Background: The genus Zingiber of the Zingiberaceae is distributed in tropical, subtropical, and in Far East Asia. This genus contains about 100–150 species, with many species valued as important agricultural, medicinal and horticultural resources. However, genomic resources and suitable molecular markers for species identification are currently sparse. Results: We conducted comparative genomics and phylogenetic analyses on Zingiber species. The Zingiber chloroplast genome (size range 162,507–163,711 bp) possess typical quadripartite structures that consist of a large single copy (LSC, 86,986–88,200 bp), a small single copy (SSC, 15,498–15,891 bp) and a pair of inverted repeats (IRs, 29,765–29,934 bp). The genomes contain 113 unique genes, including 79 protein coding genes, 30 tRNA and 4 rRNA genes. The genome structures, gene contents, amino acid frequencies, codon usage patterns, RNA editing sites, simple sequence repeats and long repeats are conservative in the genomes of Zingiber. The analysis of sequence divergence indicates that the following genes undergo positive selection (ccsA, ndhA, ndhB, petD, psbA, psbB, psbC, rbcL, rpl12, rpl20, rpl23, rpl33, rpoC2, rps7, rps12 and ycf3). Eight highly variable regions are identified including seven intergenic regions (petA-pabJ, rbcL-accD, rpl32-trnL-UAG, rps16-trnQ-UUG, trnC-GCA-psbM, psbC-trnS-UGA and ndhF-rpl32) and one genic regions (ycf1). The phylogenetic analysis revealed that the sect. Zingiber was sister to sect. Cryptanthium rather than sect. Pleuranthesis. Conclusions: This study reports 14 complete chloroplast genomes of Zingiber species. Overall, this study provided a solid backbone phylogeny of Zingiber. The polymorphisms we have uncovered in the sequencing of the genome offer a rare possibility (for Zingiber) of the generation of DNA markers. These results provide a foundation for future studies that seek to understand the molecular evolutionary dynamics or individual population variation in the genus Zingiber.

Ginger (Zingiber officinale), the type species of Zingiberaceae, is one of the most widespread medicinal plants and spices. Here, we report a high-quality, chromosome-scale reference genome of ginger ‘Zhugen’, a traditionally cultivated ginger in Southwest China used as a fresh vegetable, assembled from PacBio long reads, Illumina short reads, and high-throughput chromosome conformation capture (Hi-C) reads. The ginger genome was phased into two haplotypes, haplotype 1 (1.53 Gb with a contig N50 of 4.68 M) and haplotype 0 (1.51 Gb with a contig N50 of 5.28 M). Homologous ginger chromosomes maintained excellent gene pair collinearity. In 17,226 pairs of allelic genes, 11.9% exhibited differential expression between alleles. Based on the results of ginger genome sequencing, transcriptome analysis, and metabolomic analysis, we proposed a backbone biosynthetic pathway of gingerol analogs, which consists of 12 enzymatic gene families, PAL, C4H, 4CL, CST, C3’H, C3OMT, CCOMT, CSE, PKS, AOR, DHN, and DHT. These analyses also identified the likely transcription factor networks that regulate the synthesis of gingerol analogs. Overall, this study serves as an excellent resource for further research on ginger biology and breeding, lays a foundation for a better understanding of ginger evolution, and presents an intact biosynthetic pathway for species-specific gingerol biosynthesis.

• Modern tropical rainforests have the highest biodiversity of terrestrial biomes and are restricted to three low-latitude areas. However, the actual timeframe during which tropical rainforests began to appear on a global scale has been intensely disputed. Here, we used the moonseed family (Menispermaceae), an important physiognomic and structural component of tropical rainforests on a worldwide basis, to obtain new insights into the diversification of this biome. • We integrated phylogenetic, biogeographic and molecular dating methods to analyse temporal and spatial patterns of global diversification in Menispermaceae. • Importantly, a burst of moonseed diversification occurred in a narrow window of time, which coincides with the Cretaceous–Paleogene (K–Pg) boundary. Our data also suggest multiple independent migrations from a putative ancestral area of Indo-Malay into other tropical regions. • Our data for Menispermaceae suggest that modern tropical rainforests may have appeared almost synchronously throughout the three major tropical land areas close to, or immediately following, the K–Pg mass extinction.

Nitrogen is fundamental to all life forms and is also one of the most limiting of nutrients for plant growth. Several clades of angiosperms have developed symbiotic relationships with actinorhizal bacteria that fix atmospheric nitrogen and increase access to this nutrient. However, the evolutionary patterns of actinorhizal nitrogen-fixing symbioses remain unclear to date. Furthermore the underlying environmental pressures that led to the gain of symbiotic actinorhizal nitrogen fixation have never been investigated. Here, we present the most comprehensive genus-level phylogenetic analysis of the nitrogen-fixing angiosperms based on three plastid loci. We found that actinorhizal nitrogen-fixing species are distributed in nine distinct lineages. By dating the branching events, we determined that seven actinorhizal nitrogen-fixing lineages originated during the Late Cretaceous and two more emerged during the Eocene. We put forward a hypothesis that multiple gains of actinorhizal nitrogen-fixing symbioses in angiosperms may have been associated with increased global temperatures and high levels of atmospheric carbon dioxide during these two time periods, as well as the availability of open habitats with high light conditions. Our nearly complete genus-level time-tree for the nitrogen-fixing clade is a significant advance in understanding the evolutionary and ecological background of this important symbiosis between plants and bacteria.

Background: AP2/ERF transcription factors (TFs) constitute one of the largest TF families in plants, which play crucial roles in plant metabolism, growth, and development as well as biotic and abiotic stresses responses. Although the AP2/ERF family has been thoroughly identified in many plant species and several AP2/ERF TFs have been functionally characterized, little is known about this family in ginger (Zingiber officinale Roscoe), an important affinal drug and diet vegetable. Recent completion of the ginger genome sequencing provides an opportunity to investigate the expression profiles of AP2/ERF genes in ginger on a genome-wide basis. Results: A total of 163 AP2/ERF genes were obtained in the Z.officinale genome and renamed according to the chromosomal distribution of the ZoAP2/ERF genes. Phylogenetic analysis divided them into three subfamilies, of which 35 belonged to the AP2 subfamily, 120 to ERF, three to RAV, and five to Sololist, respectively, which is in accordance with the number of conserved domains and gene structure analysis. A total of 10 motifs were detected in ZoAP2/ERF genes, and some of the unique motifs were found to be important for the function of ZoAP2/ERF genes. The chromosomal localization, gene structure, and conserved protein motif analyses, as well as the characterization of gene duplication events provided deep insight into the evolutionary features of these ZoAP2/ERF genes. The expression profiles derived from the RNA-seq data and quantitative reserve transcription (qRT-PCR) analysis of ZoAP2/ERFs during development and responses to abiotic stresses were investigated in ginger. Conclusion: A comprehensive analysis of the AP2/ERF gene expression patterns in various tissues by RNA-seq and qRT-PCR showed that they played an important role in the growth and development of ginger, and genes that might regulate rhizome and flower development were preliminary identified. In additionally, the ZoAP2/ERF family genes that responded to abiotic stresses were also identified. This study is the first time to identify the ZoAP2/ERF family, which contributes to research on evolutionary characteristics and better understanding the molecular basis for development and abiotic stress response, as well as further functional characterization of ZoAP2/ERF genes with an aim of ginger crop improvement.