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.

HUMAN MITOCHONDRIAL tRNA MUTATIONS IN MATERNALLY INHERITED DEAFNESS

Mutations in mitochondrial tRNA genes have been shown to be associated with maternally inherited syn-dromic and non-syndromic deafness. Among those, mutations such as tRNALeu(UUR) 3243A>G associated with syndromic deafness are often present in heteroplasmy, and the non-syndromic deafness-associated tRNA mu-tations including tRNASer(UCN) 7445A>G are often in homoplasmy or in high levels of heteroplasmy. These tRNA mutations are the primary factors underlying the development of hearing loss. However, other tRNA mutations such as tRNAThr 15927G>A and tRNASer(UCN) 7444G>A are insufficient to produce a deafness phe-notype, but always act in synergy with the primary mitochondrial DNA mutations, and can modulate their phenotypic manifestation. These tRNA mutations may alter the structure and function of the corresponding mitochondrial tRNAs and cause failures in tRNAs metabolism. Thereby, the impairment of mitochondrial protein synthesis and subsequent defects in respiration caused by these tRNA mutations, results in mitochon-drial dysfunctions and eventually leads to the development of hearing loss. Here, we summarized the deaf-ness-associated mitochondrial tRNA mutations and discussed the pathophysiology of these mitochondrial tRNA mutations, and we hope these data will provide a foundation for the early diagnosis, management, and treatment of maternally inherited deafness.

Maternal Inheritance of Yellowfin Tuna （Thunnus albacares） in Captivity

Mitochondrial DNA introgression has been suggested to be responsible for the maternal consistent implications. Study on mt-DNA （mitochondrial DNA） variation in the yellowfin tuna （Thunnus albacares） using RFLP （restriction fragment length polymorphisms） has provided the evidence of maternal inheritance of yellowfin tuna in captivity. Eggs were collected in every spawning in 2004-2006 season. The mt-DNA genotypes of broodstock were compared with their eggs and the maternal inheritance of these females was determined from genotypes in the eggs. The result showed that six genotypes of female broodstock were observed in eggs and four of them were found to share a single female＇s identity and one type was shared by two females. The same genotype was observed in almost every sampling throughout the year. The female broodstocks spawned almost daily throughout the season.

Development of organelle single nucleotide polymorphism (SNP) markers and their application for the identification of cytoplasmic inheritance patterns in Pyropia yezoensis (Bangiales,Rhodophyta)

The genus Pyropia contains several important cultivated species.Genetic research in nori species has mainly focused on the cell nucleus,with few studies on organelles(chloroplast and mitochondria).Due to the high copy numbers of organelles in cells,which influence the development and traits of algae,it is necessary to study their genetic mechanism.In this study,the marine red alga Pyropia yezoensis,an important economic macroalga,was selected as the study object.To investigate organelle(chloroplast and mitochondria)inheritance in P.yezoensis,the wild type RZ(maternal strain)was crossed with the red mutant HT(paternal strain)and 30 color-sectors from 11 F1 gametophytic blades were examined.The complete chloroplast and mitochondrial genomes of the red mutant(HT)were assembled for the first time.One reliable and stable single nucleotide polymorphism(SNP)loci filtrated by bioinformatics analysis was used as a molecular marker for chloroplast and mitochondrial DNA,respectively,in subsequent experiments.PCR amplification and sequence analysis showed that the haplotypes of color-sectors detected were consistent with those of the maternal parent,confirming that both chloroplast and mitochondrial genomes were inherited maternally in P.yezoensis.The inheritance pattern of organelles in P.yezoensis can be used to guide the hybridization and breeding of nori.Additionally,the organelle SNP markers developed in this study can be applied in subsequent genetic research.

Heteroplasmy Level of the Mitochondrial tRNA^(Leu(UUR)) A3243G Mutation in a Chinese Family Is Positively Associated with Earlier Age-of-onset and Increasing Severity of Diabetes

Objective To investigate the mutations of mitochondrial genome in a pedigree with suspected maternally inherited diabetes and deafness and to explore the correlations between the mutations and clinical features. Methods Genomic DNA was isolated from blood leucocytes of each member of the pedigree. The mitochondrial genome was amplified with 24-pair primers that could cover the entire mitochondrial DNA. Direct sequencing of PCR products was used to identify any mitochondrial DNA mutations. Results Family members on the maternal side all harbored the tRNA^Lcu（UUR） A3243G mutation. The paternal side family members did not have the mutation. The age-of-onset of diabetes of the 4 maternal side family members was 15, 41, 44, and 65 years old, and their corresponding heteroplasmy level of the mutation was 34.5%, 14.9%, 14.6%, and 5.9%, respectively. The age-of-onset of diabetes and heteroplasmy level of A3243G mutation were negatively correlated with a correlation coefficient of -0.980（P=0.02）. Meanwhile, patient with high heteroplasmy level of A3243G mutation had relatively low severity of disease. Moreover, 6 reported polymorphisms and 2 new variants were found. Conclusions The main cause of diabetes in this pedigree is the tRNA^Lcu（UUR） A3243G mutation. However, other gene variants may contribute to its pathogenicity. The heteroplasmy level of the tRNA^Lcu（UUR） A3243G mutation is positively associated with earlier age-of-onset and increasing severity of diabetes.

Tolerance of Maize(Zea mays L.) to Chlorsulfuron

Fourteen inbreds of maize were tested for the tolerance to chlorsulfuron with the method of seedling water culter.Significant difference existed in the tolerance of different type maize when tested with 1 and 2 μg/kg of chlorsulfuron.The tolerance in different type maize wa dent>flint>sugar>midiem>super sugarpop.The tolerance of different inbred maize was negative correlated with the concentration concentration of chorsulfuron.The tolerance of hybrids might have some relation with their parent lines because in this test the hybrids response to chlorsulfuron showed significant positive correlation with that of tits female parent which suggented some maternal in inheritance and was not controlled by nuclear.It was possible that tolerance of maize to chlorsulfuron was cytoplasm inheritance.

The chloroplast genome comparative characteristic of artificial breeding tree,a case about Broussonetia kazinoki×Broussonetia papyrifera

Broussonetia kazinoki×Broussonetia papyrifera(ZJGS)is a hybrid species in Moraceae family,which has a very complicated hybrid origin.The excellent characteristics of fast growth,strong soil and water conservation ability,high leaf protein content and stem fiber content in ZJGS make it both ecological benefits in the mining area and economically valuable.This study aims to further understand ZJGS and other Moraceae taxa through the ZJGS chloroplast(cp)genome structure and the comparison with 12 closely related Moraceae species.Among the 13 Moraceae species,the cp genome length of seven Broussonetia species(ranges from 160,239 bp to 162,594 bp)is larger than that of six Morus species(ranges from 158,459 bp to 159,265 bp).Among the 77 shared protein-coding genes(PCGs)in Moraceae species,the obvious positive selection of Ka/Ks ratios acted on petD and rpl16 genes of B.kazinoki and B.papyrifera,respectively.Phylogenetic analysis based on shared PCGs from 28 species shows that ZJGS is closely related to maternal B.kazinoki.These findings provide data support for the origin of ZJGS hybridization and provide genomic resources for future ZJGS resource development and molecular breeding.

A boy with 9p+ resulting from maternal t(4;9) translocation:a case report

Increasing cases of 9p syndrome have been reported since the first description in 1970. In the present case, a extra segment of the end of chromosome 9p resulting from a maternally inherited translocation t（4; 9）（q31 ;p24） was described in a liveborn boy with mental retardation and multiple congenital anomalies. The extra part of chromosome 9p includes segment of the chromosome region 4q31→qter of his mother but deletes a small segment 9p24→pter. To our knowledge, this is the first ease described in a liveborn child. This paper also includes a review and tabulation of clinical features seen in the 34 reported eases. The new ease had most characteristics reported eases besides worried-face, fat and abnormal lower digestion tract, which is a modification and double expansion of the previous summarization on 9p syndrome.

Mitochondrial hepatopathy: Respiratory chain disorders- ‘breathing in and out of the liver’

Mitochondria,the powerhouse of a cell,are closely linked to the pathophysiology of various common as well as not so uncommon disorders of the liver and beyond.Evolution supports a prokaryotic descent,and,unsurprisingly,the organelle is worthy of being labeled an organism in itself.Since highly metabolically active organs require a continuous feed of energy,any dysfunction in the structure and function of mitochondria can have variable impact,with the worse end of the spectrum producing catastrophic consequences with a multisystem predisposition.Though categorized a hepatopathy,mitochondrial respiratory chain defects are not limited to the liver in time and space.The liver involvement is also variable in clinical presentation as well as in age of onset,from acute liver failure,cholestasis,or chronic liver disease.Other organs like eye,muscle,central and peripheral nervous system,gastrointestinal tract,hematological,endocrine,and renal systems are also variably involved.Diagnosis hinges on recognition of subtle clinical clues,screening metabolic investigations,evaluation of the extrahepatic involvement,and role of genetics and tissue diagnosis.Treatment is aimed at both circumventing the acute metabolic crisis and long-term management including nutritional rehabilitation.This review lists and discusses the burden of mitochondrial respiratory chain defects,including various settings when to suspect,their evolution with time,including certain specific disorders,their tiered evaluation with diagnostic algorithms,management dilemmas,role of liver transplantation,and the future research tools.

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.

Very Low-Level Heteroplasmy mtDNA Variations Are Inherited in Humans

Little is known about the inheritance of very low heteroplasmy mitochondria DNA （mtDNA） variations. Even with the development of new next-generation sequencing methods, the practical lower limit of measured heteroplasmy is still about 1% due to the inherent noise level of the sequencing. In this study, we sequenced the mitochondrial genome of 44 individuals using Illumina high-throughput sequencing technology and obtained high-coverage mitochondria sequencing data. Our study population contains many mother-offspring pairs. This unique study design allows us to bypass the usual heteroplasmy limitation by analyzing the correlation of mutation levels at each position in the mtDNA sequence between maternally related pairs and non-related pairs. The study showed that very low heteroplasmy variants, down to almost 0.1%, are inherited maternally and that this inheritance begins to decrease at about 0.5%, cor- resnondin to abottleneck of about 200 mtDNA.

Role of Heteroplasmic Mutations in the Mitochondrial Genome and the ID4 Gene Promoter Methylation Region in the Pathogenesis of Chronic Aplastic Anemia in Patients Suffering from Kidney Yin Deficiency

Objective： To analyze changes in gene amplification in the mitochondrial genome and in the ID4 gene promoter methylation region in patients with chronic aplastic anemia （CAA） suffering from Kidney （Shen） yin deficiency or Kidney yang deficiency. Methods： Bone marrow and oral epithelium samples were collected from CAA patients with Kidney yin deficiency or Kidney yang deficiency （20 cases）. Bone marrow samples were collected from 20 healthy volunteers. The mitochondrial genome was amplified by polymerase chain reaction （PCR）, and PCR products were used for sequencing and analysis. Results： Higher mutational rates were observed in the ND1-2, ND4-6, and CYTB genes in CAA patients suffering from Kidney yin deficiency. Moreover, the ID4 gene was unmethylated in bone marrow samples from healthy individuals, but was methylated in some CAA patients suffering from Kidney yin deficiency （positive rate, 60%） and Kidney yang deficiency （positive rate, 55%）. Conclusions： These data supported that gene mutations can alter the expression of respiratory chain enzyme complexes in CAA patients, resulting in energy metabolism impairment and promoting the physiological and pathological processes of hematopoietic failure. Functional impairment of the mitochondrial respiration chain induced by gene mutation may be an important reason for hematopoietic failure in patients with CA,＆,. This change is closely related to maternal inheritance and Kidney yin deficiency. Finally, these data supported the assertion that it is easy to treat disease in patients suffering from yang deficiency and difficult to treat disease in patients suffering from yin deficiency.

Whole exome sequencing and trio analysis to broaden the variant spectrum of genes in idiopathic hypogonadotropic hypogonadism

Dozens of genes are associated with idiopathic hypogonadotropic hypogonadism(IHH)and an oligogenic etiology has been suggested.However,the associated genes may account for only approximately 50%cases.In addition,a genomic systematic pedigree analysis is still lacking.Here,we conducted whole exome sequencing(WES)on 18 unrelated men affected by IHH and their corresponding parents.Notably,one reported and 10 novel variants in eight known IHH causative genes(AXL,CCDC141,CHD7,DMXL2,FGFR1,PNPLA6,POLR3A,and PR0KR2),nine variants in nine recently reported candidate genes(DCAF17,DCC,EGF,IGSF10,NOTCH1,PDE3A,RELN,SLIT2,and TRAPPC9),and four variants in four novel candidate genes for IHH(CCDC88C,CDON,GADL1,and SPRED3)were identified in 77.8%(14/18)of IHH cases.Among them,eight(8/18,44.4%)cases carried more than one variant in IHH-related genes,supporting the oligogenic model.Interestingly,we found that those variants tended to be maternally inherited(maternal with n=17 vs paternal with n=7;P=0.028).Our further retrospective investigation of published reports replicated the maternal bias(maternal with n=46 i^s paternal with n=28;P=0.024).Our study extended a variant spectrum for IHH and provided the first evidence that women are probably more tolerant to variants of IHH-related genes than men.