The Euscaphis japonica genome and the evolution of malvids.

Malvids is one of the largest clades of rosids, includes 58 families and exhibits remarkable morphological and ecological diversity. Here, we report a high-quality chromosome-level genome assembly for Euscaphis japonica, an early-diverging species within malvids. Genome-based phylogenetic analysis suggests that the unstable phylogenetic position of E. japonica may result from incomplete lineage sorting and hybridization event during the diversification of the ancestral population of malvids. Euscaphis japonica experienced two polyploidization events: the ancient whole genome triplication event shared with most eudicots (commonly known as the γ event) and a more recent whole genome duplication event, unique to E. japonica. By resequencing 101 samples from 11 populations, we speculate that the temperature has led to the differentiation of the evergreen and deciduous of E. japonica and the completely different population histories of these two groups. In total, 1012 candidate positively selected genes in the evergreen were detected, some of which are involved in flower and fruit development. We found that reddening and dehiscence of the E. japonica pericarp and long fruit-hanging time promoted the reproduction of E. japonica populations, and revealed the expression patterns of genes related to fruit reddening, dehiscence and abscission. The key genes involved in pentacyclic triterpene synthesis in E. japonica were identified, and different expression patterns of these genes may contribute to pentacyclic triterpene diversification. Our work sheds light on the evolution of E. japonica and malvids, particularly on the diversification of E. japonica and the genetic basis for their fruit dehiscence and abscission.

Genetic diversity and population structure of Euscaphis japonica, a monotypic species.

BACKGROUND: Understanding plant genetic diversity is important for effective conservation and utilization of genetic resources. Euscaphis japonica (Thunb.) Dippel, is a monotypic species with high phenotypic diversity, narrow distribution, and small population size. In this study, we estimated the genetic diversity and population structure of E. japonica using nine natural populations and inter-simple sequence repeat (ISSR) markers. Our results could provide a theoretical reference for future conservation and utilization of E. japonica. RESULTS: We obtained a total of 122 DNA bands, of which 121 (99.18%) were polymorphic. The average number of effective alleles (Ne = 1.4975), Nei's gene diversity index (H = 0.3016), and Shannon's information index (I = 0.4630) revealed that E. japonica possessed a high level of genetic diversity. We observed that E. japonica consisted of both deciduous and evergreen populations. UPGMA tree showed that the evergreen and deciduous E. japonica form a sister group. There is little genetic differentiation among geographic populations based on STRUCTURE analysis. The Dice's similarity coefficient between the deciduous and evergreen populations was low, and the Fst value was high, indicating that these two types of groups have high degree of differentiation. CONCLUSION: Rich genetic diversity has been found in E. japonica, deciduous E. japonica and evergreen E. japonica populations, and genetic variation mainly exists within the population. The low-frequency gene exchange between deciduous and evergreen populations may be the result of the differentiation of deciduous and evergreen populations. We suggest that in-situ protection, seed collection, and vegetative propagation could be the methods for maintenance and conservation of E. japonica populations.

The re-sequencing of complete chloroplast genome of Cinnamomum camphora (Lauraceae) from Quanzhou, China.

Cinnamomum camphora is a precious species for its significance of timber. It is also the main component of the subtropical evergreen broad-leaved forest. We report a chloroplast genome of C. camphora from Quanzhou, China. The complete chloroplast genome is 152,730 bp in length consisting of a pair of inverted repeat (IR) regions of 19,968 bp, a small single-copy (SSC) region of 18,874 bp, and a large single-copy (LSC) region of 93,706 bp, respectively. The chloroplast genome encoded 116 genes, including 79 protein-coding genes, 36 tRNA genes, and eight rRNA genes. This result will provide useful genomic basis for the phylogenetic research of Lauraceae.

Complete chloroplast genome sequence of Bougainvillea Spectabilis (Nyctaginaceae).

Bougainvillea spectabilis is an important ornamental plant in tropical and subtropical regions, whose complex and diverse germplasm has brought great difficulties to variety selection and identification. Here, to provide data support for the identification of the relationship between cultivars of B. spectabilis, we sequenced the chloroplast genome of B. spectabilis. The chloroplast genome is 154,520 bp in length, including a large single-copy (LSC) region of 88,101 bp and small single-copy (SSC) region of 17,729 bp, and a pair of invert repeats (IR) regions of 24,171 bp. The chloroplast genome contains 129 genes, including 83 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The phylogenetic analysis based on 14 chloroplast genome demonstrated a close relationship between B. spectabilis and other plant species in Caryophyllales. The chloroplast genome will help for further of taxonomy research and provide data support for the identification of genetic relationship among different cultivars of B. spectabilis.

Sequencing of Euscaphis konishii Endocarp Transcriptome Points to Molecular Mechanisms of Endocarp Coloration.

Flower and fruit colors are of vital importance to the ecology and economic market value of plants. The mechanisms of flower and fruit coloration have been well studied, especially among ornamental flower plants and cultivated fruits. As people pay more attention to exocarp coloration, the endocarp coloration in some species has often been ignored. Here, we report on the molecular mechanism of endocarp coloration in three development stages of Euscaphis konishii. The results show that endocarp reddening is closely related to anthocyanin accumulation, and a total of 86,120 unigenes were assembled, with a mean length of 893 bp (N50 length of 1642 bp). We identified a large number of differentially expressed genes associated with endocarp coloration, including anthocyanin biosynthesis, carotenoid biosynthesis, and chlorophyll breakdown. The genes participating in each step of the anthocyanin biosynthesis were found in the transcriptome dataset, but a few genes were found in the carotenoid biosynthesis and chlorophyll breakdown. In addition, the candidate R2R3-MYB transcription factors and candidate glutathione S-transferase transport genes, which likely regulate the anthocyanin biosynthesis, were identified. This study offers a platform for E. konishii functional genomic research and provides a reference for revealing the regulatory mechanisms of endocarp reddening.