Maternal Inheritance Of Chloroplasts Research Articles

Phylogenetic relationships and characterization of the complete chloroplast genome of Paphiopedilum ‘GZSLKY Youyou’, a hybrid of P. dianthum × P. barbigerum

Paphiopedilum ‘GZSLKY Youyou’. is a new cultivar of Paphiopedilum with highly ornamental and horticultural value developed by crossing female parent Paphiopedilum dianthum T. Tang & F. T. Wang 1940 and male parent Paphiopedilum barbigerum T. Tang & F. T. Wang 1940. In this study, the complete chloroplast genome of the cultivar has been reconstructed from the Illumina sequencing data. The circular genome was 160,503 bp in size, containing a large single-copy region (91,582 bp), a small single-copy region (3,215 bp) and a pair of IR regions (each one 32,853 bp). The overall GC contents of the chloroplast genome was 36.20%. The chloroplast genome contained 122 genes, including 76 protein coding genes, 38 tRNA genes and 8 rRNA genes. A maximum likelihood (ML) phylogenetic tree showed that the cultivar ‘GZSLKY Youyou’ was clustered into the same clade with its parents and was closest related to P. dianthum, reflecting a maternal inheritance of chloroplasts. This complete chloroplast genome resource could be further used for genomic studies, phylogenetic analyses, and genetic engineering and breeding of the genus Paphiopedilum.

Complete chloroplast genome sequence of an orchid hybrid Cymbidium sinense (♀) × C. goeringii (♂)

The complete chloroplast genome sequence of the Cymbidium hybrid, C. sinense (♀) × C. goeringii (♂) was assembled in this study. The circular genome was 150,149 bp in length with an overall GC content of 37.1% and consisted of a pair of 25,691 bp inverted repeats, and two single-copy regions that were 84,987 bp and 13,780 bp, respectively. Gene annotation analysis identified 109 genes including 75 protein-coding genes, 30 transfer RNA, and 4 ribosomal RNA genes. Phylogenetic analysis showed its closest relationship to Cymbidium sinense, reflecting a maternal inheritance of chloroplasts.

Maternal Inheritance of Chloroplasts between Brassica rapa and F1-hybrids Demonstrated by cpDNA Markers Specific to Oilseed Rape and B. rapa

Controlled reciprocal crosses between B. rapa and F1-hybrids (B. napus (♀) × B. rapa), giving 20 pair-crossings, were made to reveal possible irregularities in chloroplast inheritance during production of BC1s. Despite the close relationship of chloroplasts in B. rapa and B. napus, development of PCR-based molecular markers specific to B. rapa chloroplasts and B. napus chloroplasts was successful. Offspring from each cross were investigated and among these, we found no irregular chloroplast inheritance, since their plastid genotypes in all cases were identical to that of their mother. With a certainty of 95% our data indicate that the probability that chloroplasts are being inherited paternally is less than 0.015. In oilseed rape, pollen-mediated transgene-dispersal poses a well-known risk. Our results support development of transplastomic oilseed rape as an approach to reduce transgene dispersal.

Molecular studies in Pelargonium (Geraniaceae). A taxonomic appraisal of section Ciconium and the origin of the ?Zonal? and ?Ivy-leaved? cultivars

An RFLP analysis of chloroplast and nuclear DNA was followed in this taxonomic appraisal of section Ciconium. The section appears to be a monophyletic one, which divides into two groups, or sub-sections. The Zonal ‘Geranium’, P. × hortorum is derived from section Ciconium, and the species most likely to be its ancestors are shown to be P. inquinans and P. zonale. Maternal inheritance of chloroplasts was demonstrated by comparing chloroplast DNA from interspecific hybrids with their parents. These data also suggest that P. inquinans was probably the maternal parent of P. × hortorum in the original crosses. The ‘Ivy-leaved’ cultivars appear to be derived from P. peltatum, with some contribution from P. zonale and/or P. × hortorum.

Inheritance of the chloroplast genome in Sorbus aucuparia L. (Rosaceae).

Chloroplast DNA (cpDNA) inheritance was investigated in Sorbus aucuparia using progenies obtained from six controlled crosses between individuals of known haplotype. Polymerase chain reaction (PCR) amplification, followed by restriction analysis, was used to characterize 248 offspring for either of two polymorphic cpDNA fragments. All offspring exhibited the maternal haplotype, which indicates maternal inheritance of chloroplasts in S. aucuparia. Power analysis of the test showed that the frequency of paternal transmission of chloroplasts, if any, should not exceed 1.84% (with 99% confidence).

Chloroplast DNA phylogeography ofCunninghamia konishii(Cupressaceae), an endemic conifer of Taiwan

In this study, we investigated the genetic structure and phylogeographic pattern of the genus Cunninghamia, a member of the Cupressaceae restricted to mainland China and Taiwan, based on sequences of the trnD–trnT noncoding spacer of the chloroplast DNA. Maternal inheritance of chloroplasts was determined experimentally. No paternal leakage was detected. Both parsimony and neighbor-joining analyses revealed the polyphyly of Cunninghamia konishii, populations of which were nested in clades of C. lanceolata from mainland China. The nucleotide diversity of chloroplast DNA sequences within C. konishii (0.0118) was higher than that between species (0.0104), which agrees with a previous allozyme investigation. Based on mutational differences between sequences, a minimum spanning network consisting of five clades was constructed. Significant genetic differentiation (ΦST= 0.130, P < 0.001) was detected between the clades based on AMOVA analyses. We infer several possible refugia in the Yunnan, Zhejiang, and Guangdong provinces of south China, all located in the minimum network as interior nodes. We also infer possible migration routes of Cunninghamia populations. The phylogeographic pattern shown in the reconstructed network suggests that the present-day Cunninghamia populations in Taiwan were derived from six different sources in continental Asia via long-distance seed dispersal. A migrant-pool model explains the heterogeneous composition of the organelle DNA in Taiwan's populations and the low differentiation between populations of Taiwan and China (ΦCT= 0.012, P = 0.454). In contrast with the genetic heterogeneity within geographic populations, many local populations have attained coalescence at the trnD–trnT alleles, which has led to significant differentiation at the population level.Key words: AMOVA, coalescence, cpDNA, Cunninghamia konishii, Cunninghamia lanceolata, minimum spanning network, phylogeography.

Chloroplast DNA phylogeography of <i>Cunninghamia konishii </i>(Cupressaceae), an endemic conifer of Taiwan

In this study, we investigated the genetic structure and phylogeographic pattern of the genus Cunninghamia, a member of the Cupressaceae restricted to mainland China and Taiwan, based on sequences of the trnD-trnT noncoding spacer of the chloroplast DNA. Maternal inheritance of chloroplasts was determined experimentally. No paternal leakage was detected. Both parsimony and neighbor-joining analyses revealed the polyphyly of Cunninghamia konishii, populations of which were nested in clades of C. lanceolata from mainland China. The nucleotide diversity of chloroplast DNA sequences within C. konishii (0.0118) was higher than that between species (0.0104), which agrees with a previous allozyme investigation. Based on mutational differences between sequences, a minimum spanning network consisting of five clades was constructed. Significant genetic differentiation (phiST = 0.130, P < 0.001) was detected between the clades based on AMOVA analyses. We infer several possible refugia in the Yunnan, Zhejiang, and Guangdong provinces of south China, all located in the minimum network as interior nodes. We also infer possible migration routes of Cunninghamia populations. The phylogeographic pattern shown in the reconstructed network suggests that the present-day Cunninghamia populations in Taiwan were derived from six different sources in continental Asia via long-distance seed dispersal. A migrant-pool model explains the heterogeneous composition of the organelle DNA in Taiwan's populations and the low differentiation between populations of Taiwan and China (phiCT = 0.012, P = 0.454). In contrast with the genetic heterogeneity within geographic populations, many local populations have attained coalescence at the trnD-trnT alleles, which has led to significant differentiation at the population level.

Separate Sexes and the Mitochondrial Theory of Ageing

An hypothesis is presented by which gamete specialization resolves a conflict between the function and replication of mitochondria. The function of mitochondria is to synthesize ATP by oxidative phosphorylation, which is coupled to respiratory electron transport. This requires a mitochondrial genetic system. However, “incorrect” electron transfers produce free radicals that cause mutation, and the frequency of these events is increased by mutation. Mitochondrial function is therefore detrimental to the fidelity of mitochondrial replication. Damage to somatic mitochondrial DNA may accumulate within, and indeed determine, the life span of individual organisms. Motility of one gamete is required for fertilization, and requires ATP. It is proposed that male gametes maximize energy production for motility by sacrificing mitochondrial DNA to electron transfer and its mutagenic by-products, while female gametes, which are non-motile, repress mitochondrial oxidative phosphorylation, thus protecting mitochondrial DNA for faithful transmission between generations. Male gametes then make no contribution to the mitochondrial genome of the zygote: mitochondria are maternally inherited. This testable hypothesis may help to explain the evolution of separate sexes and a number of their characteristics. Maternal inheritance of chloroplasts may be explained in a similar way, and contribute to the maintenance of separate sexes in plants.