PATERNAL INHERITANCE OF PLASTID DNA IN GENUS PHARBITIS

The inheritance of plastid DNA in Pharbitis was studied by the method of restriction fragment length polymorphisms (RFLP).Experimental results showed that plastid DNA from Pharbitis was paternally inherited in reciprocal crosses,P. nil ×P. limbata and P. limbata×P. nil hybrids.But,in the cross of P. limbata×P. nil,the possibility of biparental inheritance of plastid DNA could not be roled out in our preliminary experiment.Thus Pharbitis became the third genus among angiosperms characterized with male plastid transmission.The mechanisms of paternal plastids DNA inheritance in Pharbitis is unclear.The authors proposed that dilution,exclusion and/or degeneration of maternal plastid,including their DNA,after fertilization should be considered.

Paternal inheritance of mitochondrial DNA in the sheep (Ovine aries)

Paternal inheritance of mitochondria DNA in sheep was discovered by examination of 152 sheep from 38 hybrid families for mtDNA D-loop polymorphisms using PCR-RFLP, amplification of repeated sequence somain, and PCR-SSCP of the D-loop 5′ end region of a 253 bp fragment. Our findings have provided the first evidence of paternal inheritance of mtDNA in sheep and possible mechanisms of paternal inheritance were discussed.

Cytological Mechanism of Cytoplasmic Inheritance in Pinus tabulaeformis: Ⅱ. Transmission of Male and Female Organelles During Fertilization and Proembryo Development

In an earlier report the ultrastructure and nucleoid organelles of male gamete in Pinus tabulaeformis Carr. have been described. Presently, the ultrastructure of the cytoplasm of the egg cell and pollen tube—immediately before fertilization and during cytoplasmic transmission of male gametophyte—has been described for the same species. The fate of parental plastids and mitochondria in the proembryo has also been followed. The mature egg cell contains a large amount of mitochondria, but seems to lack normal plastids. Most plastids have transformed into large inclusions. Apart from the large inclusions, there are abundant small inclusions and other organelles in the egg cell. During fertilization, pollen tube penetrates into the egg cell at the micropylar end and thereafter the contents are released. Plastid and mitochondrion of male origin are lacking near the fusing sperm_egg nuclei. The second sperm nucleus—not involved in karyogamy—remains at a site near the receptive vacuole. This nucleus is surrounded by large amount of male cytoplasm containing mixed organelles from the sperm cell, tube cell, and egg cell. At the free nuclear proembryo stage, organelles of male and female origin are visible in the perinucleus_cytoplasmic zone. Most of the mitochondria have the same morphological features as those in the egg cell. Some of the mitochondria appear to have originated from the sperm and tube cells. Plastids are most likely of male gametophyte origin because they have similar appearance as those of the sperm and tube cell. Large inclusions in the egg cell become vacuole_like. Paternal plastids have been incorporated into the neocytoplasm of the proembryo. In the cellular proembryo, maternal mitochondria are more abundant. Plastids resembling those of the sperm and tube cell are still present. These cytological results clearly show that in P. tabulaeformis, plastids are inherited paternally and mitochondria bipaternally. The cytological mechanism of plastid and mitochondrion inheritance in gymnosperm is discussed.

Cytological Mechanism of Cytoplasmic Inheritance in Pinus tabulaeformis: Ⅰ. Ultrastructural Aspects and Nucleoids of the Male Gametes

The cytological mechanism of plastid and mitochondrion inheritance in Pinus is an interesting research topic with only a limited number of published articles. The results indicate that the sperms of Pinus tabulaeformis Carr. contain abundant plastids, mitochondria and organelle DNA. These data provide reliable cytological evidence of paternal plastid and mitochondrion inheritance in Pinus . The results are in line with the confirmed general rule of paternal plastid inheritance in Pinaceae. But whether mitochondria in sperm cells can be transmitted into the embryos is an issue needs further developmental studies. Another important finding is that contrary to earlier classification of the male gamete of Pinaceae into the male nuclei type, the results reveal that male gametes in Pinus tabulaeformis are actually cells. However, the sperm cells are only surrounded by plasma membranes without cell walls. The larger leading sperm cell in a pollen tube section is long in shape, with a large amount of cytoplasm; while the second sperm cell is smaller, round in shape and contains less cytoplasm. Whether this feature of the male gamete type could be considered as a representative characteristic of the family is discussed and further conclusions await more experimental evidences from studies on plants from different species.

Cannabis and male reproduction:Impact on offspring via sperm epigenome

Cannabis is the most widely used drug in theWestern societies particularly among adolescent and young adults.Epidemiological studies demonstrate that men use cannabis more frequently than women with higher risk in developing cannabis-related disorders.Although the direct adverse effects of cannabis on male reproductive functions have been studied both in humans and animal models,the possible long-term risks for the health of the users and their offspring are still an area of active research.

Inheritance patterns of secondary symbionts during sexual reproduction of pea aphid biotypes

Herbivorous insects frequently harbor bacterial symbionts that affect their ecol- ogy and evolution. Aphids host the obligatory endosymbiont Buchnera, which is requiredfor reproduction, together with facultative symbionts whose frequencies vary across aphid populations. These maternally transmitted secondary symbionts have been particularlystudied in the pea aphid, Acyrthosiphon pisum, which harbors at least 8 distinct bacterial species （not counting Buchnera） having environmentally dependent effects on host fitness.In particular, these symbiont species are associated with pea aphid populations feeding on specific plants. Although they are maternally inherited, these bacteria are occasionallytransferred across insect lineages. One mechanism of such nonmaternal transfer is paternal transmission to the progeny during sexual reproduction. To date, transmission of secondarysymbionts during sexual reproduction of aphids has been investigated in only a handful of aphid lineages and 3 symbiont species. To better characterize this process, we investigatedinheritance patterns of 7 symbiont species during sexual reproduction of pea aphids through a crossing experiment involving 49 clones belonging to 9 host-specialized biotypes, and117 crosses. Symbiont species in the progeny were detected with diagnostic qualitative PCR at the fundatrix stage hatching from eggs and in later parthenogenetic generations.We found no confirmed case of paternal transmission of symbionts to the progeny, and we observed that maternal transmission of a particular symbiont species （Serratia symbiotica）was quite inefficient. We discuss these observations in respect to the ecology of the pea aphid.

Evaluation of microRNA expression profiles in human sperm frozen using permeable cryoprotectant-free droplet vitrification and conventional methods

For sperm cryopreservation,the conventional method,which requires glycerol,has been used for a long time.In addition,the permeable cryoprotectant-free vitrification method has been continuously studied.Although the differences of cryopreservation effects between the two methods have being studied,differences in microRNA(miRNA)profiles between them remain unclear.In this study,we investigated the differences in miRNA expression profiles among conventional freezing sperm,droplet vitrification freezing sperm and fresh human sperm.We also analyzed the differences between these methods in terms of differentially expressed miRNAs(DEmiRs)related to early embryonic development and paternal epigenetics.Our results showed no significant differences between the cryopreservation methods in terms of sperm motility ratio,plasma membrane integrity,DNA integrity,mitochondrial membrane potential,acrosome integrity,and ultrastructural damage.However,sperm miRNA-sequencing showed differences between the two methods in terms of the numbers of DEmiRs(28 and 19 with vitrification using a nonpermeable cryoprotectant and the conventional method,respectively)in postthaw and fresh sperm specimens.DEmiRs related to early embryonic development and paternal epigenetics mainly included common DEmiRs between the groups.Our results showed that the differences between conventional freezing and droplet vitrification were minimal in terms of miRNA expression related to embryonic development and epigenetics.Changes in sperm miRNA expression due to freezing are not always detrimental to embryonic development.This study compared differences in miRNA expression profiles before and after cryopreservation between cryopreservation by conventional and vitrification methods.It offers a new perspective to evaluate various methods of sperm cryopreservation.

Sperm Mitochondria in Reproduction:Good or Bad and Where Do They Go?

The mitochondrion is the major energy provider to power sperm motility. In mammals, aside from the nuclear genome, mitochondrial DNA （mtDNA） also contributes to oxidative phosphorylation to impact production of ATP by coding 13 polypeptides. However, the role of sperm mitochondria in fertilization and its final fate after fertilization are still controversial. The viewpoints that sperm bearing more mtDNA will have a better fertilizing capability and that sperm mtDNA is actively eliminated during early embryogenesis are widely accepted. However, this may be not true for several mammalian species, including mice and humans. Here, we review the sperm mitochondria and their mtDNA in sperm functions, and the mechanisms of maternal mitochondrial inheritance in mammals.