Low-frequency somatic mutations are heritable in tropical trees Dicorynia guianensis and Sextonia rubra.

Somatic mutations potentially play a role in plant evolution, but common expectations pertaining to plant somatic mutations remain insufficiently tested. Unlike in most animals, the plant germline is assumed to be set aside late in development, leading to the expectation that plants accumulate somatic mutations along growth. Therefore, several predictions were made on the fate of somatic mutations: mutations have generally low frequency in plant tissues; mutations at high frequency have a higher chance of intergenerational transmission; branching topology of the tree dictates mutation distribution; and exposure to UV (ultraviolet) radiation increases mutagenesis. To provide insights into mutation accumulation and transmission in plants, we produced two high-quality reference genomes and a unique dataset of 60 high-coverage whole-genome sequences of two tropical tree species, Dicorynia guianensis (Fabaceae) and Sextonia rubra (Lauraceae). We identified 15,066 de novo somatic mutations in D. guianensis and 3,208 in S. rubra, surprisingly almost all found at low frequency. We demonstrate that 1) low-frequency mutations can be transmitted to the next generation; 2) mutation phylogenies deviate from the branching topology of the tree; and 3) mutation rates and mutation spectra are not demonstrably affected by differences in UV exposure. Altogether, our results suggest far more complex links between plant growth, aging, UV exposure, and mutation rates than commonly thought.

Alcohol dehydrogenases regulated by a MYB44 transcription factor underlie Lauraceae citral biosynthesis.

Lineage-specific terpenoids have arisen throughout the evolution of land plants and are believed to play a role in interactions between plants and the environment. Species-specific gene clusters in plants have provided insight on the evolution of secondary metabolism. Lauraceae is an ecologically important plant family whose members are also of considerable economic value given their monoterpene contents. However, the gene cluster responsible for the biosynthesis of monoterpenes remains yet to be elucidated. Here, a Lauraceae-specific citral biosynthetic gene cluster (CGC) was identified and investigated using a multifaceted approach that combined phylogenetic, collinearity, and biochemical analyses. The CGC comprises MYB44 as a regulator and 2 alcohol dehydrogenases (ADHs) as modifying enzymes, which derived from species-specific tandem and proximal duplication events. Activity and substrate divergence of the ADHs has resulted in the fruit of mountain pepper (Litsea cubeba), a core Lauraceae species, consisting of more than 80% citral. In addition, MYB44 negatively regulates citral biosynthesis by directly binding to the promoters of the ADH-encoding genes. The aggregation of citral biosynthetic pathways suggests that they may form the basis of important characteristics that enhance adaptability. The findings of this study provide insights into the evolution of and the regulatory mechanisms involved in plant terpene biosynthesis.

Phylogenetic incongruence in an Asiatic species complex of the genus Caryodaphnopsis (Lauraceae).

BACKGROUND: Caryodaphnopsis, a group of tropical trees (ca. 20 spp.) in the family Lauraceae, has an amphi-Pacific disjunct distribution: ten species are distributed in Southeast Asia, while eight species are restricted to tropical rainforests in South America. Previously, phylogenetic analyses using two nuclear markers resolved the relationships among the five species from Latin America. However, the phylogenetic relationships between the species in Asia remain poorly known. RESULTS: Here, we first determined the complete mitochondrial genome (mitogenome), plastome, and the nuclear ribosomal cistron (nrDNA) sequences of C. henryi with lengths of 1,168,029 bp, 154,938 bp, and 6495 bp, respectively. We found 2233 repeats and 368 potential SSRs in the mitogenome of C. henryi and 50 homologous DNA fragments between its mitogenome and plastome. Gene synteny analysis revealed a mass of rearrangements in the mitogenomes of Magnolia biondii, Hernandia nymphaeifolia, and C. henryi and only six conserved clustered genes among them. In order to reconstruct relationships for the ten Caryodaphnopsis species in Asia, we created three datasets: one for the mitogenome (coding genes and ten intergenic regions), another for the plastome (whole genome), and the other for the nuclear ribosomal cistron. All of the 22 Caryodaphnopsis individuals were divided into four, five, and six different clades in the phylogenies based on mitogenome, plastome, and nrDNA datasets, respectively. CONCLUSIONS: The study showed phylogenetic conflicts within and between nuclear and organellar genome data of Caryodaphnopsis species. The sympatric Caryodaphnopsis species in Hekou and Malipo SW China may be related to the incomplete lineage sorting, chloroplast capture, and/or hybridization, which mixed the species as a complex in their evolutionary history.

Exploring the antileishmanial activity of dicentrine from Ocotea puberula (Lauraceae) using biomembrane models.

This study aimed to assess the antiprotozoal efficacy of dicentrine, an aporphine alkaloid isolated from Ocotea puberula, against amastigote forms of Leishmania (L.) infantum. Our findings reveal that dicentrine demonstrated a notable EC50 value of 10.3 µM, comparable to the positive control miltefosine (EC50 of 10.4 µM), while maintaining moderate toxicity to macrophages (CC50 of 51.9 µM). Utilizing an in silico methodology, dicentrine exhibited commendable adherence to various parameters, encompassing lipophilicity, water solubility, molecule size, polarity, and flexibility. Subsequently, we conducted additional investigations to unravel the mechanism of action, employing Langmuir monolayers as models for protozoan cell membranes. Tensiometry analyses unveiled that dicentrine disrupts the thermodynamic and mechanical properties of the monolayer by expanding it to higher areas and increasing the fluidity of the film. The molecular disorder was further corroborated through dilatational rheology and infrared spectroscopy. These results contribute insights into the role of dicentrine as a potential antiprotozoal drug in its interactions with cellular membranes. Beyond elucidating the mechanism of action at the plasma membrane's external surface, our study sheds light on drug-lipid interface interactions, offering implications for drug delivery and other pharmaceutical applications.

Unpredictable Chemical Diversity of Essential Oils in Cinnamomum burmanni (Lauraceae) Living Collections: Beyond Maternally Inherited Phylogenetic Relationships.

The genus Cinnamomum encompasses diverse species with various applications, particularly in traditional medicine and spice production. This study focuses on Cinnamomum burmanni, specifically on a high-D-borneol-content chemotype, known as the Meipian Tree, in Guangdong Province, South China. This research explores essential oil diversity, chemotypes, and chloroplast genomic diversity among 28 C. burmanni samples collected from botanical gardens. Essential oils were analyzed, and chemotypes classified using GC-MS and statistical methods. Plastome assembly and phylogenetic analysis were conducted to reveal genetic relationships. Results showed distinct chemotypes, including eucalyptol and borneol types, with notable variations in essential oil composition. The chloroplast genome exhibited conserved features, with phylogenetic analysis revealing three major clades. Borneol-rich individuals in clade II suggested a potential maternal inheritance pattern. However, phylogenetic signals revealed that the composition of essential oils is weakly correlated with plastome phylogeny. The study underscores the importance of botanical gardens in preserving genetic and chemical diversity, offering insights for sustainable resource utilization and selective breeding of high-yield mother plants of C. burmanni.

New insights into the plastome evolution of Lauraceae using herbariomics.

BACKGROUND: The family Lauraceae possesses ca. 50 genera and 2,500-3,000 species that are distributed in the pantropics. Only half of the genera of the family were represented in previously published plastome phylogenies because of the difficulty of obtaining research materials. Plastomes of Hypodaphnideae and the Mezilaurus group, two lineages with unusual phylogenetic positions, have not been previously reported and thus limit our full understanding on the plastome evolution of the family. Herbariomics, promoted by next generation sequencing technology, can make full use of herbarium specimens, and provides opportunities to fill the sampling gap. RESULTS: In this study, we sequenced five new plastomes (including four genera which are reported for the first time, viz. Chlorocardium, Hypodaphnis, Licaria and Sextonia) from herbarium specimens using genome skimming to conduct a comprehensive analysis of plastome evolution of Lauraceae as a means of sampling representatives of all major clades of the family. We identified and recognized six types of plastomes and revealed that at least two independent loss events at the IR-LSC boundary and an independent expansion of SSC occurred in the plastome evolution of the family. Hypodaphnis possesses the ancestral type of Lauraceae with trnI-CAU, rpl23 and rpl2 duplicated in the IR regions (Type-I). The Mezilaurus group shares the same plastome structure with the core Lauraceae group in the loss of trnI-CAU, rpl23 and rpl2 in the IRa region (Type-III). Two new types were identified in the Ocotea group: (1) the insertion of trnI-CAU between trnL-UAG and ccsA in the SSC region of Licaria capitata and Ocotea bracteosa (Type-IV), and (2) trnI-CAU and pseudogenizated rpl23 inserted in the same region of Nectandra angustifolia (Type-V). Our phylogeny suggests that Lauraceae are divided into nine major clades largely in accordance with the plastome types. The Hypodaphnideae are the earliest diverged lineage supported by both robust phylogeny and the ancestral plastome type. The monophyletic Mezilaurus group is sister to the core Lauraceae. CONCLUSIONS: By using herbariomics, we built a more complete picture of plastome evolution and phylogeny of the family, thus providing a convincing case for further use of herbariomics in phylogenetic studies of the Lauraceae.

Development of species-specific ISSR-derived SCAR marker for early discrimination between Cinnamomum verum and Cinnamomum cassia.

BACKGROUND: Cinnamomum verum (true cinnamon) and Cinnamomum cassia (cassia cinnamon) are two important species belonging to family Lauraceae. These species are recognized by morphological, chemical composition and essential oil contents. The appropriate identification of species would be considerably improved by a genetic method. The main objective of the present study was to develop molecular markers distinguishing between C. verum and C. cassia. METHODS AND RESULTS: A total 71 ISSR (Inter simple sequence repeat) and four universal barcoding (ITS, rbcL, matK, and psbA-trnH) genes were used to distinguish both the species. No sequence variation was observed between the two species for any DNA barcode gene. However, one ISSR i.e. ISSR-37 showed a clear distinction between the species and produced 570 bp and 746 bp amplicons in C. verum and C. cassia, respectively. The polymorphic bands were converted into species-specific SCAR markers. The SCAR-CV was specific to C. verum and amplified 190 bp band, however there was no amplification seen in the C. cassia samples. CONCLUSION: The SCAR marker generated in this study can be employed as efficient, economical, and reliable molecular tool for the identification of C. verum.

Acute and sub-acute toxicity study of ethanol extract from Nectandra leucantha Nees & Mart. (Lauraceae) barks.

Nectandra leucantha has been used in traditional medicine. Several metabolites isolated from N. leucantha extracts displayed immunomodulatory, antileishmanial properties, but the determination of the toxicological profile in mammals has not previously been performed. In this study, the ethanol extract from N. leucantha barks (EENl) was characterized by HPLC/HRESIMS. To study acute toxicity, female mice received EENl in a single dose of 100, 300, 1000, or 2000 mg/kg bw. Later, sub-acute toxicity was introduced in female and male mice by oral gavage at 100, 500 or 1000 mg/kg bw for 28 consecutive days. Hematological and biochemical profiles from the blood as well as histological analysis from the liver and kidney were performed. The HPLC/HRESIMS analysis of the EENl revealed the presence of six neolignans chemically related to dehydrodieugenol B. In the oral acute and sub-chronic studies, EENl did not produce in all doses evaluated any alteration in behavior, biochemical, hematological, body weight gain and food intake or sudden death in Swiss mice. In addition, histopathological data did not reveal any disturbance in liver and kidney morphology after 28 days of EENl treatment. Our results indicate that EENl at dosage levels up to 2000 mg/kg bw is non-toxic and can be considered safe for mammals.

Anti-Inflammatory Activity of Lauraceae Plant Species and Prediction Models Based on Their Metabolomics Profiling Data.

The Lauraceae is a botanical family known for its anti-inflammatory potential. However, several species have not yet been studied. Thus, this work aimed to screen the anti-inflammatory activity of this plant family and to build statistical prediction models. The methodology was based on the statistical analysis of high-resolution liquid chromatography coupled with mass spectrometry data and the ex vivo anti-inflammatory activity of plant extracts. The ex vivo results demonstrated significant anti-inflammatory activity for several of these plants for the first time. The sample data were applied to build anti-inflammatory activity prediction models, including the partial least square acquired, artificial neural network, and stochastic gradient descent, which showed adequate fitting and predictive performance. Key anti-inflammatory markers, such as aporphine and benzylisoquinoline alkaloids were annotated with confidence level 2. Additionally, the validated prediction models proved to be useful for predicting active extracts using metabolomics data and studying their most bioactive metabolites.

Chemical Composition, Mosquito Larvicidal and Antimicrobial Activities, and Molecular Docking Study of Essential Oils of Cinnamomum melastomaceum, Neolitsea buisanensis and Uvaria microcarpa from Vietnam.

The leaf oil compositions of two Lauraceae and one Annonaceae plants cultivated in Vietnam were analysed by GC/MS (gas chromatography-mass spectrometry) analysis. The leaf oil of the first Lauraceae plant Cinnamomum melastomaceum contained 34 identified compounds, in which benzyl benzoate (38.5 %), linalool (19.9 %), (E)-caryophyllene (10.5 %), and α-terpineol (6.9 %) were the major compounds. The leaves of the second Lauraceae plant Neolitsea buisanensis gave an oil with the main compounds (E)-ß-ocimene (24.0 %), benzyl benzoate (15.8 %), bicyclogermacrene (14.9 %), and (E)-caryophyllene (6.3 %). The leaf oil of the Annonaceae plant Uvaria microcarpa consisted of the principal compounds (E)-caryophyllene (18.0 %), bicyclogermacrene (8.1 %), and δ-elemene (6.1 %). Two Lauraceae oil samples exhibited strong mosquito larvicidal activity against Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus with LC50 and LD90 values of less than 50 µg/mL. The Annonaceae oil sample showed strong antimicrobial activity against the fungus Aspergillus niger ATCC 1015 with the MIC (minimum inhibitory concentration) value of 32 µg/mL. In the docking approach, the major compounds (E)-caryophyllene, bicyclogermacrene, and benzyl benzoate interacted with the mosquito odorant-binding protein 3OGN, whereas (E)-caryophyllene, bicyclogermacrene, and δ-elemene also potentially interacted with the 4ZA5 protein of fungus A. niger.

Genome Identification and Evolutionary Analysis of LBD Genes and Response to Environmental Factors in Phoebe bournei.

Phoebe bournei is nationally conserved in China due to its high economic value and positive effect on the ecological environment. P. bournei has an excellent wood structure, making it useful for industrial and domestic applications. Despite its importance, there are only a few studies on the lateral organ boundary domain (LBD) genes in P. bournei. The LBD gene family contributes to prompting rooting in multiple plant species and therefore supports their survival directly. To understand the LBD family in P. bournei, we verified its characteristics in this article. By comparing the sequences of Arabidopsis and identifying conserved domains and motifs, we found that there were 38 members of the LBD family in P. bournei, which were named PbLBD1 to PbLBD38. Through evolutionary analysis, we found that they were divided into two different populations and five subfamilies in total. The LBD gene family in P. bournei (Hemsl.) Yang species had two subfamilies, including 32 genes in Class I and 6 genes in Class II. It mainly consists of a Lateral Organ Boundary (LOB) conservative domain, and the protein structure is mostly "Y"-shaped. The gene expression pattern of the LBD gene family showed that the LBD genes were mainly expressed in lateral organs of plants, such as flowers and fruits. The response of LBD transcription factors to red and blue light was summarized, and several models of optogenetic expression regulation were proposed. The effect of regulatory mechanisms on plant rooting was also predicted. Moreover, quantitative real-time PCR (qRT-PCR) revealed that most PbLBDs were differentially expressed under cold, heat, drought, and salt stresses, indicating that PbLBDs might play different functions depending on the type of abiotic stress. This study provides the foundation for further research on the function of LBD in this tree species in the future.

Genome-Wide Identification and Expression Analysis of Calmodulin and Calmodulin-like Genes, Revealing CaM3 and CML13 Participating in Drought Stress in Phoebe bournei.

Calmodulin (CaM) and calmodulin-like (CML) proteins are major Ca2+ sensors involved in the regulation of plant development and stress responses by converting Ca2+ signals into appropriate cellular responses. However, characterization and expression analyses of CaM/CML genes in the precious species, Phoebe bournei, remain limited. In this study, five PbCaM and sixty PbCML genes were identified that only had EF-hand motifs with no other functional domains. The phylogenetic tree was clustered into 11 subgroups, including a unique clade of PbCaMs. The PbCaMs were intron-rich with four EF-hand motifs, whereas PbCMLs had two to four EF-hands and were mostly intronless. PbCaMs/CMLs were unevenly distributed across the 12 chromosomes of P. bournei and underwent purifying selection. Fragment duplication was the main driving force for the evolution of the PbCaM/CML gene family. Cis-acting element analysis indicated that PbCaMs/CMLs might be related to hormones, growth and development, and stress response. Expression analysis showed that PbCaMs were generally highly expressed in five different tissues and under drought stress, whereas PbCMLs showed specific expression patterns. The expression levels of 11 candidate PbCaMs/CMLs were responsive to ABA and MeJA, suggesting that these genes might act through multiple signaling pathways. The overexpression of PbCaM3/CML13 genes significantly increased the tolerance of yeast cells to drought stress. The identification and characterization of the CaM/CML gene family in P. bournei laid the foundation for future functional studies of these genes.

N-Methyl Costaricine and Costaricine, Two Potent Butyrylcholinesterase Inhibitors from Alseodaphne pendulifolia Gamb.

Studies have been conducted over the last decade to identify secondary metabolites from plants, in particular those from the class of alkaloids, for the development of new anti-Alzheimer's disease (AD) drugs. The genus Alseodaphne, comprising a wide range of alkaloids, is a promising source for the discovery of new cholinesterase inhibitors, the first-line treatment for AD. With regard to this, a phytochemical investigation of the dichloromethane extract of the bark of A. pendulifolia Gamb. was conducted. Repeated column chromatography and preparative thin-layer chromatography led to the isolation of a new bisbenzylisoquinoline alkaloid, N-methyl costaricine (1), together with costaricine (2), hernagine (3), N-methyl hernagine (4), corydine (5), and oxohernagine (6). Their structures were elucidated by the 1D- and 2D-NMR techniques and LCMS-IT-TOF analysis. Compounds 1 and 2 were more-potent BChE inhibitors than galantamine with IC50 values of 3.51 ± 0.80 µM and 2.90 ± 0.56 µM, respectively. The Lineweaver-Burk plots of compounds 1 and 2 indicated they were mixed-mode inhibitors. Compounds 1 and 2 have the potential to be employed as lead compounds for the development of new drugs or medicinal supplements to treat AD.

An In Vivo Assessment of the Effect of Hexane Extract from Endlicheria paniculata Branches and Its Main Compound, Methyldehydrodieugenol B, on Murine Sponge-Induced Inflammation.

The present study aims to explore the anti-inflammatory potential activity of the hexane extract from branches (HEB) of Endlicheria paniculata (Lauraceae) and its main compound, methyldehydrodieugenol B, in the inflammatory response induced by a murine implant sponge model. HPLC-ESI/MS analysis of HEB led to the identification of six chemically related neolignans, with methyldehydrodieugenol B as the main compound. An in silico analysis of the pharmacokinetic parameters of the identified compounds suggested moderate solubility but good absorption and biodistribution in vivo. Thus, the treatment of mice with HEB using in vivo assays indicated that HEB promoted pro-inflammatory, antiangiogenic, and antifibrogenic effects, whereas treatment with methyldehydrodieugenol B caused anti-inflammatory, antifibrogenic, and antiangiogenic effects. The obtained results shown the therapeutic potential of HEB and methyldehydrodieugenol B in the treatment of pathologies associated with inflammation and angiogenesis, including chronic wounds.

Seasonal Variation in Essential Oil Composition and Antioxidant Capacity of Aniba canelilla (Lauraceae): A Reliable Source of 1-Nitro-2-phenylethane.

Aniba canelilla (Kunth) Mez essential oil has many biological activities due to its main compound 1-nitro-2-phenylethane (1N2F), followed by methyleugenol, a carcinogenic agent. This study analyzed the influence of seasonality on yields, antioxidant capacity, and 1N2F content of A. canelilla leaf and twig essential oils. Essential oils (EOs) were extracted with hydrodistillation and analyzed with gas chromatography coupled to mass spectrometry and a flame ionization detector. Antioxidant capacity was measured using the free radical scavenging method (DPPH). Chemometric analyses were carried out to verify the influence of climatic factors on the production and composition of EOs. 1-Nitro-2-phenylethane was the major constituent in A. canelilla EOs throughout the seasonal period (68.0-89.9%); methyleugenol was not detected. Essential oil yields and the 1N2F average did not show a statistically significant difference between the dry and rainy seasons in leaves and twigs. Moderate and significant correlations between major compounds and climate factor were observed. The twig oils (36.0 ± 5.9%) a showed greater antioxidant capacity than the leaf oils (20.4 ± 5.0%). The PCA and HCA analyses showed no statistical differences between the oil samples from the dry and rainy seasons. The absence of methyleugenolin in all months of study, described for the first time, makes this specimen a reliable source of 1N2F.

Biseugenol from Ocotea cymbarum (Lauraceae) attenuates inflammation, angiogenesis and collagen deposition of sponge-induced fibrovascular tissue in mice.

Several species of the genus Ocotea are used in traditional medicine due to their anti-inflammatory and analgesic properties. In this work we sought to investigate the effects of biseugenol, the main component of the hexane extract from the leaves of Ocotea cymbarum (Lauraceae), during a chronic inflammatory process induced by polyester-polyurethane sponge in mice. In addition to the inflammatory component, sponge discs also allowed us to evaluate parameters associated with the formation of new blood vessels and the deposition and organization of the extracellular matrix, processes that are related to the chronification of the inflammatory response. Daily treatment with biseugenol (0.1, 1 or 10 µg in 10 µl of 0.5% DMSO) inhibited the synthesis of inflammatory cytokines (TNF-α, CXCL-1 and CCL2) and the neutrophil and macrophage infiltrate into to the implants, indirectly evaluated by the activity of myeloperoxidase and N-acetyl-ß-D-glycosaminidase enzymes, respectively. In implants treated with biseugenol, we observed a reduction in angiogenesis, assessed through histological quantification of mean number of blood vessels, the levels of the pro-angiogenic cytokines FGF and VEGF and the activity of metalloproteinases. Except for VEGF levels, all mentioned parameters showed significant reductions after treatment with biseugenol. Finally, the administration of the compound also reduced TGF-ß1 levels, collagen synthesis and deposition, in addition to modifying the organization of the newly formed matrix, presenting a potential anti-fibrotic effect. Therefore, our results demonstrate the potential therapeutic use of biseugenol for the treatment of a series of pathological conditions, where parameters associated with inflammation, angiogenesis and fibrogenesis are deregulated.

Plastome structure, phylogenomics, and divergence times of tribe Cinnamomeae (Lauraceae).

BACKGROUND: Tribe Cinnamomeae is a species-rich and ecologically important group in tropical and subtropical forests. Previous studies explored its phylogenetic relationships and historical biogeography using limited loci, which might result in biased molecular dating due to insufficient parsimony-informative sites. Thus, 15 plastomes were newly sequenced and combined with published plastomes to study plastome structural variations, gene evolution, phylogenetic relationships, and divergence times of this tribe. RESULTS: Among the 15 newly generated plastomes, 14 ranged from 152,551 bp to 152,847 bp, and the remaining one (Cinnamomum chartophyllum XTBGLQM0164) was 158,657 bp. The inverted repeat (IR) regions of XTBGLQM0164 contained complete ycf2, trnICAU, rpl32, and rpl2. Four hypervariable plastid loci (ycf1, ycf2, ndhF-rpl32-trnLUAG, and petA-psbJ) were identified as candidate DNA barcodes. Divergence times based on a few loci were primarily determined by prior age constraints rather than by DNA data. In contrast, molecular dating using complete plastid protein-coding genes (PCGs) was determined by DNA data rather than by prior age constraints. Dating analyses using PCGs showed that Cinnamomum sect. Camphora diverged from C. sect. Cinnamomum in the late Oligocene (27.47 Ma). CONCLUSIONS: This study reports the first case of drastic IR expansion in tribe Cinnamomeae, and indicates that plastomes have sufficient parsimony-informative sites for molecular dating. Besides, the dating analyses provide preliminary insights into the divergence time within tribe Cinnamomeae and can facilitate future studies on its historical biogeography.

Transcriptome analysis reveals the accelerated expression of genes related to photosynthesis and chlorophyll biosynthesis contribution to shade-tolerant in Phoebe bournei.

BACKGROUND: Phoebe bournei (P. bournei) is an important and endemic wood species in China. However, the plantation, nursing, and preservation of P. bournei are often affected by light. To investigate its physiological changes and molecular mechanism of low light tolerance, two-year-old P. bournei seedlings were subjected to different shading conditions. With the increase of light intensity in the shade, the leaf color of P. bournei seedlings became darkened, the aboveground/underground biomass significantly increased, the content of chlorophyll increased and the net photosynthetic rate significantly increased. RESULTS: de novo transcriptome analysis showed that 724 and 3,248 genes were differentially expressed due to low light intensity at T1 (35% light exposure) and T2 (10% light exposure), respectively, when compared to the controls. Furthermore, the differentially expressed genes (DEGs) were implicated in photosynthesis, nitrogen metabolism, plant hormone signal transduction, biosynthesis of secondary metabolites, and protein processing in the endoplasmic reticulum by functional enrichment analysis. Moreover, the expression of HSP, CAB, HEMA1, GSA, DVR, MYB, bHLH, PORA, CAO, GLK, and photosystem I and II complex-related genes significantly increased after low light exposure at T2 and T1. CONCLUSIONS: The present study suggests that the rapid growth of P. bournei seedlings under shading conditions may be the result of the accelerated expression of genes related to photosynthesis and chlorophyll biosynthesis, which enable plants to maintain a high photosynthesis rate even under low light conditions.

More opportunities more species: Pleistocene differentiation and northward expansion of an evergreen broad-leaved tree species Machilus thunbergii (Lauraceae) in Southeast China.

BACKGROUND: The broad continuum between tropical and temperate floras in Eastern Asia (EAS) are thought to be one of the main factors responsible for a prominent species diversity anomaly of temperate plants between EAS and eastern North America (ENS). However, how the broad continuum and niche evolution between tropical and temperate floras in EAS contributes to lineage divergence and species diversity remains largely unknown. RESULTS: Population genetic structure, demography, and determinants of genetic structure [i.e., isolation-by-distance (IBD), isolation-by-resistance (IBR), and isolation-by-environment (IBE)] of Machilus thunbergii Sieb. et Zucc. (Lauraceae) were evaluated by examining sequence variation of ten low-copy nuclear genes across 43 populations in southeast China. Climatic niche difference and potential distributions across four periods (Current, mid-Holocene, the last glacial maximum, the last interglacial) of two genetic clusters were determined by niche modelling. North and south clusters of populations in M. thunbergii were revealed and their demarcation line corresponds well with the northern boundary of tropical zone in China of Zhu & Wan. The divergence time between the clusters and demographic expansion of M. thunbergii occurred after the mid-Pleistocene climate transition (MPT, 0.8-1.2 Ma). Migration rates between clusters were asymmetrical, being much greater from north to south than the reverse. Significant effects of IBE, but non-significant effects of IBD and IBR on population genetic divergence were detected. The two clusters have different ecological niches and require different temperature regimes. CONCLUSIONS: The north-south genetic differentiation may be common across the temperate-tropical boundary in southeast China. Divergent selection under different temperature regimes (possibly above and below freezing temperature in winter) could account for this divergence pattern. The broad continuum between tropical and temperate floras in EAS may have provided ample opportunities for tropical plant lineages to acquire freezing tolerance and to colonize the temperate regions during the late-Cenozoic global cooling. Our findings shed deeper insights into the high temperate plant species diversity in EAS.

Floral morphology and phenology of Sassafras tzumu (Lauraceae).

BACKGROUND: Sassafras has been considered to belong to trib. Laureae of Lauraceae and has been assumed to have unisexual flowers. However, recent molecular phylogenetic studies have consistently suggested that Sassafras does not belong to the trib. Laureae but to Cinnamomeae and that it is nested within Cinnamomum. A recent morphological study revealed that one of the Asian species, S. randaiense, possesses bisexual flowers that are plesiomorphic in the family Lauraceae. As reports on the flower structure of the second Asian species, S. tzumu, have been contradictory, we wanted to ascertain if it has bisexual flowers or not. If the flowers were bisexual, could earlier reports that they were unisexual have been based on dichogamous flowering? RESULTS: In this study, we investigated two populations of S. tzumu. We found that this species has determinate botryoid racemes, and possesses bisexual flowers. Among the three extant species, S. tzumu is more similar to its sister species S. randaiense but markedly different from the American S. albidum: the two Asian species possess bisexual flowers while the American species has unisexual flowers. The bisexual flower of S. tzumu is protogynous, and shows two phenological phases typical of Lauraceae: 1) in a flower, the pistil functions first, the stigma is fresh and white, stamens of the outer two whorls are spreading, anthers do not open, and the staminodes secrete nectar at this stage; 2) in the second phase, the stigma becomes brown, staminodes are withered, stamens of the third whorl stand up and surround the pistil, glands of the third whorl of stamens secrete nectar, and the anthers open and release pollen. CONCLUSIONS: The similarity of racemose inflorescences between Sassafras and some members of Laureae were caused by parallel evolution; the racemose inflorescence of ancestral Sassafras originated from the thyrsoid-cymose inflorescence in Cinnamomum. The Asian species S. tzumu and S. randaiense possess bisexual flowers with two phenological phases, the American S. albidum evolved unisexual flowers independently from other clades with unisexual flowers in the Lauraceae, i.e., the Laureae, Alseodaphnopsis in the Perseeae and the unisexual clade in the Ocotea complex of the Cinnamomeae.