Chromosomal-level genome assembly of the orchid tree Bauhinia variegata (Leguminosae; Cercidoideae) supports the allotetraploid origin hypothesis of Bauhinia

Cercidoideae, one of the six subfamilies of Leguminosae, contains one genus Cercis with its chromosome number 2n = 14 and all other genera with 2n = 28. An allotetraploid origin hypothesis for the common ancestor of non-Cercis genera in this subfamily has been proposed; however, no chromosome-level genomes from Cercidoideae have been available to test this hypothesis. Here, we conducted a chromosome-level genome assembly of Bauhinia variegata to test this hypothesis. The assembled genome is 326.4 Mb with the scaffold N50 of 22.1 Mb and contains 37,996 protein-coding genes. The Ks distribution between gene pairs in the syntenic regions indicates two whole-genome duplications (WGDs): one is B. variegata-specific, and the other is shared among core eudicots. Although Ks between gene pairs generated by the recent WGD in Bauhinia is greater than that between Bauhinia and Cercis, the WGD was not detected in Cercis, which can be explained by an accelerated evolutionary rate in Bauhinia after divergence from Cercis. Ks distribution and phylogenetic analysis for gene pairs generated by the recent WGD in Bauhinia and their corresponding orthologs in Cercis support the allopolyploidy origin hypothesis of Bauhinia. The genome of B. variegata also provides a genomic resource for dissecting genetic basis of its ornamental traits.     

Genomic Analysis of the Basal Lineage Fungus Rhizopus oryzae Reveals a Whole-Genome Duplication

Rhizopus oryzae is the primary cause of mucormycosis, an emerging, life-threatening infection characterized by rapid angioinvasive growth with an overall mortality rate that exceeds 50%. As a representative of the paraphyletic basal group of the fungal kingdom called “zygomycetes,” R. oryzae is also used as a model to study fungal evolution. Here we report the genome sequence of R. oryzae strain 99–880, isolated from a fatal case of mucormycosis. The highly repetitive 45.3 Mb genome assembly contains abundant transposable elements (TEs), comprising approximately 20% of the genome. We predicted 13,895 protein-coding genes not overlapping TEs, many of which are paralogous gene pairs. The order and genomic arrangement of the duplicated gene pairs and their common phylogenetic origin provide evidence for an ancestral whole-genome duplication (WGD) event. The WGD resulted in the duplication of nearly all subunits of the protein complexes associated with respiratory electron transport chains, the V-ATPase, and the ubiquitin–proteasome systems. The WGD, together with recent gene duplications, resulted in the expansion of multiple gene families related to cell growth and signal transduction, as well as secreted aspartic protease and subtilase protein families, which are known fungal virulence factors. The duplication of the ergosterol biosynthetic pathway, especially the major azole target, lanosterol 14α-demethylase (ERG11), could contribute to the variable responses of R. oryzae to different azole drugs, including voriconazole and posaconazole. Expanded families of cell-wall synthesis enzymes, essential for fungal cell integrity but absent in mammalian hosts, reveal potential targets for novel and R. oryzae-specific diagnostic and therapeutic treatments.     

A chromosome-level genome assembly of Ostrea denselamellosa provides initial insights into its evolution

The oyster Ostrea denselamellosa is a live-bearing species with a sharp decline in the natural population. Despite recent breakthroughs in long-read sequencing, high quality genomic data are very limited in O. denselamellosa. Here, we carried out the first whole genome sequencing at the chromosome-level in O. denselamellosa. Our studies yielded a 636 Mb assembly with scaffold N50 around 71.80 Mb. 608.3 Mb (95.6% of the assembly) were anchored to 10 chromosomes. A total of 26,412 protein-coding genes were predicted, of which 22,636 (85.7%) were functionally annotated. By comparative genomics, we found that long interspersed nuclear element (LINE) and short interspersed nuclear element (SINE) made up a larger proportion in O. denselamellosa genome than in other oysters'. Moreover, gene family analysis showed some initial insight into its evolution. This high-quality genome of O. denselamellosa provides a valuable genomic resource for studies of evolution, adaption and conservation in oysters.     

The application of multiplex fluorimetric sensor for the analysis of flavonoids content in the medicinal herbs family Asteraceae,Lamiaceae, Rosaceae

Background

The aim of our research work was to quantify total flavonoid contents in the leaves of 13 plant species family Asteraceae, 8 representatives of family Lamiaceae and 9 plant species belonging to family Rosaceae, using the multiplex fluorimetric sensor. Fluorescence was measured using optical fluorescence apparatus Multiplex(R) 3 (Force-A, France) for non-destructive flavonoids estimation. The content of total flavonoids was estimated by FLAV index (expressed in relative units), that is deduced from flavonoids UV absorbing properties.

Results

Among observed plant species, the highest amount of total flavonoids has been found in leaves of Helianthus multiflorus (1.65 RU) and Echinops ritro (1.27 RU), Rudbeckia fulgida (1.13 RU) belonging to the family Asteraceae. Lowest flavonoid content has been observed in the leaves of marigold (Calendula officinalis) (0.14 RU) also belonging to family Asteraceae. The highest content of flavonoids among experimental plants of family Rosaceae has been estimated in the leaves of Rosa canina (1.18 RU) and among plant species of family Lamiaceae in the leaves of Coleus blumei (0.90 RU).

Conclusions

This research work was done as pre-screening of flavonoids content in the leaves of plant species belonging to family Asteraceae, Lamiaceae and Rosaceae. Results indicated that statistically significant differences (P > 0.05) in flavonoids content were observed not only between families, but also among individual plant species within one family.     

The Chimonanthus salicifolius genome provides insight into magnoliid evolution and flavonoid biosynthesis

Chimonanthus salicifolius, a member of the Calycanthaceae of magnoliids, is one of the most famous medicinal plants in Eastern China. Here, we report a chromosome‐level genome assembly of C. salicifolius, comprising 820.1 Mb of genomic sequence with a contig N50 of 2.3 Mb and containing 36 651 annotated protein‐coding genes. Phylogenetic analyses revealed that magnoliids were sister to the eudicots. Two rounds of ancient whole‐genome duplication were inferred in the C. salicifolious genome. One is shared by Calycanthaceae after its divergence with Lauraceae, and the other is in the ancestry of Magnoliales and Laurales. Notably, long genes with > 20 kb in length were much more prevalent in the magnoliid genomes compared with other angiosperms, which could be caused by the length expansion of introns inserted by transposon elements. Homologous genes within the flavonoid pathway for C. salicifolius were identified, and correlation of the gene expression and the contents of flavonoid metabolites revealed potential critical genes involved in flavonoids biosynthesis. This study not only provides an additional whole‐genome sequence from the magnoliids, but also opens the door to functional genomic research and molecular breeding of C. salicifolius.     

Complete genome sequencing of Agrobacterium sp. H13-3, the former Rhizobium lupini H13-3, reveals a tripartite genome consisting of a circular and a linear chromosome and an accessory plasmid but lacking a tumor-inducing Ti-plasmid

Agrobacterium sp. H13-3, formerly known as Rhizobium lupini H13-3, is a soil bacterium that was isolated from the rhizosphere of Lupinus luteus. The isolate has been established as a model system for studying novel features of flagellum structure, motility and chemotaxis within the family Rhizobiaceae. The complete genome sequence of Agrobacterium sp. H13-3 has been established and the genome structure and phylogenetic assignment of the organism was analysed. For de novo sequencing of the Agrobacterium sp. H13-3 genome, a combined strategy comprising 454-pyrosequencing on the Genome Sequencer FLX platform and PCR-based amplicon sequencing for gap closure was applied. The finished genome consists of three replicons and comprises 5,573,770 bases. Based on phylogenetic analyses, the isolate could be assigned to the genus Agrobacterium biovar I and represents a genomic species G1 strain within this biovariety. The highly conserved circular chromosome (2.82 Mb) of Agrobacterium sp. H13-3 mainly encodes housekeeping functions characteristic for an aerobic, heterotrophic bacterium. Agrobacterium sp. H13-3 is a motile bacterium driven by the rotation of several complex flagella. Its behaviour towards external stimuli is regulated by a large chemotaxis regulon and a total of 17 chemoreceptors. Comparable to the genome of Agrobacterium tumefaciens C58, Agrobacterium sp. H13-3 possesses a linear chromosome (2.15 Mb) that is related to its reference replicon and features chromosomal and plasmid-like properties. The accessory plasmid pAspH13-3a (0.6 Mb) is only distantly related to the plasmid pAtC58 of A. tumefaciens C58 and shows a mosaic structure. A tumor-inducing Ti-plasmid is missing in the sequenced strain H13-3 indicating that it is a non-virulent isolate.     

Brassicales: an update on chromosomal evolution and ancient polyploidy

Brassicales comprise 17 families, c. 400 genera and more than 4600 species. Despite the mustard family (crucifers, Brassicaceae) continuing to be the subject of intensive research, the remaining 16 families are largely under studied. Here I summarize the available data on chromosome number and genome size variation across Brassicales in the context of a robust phylogenetic framework. This analysis has revealed extensive knowledge gaps in karyological data for non-crucifer and species-rich families in particular (i.e., Capparaceae, Cleomaceae, Resedaceae and Tropaeolaceae). A parsimonious interpretation of the combined chromosomal and phylogenetic data set suggests that the ancestral pre-Brassicales genome had 9 or 14 chromosome pairs, later multiplied by the At-β (beta) whole-genome duplication (WGD) to n?=?18 or 28. This WGD was followed by post-polyploid diploidization marked by diversification to 12 or 13 families and independent decreases in chromosome numbers. Family-specific WGDs are proposed to precede the diversification of Capparaceae, Resedaceae and Tropaeolaceae.     

The Melastoma dodecandrum genome and the evolution of Myrtales

Melastomataceae has abundant morphological diversity with high economic and ornamental merit in Myrtales. The phylogenetic position of Myrtales is still contested. Here, we report the chromosome-level genome assembly of Melastoma dodecandrum in Melastomataceae. The assembled genome size is 299.81 Mb with a contig N50 value of 3.00 Mb. Genome evolution analysis indicated that M. dodecandrum, Eucalyptus grandis, and Punica granatum were clustered into a clade of Myrtales and formed a sister group with the ancestor of fabids and malvids. We found that M. dodecandrum experienced four whole-genome polyploidization events: the ancient event was shared with most eudicots, one event was shared with Myrtales, and the other two events were unique to M. dodecandrum. Moreover, we identified MADS-box genes and found that the AP1-like genes expanded, and AP3-like genes might have undergone subfunctionalization. The SUAR63-like genes and AG-like genes showed different expression patterns in stamens, which may be associated with heteranthery. In addition, we found that LAZY1-like genes were involved in the negative regulation of stem branching development, which may be related to its creeping features. Our study sheds new light on the evolution of Melastomataceae and Myrtales, which provides a comprehensive genetic resource for future research.     

Genome analysis of species in the genus Hystrix (Triticeae; Poaceae)

Genomic in situ hybridisation (GISH) and Southern genomic hybridisation were applied in order to gain further knowledge regarding generic delimitation of the genus Hystrix as well as to clarify the genomes of the Hystrix species H. patula, H. longearistata, H. coreana, H. duthiei and H. komarovii. The hybridisation intensity of different genomic probes was compared among the Hystrix species and with other Triticeae species. The Southern- and GISH results confirm that H. patula contains the StH genome and show that H. komarovii most likely has a variant of this StH genome. The other Hystrix species under study, i.e. H. longearistata, H. coreana and H. duthiei, contain an Ns basic genome, and most probably two variants of this basic genome, Ns ¹ Ns ² . The genus Hystrix is thus not a monophyletic group of species.     

Molecular reexamination of korean umbelliferae based on internal transcribed spacer sequences of rDNA:Ligusticum tenuissimum (Nakai) Kitagawa andLibanotis coreana (Wolff) kitagawa

The taxonomic status ofLigusticum tenuissimum (Nakai) Kitagawa andLibanotis coreana (Wolff) Kitagawa has been controversial in Korea. We examined their phylogenetic relationships by comparing the internal transcribed spacer (=ITS) sequences of the nuclear ribosomal RNA gene (=rDNA) with another seven species in the Korean Umbelliferae. Our results support the legitimacy of the nomenclatural combination withL. tenuissimum Kitagawa rather than withAngelica tenuissima Nakai. We also suggest usingL coreana (Wolff) Kitagawa instead ofSeseli coreanum Wolff becauseL. coreana has been completely separated from most taxa of the genusSeseli. In addition, we have confirmed at least three phylogenetic lines in the genusLigusticum. One is the core group ofLigusticum that comprisesL tenuissimum and four other species. This clade includes theLigusticum hultenii line andLigusticum scothicum, known as an anomaly ofLigusticum. The second clade is composed ofLigusticum physospermifolium withSeseli monatum, which indicates the polyphyly ofLigusticum. The third line isLigusticum acutilobum, clustered as a sister grade ofDystaenia.     

淫羊藿属植物查耳酮合成酶启动子序列的克隆及比较分析

采用TAIL-PCR技术从箭叶淫羊藿(Epimedium sagittatum)叶片中克隆得到查耳酮合成酶基因(Chalcone synthase)的启动子,命名为ECHSP, 长度为750 bp,其具有TATA BOX、CAAT BOX、MYB结合位点、MYC结合位点等元件。对箭叶淫羊藿、木鱼坪淫羊藿(E. franchetii)、粗毛淫羊藿(E. acuminatum)、直距淫羊藿(E. mikinorii)、黔岭淫羊藿(E. leptorrhizum)等5种植物的CHS启动子序列进行比较分析,结果表明,CHS启动子的核苷酸多态性丰富,表明CHS 的表达可能受到多种因素的灵活调节。ECHSP与其他植物的CHS启动子序列进行比较,其TATA box的位置可能与黄酮类化合物的积累相关。此外,进化分析表明ECHSP的核苷酸序列可应用于淫羊藿属植物的系统进化研究。     

Isolation and functional characterization of a novel gene coding for flavonoid 3′-hydroxylase from globe artichoke

Globe artichoke (Cynara cardunculus L. var. scolymus) is rich in flavonoids which contribute to its health-promoting properties. With the aim of understanding the genetic control of flavonoid accumulation in artichoke, we isolated an artichoke full-length cDNA sequence encoding flavonoid 3′-hydroxylase (F3′H), a major enzyme of the flavonoid hydroxylation pattern. In silico studies confirmed that the deduced amino acid sequence of CcF3′H is highly similar to F3′Hs isolated from other Asteraceae. The Northern blot analysis demonstrated that CcF3′H was highly expressed in leaves and in specific parts of the heads. Its expression differed slightly among artichoke cultivars. The overexpression of CcF3′H in tobacco plants led to the accumulation of flavonoids and to an increase of flower colour intensity, thus identifying CcF3′H as promising candidate for genetic engineering. CcF3′H represents the first structural gene of the flavonoid biosynthesis isolated from C. cardunculus, and its characterization sheds light on the accumulation of flavonoids.     

植物乳杆菌天然质粒系统进化和起源

【目的】为了探索植物乳杆菌天然质粒系统进化关系和起源。【方法】本文利用复制起始蛋白(replication initiation protein,Rep)系统进化树、基因组共线性、基因组GC含量和宿主范围分析方法,对植物乳杆菌75个天然质粒的系统进化关系和起源进行了详细和多角度的分析。【结果】首先,Rep系统进化树和基因组共线性分析结果均表明,植物乳杆菌所有天然质粒可以划分为6个进化关系亲密的家族、2个进化形态特殊的杂合质粒和1个独立进化质粒pLP2140。杂合质粒pMRI5.2、pLP12-1分别由家族1-2和5-6质粒融合形成,因此植物乳杆菌质粒可能起源于7个祖先。其次,基因组共线性分析可以将6个家族质粒进一步划分为17个进化关系更近的亚家族类群,并清晰、有效地揭示类群内质粒之间的系统进化关系。最后,基因组GC含量和宿主范围分析为植物乳杆菌质粒的系统进化关系和起源提供了进一步的证据。【结论】因此上述研究可以准确、有效地揭示植物乳杆菌天然质粒的系统进化关系和起源,这对植物乳杆菌天然质粒系统进化和起源的了解和研究具有重要的参考价值。通过Rep系统进化树和基因组共线性两种分析方法优缺点的比较和组合,我们提出了一种更加有效的研究思路和分析方法,同时这种方法很可能适用于所有细菌天然质粒,因此对于天然质粒进化和起源研究具有普遍的方法学意义。     

New high-quality peach (Prunus persica L. Batsch) genome assembly to analyze the molecular evolutionary mechanism of volatile compounds in peach fruits

Peach (Prunus persica L. Batsch) is an economically important fruit crop worldwide. Although a high-quality peach genome has previously been published, Sanger sequencing was used for its assembly, which generated short contigs. Here, we report a chromosome-level genome assembly and sequence analysis of Chinese Cling, an important founder cultivar for peach breeding programs worldwide. The assembled genome contained 247.33 Mb with a contig N50 of 4.13 Mb and a scaffold N50 of 29.68 Mb, representing 99.8% of the estimated genome. Comparisons between this genome and the recently published one (Lovell peach) uncovered 685 407 single nucleotide polymorphisms, 162 655 insertions and deletions, and 16 248 structural variants. Gene family analysis highlighted the contraction of the gene families involved in flavone, flavonol, flavonoid, and monoterpenoid biosynthesis. Subsequently, the volatile compounds of 256 peach varieties were quantitated in mature fruits in 2015 and 2016 to perform a genome-wide association analysis. A comparison with the identified domestication genomic regions allowed us to identify 25 quantitative trait loci, associated with seven volatile compounds, in the domestication region, which is consistent with the differences in volatile compounds between wild and cultivated peaches. Finally, a gene encoding terpene synthase, located within a previously reported quantitative trait loci region, was identified to be associated with linalool synthesis. Such findings highlight the importance of this new assembly for the analysis of evolutionary mechanisms and gene identification in peach species. Furthermore, this high-quality peach genome provides valuable information for future fruit improvement.     

Comprehensive genomics and expression analysis of eceriferum (CER) genes in sunflower (Helianthus annuus)

Sunflower occupies the fourth position among oilseed crops the around the world. Eceriferum (CER) is an important gene family that plays critical role in very-long-chain fatty acids elongation and biosynthesis of epicuticular waxes under both biotic and abiotic stress conditions. The aim of present study was to investigate the effect of sunflower CER genes during drought stress condition. Thus, comparative analysis was undertaken for sunflower CER genes with Arabidopsis genome to determine phylogenetic relationship, chromosomal mapping, gene structures, gene ontology and conserved motifs. Furthermore, we subjected the sunflower cultivars under drought stress and used qRT-PCR analysis to explore the expression pattern of CER genes during drought conditions. We identified thirty-seven unevenly distributed CER genes in the sunflower genome. The phylogenetic analysis revealed that CER genes were grouped into seven clades in Arabidopsis, Helianthus annuus, and Gossypium hirsutum. Expression analysis showed that genes CER10 and CER60 were upregulated in sunflower during drought conditions, indicating that these genes are activated during drought stress. The results obtained will serve to characterize the CER gene family in sunflower and exploit the role of these genes in wax biosynthesis under limited water conditions.Key messageCuticular waxes protect the plants from drought stress, so we observed the expression of wax bio synthesis genes in recently sequences genome of Helianthus annuus. We observed that expression of wax biosynthesis genes CER10 and CER60 was upregulated when the plants were subjected to drought stress.     

Chemodiversity of exudate flavonoids in Dionysia (Primulaceae): A comparative study

More than 60 accessions of various Dionysia spp. were analysed for their exudate flavonoid composition. Many Dionysia spp. accumulate the typical Primula flavonoids with irregular substitution (unsubstituted flavone, its 2′,5′-substituted derivatives and corresponding 5-OH-flavones), but flavones, flavonols and flavanones with regular 5,7-diOH-substitution are also encountered in their exudates. The formation of both types of flavonoids is not mutually exclusive. This paper analyses the chemodiversity of Dionysia exudates with respect to infraspecific variability, infrageneric distribution, patterns in hybrid taxa, and comparisons of biogenetic tendencies between Dionysia and closest related species of Primula. The uniqueness of occurrence of Primula-type flavonoids in the family Primulaceae, and their presumed different biosynthetic origin, suggest significance as further character in the Primula–Dionysia assemblage. Principal component analysis was applied to test the significance of variation of flavonoid composition across Dionysia. Comparative analysis of flavonoid profiles against the current taxonomic views yielded correlations, confined to the level of smaller groups, and only in parts at level of the current infrageneric concept. Flavonoid data are further discussed against the background of morphological and biogeographic differentiation of the genus. Increased diversification of flavonoid profiles may be interpreted as a derived status in Dionysia, which agrees with current views on the phylogeny of Dionysia as a specialised group within Primula. Functional aspects of exudate flavonoid formation are shortly addressed.