Plastid genome characterisation in Brassica and Brassicaceae using a new set of nine SSRs

Complete organellar genomes of six Sargassum species and development of species-specific markers

Sargassum is one of the most important brown algal genera that can be used as food and raw material for medicinal purpose, and has various beneficial effects. As the classification of Sargassum species is currently based on their morphological characteristics, organellar genome sequences of Sargassum would provide important information for accurate identification of species and developing species-specific markers. We sequenced the complete organellar genomes of six Sargassum species, including the first complete chloroplast genome sequences of S. fulvellum, S. serratifolium, S. macrocarpum, and S. siliquastrum, and the first complete mitochondrial genome sequences of S. fulvellum, S. serratifolium, and S. macrocarpum. The chloroplast genomes of the 6 Sargassum species contained 139 protein-coding genes (PCGs), and the mitochondrial genomes possessed 37 PCGs. A comparative study was performed between the newly sequenced organellar genomes and 44 other species belonging to class Phaeophyceae. Phylogenetic relationships using PCGs shared by Phaeophyceae species were constructed with IQ-TREE 2 using the maximum likelihood method. In addition, we developed real-time PCR markers based on SNPs to distinguish the 6 Sargassum species. Our results provide useful information for establishing phylogenetic relationships between brown algae.

Genetic Relationship of Brassicaceae Hybrids with Various Resistance to Blackleg Is Disclosed by the Use of Molecular Markers

Brassica napus is an important oil source. Its narrow gene pool can be widened by interspecific hybridization with the Brassicaceae species. One of the agronomically important traits, that can be transferred through the hybridization, is the resistance to blackleg, a dangerous disease mainly caused by Leptosphaeria maculans. Hybrid individuals can be analyzed with various molecular markers, including Simple Sequence Repeats (SSR). We investigated the genetic similarity of 32 Brassicaceae hybrids and 19 parental components using SSR markers to reveal their genetic relationship. Furthermore, we compared the field resistance to blackleg of the interspecific progenies. The tested set of 15 SSR markers proved to be useful in revealing the genetic distances in the Brassicaceae hybrids and species. However, genetic similarity of the studied hybrids could not be correlated with the level of field resistance to L. maculans. Moreover, our studies confirmed the usefulness of the Brassicaceae hybrids in terms of blackleg management.

The complete chloroplast genome of Persicaria perfoliata and comparative analysis with Four Medicinal Plants of Polygonaceae

Polygonaceae is a large family of medicinal herbs that includes many species used as traditional Chinese medicine, such as Persicaria perfoliate. Here, we sequenced the complete cp genome of P. perfoliata using Illumina sequencing technology with the purpose to provide a method to facilitate accurate identification. After being annotated, the cp genome of P. perfoliata was compared with Fagopyrum tataricum, Persicaria chinensis, Fagopyrum dibotrys and Fallopia multiflora. The complete cp genome of P. perfoliata is 160,730 bp in length, containing a small single copy (SSC) region of 12,927 bp, a large single copy (LSC) region of 85,433 bp and a pair of inverted repeats (IR) regions of 62,370 bp. A total of 131 genes were annotated, including eight rRNA genes, 34 tRNA genes and 84 protein-coding genes. Forty-two simple sequence repeats and fifty-five repeat sequences were identified. Mutational hot spots analyses indicated that five genes (matK, ndhF, ccsA, cemA, rpl20) could be selected as candidates for molecular markers. Moreover, phylogenetic analysis showed that all the Polygonaceae species formed a monophyletic clade, and P. perfoliata showed the closest relationship with P. chinense. The study provides valuable molecular information to accurately identify P. perfoliata and assist in its development and application.

A Comparative Analysis of the Chloroplast Genomes of Four Polygonum Medicinal Plants

Polygonum is a generalized genus of the Polygonaceae family that includes various herbaceous plants. In order to provide aid in understanding the evolutionary and phylogenetic relationship in Polygonum at the chloroplast (cp) genome-scale level, we sequenced and annotated the complete chloroplast genomes of four Polygonum species using next-generation sequencing technology and CpGAVAS. Then, repeat sequences, IR contractions, and expansion and transformation sites of chloroplast genomes of four Polygonum species were studied, and a phylogenetic tree was built using the chloroplast genomes of Polygonum. The results indicated that the chloroplast genome construction of Polygonum also displayed characteristic four types of results, comparable to the published chloroplast genome of recorded angiosperms. The chloroplast genomes of the four Polygonum plants are highly consistent in genome size (159,015 bp-163,461 bp), number of genes (112 genes, including 78 protein-coding genes, 30 tRNA genes, and 4 rRNA genes), gene types, gene order, codon usage, and repeat sequence distribution, which identifies the high preservation among the Polygonum chloroplast genomes. The Polygonum phylogenetic tree was recreated by a full sequence of the chloroplast genome, which illustrates that the P. bistorta, P. orientale, and P. perfoliatum are divided into the same branch, and P. aviculare belongs to Fallopia. The precise system site of lots base parts requires further verification, but the study would provide a basis for developing the available genetic resources and evolutionary relationships of Polygonum.

The complete chloroplast genome sequence of the medicinal plant Abrus pulchellus subsp. cantoniensis: genome structure, comparative and phylogenetic relationship analysis

Abrus pulchellus subsp. cantoniensis, an endemic medicinal plant in southern China, is clinically used to treat jaundice hepatitis, cholecystitis, stomachache and breast carbuncle. Here, we assembled and analyzed the first complete chloroplast (cp) genome of A. pulchellus subsp. cantoniensis. The A. pulchellus subsp. cantoniensis cp genome size is 156,497 bp with 36.5% GC content. The cp genome encodes 130 genes, including 77 protein-coding genes, 30 tRNA genes and four rRNA genes, of which 19 genes are duplicated in the inverted repeats (IR) regions. A total of 30 codons exhibited codon usage bias with A/U-ending. Moreover, 53 putative RNA editing sites were predicted in 20 genes, all of which were cytidine to thymine transitions. Repeat sequence analysis identified 45 repeat structures and 125 simple-sequence repeats (SSRs) in A. pulchellus subsp. cantoniensis cp genome. In addition, 19 mononucleotides (located in atpB, trnV-UAC, ycf3, atpF, rps16, rps18, clpP, rpl16, trnG-UCC and ndhA) and three compound SSRs (located in ndhA, atpB and rpl16) showed species specificity between A. pulchellus subsp. cantoniensis and Abrus precatorius, which might be informative sources for developing molecular markers for species identification. Furthermore, phylogenetic analysis inferred that A. pulchellus subsp. cantoniensis was closely related to A. precatorius, and the genus Abrus formed a subclade with Canavalia in the Millettioid/Phaseoloid clade. These data provide a valuable resource to facilitate the evolutionary relationship and species identification of this species.

Comparison of the Chloroplast Genome Sequences of 13 Oil-Tea Camellia Samples and Identification of an Undetermined Oil-Tea Camellia Species From Hainan Province

The comparison of chloroplast genome (cpDNA) sequences among different plant species is an important source of plant molecular phylogenetic data. In this paper, the cpDNA sequences of 13 different oil-tea camellia samples were compared to identify an undetermined oil-tea camellia species from Hainan Province. The cpDNA of the samples was sequenced and resequenced, and divergence hotspots and simple sequence repeat (SSR) variations were analyzed. Bayesian inference (BI) and maximum-likelihood (ML) phylogenetic trees were constructed based on the full cpDNA sequences. The cpDNA sequences were 156512∼157089 bp in length and had the circular tetrad structure typical of angiosperms. The inverted repeats (IRs) of different species included varying contractions and expansions. The cpDNA sequences of the samples of the undetermined species of oil-tea camellia from Hainan Province and Camellia gauchowensis from Xuwen County were identical. In total, 136 genes were annotated, including 91 protein-coding genes (PCGs), 37 tRNA genes and 8 rRNA genes. The GC content of the cpDNA was 37.3%. The small single-copy (SSC)/IR boundary was rich in variation. Divergence hotspots were mainly located in the intergenic space (IGS) and coding sequences (CDSs), and there were obvious differences in divergence hotspots among species. The same divergence hotspots were found in Camellia vietnamensis, Camellia gauchowensis and the undetermined species of oil-tea camellia from Hainan Province. A total of 191∼198 SSR loci were detected. Most of the SSRs included A or T, and the distribution of SSRs in the cpDNA was uneven. Different species shared common SSRs and exhibited unique SSRs. Based on the full cpDNA sequences, the evolutionary relationships of different species of Camellia were well identified. The thirteen samples were classified into 2 clades and 6 subclades, and the different sections of Camellia clustered on the same branch in 2 clades and 2 subclades. Camellia vietnamensis was more closely related to the undetermined species of oil-tea camellia from Hainan Province and the sample of Camellia gauchowensis from Xuwen County than to the sample of Camellia gauchowensis from Luchuan County. Camellia osmantha was closely related to Camellia gauchowensis and Camellia vietnamensis. In conclusion, the cpDNA of different oil-tea camellia species has a conserved tetrad structure with certain length polymorphisms. SSRs are expected to be developed as "barcodes" or "identity cards" for species identification. SSR variations and other factors result in abundant divergence hotspots in the CDSs and IGS (one non-CDS region), indicating that full cpDNA sequences can be used for the species identification and phylogenetic analysis of Camellia. Accordingly, the undetermined species of oil-tea camellia from Hainan Province is likely Camellia vietnamensis, Camellia vietnamensis and Camellia gauchowensis may be the same species, and additional genetic evidence is needed to determine whether Camellia osmantha is a new independent species. The previous division of related sections of Camellia may need readjustment based on full cpDNA sequences.

Different Shades of Kale-Approaches to Analyze Kale Variety Interrelations

Brassica oleracea is a vegetable crop with an amazing morphological diversity. Among the various crops derived from B. oleracea, kale has been in the spotlight globally due to its various health-benefitting compounds and many different varieties. Knowledge of the existing genetic diversity is essential for the improved breeding of kale. Here, we analyze the interrelationships, population structures, and genetic diversity of 72 kale and cabbage varieties by extending our previous diversity analysis and evaluating the use of summed potential lengths of shared haplotypes (SPLoSH) as a new method for such analyses. To this end, we made use of the high-density Brassica 60K SNP array, analyzed SNPs included in an available Brassica genetic map, and used these resources to generate and evaluate the information from SPLoSH data. With our results we could consistently differentiate four groups of kale across all analyses: the curly kale varieties, Italian, American, and Russian varieties, as well as wild and cultivated types. The best results were achieved by using SPLoSH information, thus validating the use of this information in improving analyses of interrelations in kale. In conclusion, our definition of kale includes the curly varieties as the kales in a strict sense, regardless of their origin. These results contribute to a better understanding of the huge diversity of kale and its interrelations.

Complete Chloroplast Genome Analysis of Two Important Medicinal Alpinia Species: Alpinia galanga and Alpinia kwangsiensis

Most Alpinia species are valued as foods, ornamental plants, or plants with medicinal properties. However, morphological characteristics and commonly used DNA barcode fragments are not sufficient for accurately identifying Alpinia species. Difficulties in species identification have led to confusion in the sale and use of Alpinia for medicinal use. To mine resources and improve the molecular methods for distinguishing among Alpinia species, we report the complete chloroplast (CP) genomes of Alpinia galanga and Alpinia kwangsiensis species, obtained via high-throughput Illumina sequencing. The CP genomes of A. galanga and A. kwangsiensis exhibited a typical circular tetramerous structure, including a large single-copy region (87,565 and 87,732 bp, respectively), a small single-copy region (17,909 and 15,181 bp, respectively), and a pair of inverted repeats (27,313 and 29,705 bp, respectively). The guanine-cytosine content of the CP genomes is 36.26 and 36.15%, respectively. Furthermore, each CP genome contained 133 genes, including 87 protein-coding genes, 38 distinct tRNA genes, and 8 distinct rRNA genes. We identified 110 and 125 simple sequence repeats in the CP genomes of A. galanga and A. kwangsiensis, respectively. We then combined these data with publicly available CP genome data from four other Alpinia species (A. hainanensis, A. oxyphylla, A. pumila, and A. zerumbet) and analyzed their sequence characteristics. Nucleotide diversity was analyzed based on the alignment of the complete CP genome sequences, and five candidate highly variable site markers (trnS-trnG, trnC-petN, rpl32-trnL, psaC-ndhE, and ndhC-trnV) were found. Twenty-eight complete CP genome sequences belonging to Alpinieae species were used to construct phylogenetic trees. The results fully demonstrated the phylogenetic relationship among the genera of the Alpinieae, and further proved that Alpinia is a non-monophyletic group. The complete CP genomes of the two medicinal Alpinia species provides lays the foundation for the use of CP genomes in species identification and phylogenetic analyses of Alpinia species.

Agro-morphological and molecular diversity in different maturity groups of Indian cauliflower (Brassica oleracea var. botrytis L.)

The present study analysed the molecular and agro-morphological diversity in a set of 92 diverse cauliflower genotypes and two each of cabbage and broccoli. Field evaluation of the genotypes was done in randomized block design (RBD) at two locations (i.e. IARI, New Delhi and ICAR-RC-NEH Region, Barapani) during Rabi2019-20. Genotypes showed variation for all the eight observed traits at both locations and, the differences in early and snowball groups were distinct. Pusa Meghna, DC-33-8, Pusa Kartiki and CC-14 were earliest for curd initiation. Genotypes showed higher values for curd traits at Delhi. Molecular diversity was detected with 90 polymorphic simple sequence repeats (SSR). Number of alleles ranged from 1 to 9 with mean value of 2.16 and the highest polymorphic information content (PIC) value was observed for primer BoGMS0742 (0.68) with a mean value of 0.18. Cluster analysis using agro-morphological traits substantiated classification of the genotypes for maturity groups. However, SSR analysis revealed four clusters and with a composite pattern of genotype distribution. STRUCTURE analysis also supported the admixture and four subpopulations. The studyindicates for introgression of genetic fragments across the maturity groups, thereby, potential for use in further genetic improvement and heterosis breeding.

Decoding first complete chloroplast genome of toothbrush tree (Salvadora persica L.): insight into genome evolution, sequence divergence and phylogenetic relationship within Brassicales

BACKGROUND

Salvadora persica L. (Toothbrush tree - Miswak; family-Salvadoraceae) grows in the arid-land ecosystem and possesses economic and medicinal importance. The species, genus and the family have no genomic datasets available specifically on chloroplast (cp) genomics and taxonomic evolution. Herein, we have sequenced the complete chloroplast genome of S. persica for the first time and compared it with 11 related specie's cp genomes from the order Brassicales.

RESULTS

The S. persica cp genome was 153,379 bp in length containing a sizeable single-copy region (LSC) of 83,818 bp which separated from the small single-copy region (SSC) of 17,683 bp by two inverted repeats (IRs) each 25,939 bp. Among these genomes, the largest cp genome size (160,600 bp) was found in M. oleifera, while in S. persica it was the smallest (153,379 bp). The cp genome of S. persica encoded 131 genes, including 37 tRNA genes, eight rRNA genes and 86 protein-coding genes. Besides, S. persica contains 27 forward, 36 tandem and 19 palindromic repeats. The S. persica cp genome had 154 SSRs with the highest number in the LSC region. Complete cp genome comparisons showed an overall high degree of sequence resemblance between S. persica and related cp genomes. Some divergence was observed in the intergenic spaces of other species. Phylogenomic analyses of 60 shared genes indicated that S. persica formed a single clade with A. tetracantha with high bootstrap values. The family Salvadoraceae is closely related to Capparaceae and Petadiplandraceae rather than to Bataceae and Koberliniacaea.

CONCLUSION

The current genomic datasets provide pivotal genetic resources to determine the phylogenetic relationships, genome evolution and future genetic diversity-related studies of S. persica in complex angiosperm families.

Development of a Yellow-Seeded Stable Allohexaploid Brassica Through Inter-Generic Somatic Hybridization With a High Degree of Fertility and Resistance to Sclerotinia sclerotiorum

The Brassica coenospeceis have treasure troves of genes that could be beneficial if introgressed into cultivated Brassicas to combat the current conditions of climate change. Introducing genetic variability through plant speciation with polyploidization is well documented, where ploidy augmentation of inter-generic allohexaploids using somatic hybridization has significantly contributed to genetic base broadening. Sinapis alba is a member of the Brassicaceae family that possesses valuable genes, including genes conferring resistance to Sclerotinia sclerotiorum, Alternaria brassicae, pod shattering, heat, and drought stress. This work aimed to synthesize stable allohexaploid (AABBSS) Brassica while incorporating the yellow-seed trait and resistance to S. sclerotiorum stem rot. The two fertile and stable allohexaploids were developed by polyethylene glycol mediated protoplast fusions between Brassica juncea (AABB) and S. alba (SS) and named as JS1 and JS2. These symmetric hybrids (2n = 60) were validated using morphological and molecular cytology techniques and were found to be stable over consecutive generations. The complete chromosome constitution of the three genomes was determined through genomic in situ hybridization of mitotic cells probed with S. alba genomic DNA labeled with fluorescein isothiocyanate. These two allohexaploids showed 24 hybridization signals demonstrating the presence of complete diploid chromosomes from S. alba and 36 chromosomes from B. juncea. The meiotic pollen mother cell showed 30 bivalent sets of all the 60 chromosomes and none of univalent or trivalent observed during meiosis. Moreover, the backcross progeny 1 plant revealed 12 hybridization signals out of a total of 48 chromosome counts. Proper pairing and separation were recorded at the meiotic metaphase and anaphase, which proved the stability of the allohexaploid and their backcross progeny. When screening, the allohexaploid (JS2) of B. juncea and S. alba displayed a high degree of resistance to S. sclerotiorum rot along with a half-yellow and half-brown (mosaic) seed coat color, while the B. juncea and S. alba allohexaplopid1 (JS1) displayed a yellow seed coat color with the same degree of resistance to Sclerotinia rot.

Comparing and phylogenetic analysis chloroplast genome of three Achyranthes species

In this study, the chloroplast genome sequencing of the Achyranthes longifolia, Achyranthes bidentata and Achyranthes aspera were performed by Next-generation sequencing technology. The results revealed that there were a length of 151,520 bp (A. longifolia), 151,284 bp (A. bidentata), 151,486 bp (A. aspera), respectively. These chloroplast genome have a highly conserved structure with a pair of inverted repeat (IR) regions (25,150 bp; 25,145 bp; 25,150 bp), a large single copy (LSC) regions (83,732 bp; 83,933 bp; 83,966 bp) and a small single copy (SSC) regions (17,252 bp; 17,263 bp; 17,254 bp) in A. bidentate, A. aspera and A. longifolia. There were 127 genes were annotated, which including 8 rRNA genes, 37 tRNA genes and 82 functional genes. The phylogenetic analysis strongly revealed that Achyranthes is monophyletic, and A. bidentata was the closest relationship with A. aspera and A. longifolia. A. bidentata and A. longifolia were clustered together, the three Achyranthes species had the same origin, then the gunes of Achyranthes is the closest relative to Alternanthera, and that forms a group with Alternanthera philoxeroides. The research laid a foundation and provided relevant basis for the identification of germplasm resources in the future.

Comparative analysis of four Zantedeschia chloroplast genomes: expansion and contraction of the IR region, phylogenetic analyses and SSR genetic diversity assessment

The horticulturally important genus Zantedeschia (Araceae) comprises eight species of herbaceous perennials. We sequenced, assembled and analyzed the chloroplast (cp) genomes of four species of Zantedeschia (Z. aethiopica, Z. odorata, Z. elliottiana, and Z. rehmannii) to investigate the structure of the cp genome in the genus. According to our results, the cp genome of Zantedeschia ranges in size from 169,065 bp (Z. aethiopica) to 175,906 bp (Z. elliottiana). We identified a total of 112 unique genes, including 78 protein-coding genes, 30 transfer RNA (tRNA) genes and four ribosomal RNA (rRNA) genes. Comparison of our results with cp genomes from other species in the Araceae suggests that the relatively large sizes of the Zantedeschia cp genomes may result from inverted repeats (IR) region expansion. The sampled Zantedeschia species formed a monophylogenetic clade in our phylogenetic analysis. Furthermore, the long single copy (LSC) and short single copy (SSC) regions in Zantedeschia are more divergent than the IR regions in the same genus, and non-coding regions showed generally higher divergence than coding regions. We identified a total of 410 cpSSR sites from the four Zantedeschia species studied. Genetic diversity analyses based on four polymorphic SSR markers from 134 cultivars of Zantedeschia suggested that high genetic diversity (I = 0.934; Ne = 2.371) is present in the Zantedeschia cultivars. High genetic polymorphism from the cpSSR region suggests that cpSSR could be an effective tool for genetic diversity assessment and identification of Zantedeschia varieties.

Complete Chloroplast Genome Sequence and Phylogenetic Analysis of Quercus bawanglingensis Huang, Li et Xing, a Vulnerable Oak Tree in China

Quercus bawanglingensis Huang, Li et Xing, an endemic evergreen oak of the genus Quercus (Fagaceae) in China, is currently listed in the Red List of Chinese Plants as a vulnerable (VU) plant. No chloroplast (cp) genome information is currently available for Q. bawanglingensis, which would be essential for the establishment of guidelines for its conservation and breeding. In the present study, the cp genome of Q. bawanglingensis was sequenced and assembled into double-stranded circular DNA with a length of 161,394 bp. Two inverted repeats (IRs) with a total of 51,730 bp were identified, and the rest of the sequence was separated into two single-copy regions, namely, a large single-copy (LSC) region (90,628 bp) and a small single-copy (SSC) region (19,036 bp). The genome of Q. bawanglingensis contains 134 genes (86 protein-coding genes, 40 tRNAs and eight rRNAs). More forward (29) than inverted long repeats (21) are distributed in the cp genome. A simple sequence repeat (SSR) analysis showed that the genome contains 82 SSR loci, involving 84.15% A/T mononucleotides. Sequence comparisons among the nine complete cp genomes, including the genomes of Q. bawanglingensis, Q. tarokoensis Hayata (NC036370), Q. aliena var. acutiserrata Maxim. ex Wenz. (KU240009), Q. baronii Skan (KT963087), Q. aquifolioides Rehd. et Wils. (KX911971), Q. variabilis Bl. (KU240009), Fagus engleriana Seem. (KX852398), Lithocarpus balansae (Drake) A. Camus (KP299291) and Castanea mollissima Bl. (HQ336406), demonstrated that the diversity of SC regions was higher than that of IR regions, which might facilitate identification of the relationships within this extremely complex family. A phylogenetic analysis showed that Fagus engleriana and Trigonobalanus doichangensis form the basis of the produced evolutionary tree. Q. bawanglingensis and Q. tarokoensis, which belong to the group Ilex, share the closest relationship. The analysis of the cp genome of Q. bawanglingensis provides crucial genetic information for further studies of this vulnerable species and the taxonomy, phylogenetics and evolution of Quercus.

Complete Chloroplast Genome Sequence and Phylogenetic Analysis of Quercus acutissima

Quercus acutissima, an important endemic and ecological plant of the Quercus genus, is widely distributed throughout China. However, there have been few studies on its chloroplast genome. In this study, the complete chloroplast (cp) genome of Q. acutissima was sequenced, analyzed, and compared to four species in the Fagaceae family. The size of the Q. acutissima chloroplast genome is 161,124 bp, including one large single copy (LSC) region of 90,423 bp and one small single copy (SSC) region of 19,068 bp, separated by two inverted repeat (IR) regions of 51,632 bp. The GC content of the whole genome is 36.08%, while those of LSC, SSC, and IR are 34.62%, 30.84%, and 42.78%, respectively. The Q. acutissima chloroplast genome encodes 136 genes, including 88 protein-coding genes, four ribosomal RNA genes, and 40 transfer RNA genes. In the repeat structure analysis, 31 forward and 22 inverted long repeats and 65 simple-sequence repeat loci were detected in the Q. acutissima cp genome. The existence of abundant simple-sequence repeat loci in the genome suggests the potential for future population genetic work. The genome comparison revealed that the LSC region is more divergent than the SSC and IR regions, and there is higher divergence in noncoding regions than in coding regions. The phylogenetic relationships of 25 species inferred that members of the Quercus genus do not form a clade and that Q. acutissima is closely related to Q. variabilis. This study identified the unique characteristics of the Q. acutissima cp genome, which will provide a theoretical basis for species identification and biological research.

The Complete Chloroplast Genome of a Key Ancestor of Modern Roses, Rosa chinensis var. spontanea, and a Comparison with Congeneric Species

Rosa chinensis var. spontanea, an endemic and endangered plant of China, is one of the key ancestors of modern roses and a source for famous traditional Chinese medicines against female diseases, such as irregular menses and dysmenorrhea. In this study, the complete chloroplast (cp) genome of R. chinensis var. spontanea was sequenced, analyzed, and compared to congeneric species. The cp genome of R. chinensis var. spontanea is a typical quadripartite circular molecule of 156,590 bp in length, including one large single copy (LSC) region of 85,910 bp and one small single copy (SSC) region of 18,762 bp, separated by two inverted repeat (IR) regions of 25,959 bp. The GC content of the whole genome is 37.2%, while that of LSC, SSC, and IR is 42.8%, 35.2% and 31.2%, respectively. The genome encodes 129 genes, including 84 protein-coding genes (PCGs), 37 transfer RNA (tRNA) genes, and eight ribosomal RNA (rRNA) genes. Seventeen genes in the IR regions were found to be duplicated. Thirty-three forward and five inverted repeats were detected in the cp genome of R. chinensis var. spontanea. The genome is rich in SSRs. In total, 85 SSRs were detected. A genome comparison revealed that IR contraction might be the reason for the relatively smaller cp genome size of R. chinensis var. spontanea compared to other congeneric species. Sequence analysis revealed that the LSC and SSC regions were more divergent than the IR regions within the genus Rosa and that a higher divergence occurred in non-coding regions than in coding regions. A phylogenetic analysis showed that the sampled species of the genus Rosa formed a monophyletic clade and that R. chinensis var. spontanea shared a more recent ancestor with R. lichiangensis of the section Synstylae than with R. odorata var. gigantea of the section Chinenses. This information will be useful for the conservation genetics of R. chinensis var. spontanea and for the phylogenetic study of the genus Rosa, and it might also facilitate the genetics and breeding of modern roses.

The Complete Amomum kravanh Chloroplast Genome Sequence and Phylogenetic Analysis of the Commelinids

Amomum kravanh is an important edible and medicinal herb, the dried fruits of which are widely used in traditional herbal medicine as cardamom. We sequenced and analyzed the complete chloroplast (cp) genome of A. kravanh with herbgenomics technologies. The size of the A. kravanh cp genome was 162,766 bp, which consisted of long (LSC; 87,728 bp) and short (SSC; 15,390 bp) single-copy regions, separated by a pair of inverted repeats (IRs; 29,824 bp). The genome encoded 114 unique genes, including 80 protein-coding genes, 30 tRNAs and four rRNAs. A total of 299 simple sequence repeats (SSRs) were identified in the A. kravanh cp genome, which provides an effective method to study species identification and population genetics of the medicinal plant. Moreover, one complement, 12 forward, 12 palindrome and two reverse repeats were detected. Comparative cp genome sequence analysis of four Zingiberaceae species indicated that their intergenic spacers are highly divergent, although the gene order, gene content and genome structure differed only minimally. In particular, there was a remarkable expansion of the IR regions in the A. kravanh cp genome. Phylogenetic analysis strongly supported a sister relationship between A. kravanh and Alpinia zerumbet. This study identified the unique characteristics of the A. kravanh cp genome and might provide valuable information for future studies aiming for Amomum identification, and provide insights into the taxonomy of the commelinids.

Complete Chloroplast Genome Sequence and Phylogenetic Analysis of the Medicinal Plant Artemisia annua

The complete chloroplast genome of Artemisia annua (Asteraceae), the primary source of artemisinin, was sequenced and analyzed. The A. annua cp genome is 150,995 bp, and harbors a pair of inverted repeat regions (IRa and IRb), of 24,850 bp each that separate large (LSC, 82,988 bp) and small (SSC, 18,267 bp) single-copy regions. Our annotation revealed that the A. annua cp genome contains 113 genes and 18 duplicated genes. The gene order in the SSC region of A. annua is inverted; this fact is consistent with the sequences of chloroplast genomes from three other Artemisia species. Fifteen (15) forward and seventeen (17) inverted repeats were detected in the genome. The existence of rich SSR loci in the genome suggests opportunities for future population genetics work on this anti-malarial medicinal plant. In A. annua cpDNA, the rps19 gene was found in the LSC region rather than the IR region, and the rps19 pseudogene was absent in the IR region. Sequence divergence analysis of five Asteraceae species indicated that the most highly divergent regions were found in the intergenic spacers, and that the differences between A. annua and A. fukudo were very slight. A phylogenetic analysis revealed a sister relationship between A. annua and A. fukudo. This study identified the unique characteristics of the A. annua cp genome. These results offer valuable information for future research on Artemisia species identification and for the selective breeding of A. annua with high pharmaceutical efficacy.

Comparative mitochondrial genome analysis reveals the evolutionary rearrangement mechanism in Brassica

The genus Brassica has many species that are important for oil, vegetable and other food products. Three mitochondrial genome types (mitotype) originated from its common ancestor. In this paper, a B. nigra mitochondrial main circle genome with 232,407 bp was generated through de novo assembly. Synteny analysis showed that the mitochondrial genomes of B. rapa and B. oleracea had a better syntenic relationship than B. nigra. Principal components analysis and development of a phylogenetic tree indicated maternal ancestors of three allotetraploid species in Us triangle of Brassica. Diversified mitotypes were found in allotetraploid B. napus, in which napus-type B. napus was derived from B. oleracea, while polima-type B. napus was inherited from B. rapa. In addition, the mitochondrial genome of napus-type B. napus was closer to botrytis-type than capitata-type B. oleracea. The sub-stoichiometric shifting of several mitochondrial genes suggested that mitochondrial genome rearrangement underwent evolutionary selection during domestication and/or plant breeding. Our findings clarify the role of diploid species in the maternal origin of allotetraploid species in Brassica and suggest the possibility of breeding selection of the mitochondrial genome.

Identification of Polymorphisms Associated with Drought Adaptation QTL in Brassica napus by Resequencing

Brassica napus is a globally important oilseed for which little is known about the genetics of drought adaptation. We previously mapped twelve quantitative trait loci (QTL) underlying drought-related traits in a biparental mapping population created from a cross between winter and spring B. napus cultivars. Here we resequence the genomes of the mapping population parents to identify genetic diversity across the genome and within QTL regions. We sequenced each parental cultivar on the Illumina HiSeq platform to a minimum depth of 23 × and performed a reference based assembly in order to describe the molecular variation differentiating them at the scale of the genome, QTL and gene. Genome-wide patterns of variation were characterized by an overall higher single nucleotide polymorphism (SNP) density in the A genome and a higher ratio of nonsynonymous to synonymous substitutions in the C genome. Nonsynonymous substitutions were used to categorize gene ontology terms differentiating the parent genomes along with a list of putative functional variants contained within each QTL. Marker assays were developed for several of the discovered polymorphisms within a pleiotropic QTL on chromosome A10. QTL analysis with the new, denser map showed the most associated marker to be that developed from an insertion/deletion polymorphism located in the candidate gene Bna.FLC.A10, and it was the only candidate within the QTL interval with observed polymorphism. Together, these results provide a glimpse of genome-wide variation differentiating annual and biennial B. napus ecotypes as well as a better understanding of the genetic basis of root and drought phenotypes.

Insight into infrageneric circumscription through complete chloroplast genome sequences of two Trillium species

Genomic events including gene loss, duplication, pseudogenization and rearrangement in plant genomes are valuable sources for exploring and understanding the process of evolution in angiosperms. The family Melanthiaceae is distributed in temperate regions of the Northern Hemisphere and divided into five tribes (Heloniadeae, Chionographideae, Xerophylleae, Melanthieae and Parideae) based on the molecular phylogenetic analyses. At present, complete chloroplast genomes of the Melanthiaceae have been reported from three species. In the previous genomic study of Liliales, atrnI-CAU gene duplication event was reported fromParis verticillata, a member of Parideae. To clarify the significant genomic events of the tribe Parideae, we analysed the complete chloroplast genome sequences of twoTrilliumspecies representing two subgenera:TrilliumandPhyllantherum InTrillium tschonoskii(subgenusTrillium), the circular double-stranded cpDNA sequence of 156 852 bp consists of two inverted repeat (IR) regions of 26 501 bp each, a large single-copy (LSC) region of 83 981 bp and a small single-copy (SSC) region of 19 869 bp. The chloroplast genome sequence ofT. maculatum(subgenusPhyllantherum) is 157 359 bp in length, consisting of two IRs (25 535 bp), one SSC (19 949 bp) and one LSC (86 340 bp), and is longer than that ofT. tschonoskii The results showed that the cpDNAs of Parideae are highly conserved across genome structure, gene order and contents. However, the chloroplast genome ofT. maculatumcontained a 3.4-kb inverted sequence betweenndhCandrbcLin the LSC region, and it was a unique feature for subgeneraPhyllantherum In addition, we found three different types of gene duplication in the intergenic spacer betweenrpl23andycf2containingtrnI-CAU, which were in agreement with the circumscription of subgenera and sections in Parideae excludingT. govanianum These genomic features provide informative molecular markers for identifying the infrageneric taxa ofTrilliumand improve our understanding of the evolution patterns of Parideae in Melanthiaceae.

The Sequence and Structure Determine the Function of Mature Human miRNAs

Micro RNAs (miRNAs) (19–25 nucleotides in length) belong to the group of non-coding RNAs are the most abundant group of posttranscriptional regulators in multicellular organisms. They affect a gene expression by binding of fully or partially complementary sequences to the 3’-UTR of target mRNA. Furthermore, miRNAs present a mechanism by which genes with diverse functions on multiple pathways can be simultaneously regulated at the post-transcriptional level. However, little is known about the specific pathways through which miRNAs with specific sequence or structural motifs regulate the cellular processes. In this paper we showed the broad and deep characteristics of mature miRNAs according to their sequence and structural motifs. We investigated a distinct group of miRNAs characterized by the presence of specific sequence motifs, such as UGUGU, GU-repeats and purine/pyrimidine contents. Using computational function and pathway analysis of their targeted genes, we were able to observe the relevance of sequence and the type of targeted mRNAs. As the consequence of the sequence analysis we finally provide the comprehensive description of pathways, biological processes and proteins associated with the distinct group of characterized miRNAs. Here, we found that the specific group of miRNAs with UGUGU can activate the targets associated to the interferon induction pathway or pathways prominently observed during carcinogenesis. GU-rich miRNAs are prone to regulate mostly processes in neurogenesis, whereas purine/pyrimidine rich miRNAs could be involved rather in transport and/or degradation of RNAs. Additionally, we have also analyzed the simple sequence repeats (SSRs). Their variation within mature miRNAs might be critical for normal miRNA regular activity. Expansion or contraction of SSRs in mature miRNA might directly affect its mRNA interaction or even change the function of that distinct miRNA. Our results prove that due to the specific sequence features, these molecules can also be involved in well-defined cellular processes depending on their sequence contents. The pathway mapping and theoretical gene target identification allowed us to create a biological framework to show the relevance of the specific miRNAs in regulation the distinct type of targets.

Genetic diversity and population structure of Brassica oleracea germplasm in Ireland using SSR markers

The most economically important Brassica oleracea species is endangered in Ireland, with no prior reported genetic characterization studies. This study assesses the genetic diversity, population structure and relationships of B. oleracea germplasm in Ireland using microsatellite (SSRs) markers. A total of 118 individuals from 25 accessions of Irish B. oleracea were genotyped. The SSR loci used revealed a total of 47 alleles. The observed heterozygosity (0.699) was higher than the expected one (0.417). Moreover, the average values of fixation indices (F) were negative, indicating excess of heterozygotes in all accessions. Polymorphic information content (PIC) values of SSR loci ranged from 0.27 to 0.66, with an average of 0.571, and classified 10 loci as informative markers (PIC>0.5) to differentiate among the accessions studied. The genetic differentiation among accessions showed that 27.1% of the total genetic variation was found among accessions, and 72.9% of the variation resided within accessions. The averages of total heterozygosity (H(T)) and intra-accession genetic diversity (H(S)) were 0.577 and 0.442, respectively. Cluster analysis of SSR data distinguished among kale and Brussels sprouts cultivars. This study provided a new insight into the exploitation of the genetically diverse spring cabbages accessions, revealing a high genetic variation, as potential resources for future breeding programs. SSR loci were effective for differentiation among the accessions studied.

Divergent Population Genetic Structure of the Endangered Helianthemum (Cistaceae) and Its Implication to Conservation in Northwestern China

Population genetic studies provide a foundation for conservation planning, especially for endangered species. Three chloroplast SSRs (mtrnSf-trnGr, mtrnL2-trnF, and mtrnL5-trnL3) and the internal transcribed spacer were used to examine the population structure of Helianthemum in northwestern China. A total of 15 populations of the genus were collected. Nine chloroplast haplotypes and two nuclear genotypes were detected. Both the nuclear and chloroplast data showed two lineages in Helianthemum songaricum, respectively, distributed in Yili Valley and western Ordos Plateau. A total of 66.81% (p < 0.001) of the genetic variation was supported by this lineage split. A Mantel test showed a significant correlation between genetic distance and geographical distance (r = 0.937, p < 0.001). Based on genetic analyses, cpSSRs data support strong genetic divergence between regions. We speculate that the climate change during the late Tertiary and early Quaternary isolated H. songaricum into their current distribution, resulting in interruption of gene flow, leading to isolation and genetic divergence between the two regions. Meanwhile, possible selfing would increase genetic drift in small fragmented populations, that might account for the observed genetic divergence in both regions. Given the loss of genetic diversity and genetic divergence in small populations of Helianthemum in northwestern China immediate conservation management steps should be taken on the species.

Organelle Simple Sequence Repeat Markers Help to Distinguish Carpelloid Stamen and Normal Cytoplasmic Male Sterile Sources in Broccoli

We previously discovered carpelloid stamens when breeding cytoplasmic male sterile lines in broccoli (Brassica oleracea var. italica). In this study, hybrids and multiple backcrosses were produced from different cytoplasmic male sterile carpelloid stamen sources and maintainer lines. Carpelloid stamens caused dysplasia of the flower structure and led to hooked or coiled siliques with poor seed setting, which were inherited in a maternal fashion. Using four distinct carpelloid stamens and twelve distinct normal stamens from cytoplasmic male sterile sources and one maintainer, we used 21 mitochondrial simple sequence repeat (mtSSR) primers and 32 chloroplast SSR primers to identify a mitochondrial marker, mtSSR2, that can differentiate between the cytoplasm of carpelloid and normal stamens. Thereafter, mtSSR2 was used to identify another 34 broccoli accessions, with an accuracy rate of 100%. Analysis of the polymorphic sequences revealed that the mtSSR2 open reading frame of carpelloid stamen sterile sources had a deletion of 51 bases (encoding 18 amino acids) compared with normal stamen materials. The open reading frame is located in the coding region of orf125 and orf108 of the mitochondrial genomes in Brassica crops and had the highest similarity with Raphanus sativus and Brassica carinata. The current study has not only identified a useful molecular marker to detect the cytoplasm of carpelloid stamens during broccoli breeding, but it also provides evidence that the mitochondrial genome is maternally inherited and provides a basis for studying the effect of the cytoplasm on flower organ development in plants.

Digital gene expression analysis of gene expression differences within Brassica diploids and allopolyploids

BACKGROUND

Brassica includes many successfully cultivated crop species of polyploid origin, either by ancestral genome triplication or by hybridization between two diploid progenitors, displaying complex repetitive sequences and transposons. The U's triangle, which consists of three diploids and three amphidiploids, is optimal for the analysis of complicated genomes after polyploidization. Next-generation sequencing enables the transcriptome profiling of polyploids on a global scale.

RESULTS

We examined the gene expression patterns of three diploids (Brassica rapa, B. nigra, and B. oleracea) and three amphidiploids (B. napus, B. juncea, and B. carinata) via digital gene expression analysis. In total, the libraries generated between 5.7 and 6.1 million raw reads, and the clean tags of each library were mapped to 18547-21995 genes of B. rapa genome. The unambiguous tag-mapped genes in the libraries were compared. Moreover, the majority of differentially expressed genes (DEGs) were explored among diploids as well as between diploids and amphidiploids. Gene ontological analysis was performed to functionally categorize these DEGs into different classes. The Kyoto Encyclopedia of Genes and Genomes analysis was performed to assign these DEGs into approximately 120 pathways, among which the metabolic pathway, biosynthesis of secondary metabolites, and peroxisomal pathway were enriched. The non-additive genes in Brassica amphidiploids were analyzed, and the results indicated that orthologous genes in polyploids are frequently expressed in a non-additive pattern. Methyltransferase genes showed differential expression pattern in Brassica species.

CONCLUSION

Our results provided an understanding of the transcriptome complexity of natural Brassica species. The gene expression changes in diploids and allopolyploids may help elucidate the morphological and physiological differences among Brassica species.

Complete chloroplast genome sequences of Mongolia medicine Artemisia frigida and phylogenetic relationships with other plants

Background

Artemisia frigida Willd. is an important Mongolian traditional medicinal plant with pharmacological functions of stanch and detumescence. However, there is little sequence and genomic information available for Artemisia frigida, which makes phylogenetic identification, evolutionary studies, and genetic improvement of its value very difficult. We report the complete chloroplast genome sequence of Artemisia frigida based on 454 pyrosequencing.

Methodology/Principal Findings

The complete chloroplast genome of Artemisia frigida is 151,076 bp including a large single copy (LSC) region of 82,740 bp, a small single copy (SSC) region of 18,394 bp and a pair of inverted repeats (IRs) of 24,971 bp. The genome contains 114 unique genes and 18 duplicated genes. The chloroplast genome of Artemisia frigida contains a small 3.4 kb inversion within a large 23 kb inversion in the LSC region, a unique feature in Asteraceae. The gene order in the SSC region of Artemisia frigida is inverted compared with the other 6 Asteraceae species with the chloroplast genomes sequenced. This inversion is likely caused by an intramolecular recombination event only occurred in Artemisia frigida. The existence of rich SSR loci in the Artemisia frigida chloroplast genome provides a rare opportunity to study population genetics of this Mongolian medicinal plant. Phylogenetic analysis demonstrates a sister relationship between Artemisia frigida and four other species in Asteraceae, including Ageratina adenophora, Helianthus annuus, Guizotia abyssinica and Lactuca sativa, based on 61 protein-coding sequences. Furthermore, Artemisia frigida was placed in the tribe Anthemideae in the subfamily Asteroideae (Asteraceae) based on ndhF and trnL-F sequence comparisons.

Conclusion

The chloroplast genome sequence of Artemisia frigida was assembled and analyzed in this study, representing the first plastid genome sequenced in the Anthemideae tribe. This complete chloroplast genome sequence will be useful for molecular ecology and molecular phylogeny studies within Artemisia species and also within the Asteraceae family.

High-throughput discovery of chloroplast and mitochondrial DNA polymorphisms in Brassicaceae species by ORG-EcoTILLING

Background

Information on polymorphic DNA in organelle genomes is essential for evolutionary and ecological studies. However, it is challenging to perform high-throughput investigations of chloroplast and mitochondrial DNA polymorphisms. In recent years, EcoTILLING stands out as one of the most universal, low-cost, and high-throughput reverse genetic methods, and the identification of natural genetic variants can provide much information about gene function, association mapping and linkage disequilibrium analysis and species evolution. Until now, no report exists on whether this method is applicable to organelle genomes and to what extent it can be used.

Methodology/Principal Findings

To address this problem, we adapted the CEL I-based heteroduplex cleavage strategy used in Targeting Induced Local Lesions in Genomes (TILLING) for the discovery of nucleotide polymorphisms in organelle genomes. To assess the applicability and accuracy of this technology, designated ORG-EcoTILLING, at different taxonomic levels, we sampled two sets of taxa representing accessions from the Brassicaceae with three chloroplast genes (accD, matK and rbcL) and one mitochondrial gene (atp6). The method successfully detected nine, six and one mutation sites in the accD, matK and rbcL genes, respectively, in 96 Brassica accessions. These mutations were confirmed by DNA sequencing, with 100% accuracy at both inter- and intraspecific levels. We also detected 44 putative mutations in accD in 91 accessions from 45 species and 29 genera of seven tribes. Compared with DNA sequencing results, the false negative rate was 36%. However, 17 SNPs detected in atp6 were completely identical to the sequencing results.

Conclusions/Significance

These results suggest that ORG-EcoTILLING is a powerful and cost-effective alternative method for high-throughput genome-wide assessment of inter- and intraspecific chloroplast and mitochondrial DNA polymorphisms. It will play an important role in evolutionary and ecological biology studies, in identification of related genes associated with agronomic importance such as high yield and improved cytoplasmic quality, and for identifying mitochondrial point mutations responsible for diseases in humans and other animals.

New chloroplast microsatellite markers suitable for assessing genetic diversity of Lolium perenne and other related grass species

BACKGROUND AND AIMS

Lolium perenne (perennial ryegrass) is the most important forage grass species of temperate regions. We have previously released the chloroplast genome sequence of L. perenne 'Cashel'. Here nine chloroplast microsatellite markers are published, which were designed based on knowledge about genetically variable regions within the L. perenne chloroplast genome. These markers were successfully used for characterizing the genetic diversity in Lolium and different grass species.

METHODS

Chloroplast genomes of 14 Poaceae taxa were screened for mononucleotide microsatellite repeat regions and primers designed for their amplification from nine loci. The potential of these markers to assess genetic diversity was evaluated on a set of 16 Irish and 15 European L. perenne ecotypes, nine L. perenne cultivars, other Lolium taxa and other grass species.

KEY RESULTS

All analysed Poaceae chloroplast genomes contained more than 200 mononucleotide repeats (chloroplast simple sequence repeats, cpSSRs) of at least 7 bp in length, concentrated mainly in the large single copy region of the genome. Nucleotide composition varied considerably among subfamilies (with Pooideae biased towards poly A repeats). The nine new markers distinguish L. perenne from all non-Lolium taxa. TeaCpSSR28 was able to distinguish between all Lolium species and Lolium multiflorum due to an elongation of an A(8) mononucleotide repeat in L. multiflorum. TeaCpSSR31 detected a considerable degree of microsatellite length variation and single nucleotide polymorphism. TeaCpSSR27 revealed variation within some L. perenne accessions due to a 44-bp indel and was hence readily detected by simple agarose gel electrophoresis. Smaller insertion/deletion events or single nucleotide polymorphisms detected by these new markers could be visualized by polyacrylamide gel electrophoresis or DNA sequencing, respectively.

CONCLUSIONS

The new markers are a valuable tool for plant breeding companies, seed testing agencies and the wider scientific community due to their ability to monitor genetic diversity within breeding pools, to trace maternal inheritance and to distinguish closely related species.

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.

Cytoplasmic and genomic effects on meiotic pairing in Brassica hybrids and allotetraploids from pair crosses of three cultivated diploids

Interspecific hybridization and allopolyploidization contribute to the origin of many important crops. Synthetic Brassica is a widely used model for the study of genetic recombination and "fixed heterosis" in allopolyploids. To investigate the effects of the cytoplasm and genome combinations on meiotic recombination, we produced digenomic diploid and triploid hybrids and trigenomic triploid hybrids from the reciprocal crosses of three Brassica diploids (B. rapa, AA; B. nigra, BB; B. oleracea, CC). The chromosomes in the resultant hybrids were doubled to obtain three allotetraploids (B. juncea, AA.BB; B. napus, AA.CC; B. carinata, BB.CC). Intra- and intergenomic chromosome pairings in these hybrids were quantified using genomic in situ hybridization and BAC-FISH. The level of intra- and intergenomic pairings varied significantly, depending on the genome combinations and the cytoplasmic background and/or their interaction. The extent of intragenomic pairing was less than that of intergenomic pairing within each genome. The extent of pairing variations within the B genome was less than that within the A and C genomes, each of which had a similar extent of pairing. Synthetic allotetraploids exhibited nondiploidized meiotic behavior, and their chromosomal instabilities were correlated with the relationship of the genomes and cytoplasmic background. Our results highlight the specific roles of the cytoplasm and genome to the chromosomal behaviors of hybrids and allopolyploids.

Polymorphic minisatellites in the mitochondrial DNAs of Oryza and Brassica

Polymorphic analyses of angiosperm mitochondrial DNA are rare in comparison with chloroplast DNA, because few target sequences in angiosperm mitochondrial DNA are known. Minisatellites, a tandem array of repeated sequences with a repeat unit of 10 to ~100 bp, are popular target sequences of animal mitochondria, but Beta vulgaris is the only known angiosperm species for which such an analysis has been conducted. From this lack of information, it was uncertain as to whether polymorphic minisatellites existed in other angiosperm species. Ten plant mitochondrial DNAs were found to contain minisatellite-like repeated sequences, most of which were located in intergenic regions but a few occurred in gene coding and intronic regions. Oryza and Brassica accessions were selected as models for the investigation of minisatellite polymorphism because substantial systematic information existed. PCR analysis of 42 Oryza accessions revealed length polymorphisms in four of the five minisatellites. The mitochondrial haplotypes of the 16 Oryza accessions with chromosomal complement (genome) types of CC, BBCC and CCDD were identical but were clearly distinguished from BB-genome accessions, a result consistent with the notion that the cytoplasmic donor parent of the amphidiploid species might be the CC-genome species. Twenty-nine accessions of six major cultivated species of Brassica were classified into five mitochondrial haplotypes based on two polymorphic minisatellites out of six loci. The haplotypes of Brassica juncea and Brassica carinata accessions were identical to Brassica rapa and Brassica nigra accessions, respectively. The haplotypes of Brassica napus accessions were heterogeneous and unique, results that were consistent with previous studies.

Polyploid genome of Camelina sativa revealed by isolation of fatty acid synthesis genes

BACKGROUND

Camelina sativa, an oilseed crop in the Brassicaceae family, has inspired renewed interest due to its potential for biofuels applications. Little is understood of the nature of the C. sativa genome, however. A study was undertaken to characterize two genes in the fatty acid biosynthesis pathway, fatty acid desaturase (FAD) 2 and fatty acid elongase (FAE) 1, which revealed unexpected complexity in the C. sativa genome.

RESULTS

In C. sativa, Southern analysis indicates the presence of three copies of both FAD2 and FAE1 as well as LFY, a known single copy gene in other species. All three copies of both CsFAD2 and CsFAE1 are expressed in developing seeds, and sequence alignments show that previously described conserved sites are present, suggesting that all three copies of both genes could be functional. The regions downstream of CsFAD2 and upstream of CsFAE1 demonstrate co-linearity with the Arabidopsis genome. In addition, three expressed haplotypes were observed for six predicted single-copy genes in 454 sequencing analysis and results from flow cytometry indicate that the DNA content of C. sativa is approximately three-fold that of diploid Camelina relatives. Phylogenetic analyses further support a history of duplication and indicate that C. sativa and C. microcarpa might share a parental genome.

CONCLUSIONS

There is compelling evidence for triplication of the C. sativa genome, including a larger chromosome number and three-fold larger measured genome size than other Camelina relatives, three isolated copies of FAD2, FAE1, and the KCS17-FAE1 intergenic region, and three expressed haplotypes observed for six predicted single-copy genes. Based on these results, we propose that C. sativa be considered an allohexaploid. The characterization of fatty acid synthesis pathway genes will allow for the future manipulation of oil composition of this emerging biofuel crop; however, targeted manipulations of oil composition and general development of C. sativa should consider and, when possible take advantage of, the implications of polyploidy.

Comprehensive analysis of simple sequence repeats in pre-miRNAs

Simple sequence repeats (SSRs) are tandem repeat units of 1-6 bp that are identified in various complete sequences. However, the distribution, nature, and origination of SSRs in pre-miRNAs, which are characteristic stem-loop sequences and are finally processed into ∼22 nt functional miRNAs contributing to regulate several biological processes, are still not well studied. The availability of large numbers of pre-miRNAs makes it possible to analyze and compare the occurrences of SSRs, the relative count of SSRs, or the longest SSRs in pre-miRNAs. In this study, we analyzed SSRs in 8,619 pre-miRNAs from 87 species, including Arthropoda, Nematoda, Platyhelminthes, Urochordata, Vertebrata, Mycetozoa, Protistae, Viridiplantae, and Viruses. We find that SSRs widely exist in the pre-miRNAs analyzed. Our analysis shows that mononucleotide repeats are the most abundant repeats, followed by dinucleotide repeats, whereas tri-, tetra-, penta-, and hexanucleotide repeats rarely occurred in pre-miRNAs. The number of SSRs per pre-miRNA on average ranges from 4.1 for viruses to 13.5 for Mycetozoa. Our results confirm that the number of repeats correlates inversely to the length of repeats. Generally, in each taxonomic group, the occurrence and relative count of SSRs decrease with the increase of repeat unit. SSRs do not exhibit obvious preference for special location in pre-miRNAs. The repeats in pre-miRNAs are complementary to repeats in coding or noncoding regions of genomes, and no significant difference is observed between these two classes with respect to the occurrence of repeats. These data on SSRs may become a useful resource of pre-miRNAs, and their possible functions are discussed.

Origins of the amphiploid species Brassica napus L. investigated by chloroplast and nuclear molecular markers

BACKGROUND

The amphiploid species Brassica napus (oilseed rape, Canola) is a globally important oil crop yielding food, biofuels and industrial compounds such as lubricants and surfactants. Identification of the likely ancestors of each of the two genomes (designated A and C) found in B. napus would facilitate incorporation of novel alleles from the wider Brassica genepool in oilseed rape crop genetic improvement programmes. Knowledge of the closest extant relatives of the genotypes involved in the initial formation of B. napus would also allow further investigation of the genetic factors required for the formation of a stable amphiploid and permit the more efficient creation of fully fertile re-synthesised B. napus. We have used a combination of chloroplast and nuclear genetic markers to investigate the closest extant relatives of the original maternal progenitors of B. napus. This was based on a comprehensive sampling of the relevant genepools, including 83 accessions of A genome B. rapa L. (both wild and cultivated types), 94 accessions of B. napus and 181 accessions of C genome wild and cultivated B. oleracea L. and related species.

RESULTS

Three chloroplast haplotypes occurred in B. napus. The most prevalent haplotype (found in 79% of accessions) was not present within the C genome accessions but was found at low frequencies in B. rapa. Chloroplast haplotypes characteristic of B. napus were found in a small number of wild and weedy B. rapa populations, and also in two accessions of cultivated B. rapa 'brocoletto'. Whilst introgression of the B. napus chloroplast type in the wild and weedy B. rapa populations has been proposed by other studies, the presence of this haplotype within the two brocoletto accessions is unexplained.

CONCLUSIONS

The distribution of chloroplast haplotypes eliminate any of the C genome species as being the maternal ancestor of the majority of the B. napus accessions. The presence of multiple chloroplast haplotypes in B. napus and B. rapa accessions was not correlated with nuclear genetic diversity as determined by AFLPs, indicating that such accessions do not represent recent hybrids. Whilst some chloroplast diversity observed within B. napus can be explained by introgression from inter-specific crosses made during crop improvement programmes, there is evidence that the original hybridisation event resulting in to B. napus occurred on more than one occasion, and involved different maternal genotypes.

Chloroplast simple sequence repeats (cpSSRs): technical resources and recommendations for expanding cpSSR discovery and applications to a wide array of plant species

Chloroplast microsatellites, or simple sequence repeats (cpSSRs), are typically mononucleotide tandem repeats. When located in the noncoding regions of the chloroplast genome (cpDNA), they commonly show intraspecific variation in repeat number. Despite the growing number of studies applying cpSSRs, studies of economically important plants and their relatives remain over-represented. Thus, the potential of cpSSRs to offer unique insights into ecological and evolutionary processes in wild plant species has yet to be fully realized. This review provides an overview of the technical resources available to aid cpSSR discovery including a list of cpSSR primer sets available and cpDNA sequencing resources. Our updated analysis of 99 whole chloroplast genomes downloaded from GenBank confirms that potentially variable cpSSRs are abundant in the noncoding cpDNA of plants. Overall variation in the frequency of cpSSRs was extreme, ranging from one to 700 per genome (median = 93), while in 81 vascular plants, between 35 and 160 cpSSRs were detected per genome (median = 86). We offer five recommendations to aid wider development and application of cpSSRs: (i) When genus-specific cpSSR primers are available, cross-species amplification can often be fruitful. (ii) While potentially useful, universal cpSSR primers at best provide access to only a small number of variable markers. (iii) De novo sequencing of noncoding cpDNA is the most effective and efficient way to develop cpSSR markers in wild species. (iv) DNA sequencing of cpSSR alleles is essential, given the complex nature of the genetic variation associated with hypervariable cpDNA regions. (v) The reliability of cpSSR length based genetic assays need to be validated in all studies.

Fatty acid and stable carbon isotope characterization of Camelina sativa oil: implications for authentication

The importance of authenticity characterization is an increasing and pressing requirement for all foods. Vegetable oil is one of the most studied foods because of its nutritional and medicinal properties in a correct diet. In this study, a total of 53 Camelina sativa samples, from all known growing areas, were chemically and isotopically characterized. The fatty acid content of camelina oil was determined by gas chromatography (GC), and the ratios of stable carbon isotopes ((13)C/(12)C) of individual fatty acids and seed/bulk oil were determined by gas chromatography-combustion-stable isotope ratio mass spectrometry (GC/C/IRMS) and elemental analysis-stable isotope ratio mass spectrometry (IRMS). A total of 17 different fatty acids were detected by GC, with omega3 R-linolenic acid (C(18:3n3)) being the most abundant (29.7-40.0 wt %). Oleic acid (C(18:1n9)), linoleic acid (C(18:2n6)) and eicosenoic acid (C(20:1n9)) all belong to the second group of major fatty acids. The stable carbon isotopic values (delta(13)C) fell into a range typical for C(3) plants. The use of delta(13)C(18:2n6) vs delta(13)C(18:3n3) correlation could show cases where impurity or adulteration is suspected, whereas principal component analysis clearly separates oil samples from different continents. Preliminary results on the camelina oil authentication procedure provide a basis for the investigation of geographical origin and the further distinction between camelina and camelina refined or other, less expensive oils.

Extremely high cytoplasmic diversity in natural and breeding populations of Lolium (Poaceae)

Ten chloroplast microsatellite markers were used to characterise chloroplast genetic diversity at allelic and haplotypic level in 104 accessions of Lolium perenne, other Lolium species, Festuca species and x Festulolium cultivars. Furthermore, genetic relationships between the accessions and biogeographic distribution of haplotypes were investigated using a range of Nei's population genetic diversity measures and analysis of molecular variance (AMOVA). An extremely high number (511) of haplotypes was detected in 1575 individuals. Nei's gene diversity values among L. perenne accessions ranged between 0 and 0.333. Much of the L. perenne European ecotype diversity (61%), as calculated using AMOVA, could be attributed to within-population variance and this is likely caused by, and maintained by, high levels of natural and anthropogenic seed dispersal. Plastid gene pools and maternal lineages for L. perenne could be clearly identified. Evidence was found, using AMOVA, to show a likely migration route of L. perenne from Southern regions of Europe northwards.