SMRT sequencing of the Oryza rufipogon genome reveals the genomic basis of rice adaptation.

Asian cultivated rice is believed to have been domesticated from a wild progenitor, Oryza rufipogon, offering promising sources of alleles for world rice improvement. Here we first present a high-quality chromosome-scale genome of the typical O. rufipogon. Comparative genomic analyses of O. sativa and its two wild progenitors, O. nivara and O. rufipogon, identified many dispensable genes functionally enriched in the reproductive process. We detected millions of genomic variants, of which large-effect mutations could affect agronomically relevant traits. We demonstrate how lineage-specific expansion of gene families may have contributed to the formation of reproduction isolation. We document thousands of genes with signatures of positive selection that are mainly involved in the reproduction and response to biotic- and abiotic stresses. We show that selection pressures may serve as forces to govern substantial genomic alterations that form the genetic basis of rapid evolution of mating and reproductive systems under diverse habitats.

Deciphering tea tree chloroplast and mitochondrial genomes of Camellia sinensis var. assamica.

Tea is the most popular non-alcoholic caffeine-containing and the oldest beverage in the world. In this study, we de novo assembled the chloroplast (cp) and mitochondrial (mt) genomes of C. sinensis var. assamica cv. Yunkang10 into a circular contig of 157,100 bp and two complete circular scaffolds (701719 bp and 177329 bp), respectively. We correspondingly annotated a total of 141 cp genes and 71 mt genes. Comparative analysis suggests repeat-rich nature of the mt genome compared to the cp genome, for example, with the characterization of 37,878 bp and 149 bp of long repeat sequences and 665 and 214 SSRs, respectively. We also detected 478 RNA-editing sites in 42 protein-coding mt genes, which are ~4.4-fold more than 54 RNA-editing sites detected in 21 protein-coding cp genes. The high-quality cp and mt genomes of C. sinensis var. assamica presented in this study will become an important resource for a range of genetic, functional, evolutionary and comparative genomic studies in tea tree and other Camellia species of the Theaceae family.

Evolution of Oryza chloroplast genomes promoted adaptation to diverse ecological habitats.

The course, tempo and mode of chloroplast genome evolution remain largely unknown, resulting in limited knowledge about how plant plastome gene and genome evolve during the process of recent plant speciation. Here, we report the complete plastomes of 22 closely related Oryza species in chronologically ordered stages and generate the first precise map of genomic structural variation, to our knowledge. The occurrence rapidity was estimated on average to be ~7 insertions and ~15 deletions per Myr. Relatively fewer deletions than insertions result in an increased repeat density that causes the observed growth of Oryza chloroplast genome sizes. Genome-wide scanning identified 14 positively selected genes that are relevant to photosynthesis system, eight of which were found independently in shade-tolerant or sun-loving rice species. psaA seemed positively selected in both shade-tolerant and sun-loving rice species. The results show that adaptive evolution of chloroplast genes makes rice species adapt to diverse ecological habitats related to sunlight preferences.

The complete chloroplast genome sequence of flowering banana, Musa ornata.

Musa ornata (flowering banana) is one of more than 50 species of banana in the genus Musa of the family Musaceae. As sources of resistance to pathogens exist in germplasm, M. ornata is one of the possible hybrid parents for ameliorate commercial banana varieties. Herein, we report the complete chloroplast genome of M. ornata. The total length of the chloroplast genome is 169,989 bp with 36.82% GC content. The genome consisted of 35,426 bp of a pair of inverted repeat regions (IRs), 10,775 bp of small single copy region (SSC) and 88,362 bp of large single-copy region (LSC). A total of 136 functional genes were annotated, including 113 unique genes comprising 79 protein-coding genes, 4 ribosomal RNA (rRNA) genes and 30 transfer RNA (tRNA) genes. Maximum-likelihood phylogenetic analysis with Musaceae and Zingiberaceae species revealed that M. ornata is most closely grouped with Musa acuminata.

The complete chloroplast genome sequence of wild banana, Musa balbisiana variety 'Pisang Klutuk Wulung' (Musaceae).

Musa balbisiana is a wild-type species of banana, endemic to Southern China, Eastern South Asia, and Northern Southeast Asia. The M. balbisiana variety 'Pisang Klutuk Wulung' is one of the possible ancestral parents of modern cultivated bananas, but its wild populations are now in decline. In this study, we report the complete chloroplast genome sequence of wild banana, M. balbisiana diploid variety 'Pisang Klutuk Wulung'. The M. balbisiana chloroplast genome is found to be 169,458 bp in length and has a base composition of A (31.44%), G (18.16%), C (18.61%), and T (31.79%). The genome contained two short inverted repeat (IRa and IRb) regions (35,084 bp), which were separated by a large single copy (LSC) region (87,805 bp) and a small single copy (SSC) region (11,485 bp). The genome encodes 113 unique genes, including 79 protein-coding genes, 30 transfer RNA (tRNA) genes, and four ribosomal RNA (rRNA) genes. Further, phylogenetic analysis suggested that M. balbisiana is closely related to the species of M. textilis. This complete chloroplast genome will provide valuable information for the development of DNA markers for future population and conservation studies of M. balbisiana.

Lowered Diversity and Increased Inbreeding Depression within Peripheral Populations of Wild Rice Oryza rufipogon.

BACKGROUND: The distribution of genetic variability from the interior towards the periphery of a species' range is of great interest to evolutionary biologists. Although it has been long presumed that population genetic variation should decrease as a species' range is approached, results of empirical investigations still remain ambiguous. Knowledge regarding patterns of genetic variability as well as affected factors is particularly not conclusive in plants. METHODOLOGY/PRINCIPAL FINDINGS: To determine genetic divergence in peripheral populations of the wild rice Oryza rufipogon Griff. from China, genetic diversity and population structure were studied in five northern & northeastern peripheral and 16 central populations using six microsatellite loci. We found that populations resided at peripheries of the species possessed markedly decreased microsatellite diversity than those located in its center. Population size was observed to be positively correlated with microsatellite diversity. Moreover, there are significantly positive correlations between levels of microsatellite diversity and distances from the northern and northeastern periphery of this species. To investigate genetic structure and heterozygosity variation between generations of O. rufipogon, a total of 2382 progeny seeds from 186 maternal families were further assayed from three peripheral and central populations, respectively. Peripheral populations exhibited significantly lower levels of heterozygosities than central populations for both seed and maternal generations. In comparisons with maternal samples, significantly low observed heterozygosity (HO) and high heterozygote deficit within populations (FIS) values were detected in seed samples from both peripheral and central populations. Significantly lower observed heterozygosity (HO) and higher FIS values were further observed in peripheral populations than those in central populations for seed samples. The results indicate an excess of homozygotes and thus high inbreeding depression in peripheral populations. CONCLUSIONS/SIGNIFICANCE: Our results together suggest that historical contraction of geographical range, demographic changes, and environmental conditions near the northern and northeastern margins of O. rufipogon favor inbreeding and possibly selfing, leading to the rapidly decreased effective population size. Genetic drift, reduced gene flow, and possible local selection, consequently lead to lowered gene diversity, accelerated genetic divergence and increased inbreeding depression found in peripheral populations of O. rufipogon. Given these characteristics observed, northern and northeastern peripheral populations deserve relatively different conservation strategies for either germplasm sampling of ex situ conservation or setting in situ reserves for the adaptation to possible environmental changes and the future germplasm utilization of wild rice.

The complete mitochondrial genome of western painted turtle, Chrysemys picta bellii (Chrysemys, Emydidae).

In this study, we report the complete mitochondrial genome sequence of western painted turtle, Chrysemys picta bellii. The genome is found to be 16,875 bp in length and has a base composition of A (34.4%), G (13.0%), C (26.0%), and T (26.6%). Similar to other turtles, it contains a typically conserved structure including 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 control region (D-loop). Most of the genes are encoded on H-strand, except for the eight tRNA and ND6 genes. All protein-coding genes start with an ATN codon except for COX1 and ND4, which initiate with GTG instead, and terminate with the typical stop codon (TAA/TAG) or a single T (T-) or an unexpected codon of AGG. The complete mitochondrial genome sequence provided here would be useful for further phylogenetic analysis and conservation genetic studies in C. p. bellii.

Mitochondrial genome of the black flying fox, Pteropus alecto (Chiroptera: Megachiroptera: Pteropodidae).

In this article we report the complete mitochondrial genome of black flying fox, Pteropus alecto, with the sequence length of 16,739 bp for the first time. The mitogenome contained a total of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 1 control region. The base composition was A (33.1%), G (14.5%), C (27.2%) and T (25.2%), indicating that the percentage of A and T (58.3%) was higher than that of G and C. Most of these genes were distributed on the H-strand, except for the ND6 subunit gene and eight tRNA genes. The mitochondrial genome analyzed here will provide new genetic information to study the evolution of bats.

The complete chloroplast genome sequence of American bird pepper (Capsicum annuum var. glabriusculum).

The complete chloroplast genome sequence of American bird pepper (Capsicum annuum var. glabriusculum) is reported and characterized in this study. The genome size is 156,612 bp, containing a pair of inverted repeats (IRs) of 25,776 bp separated by a large single-copy region of 87,213 bp and a small single-copy region of 17,851 bp. The chloroplast genome harbors 130 known genes, including 89 protein-coding genes, 8 ribosomal RNA genes, and 37 tRNA genes. A total of 18 of these genes are duplicated in the inverted repeat regions, 16 genes contain 1 intron, and 2 genes and one ycf have 2 introns.

Plastid genome sequence of an ornamental and editable fruit tree of Rosaceae, Prunus mume.

Here we assembled and analyzed the complete chloroplast genome of Prunus mume, a popular ornamental and editable fruit tree of Rosaceae. The cp genome exhibited a circular DNA molecule of 157 712 bp with a typical quadripartite structure consisted of two inverted repeat regions (IRa and IRb) of 26 394 bp separated by large (LSC) and small (SSC) single-copy regions of 85 861 and 19 063 bp, respectively. It encoded 112 unique genes, 19 of which were duplicated in the IR regions, giving a total of 131 genes. Eighteen of these genes harbored one or two introns. GC content was 38.9%, and coding regions accounted for 51.3% of the genome. Phylogenetic analysis showed that P. mume clustered with P. persica and P. kansuensis in the genus Punus. This newly determined chloroplast genome will enhance modern breeding programs for the purpose of genetic improvement of this valuable plant.