Maternal inheritance of chloroplast DNA in <Emphasis Type="Italic">Pinus mugo</Emphasis> Turra: a case study of <Emphasis Type="Italic">Pinus mugo</Emphasis> × <Emphasis Type="Italic">Pinus sylvestris</Emphasis> crossing

The opposite modes of chloroplast DNA (cpDNA) inheritance were found to operate in the reciprocal crossings of Scots pine (Pinus sylvestris L.) and mountain dwarf pine (Pinus mugo Turra). The crossings were found to be partially compatible. In P. sylvestris × P. mugo crossing, the paternal transmission of cpDNA to the offspring takes place corroborating the generally acknowledged concept of the paternal cpDNA inheritance in gymnosperms. On the contrary, in P. mugo × P. sylvestris crossing the seed progeny exhibited P. mugo haplotype of the mother tree deviating conspicuously from the above concept. In the open pollination offspring of the putatively hybrid individuals of the Scots and mountain dwarf pines, a biparental inheritance of cpDNA was revealed in mother tree with P. mugo haplotype indicating a loosened control of the maternal inheritance of cpDNA in the putative hybrids. Implications and impacts of this finding for further studies are discussed.     

Strict paternal inheritance of chloroplast DNA and maternal inheritance of mitochondrial DNA in intraspecific crosses of kiwifruit

 Previous studies have established that chloroplasts are inherited paternally in Actinidia interspecific crosses. However, fertilisation problems in interspecific crosses may affect the transmission of organelles. Six female clones, i.e. ‘Abbott’, ‘Bruno’, ‘Greensill’, ‘Hayward’, ‘Jones’, ‘Monty’, and four male clones were used to identify cpDNA polymorphisms within the cultivated kiwifruit species A. deliciosa. The restriction patterns by HpaII of a chloroplast fragment amplified by PCR with a pair of universal primers revealed a polymorphism at the intraspecific level. The inheritance of cpDNA in 143 seedlings from three intraspecific crosses in kiwifruit (Actinidia deliciosa) was studied. All offspring displayed the restriction pattern of the paternal parent, indicating that maternal inheritance of cpDNA in kiwifruit is rare at best. Strict maternal inheritance of mtDNA was confirmed in the same crosses used to investigate cpDNA transmission. Studies of cytoplasmic inheritance in the Actinidia genus represent to date the best documented report of differential organelle inheritance of cpDNA and mtDNA in angiosperms. Received: 10 November 1998 / Accepted: 14 December 1998     

Chloroplast subspecies-specific SNP detection and its maternal inheritance in Brassica oleracea L. by using a dCAPS marker

Chloroplast simple sequence repeats amplicons in 5 subspecies of Brassica oleracea were sequenced, and one chloroplast SNP was detected in amplicon ACP43. Through the introduction of an RsaI recognition site by adding one mismatch in the forward primer, combined with the increased primer length and raised annealing temperature, the dCAPS (derived cleaved amplified polymorphic sequences) marker ACP43-93 RsaI was successfully developed. By using the dCAPS marker, the subspecies-specific SNP was assayed in 206 materials representing the wide distribution of B. oleracea. This is the first report of chloroplast DNA (cpDNA) variation in cultivated subspecies of B. oleracea, which showed that chloroplast diversity existed at the intersubspecies level. Unlike other subspecies, most of the broccoli and all of the cauliflower materials sharing the same haplotype showed closer relationships in cpDNA level. Furthermore, the dCAPS haplotype of the offspring from 7 male sterile backcross populations was the same as the female parents, indicating maternal inheritance.     

Association between chloroplast DNA and mitochondrial DNA haplotypes in Prunus spinosa L. (Rosaceae) populations across Europe

Chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) were studied in 24 populations of Prunus spinosa sampled across Europe. The cpDNA and mtDNA fragments were amplified using universal primers and subsequently digested with restriction enzymes to obtain the polymorphisms. Combinations of all the polymorphisms resulted in 33 cpDNA haplotypes and two mtDNA haplotypes. Strict association between the cpDNA haplotypes and the mtDNA haplotypes was detected in most cases, indicating conjoint inheritance of the two genomes. The most frequent and abundant cpDNA haplotype (C20; frequency, 51 %) is always associated with the more frequent and abundant mtDNA haplotype (M1; frequency, 84 %). All but two of the cpDNA haplotypes associated with the less frequent mtDNA haplotype (M2) are private haplotypes. These private haplotypes are phylogenetically related but geographically unrelated. They form a separate cluster on the minimum-length spanning tree.     

Inheritance of mitochondrial and chloroplast genomes in the isogamous brown alga Scytosiphon lomentaria (Phaeophyceae)

Patterns of inheritance of chloroplasts and mitochondria were examined by fluorescence microscopy and haplotype genome markers in the isogamous brown alga Scytosiphon lomentaria (Lyngbye) Link. Germination of the zygote in this species was unilateral, the growing thallus developed entirely from the germ tube, and the original zygote cell did not develop except for the formation of a hair. Inheritance of chloroplasts was biparental, and partitioning of the two parental chloroplasts into the first sporophytic cells was accidental: either the maternal or the paternal chloroplast was migrated from the zygote into the germ tube cell, whereas the other chloroplast remained in the original cell. In contrast, the mitochondrial genome in all cells of the sporophyte came only from the female gamete (maternal inheritance). These inheritance patterns are similar to those of the isogamous brown alga Ectocarpus siliculosus (Dillwyn) Lyngbye. Maternal inheritance of mitochondria might be universal in brown algae.     

Inheritance of chloroplast DNA is not strictly maternal in Silene vulgaris (Caryophyllaceae): evidence from experimental crosses and natural populations

Chloroplast DNA (cpDNA) is maternally inherited in the majority, but not all, of angiosperm species. The mode of inheritance of cpDNA is a critical determinant of its molecular evolution and of its population genetic structure. Here, we present the results of investigations of the inheritance of cpDNA in Silene vulgaris, a plant used in a variety of studies in which cpDNA is an important component. PCR/RFLP markers were used to compare mother and offspring cpDNA genotypes sampled from two natural populations, and mother, father, and offspring genotypes obtained from controlled greenhouse crosses. Ten of 215 offspring cpDNA genotypes studied in the controlled crosses and three of 156 offspring from natural populations did not match that of the mother, demonstrating rare nonmaternal inheritance. That the chloroplast genome is occasionally transmitted through pollen is discussed in the context of using S. vulgaris cpDNA as a marker in studies of seed dispersal and when considering the joint evolution of the chloroplast and mitochondrial genomes.     

Chloroplast DNA haplotype variation and population differentiation in Sorbus aucuparia L. (Rosaceae: Maloideae)

Intra-specific chloroplast DNA (cpDNA) variation was studied in Sorbus aucuparia L., an entomophilous, mid-or early successional tree producing fleshy fruits. Eight PCR-amplified fragments of the chloroplast genome were screened for restriction fragment length polymorphisms, using one or two 4 bp-cutter restriction endonucleases. cpDNA variation was investigated on two geographical scales: (1) among four regions in France and Belgium; and (2) within the Belgian region. A total of 150 individuals from six populations were analysed. Fourteen polymorphisms were detected in six of the cpDNA fragments. All polymorphisms probably resulted from insertions or deletions, and allowed the identification of 12 haplotypes. The level of genetic differentiation computed on the basis of haplotype frequencies was similar on the two geographical scales considered (G(STc) = 0.286 among regions, G(STc) = 0.259 among populations within the Belgian region). These values are much lower than those obtained in nine previously studied temperate tree species, which are all wind-pollinated, late-successional species producing dry fruits. These results might primarily be accounted for by the contrasting life history traits of S. aucuparia. In order to obtain insights into the relative contribution of pollen and seeds to gene flow, G(STc) was also compared with previously obtained G(ST) estimates based on allozyme data.     

Detection of rare paternal chloroplast inheritance in controlled crosses of the endangered sunflower Helianthus verticillatus

A variety of questions in population and evolutionary biology are studied using chloroplast DNA (cpDNA). The presumed maternal inheritance in angiosperms allows for certain assumptions and calculations to be made when studying plant hybridization, phylogeography, molecular systematics and seed dispersal. Further, the placement of transgenes in the chloroplast to lessen the probability of 'escape' to weedy relatives has been proposed since such genes would not move through pollen. In many studies, however, strict maternal inheritance is assumed but not tested directly, and some studies may have sample sizes too small to be able to detect rare paternal leakage. Here, we study the inheritance of cpDNA simple sequence repeats in 323 offspring derived from greenhouse crosses of the rare sunflower Helianthus verticillatus Small. We found evidence for rare chloroplast paternal leakage and heteroplasmy in 1.86% of the offspring. We address the question of whether one can extrapolate the mode of chloroplast transmission within a genus by comparing our results to the findings of another sunflower species study. The findings of occasional paternal transmission of the chloroplast genome are discussed in the framework of using these markers in studies of population and evolutionary biology both in Helianthus and other angiosperms.     

Inheritance of chloroplast DNA inPopulus

Summary Restriction fragment length polymorphisms (RFLPs) were used as markers to determine the transmission of chloroplast DNA (cpDNA) in poplar crosses. The plant material studied included individual trees ofPopulus trichocarpa, P. maximowiczii xtrichocarpa, P. maximowiczii xnigra, and offspring from controlled crosses between these trees. RFLPs were identified by direct observation of stained restriction fragments, as well as by molecular hybridization with heterologous cpDNA probes. Analysis of the restriction fragment patterns in the parents and their progeny showed only the patterns of the maternal tree in the progeny, while no paternal type was found. These results provide clear evidence of a maternal mode of chloroplast inheritance in the poplar clones studied.     

Maternal inheritance of mitochondrial genomes and complex inheritance of chloroplast genomes in Actinidia Lind.: evidences from interspecific crosses

The inheritance pattern of chloroplast and mitochondria is a critical determinant in studying plant phylogenetics, biogeography and hybridization. To better understand chloroplast and mitochondrial inheritance patterns in Actinidia (traditionally called kiwifruit), we performed 11 artificial interspecific crosses and studied the ploidy levels, morphology, and sequence polymorphisms of chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) of parents and progenies. Sequence analysis showed that the mtDNA haplotypes of F1 hybrids entirely matched those of the female parents, indicating strictly maternal inheritance of Actinidia mtDNA. However, the cpDNA haplotypes of F1 hybrids, which were predominantly derived from the male parent (9 crosses), could also originate from the mother (1 cross) or both parents (1 cross), demonstrating paternal, maternal, and biparental inheritance of Actinidia cpDNA. The inheritance patterns of the cpDNA in Actinidia hybrids differed according to the species and genotypes chosen to be the parents, rather than the ploidy levels of the parent selected. The multiple inheritance modes of Actinidia cpDNA contradicted the strictly paternal inheritance patterns observed in previous studies, and provided new insights into the use of cpDNA markers in studies of phylogenetics, biogeography and introgression in Actinidia and other angiosperms.     

Chloroplast DNA inheritance in the orchid Anacamptis palustris using single-seed polymerase chain reaction

The modality of chloroplast inheritance in orchids has been investigated only in a few species due to the difficulties associated with the analysis of large progeny numbers from experimental crosses. To test chloroplast DNA inheritance in the orchid Anacamptis palustris, we took advantage of the presence of a highly variable minisatellite repeat located in the tRNA(LEU) intron in the chloroplast genome. Seed progeny obtained from experimental crosses between parental individuals carrying different chloroplast DNA (cpDNA) minisatellite repeat numbers were analyzed using a single-seed polymerase chain reaction (PCR) protocol. All examined seeds displayed the maternal cpDNA haplotypes, indicating that cpDNA inheritance is strictly maternal in this Mediterranean orchid species. No evidence for paternal leakage was found. This finding concurs with results obtained from PCR amplifications of pollen massulae that exclude the presence of chloroplast DNA in the pollen tetrads.     

甘薯质体遗传方式的DNA指纹图谱分析

用DNA指纹图谱分析了甘薯（Ipomoea batatasLam.)徐薯18和AB78-1品系及它们的正反交子代叶绿体DNA,结果显示子代叶绿体DNA指纹均与母本相同,而未发现与父本或双亲相同的指纹图谱,因此在该杂交组合中质体遗传方式为母系遗传,这个结论与先前根据细胞学研究所推测的甘薯质体遗传试不同。表明旋花科植物可能并不存在一个一致的父系或双亲质体传递模式。DNA指纹图谱分析用于质体遗传的研究尚未见报道,本文对其优越性进行了讨论。     

甘薯质体遗传方式的DNA指纹图谱分析

用DNA指纹图谱分析了甘薯(Ipomoea batatas Lam.)徐薯18和AB78-1品系及它们的正反交子代叶绿体DNA,结果显示子代叶绿体DNA指纹均与母本相同,而未发现与父本或双亲相同的指纹图谱,因此在该杂交组合中质体遗传方式为母系遗传.这个结论与先前根据细胞学研究所推测的甘薯质体遗传方式不同,表明旋花科植物可能并不存在一个一致的父系或双亲质体传递模式.DNA指纹图谱分析用于质体遗传的研究尚未见报道,本文对其优越性进行了讨论.     

High‐throughput multiplex cpDNA resequencing clarifies the genetic diversity and genetic relationships among Brassica napus,Brassica rapa and Brassica oleracea

Brassica napus (rapeseed) is a recent allotetraploid plant and the second most important oilseed crop worldwide. The origin of B. napus and the genetic relationships with its diploid ancestor species remain largely unresolved. Here, chloroplast DNA (cpDNA) from 488 B. napus accessions of global origin, 139 B. rapa accessions and 49 B. oleracea accessions were populationally resequenced using Illumina Solexa sequencing technologies. The intraspecific cpDNA variants and their allelic frequencies were called genomewide and further validated via EcoTILLING analyses of the rpo region. The cpDNA of the current global B. napus population comprises more than 400 variants (SNPs and short InDels) and maintains one predominant haplotype (Bncp1). Whole‐genome resequencing of the cpDNA of Bncp1 haplotype eliminated its direct inheritance from any accession of the B. rapa or B. oleracea species. The distribution of the polymorphism information content (PIC) values for each variant demonstrated that B. napus has much lower cpDNA diversity than B. rapa; however, a vast majority of the wild and cultivated B. oleracea specimens appeared to share one same distinct cpDNA haplotype, in contrast to its wild C‐genome relatives. This finding suggests that the cpDNA of the three Brassica species is well differentiated. The predominant B. napus cpDNA haplotype may have originated from uninvestigated relatives or from interactions between cpDNA mutations and natural/artificial selection during speciation and evolution. These exhaustive data on variation in cpDNA would provide fundamental data for research on cpDNA and chloroplasts.     

Paternally biased cpDNA inheritance in Turnera ulmifolia (Turneraceae)

We end-labeled Hin fI restriction digests of a PCR-amplified plastid encoded gene, the large subunit of ribulose bisphosphate carboxylase, to investigate patterns of cpDNA inheritance in Turnera ulmifolia. A total of 70 progeny from crosses among plants taken from ten populations revealed varying patterns of inheritance. A majority of progeny inherited the paternal cpDNA (64%), while 19% exhibited maternal and 17% biparental inheritance. Eight variegated progeny showed biparental inheritance and were analyzed in greater detail. We extracted and analyzed the cpDNA content of light- vs. dark- green leaf sectors from these plants. The results showed that vegetative segregation of cpDNA had occurred for seven of the eight plants.     

Chloroplast DNA inheritance in theStellaria longipes complex (Caryophyllaceae)

Inheritance of chloroplast DNA (cpDNA) was examined in F₁ progenies derived from three crosses and three corresponding reciprocal crosses betweenStellaria porsildii andS. longifolia. Chloroplast DNA restriction fragments were analyzed using methods of nonradioactive digoxigenin-11-dUTP labeling and chemiluminescent detection with Lumi-Phos 530. Distinct interspecific restriction fragment polymorphisms were identified and used to demonstrate the mode of cpDNA inheritance. Mode of cpDNA inheritance differed among crosses. Two crosses in whichS. porsildii, SP2920-21, was the maternal parent exhibited three different types of plastids, maternal, paternal and biparental, among the F₁ hybrids, suggesting a biparental cpDNA inheritance and plastid sorting-out inStellaria.     

Paternal inheritance of mitochondria and chloroplasts in Festuca pratensis-Lolium perenne intergeneric hybrids

Organelle inheritance in intergeneric hybrids of Festuca pratensis and Lolium perenne was investigated by restriction enzyme and Southern blot analyses of chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA). All F₁ hybrids exhibited maternal inheritance of both cpDNA and mtDNA. However, examination of backcross hybrids, obtained by backcrossing the intergeneric F₁ hybrids to L. Perenne, indicated that both uniparental maternal organelle inheritance and uniparental paternal organelle inheritance can occur in different backcross hybrids.     

Paternal inheritance of chloroplast DNA in interspecific hybrids in the genus Larrea (Zygophyllaceae)

The mode of chloroplast DNA (cpDNA) inheritance was investigated in the genus Larrea (Zygophyllaceae) by polymerase chain reaction (PCR) amplification of cpDNA fragments using three pairs of chloroplast universal primers. A total of 20 F(1)s from interspecific crosses among five different taxa in the section Bifolium was examined. Twelve F(1)s were from six crosses between L. cuneifolia (4x) and L. divaricata (2x) (Peru or Argentina) or L. tridentata (2x or 4x). Eight F(1)s were from two sets of reciprocal crosses between L. divaricata (2x) (Argentina) and L. tridentata (2x). Length polymorphism was observed in all three regions of cpDNA that separated L. cuneifolia parents from L. divaricata and L. tridentata parents and in one of the three cpDNA regions that differentiated L. divaricata (Argentina) parents from L. tridentata (2x) parents. In each case, it was the paternal cpDNA marker that appeared in the F(1) individuals. This was further confirmed by restriction fragment length polymorphism (RFLP) analysis of the amplified cpDNA fragments. Larrea may be the fifth genus reported in angiosperms with a paternal bias in cpDNA transmission. Possible mechanisms that may result in paternal cpDNA inheritance were briefly reviewed. Based on the observed uniparental paternal inheritance of cpDNA, restriction analysis of the three cpDNA regions and previous cytogenetic studies, L. divaricata was probably the maternal progenitor of L. cuneifolia.     

Extensive Mitochondrial Introgression from Pinus pumila to P. parviflora var. pentaphylla (Pinaceae)

Pinus species exhibit a paternal chloroplast inheritance and a maternal mitochondrial inheritance. The levels and patterns of cpDNA and mtDNA introgression between the two pine species, P. pumila and P. parviflora var. pentaphylla, were examined at three mountain sites in Japan. The pine species were examined by using PCR-based diagnostic genetic markers of cpDNA and mtDNA. The survey which was carried out in multiple hybrid zones demonstrated a generality in the uni-directional pattern of cytoplasmic gene flow between the two pine species, i.e. paternal cpDNA flowed from P. parviflora var. pentaphylla to P. pumila, and in contrast, maternal mtDNA flowed from P. pumila to P. parviflora var. pentaphylla. Whenever plants which had a non-native combination of cpDNA and mtDNA were observed, they always had the cpDNA haplotype of P. parviflora var. pentaphylla and the mtDNA haplotype of P. pumila. The existence of only this type of cytoplasmic chimera may suggest that F₁ hybrids are successfully produced only in the crossing of P. pumila as the maternal parent and P. parviflora var. pentaphylla as the paternal parent. The present study also detected extensive mtDNA capture in populations of P. parviflora var. pentaphylla located in the southern and middle parts of the Ohu Mountains, Tohoku, Japan. In that area, nearly all of the plants examined had the mtDNA haplotype of P. pumila. The extensive mtDNA introgression suggests that seed flow could be an effective medium for interspecific gene exchange. Received 17 August 1998/ Accepted in revised form 7 January 1999     

Incomplete paternal inheritance of chloroplast DNA recognized in Chamaecyparis obtusa using an intraspecific polymorphism of the trnD-trnY intergenic spacer region

Using a fluorescence-based PCR-SSCP (single-strand conformation polymorphism), we verified imperfectibility in the paternal inheritance of chloroplast DNA (cpDNA) in Chamaecyparis obtusa (Cupressaceae) controlled crosses. An intraspecific sequence polymorphism of the intergenic spacer region between the trnD and trnY genes was utilized as a molecular marker. Of 361 progenies, in which the cpDNA haplotypes of their female and male parents were different, 352 (97.5%) possessed the same haplotypes as their male parents, and nine (2.5%) the same haplotypes as their female parents. The parentage of the nine progenies with female parental types was diagnosed using DNA fingerprinting based on fluorescence-based RAPD profiles. Their parentage showed convincing evidence of the low frequency of maternal inheritance. Moreover, heteroplasmy was observed in the open-pollinated seeds collected in a seed orchard. The confirmation of maternal plastid transmission in the full-sib families and the observation of heteroplasmy in seeds reveal that the paternal inheritance of cpDNA is not an exclusive phenomenon and that the mode of its inheritance is biparental in C. obtusa. Received: 15 April 2000 / Accepted: 13 July 2000