent start degradation at this point, a process that could involve mitophagy. (D) The zygote contains the two nuclei, as well as the mitochondria from the MATa parent. It is possible that trace amounts of mitochondria from the MATα parent also migrate into the zygote. The mitochondria remaining in the conjugation tube and the MATα parent cell continue degradation. (E) Hyphae are initiated from the zygote on the opposite side of the conjugation tube. This further increases the chances of mitochondria from the MATa parent being included in the hyphae, and consequently, the eventual mating progeny inherit mitochondria mostly from the MATa parent. Additionally, the trace amount of mitochondria from the MATα parent would be degraded through mechanisms such as mitophagy. mito-UPI, mitochondrial uniparental inheritance.