Basal Eudicot Research Articles

In silico analysis of R2R3-MYB transcription factors in the basal eudicot model, Aquilegia coerulea

R2R3-MYBs are an important group of transcription factors that regulate crucial developmental processes across the plant kingdom; yet no comprehensive analysis of the R2R3-MYBs in the early-diverging eudicot clade of Ranunculaceae has been conducted so far. In the present study, Aquilegia coerulea is chosen to understand the extent of conservation and divergence of R2R3-MYBs as a representative of the family by analysing the genomic distribution, organization, gene structure, physiochemical properties, protein architecture, evolution and possible mode of expansion. Genome-wide analysis showed the presence of 82 putative homologues classified into 21 subgroups, based on phylogenetic analysis of full-length protein sequences. The domain has remained largely conserved across all homologues with few differences from the characterized Arabidopsis thaliana R2R3-MYBs. The topology of the phylogenetic tree remains the same when full-length protein sequences are used, indicating that the evolution of R2R3-MYBs is driven by the domain region only. This is supported by the presence of similar structures of exon–intron and conserved motifs within the same subgroup. Furthermore, comparisons of the AqcoeR2R3-MYB members with monocots and core-eudicots revealed the evolutionary expansion of a few functional clades, such as A. thaliana R2R3-MYB subgroup 6 (SG6), the upstream regulatory factors of floral pigment biosynthesis and floral color. The reconstructed evolutionary history of SG6-like genes across angiosperms highlights the occurrence of independent duplication events in the genus Aquilegia. AqcoeR2R3-MYB genes are present in all seven chromosomes of A. coerulea, most of which result from local and segmental duplications. Selection analysis of these duplicated gene pairs indicates purifying selection except one, and the physiochemical analyses of R2R3-MYBs reveal differences among the MYBs signifying their functional diversification. This study paves the way for further investigation of paralogous copies and their probable role in the evolution of different floral traits in A. coerulea. It lays the foundation for functional genomic studies of R2R3-MYBs in the basal eudicots and facilitates comparative studies among angiosperms. The work also provides a framework for deciphering novel genetic regulatory pathways that govern the diversity of floral morphology.

Leaf architecture and functional traits for 122 species at the University of California Botanical Garden at Berkeley.

The dataset contains leaf venation architecture and functional traits for a phylogenetically diverse set of 122 plant species (including ferns, basal angiosperms, monocots, basal eudicots, asterids, and rosids) collected from the living collections of the University of California Botanical Garden at Berkeley (37.87° N, 122.23° W; CA, USA) from February to September 2021. The sampled species originated from all continents, except Antarctica, and are distributed in different growth forms (aquatic, herb, climbing, tree, shrub). The functional dataset comprises 31 traits (mechanical, hydraulic, anatomical, physiological, economical, and chemical) and describes six main leaf functional axes (hydraulic conductance, resistance and resilience to damages caused by drought and herbivory, mechanical support, and construction cost). It also describes how architecture features vary across venation networks. Our trait dataset is suitable for (1) functional and architectural characterization of plant species; (2) identification of venation architecture-function trade-offs; (3) investigation of evolutionary trends in leaf venation networks; and (4) mechanistic modeling of leaf function. Data are made available under the Open Data Commons Attribution License.

An inquiry into the radial patterning of root hair cell distribution in eudicots.

The root epidermis of tracheophytes consists of hair-forming cells (HCs) and nonhair cells (NCs). The HC distribution pattern is classified into three types: random (Type I), vertically alternating (Type II), and radial (Type III). Type III is found only in core eudicots and is known to be position-dependent in superrosids with HCs positioned between two underlying cortical cells. However, the evolution of Type III and the universality of its position dependency in eudicots remain unclear. We surveyed the HC distribution in basal and Type III-exhibiting core eudicots and conducted genomic analyses to get insight into whether eudicots share the same genetic network to establish Type III. Our survey revealed no canonical Type III in basal eudicots but a reverse Type III, with NCs between two cortical cells and HCs on a single cortical cell, in Papaveraceae of basal eudicots. Type III-exhibiting species from both superrosids and superasterids showed the canonical position dependency of HCs. However, some key components for Type III determination were absent in the genomes of Papaveraceae and Type III-exhibiting superasterids. Our findings identify a novel position-dependent type of HC patterning, reverse Type III, and suggest that Type III emerged independently or diversified during eudicot evolution.

Evolution and seed development responses of Nelumbo SWEET genes

The Sugars Will Eventually be Exported Transporter (SWEET) proteins are a group of sugar transporters that are present in various organisms and facilitate the flux of sugars across cell membranes. In this study, we identified SWEET proteins from 13 representative plant species and further classified them phylogenetically into four clades. Different rates of contraction and expansion of SWEET genes were observed among different species. Our focus was on the characteristics and biological functions of SWEET genes in the basal eudicot lotus. A total of 26 SWEET genes were identified in Nelumbo, including 14 NnSWEETs in N. nucifera and 12 NlSWEETs in N. lutea. The expansion of SWEET genes in Nelumbo was driven by tandem and segmental duplication events. Analysis of three-dimensional (3D) structures revealed that SWEET proteins typically consist of two 3-TM units (THB1 and THB2) and are attached via the center TM4. Subcellular localization assays demonstrated that the NnSWEET proteins were localized in the plasma membrane. The potential transcriptional regulation mechanisms were investigated by systematically scanning for binding transcription factor in the promoter regions of NnSWEET genes. Some NnSWEETs were found to be preferentially expressed during lotus seed development, and co-expression analysis revealed that certain NnSWEET genes were involved in sugar and starch metabolism. Moreover, transient overexpression of NnSWEET14 significantly increased the soluble sugar content in lotus seed. These findings not only lay the groundwork for functional characterization of SWEET genes in Nelumbo, but also provide valuable genetic resources for future improvement of lotus seed quality.

Genome sequencing and functional analysis of a multipurpose medicinal herb Tinospora cordifolia (Giloy).

Tinospora cordifolia (Willd.) Hook.f. & Thomson, also known as Giloy, is among the most important medicinal plants that have numerous therapeutic applications in human health due to the production of a diverse array of secondary metabolites. To gain genomic insights into the medicinal properties of T. cordifolia, the genome sequencing was carried out using 10× Genomics linked read and Nanopore long-read technologies. The draft genome assembly of T. cordifolia was comprised of 1.01 Gbp, which is the genome sequenced from the plant family Menispermaceae. We also performed the genome size estimation for T. cordifolia, which was found to be 1.13 Gbp. The deep sequencing of transcriptome from the leaf tissue was also performed. The genome and transcriptome assemblies were used to construct the gene set, resulting in 17,245 coding gene sequences. Further, the phylogenetic position of T. cordifolia was also positioned as basal eudicot by constructing a genome-wide phylogenetic tree using multiple species. Further, a comprehensive comparative evolutionary analysis of gene families contraction/expansion and multiple signatures of adaptive evolution was performed. The genes involved in benzyl iso-quinoline alkaloid, terpenoid, lignin and flavonoid biosynthesis pathways were found with signatures of adaptive evolution. These evolutionary adaptations in genes provide genomic insights into the presence of diverse medicinal properties of this plant. The genes involved in the common symbiosis signalling pathway associated with endosymbiosis (Arbuscular Mycorrhiza) were found to be adaptively evolved. The genes involved in adventitious root formation, peroxisome biogenesis, biosynthesis of phytohormones, and tolerance against abiotic and biotic stresses were also found to be adaptively evolved in T. cordifolia.

Nuclear phylogenomics of angiosperms and insights into their relationships and evolution.

Angiosperms (flowering plants) are by far the most diverse land plant group with over 300,000 species. The sudden appearance of diverse angiosperms in the fossil record was referred to by Darwin as the "abominable mystery," hence contributing to the heightened interest in angiosperm evolution. Angiosperms display wide ranges of morphological, physiological, and ecological characters, some of which have probably influenced their species richness. The evolutionary analyses of these characteristics help to address questions of angiosperm diversification and require well resolved phylogeny. Following the great successes of phylogenetic analyses using plastid sequences, dozens to thousands of nuclear genes from next-generation sequencing have been used in angiosperm phylogenomic analyses, providing well resolved phylogenies and new insights into the evolution of angiosperms. In this review we focus on recent nuclear phylogenomic analyses of large angiosperm clades, orders, families, and subdivisions of some families and provide a summarized Nuclear Phylogenetic Tree of Angiosperm Families. The newly established nuclear phylogenetic relationships are highlighted and compared with previous phylogenetic results. The sequenced genomes of Amborella, Nymphaea, Chloranthus, Ceratophyllum, and species of monocots, Magnoliids, and basal eudicots, have facilitated the phylogenomics of relationships among five major angiosperms clades. All but one of the 64 angiosperm orders were included in nuclear phylogenomics with well resolved relationships except the placements of several orders. Most families have been included with robust and highly supported placements, especially for relationships within several large and important orders and families. Additionally, we examine the divergence time estimation and biogeographic analyses of angiosperm on the basis of the nuclear phylogenomic frameworks and discuss the differences compared with previous analyses. Furthermore, we discuss the implications of nuclear phylogenomic analyses on ancestral reconstruction of morphological, physiological, and ecological characters of angiosperm groups, limitations of current nuclear phylogenomic studies, and the taxa that require future attention.

Leaf Area Estimation by Photographing Leaves Sandwiched between Transparent Clear File Folder Sheets

Image analysis is a promising method for in situ leaf area measurement. However, as leaves are three-dimensional, the use of two-dimensional images captured using a digital camera can result in underestimation. To overcome this problem, we tested a clear folder method. Before photographing leaves with a digital camera, we flattened the leaves by sandwiching them between a pair of transparent plastic clear file folder sheets, which are stationery implements for carrying documents. Although similar methods have been previously proposed, their applicability to species with different leaf shapes has never been investigated. We tested the efficacy of this method using 12 species from various taxa (monocots, magnoliids, and basal and core eudicots) and leaf morphology (entire vs. lobed, simple vs. compound leaves, small and large leaves). Individual leaf areas and the Montgomery parameters obtained using this method were then compared with those obtained using the standard method, which employs a flatbed digital scanner. We observed strong correlations (R2 > 0.98) between the camera and scanner data. The regression slopes were close to unity (0.96–1.01) and the intercepts were close to zero. These findings suggest that the clear folder method can be used as an inexpensive alternative method to estimate the area of leaves in situ with acceptable accuracy. An introductory manual for readers unfamiliar with image analysis using ImageJ is presented in the end of the paper.

Functional characterization of three TERMINAL FLOWER 1-like genes from Platanus acerifolia.

TFL1-like genes of the basal eudicot Platanus acerifolia have conserved roles in maintaining vegetative growth and inhibiting flowering, but may act through distinct regulatory mechanism. Three TERMINAL FLOWER 1 (TFL1)-like genes were isolated and characterized from London plane tree (Platanus acerifolia). All genes have conserved genomic organization and characteristic of the phosphatidylethanolamine-binding protein (PEBP) family. Sequence alignment and phylogenetic analysis indicated that two genes belong to the TFL1 clade, designated as PlacTFL1a and PlacTFL1b, while another one was grouped in the BFT clade, named as PlacBFT. qRT-PCR analysis showed that all three genes primarily expressed in vegetative phase, but the expression of PlacTFL1a was much higher and wider than that of PlacTFL1b, with the latter only detected at relatively low expression levels in apical and lateral buds in April. PlacBFT was mainly expressed in young stems of adult trees followed by juvenile tissues. Ectopic expression of any TFL1-like gene in Arabidopsis showed phenotypes of delayed or repressed flowering. Furthermore, overexpression of PlacTFL1a gene in petunia also resulted in extremely delayed flowering. In non-flowering 35:PlacTFL1a transgenic petunia plants, the FT-like gene (PhFT) gene was significantly upregulated and AP1 homologues PFG, FBP26 and FBP29 were significantly down-regulated in leaves. Yeast two-hybrid analysis indicated that only weak interactions were detected between PlacTFL1a and PlacFDL, and PlacTFL1a showed no interaction with PhFDL1/2. These results indicated that the TFL1-like genes of Platanus have conserved roles in repressing flowering, but probably via a distinct regulatory mechanism.

Plant-Insect Interactions on Aquatic and Terrestrial Angiosperms from the Latest Albian (Early Cretaceous) of Estercuel (Northeastern Spain) and Their Paleoenvironmental Implications.

Fossils of plant-insect interactions are direct evidence of paleoecological relationships between these two dominant groups in terrestrial ecosystems. We present a variety of plant-insect interactions from the late Early Cretaceous (latest Albian) in the Estercuel locality in northeastern Spain (Iberian Peninsula), affecting two types of terrestrial angiosperms and the basal eudicot Klitzschophyllites, which is one of the oldest putative members of aquatic Ranunculales found to date. The study of these interactions revealed 23 different damage types belonging to eight functional feeding groups (hole feeding, margin feeding, skeletonization, surface feeding, piercing and sucking, mining, oviposition and galling), suggesting these angiosperms were an important source of food and lodging for insects in the Iberian ecosystems during the late Early Cretaceous. Notably, the diversity of damage in the leaves of angiosperms suggests a diverse community of herbivorous insects and a variety of strategies of interactions with plants at the end of the Early Cretaceous in the southwestern Tethys realm.

Single-cell transcriptomics unveils xylem cell development and evolution

BackgroundXylem, the most abundant tissue on Earth, is responsible for lateral growth in plants. Typical xylem has a radial system composed of ray parenchyma cells and an axial system of fusiform cells. In most angiosperms, fusiform cells comprise vessel elements for water transportation and libriform fibers for mechanical support, while both functions are performed by tracheids in other vascular plants such as gymnosperms. Little is known about the developmental programs and evolutionary relationships of these xylem cell types.ResultsThrough both single-cell and laser capture microdissection transcriptomic profiling, we determine the developmental lineages of ray and fusiform cells in stem-differentiating xylem across four divergent woody angiosperms. Based on cross-species analyses of single-cell clusters and overlapping trajectories, we reveal highly conserved ray, yet variable fusiform, lineages across angiosperms. Core eudicots Populus trichocarpa and Eucalyptus grandis share nearly identical fusiform lineages, whereas the more basal angiosperm Liriodendron chinense has a fusiform lineage distinct from that in core eudicots. The tracheids in the basal eudicot Trochodendron aralioides, an evolutionarily reversed trait, exhibit strong transcriptomic similarity to vessel elements rather than libriform fibers.ConclusionsThis evo-devo framework provides a comprehensive understanding of the formation of xylem cell lineages across multiple plant species spanning over a hundred million years of evolutionary history.

Allotetraploidization event of Coptis chinensis shared by all Ranunculales

Coptis chinensis Franch., also named Chinese goldthread is a member of Ranunculaceae in the order Ranunculales and represents an important lineage of early eudicots with traditional medicinal value. In our study, by using syntenic analysis combined with phylogenomic analysis of C. chinensis and four other representative genomes from basal and core eudicots, we confirmed that the WGD event in C. chinensis was shared by Aquilegia coerulea and Papaver somniferum L. and quickly occurred after Ranunculales diverged from other eudicots, likely a Ranunculales common tetraploidization (RCT). The synonymous nucleotide substitutions at synonymous sites distribution of syntenic blocks across these genomes showed that the evolutionary rate of the P. somniferum genome is faster than that of the C. chinensis genome by approximately 13.7%, possibly due to Papaveraceaes having an additional special tetraploidization event (PST). After Ks correction, the RCT dated to 115–130 million years ago (MYA), which was close to the divergence of Ranunculaceaes and Papaveraceaes approximately 115.45–130.51 MYA. Moreover, we identified homologous genes related to polyploidization and speciation and constructed multiple sequence alignments with different reference genomes. Notably, the event-related subgenomes in the basal genomes all showed genomic fractionation bias, suggesting a likely allopolyploid nature of the RCT, PST and T-Alpha and T-Beta events in Tetracentron sinense. In addition, we detected that the sixteen P450 subfamilies were markedly expanded in the genomes of Ranunculales, and most of them were related to the RCT and PST events. We constructed a new platform for Early Eudicot Comparative Genomic Research (http://www.cgrpoee.top/index.html) to store more information. In summary, our findings support the WGD of C. chinensis shared by Ranunculales, which is likely an allotetraploidization event. This present effort offered new insights into the evolution of key polyploidization events and the genes related to secondary metabolites during the diversification of early eudicots.

Characterization of B- and C-class MADS-box genes in medicinal plant <i>Epimedium sagittatum</i>

The basal eudicot Epimedium (Barrenwort) exhibits innovative floral morphology in the form of petal spurs filled with nectar and petaloid sepals. The B-class MADS-box genes <italic>APETALAS3</italic> (<italic>AP3</italic>) and <italic>PISTILLA</italic> (<italic>PI</italic>) determine sepal and petal identity while the C-class gene <italic>AGAMOUS</italic> (<italic>AG</italic>) determines carpel and stamen identity in <italic>Arabidopsis</italic>. Complex histories of gene duplication resulted in subsequent subfunctionalization or neofunctionalization of paralogs. Here, a total of four B- and two C-class genes were successfully isolated from <italic>E. sagittatum</italic>. Phylogenetic analysis showed that <italic>EsAP3-1</italic>, <italic>EsAP3-2</italic>, and <italic>EsAP3-3</italic> are part of the AP3 clade; <italic>EsPI</italic> is part of the PI group; and <italic>EsAG</italic> and <italic>EsAG11</italic> clustered into the AG and AG11 groups, respectively. Quantitative real-time PCR was utilized to detect the expression patterns of these genes, and all B-class genes except for <italic>EsAP3-3</italic> were found to be universally expressed. The transcribed <italic>EsAG</italic> and <italic>EsAG11</italic> genes were confined to reproductive organs. In addition, yeast three and two hybrid assays were used to explore the status of protein complexes. EsAP3-1 was found to have broadly interactive partners, and EsPI can form a heterodimer with EsAP3-1 and EsAP3-2. Transgenic EsAG overexpression in wild-type Arabidopsis confirmed the conserved function determining carpel development.

Exploring Splicing Variants and Novel Genes in Sacred Lotus Based on RNA-seq Data

Sacred lotus (<i>Nelumbo nucifera</i>) is a typical aquatic plant, belonging to basal eudicot plant, which is ideal for genome and genetic evolutionary study. Understanding lotus gene diversity is important for the study of molecular genetics and breeding. In this research, public RNA-seq data and the annotated reference genome were used to identify the genes in lotus. A total of 26,819 consensus and 1,081 novel genes were identified. Meanwhile, a comprehensive analysis of gene alternative splicing events was conducted, and a total of 19,983 “internal” alternative splicing (AS) events and 14,070 “complete” AS events were detected in 5,878 and 5,881 multi-exon expression genes, respectively. Observations made from the AS events show the predominance of intron retention (IR) subtype of AS events representing 33%. IR is followed by alternative acceptor (AltA), alternative donor (AltD) and exon skipping (ES), highlighting the universality of the intron definition model in plants. In addition, functional annotations of the gene with AS indicated its relationship to a number of biological processes such as cellular process and metabolic process, showing the key role for alternative splicing in influencing the growth and development of lotus. The results contribute to a better understanding of the current gene diversity in lotus, and provide an abundant resource for future functional genome analysis in lotus.

The chromosome-level genome of Akebia trifoliata as an important resource to study plant evolution and environmental adaptation in the Cretaceous.

The environmental adaptation of eudicots is the most reasonable explanation for why they compose the largest clade of modern plants (>70% of angiosperms), which indicates that the basal eudicots would be valuable and helpful to study their survival and ability to thrive throughout evolutionary processes. Here, we detected two whole-genome duplication (WGD) events in the high-quality assembled Akebia trifoliata genome (652.73Mb) with 24 138 protein-coding genes based on the evidence of intragenomic and intergenomic collinearity, synonymous substitution rate (KS ) values and polyploidization and diploidization traces; these events putatively occurred at 85.15 and 146.43million years ago (Mya). The integrated analysis of 16 species consisting of eight basal and eight core eudicots further revealed that there was a putative ancient WGD at the early stage of eudicots (temporarily designated θ) at 142.72Mya, similar to the older WGD of Akebia trifoliata, and a putative core eudicot-specific WGD (temporarily designated ω). Functional enrichment analysis of retained duplicate genes following the θ event is suggestive of adaptation to the extreme environment change in both the carbon dioxide concentration and desiccation around the Jurassic-Cretaceous boundary, while the retained duplicate genes following the ω event is suggestive of adaptation to the extreme droughts, possibly leading to the rapid spread of eudicots in the mid-Cretaceous. Collectively, the A. trifoliata genome experienced two WGD events, and the older event may have occurred at the early stage of eudicots, which likely increased plant environmental adaptability and helped them survive in ancient extreme environments.

The discovery of a key prenyltransferase gene assisted by a chromosome-level Epimedium pubescens genome.

Epimedium pubescens is a species of the family Berberidaceae in the basal eudicot lineage, and a main plant source for the traditional Chinese medicine "Herba Epimedii". The current study achieved a chromosome-level genome assembly of E. pubescens with the genome size of 3.34 Gb, and the genome guided discovery of a key prenyltransferase (PT) in E. pubescens. Our comparative genomic analyses confirmed the absence of Whole Genome Triplication (WGT-γ) event shared in core eudicots and further revealed the occurrence of an ancient Whole Genome Duplication (WGD) event approximately between 66 and 81 Million Years Ago (MYA). In addition, whole genome search approach was successfully applied to identify 19 potential flavonoid PT genes and an important flavonoid PT (EpPT8) was proven to be an enzyme for the biosynthesis of medicinal compounds, icaritin and its derivatives in E. pubescens. Therefore, our results not only provide a good reference genome to conduct further molecular biological studies in Epimedium genus, but also give important clues for synthetic biology and industrial production of related prenylated flavonoids in future.

Characterization of the MADS-Box Gene Family in Akebia trifoliata and Their Evolutionary Events in Angiosperms.

As the largest clade of modern plants, flower plants have evolved a wide variety of flowers and fruits. MADS-box genes play key roles in regulating plant morphogenesis, while basal eudicots have an evolutionarily important position of acting as an evolutionary bridge between basal angiosperms and core eudicots. Akebia trifoliata is an important member of the basal eudicot group. To study the early evolution of angiosperms, we identified and characterized the MADS-Box gene family on the whole-genome level of A. trifoliata. There were 47 MADS-box genes (13 type I and 34 type II genes) in the A. trifoliata genome; type I genes had a greater gene length and coefficient of variation and a smaller exon number than type II genes. A total of 27 (57.4%) experienced whole or segmental genome duplication and purifying selection. A transcriptome analysis suggested that three and eight genes were involved in whole fruit and seed development, respectively. The diversification and phylogenetic analysis of 1479 type II MADS-box genes of 22 angiosperm species provided some clues indicating that a γ whole genome triplication event of eudicots possibility experienced a two-step process. These results are valuable for improving A. trifoliata fruit traits and theoretically elucidating evolutionary processes of angiosperms, especially eudicots.

Distinct composition and amplification dynamics of transposable elements in sacred lotus (Nelumbo nucifera Gaertn.).

Sacred lotus (Nelumbo nucifera Gaertn.) is a basal eudicot plant with a unique lifestyle, physiological features, and evolutionary characteristics. Here we report the unique profile of transposable elements (TEs) in the genome, using a manually curated repeat library. TEs account for 59% of the genome, and hAT (Ac/Ds) elements alone represent 8%, more than in any other known plant genome. About 18% of the lotus genome is comprised of Copia LTR retrotransposons, and over 25% of them are associated with non-canonical termini (non-TGCA). Such high abundance of non-canonical LTR retrotransposons has not been reported for any other organism. TEs are very abundant in genic regions, with retrotransposons enriched in introns and DNA transposons primarily in flanking regions of genes. The recent insertion of TEs in introns has led to significant intron size expansion, with a total of 200 Mb in the 28 455 genes. This is accompanied by declining TE activity in intergenic regions, suggesting distinct control efficacy of TE amplification in different genomic compartments. Despite the prevalence of TEs in genic regions, some genes are associated with fewer TEs, such as those involved in fruit ripening and stress responses. Other genes are enriched with TEs, and genes in epigenetic pathways are the most associated with TEs in introns, indicating a dynamic interaction between TEs and the host surveillance machinery. The dramatic differential abundance of TEs with genes involved in different biological processes as well as the variation of target preference of different TEs suggests the composition and activity of TEs influence the path of evolution.

Morphological and Genotypic Characterization Of Different Lotus (Nelumbo Nucifera Gaertn.) Samples Available in Bangladesh

Asian lotus (Nelumbo nucifera Gaertn.), commonly known as sacred lotus is a basal eudicot. It has been grown and cultivated as food, medicine and for cultural, and religious activities. In the current study, samples were collected from six different locations to evaluate the variation among different lotus germplasm based on external morphological characteristics, as well as, to study the genetic variation and the molecular characterization. Analysis of variance showed a higher level of variations among the germplasm for all the morphological features. Based on the morphological features, a dendrogram was constructed to assess the linkage among the germplasm. The yellow lotus of Cumilla was considered superior among the germplasm studied. To assess the genetic diversity and the correct identification of lotus germplasm, molecular method “Barcoding” was performed. To achieve the goal, two plastidial regions: rpoB and rpoC1 were employed. The germplasm showing successful PCR were subjected to sequence analysis of their barcode genes. All the selected barcode genes showed successful identification of all the germplasm as N. nucifera in multilocus identification based on their sequences except for the germplasm of Rajshahi and also confirmed the yellowish lotus of Cumilla considered as a new cultivar N. nucifera ‘Gomoti’, newly found in Bangladesh. Genetic sequences obtained in the context of DNA barcoding had also been used to create a phylogenetic tree in which the germplasm were clustered into five main clades. The current study was successful in establishing an efficient protocol for the correct identification of lotus germplasm and was capable of establishing an elite gene source. Moreover, future studies are warranted to see the identifying capability and diverging power of the barcodes. Bangladesh J. Plant Taxon. 29(1): 85-95, 2022 (June)

Comparative analyses of American and Asian lotus genomes reveal insights into petal color, carpel thermogenesis and domestication.

SUMMARY Nelumbo lutea (American lotus), which differs from Nelumbo nucifera (Asian lotus) morphologically, is one of the two remaining species in the basal eudicot family Nelumbonaceae. Here, we assembled the 843‐Mb genome of American lotus into eight pseudochromosomes containing 31 382 protein‐coding genes. Comparative analyses revealed conserved synteny without large chromosomal rearrangements between the genomes of American and Asian lotus and identified 29 533 structural variants (SVs). Carotenoid and anthocyanin pigments determine the yellow and red petal colors of American and Asian lotus, respectively. The structural genes encoding enzymes of the carotenoid and anthocyanin biosynthesis pathways were conserved between two species but differed in expression. We detected SVs caused by repetitive sequence expansion or contraction among the anthocyanin biosynthesis regulatory MYB genes. Further transient overexpression of candidate NnMYB5 induced anthocyanin accumulation in lotus petals. Alternative oxidase (AOX), uncoupling proteins (UCPs), and sugar metabolism and transportation contributed to carpel thermogenesis. Carpels produce heat with sugars transported from leaves as the main substrates, because there was weak tonoplast sugar transporter (TST) activity, and with SWEETs were highly expressed during thermogenesis. Cell proliferation‐related activities were particularly enhanced in the warmer carpels compared with stamens during the cold night before blooming, which suggested that thermogenesis plays an important role in flower protogyny. Population genomic analyses revealed deep divergence between American and Asian lotus, and independent domestication affecting seed, rhizome, and flower traits. Our findings provide a high‐quality reference genome of American lotus for exploring the genetic divergence and variation between two species and revealed possible genomic bases for petal color, carpel thermogenesis and domestication in lotus.

Yezopollis mikasaensis gen. et sp. nov., a new Normapolles-type angiosperm pollen from the Upper Cretaceous of Hokkaido, Japan

A new taxon, Yezopollis mikasaensis gen. et sp. nov., is described based on Normapolles-type angiosperm pollen grains obtained from the upper Cenomanian–lower Turonian Mikasa Formation of the Yezo Group outcropping in Mikasa City, central Hokkaido, Japan. The grains are triangular to subcircular, with three or sometimes four equatorial apertures that are thickened and slightly protruding, and externally extended into a vertical slit. The surface is coarsely reticulate with a marked broad, psilate zone at the aperture margin. They are morphologically most similar to Siberiapollis within the Normapolles complex, but are distinct in their rounder outline and vermiculate reticulum. Yezopollis adds a new record of this group, which is markedly different from other genera of the same age, and is the earliest Normapolles-type representative found outside of the province. Yezopollis mikasaensis was the sole angiosperm pollen contained in a leaflitter bed exclusively composed of the platanoid Ettingshausenia cuneifolia. Ettingshausenia-type leaves are found in Menispermaceae and Platanaceaeas which diverge at the base of all eudicots, as well as in Hamamelidaceae of the basalmost superrosids. Yezopollis-type pollen has not been reported for these families, but is usually reported in Proteaceae of the basal eudicots. The co-occurrence of Y. mikasaensis and E. cuneifolia might imply that some early eudicots exhibited intermixed features of extant basal eudicot families if they were shed by the same plant species.