An ethnobotany survey of wild plants used by the Tibetan people of the Yadong River Valley, Tibet, China.

INTRODUCTION: Plant resources gathered from the wild are important sources of livelihood needs, especially for low-income populations living in remote areas, who rely on these plants for food, fuelwood, medicine and building materials. Yadong County is a valley at the border between the China, India and Bhutan in southern Tibet. Yadong is rich in biodiversity and culture, but ethnobotanical knowledge has not been systematically studied. This study aimed to document the ethnobotanical knowledge of Tibetans in Yadong County. METHODS: Ethnobotanical data were documented through free listings, key informant interviews, and semi-structured interviews during fieldwork. The culture importance index (CI) and informant consensus factor index (FIC) were used as the quantitative indices. RESULTS: In total, 163 informants (46 women and 117 men). A total of 3,031 use reports and 121 plant species belonging to 52 families and 91 genera were included. These use reports were then classified into 20 categories belonging to 9 major categories. The utilisation category that containing the most plant species was food, followed by economic, medicine, animal feed, social uses, other uses, environmental uses, materials and fuels. Among the economic plants, 32 medicinal plants are traditionally used in the local region. Plants with high CI included Fritillaria cirrhosa, Neopicrorhiza scrophulariiflora, Betula utilis, Rheum nobile, and Urtica hyperborean. CONCLUSION: This research demonstrates the diversity of the types and functions of Yadong Tibetan traditional plant knowledge. Knowledge of edible and medicinal plants in this area is prominent, reflecting the ability to cope with the lack of fruits and vegetables and basic family medical care. There were exchanges between the traditional plant culture in the study area and its surroundings. With socioeconomic development, the commercial value of medicinal plants has increased, and locals are also seeking ways to adoptsustainable development to cope with the excessive consumption of plant resources.

Collection calendar: the diversity and local knowledge of wild edible plants used by Chenthang Sherpa people to treat seasonal food shortages in Tibet, China.

BACKGROUND: Wild edible plants (WEPs) are non-cultivated and non-domesticated plants used for food. WEPs provided food, nutrition, herbs and other plant products for people in underdeveloped areas, such as the Everest region, to maintain their daily lives. Chenthang Town is the only Sherpa ethnic township in Tibet, China. The core purpose of this research is to investigate, collect and record the WEPs and related local knowledge and functions within the Sherpa community. The ultimate goal is to answer the question of why Sherpa people choose these particular plants. MATERIALS AND METHODS: The field study was carried out in the six Sherpa communities of Chenthang Township from September 2019 to August 2020. The WEPs and related local knowledge were collected through semistructured interviews and direct observations. The field work was performed with the assistance of local guides. During the field survey, we collected plant specimens based on the principle of one plant with one vernacular name. In this study, we utilised a use report (UR) and cultural importance index (CI) to evaluate the comprehensive utilization value of WEPs in the daily diet of Sherpa people. RESULTS: We interviewed 78 people individually who provided us with 1199 use reports. In total, we collected 84 WEPs belonging to 65 genera in 41 families. These species were identified as 78 distinct ethno-species by local people, and the vernacular name of each ethno-species was recorded. Then, these use reports were classified into six use categories. All these plants were native wild plants. In these plants, Arisaema utile, Sorbus cuspidata and Elaeagnus umbellata have been introduced into home gardens by local people. Following the description of the Sherpa people, we articulated a collection calendar for WEPs. The Sherpa collect WEPs throughout nearly the entire year, January and February being the exceptions. CONCLUSION: The collection calendar of wild edible plants reflects the wisdom of the Sherpa in terms of survival. The Sherpa cleverly survive the food shortage periods by harnessing the phenology of different species. In general, WEPs can provide the Sherpa with seasonal carbohydrates, nutrition, healthcare supplements and other products and services necessary for survival, which is likely why the Sherpa choose these plants.

Native useful vascular plants of China: A checklist and use patterns.

Of all types of interactions between humans and plants, the utilization of plants by people is the most direct and influential. China has a long history of using native plants and a large body of recorded knowledge on uses. Here, we present an inventory of plant uses in China based on an extensive survey of the literature. Twelve categories of usage are recognized (medicinal, edible, etc.), these categories being chosen according to an integration of various current standards. A total of 50,521 use-citations were recorded, covering 10,808 species and infraspecies, representing 28% of the Chinese flora. Additional information is included in the dataset on taxonomy and endangerment status. Analysis of the data reveals that the eight plant families with the greatest numbers of species used in China, namely Asteraceae, Fabaceae, Rosaceae, Ranunculaceae, Poaceae, Lamiaceae, Orchidaceae, and Liliaceae, are also the top eight most species-rich Chinese plant families. However, there are some families that are over-represented or under-representation in certain use categories, compared with their relative abundance in the total flora. There are indications that rare and endangered species are being subject to some degree of over-exploitation. A disproportionately high number of used species are Chinese endemics (3552 species, representing over 33% of used species). A total of 20% of used species have been classified as threatened nationally or globally, according to at least one of the various threat assessments that have been made for the Chinese flora. This comprehensive inventory of the useful plants of China, with relevant ethnobotanical information included, provides a baseline for further studies of plant resources. It will be useful in follow-up research. The scientific dataset it contains will be useful for the protection and sustainable utilization of plant resources in China.

A review of the aromatic genus Adenosma: Geographical distribution, traditional uses, phytochemistry and biological activities.

ETHNOPHARMACOLOGICAL RELEVANCE: The strongly scented genus Adenosma R. Brown (Plantaginaceae) comprises between 26 and 29 species with mainly southeast Asian distributions. Several species are used traditionally, mostly in Asian countries, for medicinal purposes including the treatment of colds and tumors, as well as stomach, liver, and skin disorders. Some species are also used as insecticides and/or insect repellents against mosquitoes or fleas. AIM OF THE REVIEW: Although the potential health benefits of Adenosma spp. are not yet well-known or well-studied in modern medicine, the aim of the present review is to provide a critical appraisal of the current state of knowledge regarding the geographical distribution, traditional uses, phytochemistry, phytochemicals and biological properties of Adenosma spp. MATERIALS AND METHODS: Electronic databases (Web of Science, Science Direct, Google Scholar, Scifinder, Microsoft Academic, eFloras), Biodiversity Heritage Library (BHL), and the China National Knowledge Infrastructure (CNKI), were searched using the key words "Adenosma", "", "", "", "nhân tran", as well as the scientific names of the species, and a library search was also conducted for articles and books related to the subject published in English, Chinese or Vietnamese, as well as Ph.D. theses and M.Sc. dissertations published before April 2020. RESULTS: Adenosma spp. is traditionally used to treat gastrointestinal disorders, hepatitis, colds, and skin problems. Phenolic acids, flavonoids, and terpenoids constitute the main phytochemicals in these plants. Several evaluations based on bioassays have demonstrated biological activity for Adenosma spp., including antidiabetic, anticancer, and insecticidal activities; extracts and isolated compounds have also shown effective biological activity. However, current research has focused only on a few species, and on limited geographical regions, mainly in China and Vietnam. More and broader ethnopharmacological studies are therefore needed to provide further evidence of the health benefits of these plants. CONCLUSIONS: Adenosma spp. are plants rich in essential oils, particularly terpenoids, and the crude extracts have valuable bioactive properties. Certain lines of research based on cell lines and animal models show the potential value in different areas of health management. Further investigation into the traditional knowledge in southeast Asian and Pacific island regions, as well as the into the toxicity and identity of the bioactive compounds and their mechanisms of action is necessary.

Parasite dodder enables transfer of bidirectional systemic nitrogen signals between host plants.

Dodder (Cuscuta spp., Convolvulaceae) is a genus of parasitic plants with worldwide distribution. Dodders are able to simultaneously parasitize two or more adjacent hosts, forming dodder-connected plant clusters. Nitrogen (N) deficiency is a common challenge to plants. To date, it has been unclear whether dodder transfers N-systemic signals between hosts grown in N-heterogeneous soil. Transcriptome and methylome analyses were carried out to investigate whether dodder (Cuscuta campestris) transfers N-systemic signals between N-replete and N-depleted cucumber (Cucumis sativus) hosts, and it was found that N-systemic signals from the N-deficient cucumber plants were rapidly translocated through C. campestris to the N-replete cucumber plants. Unexpectedly, certain systemic signals were also transferred from the N-replete to N-depleted cucumber hosts. We demonstrate that these systemic signals are able to regulate large transcriptome and DNA methylome changes in the recipient hosts. Importantly, N stress also induced many long-distance mobile mRNA transfers between C. campestris and hosts, and the bilateral N-systemic signaling between N-replete and N-depleted hosts had a strong impact on the inter-plant mobile mRNAs. Our 15N labeling experiment indicated that under N-heterogeneous conditions, N-systemic signals from the N-deficient cucumber hosts did not obviously change the N-uptake activity of the N-replete cucumber hosts; however, in plant clusters comprising C. campestris-connected cucumber and soybean (Glycine max) plants, if the soybean plants were N-starved, the cucumber plants exhibited increased N-uptake activity. This study reveals that C. campestris facilitates plant-plant communications under N-stress conditions by enabling extensive bilateral N-systemic signaling between different hosts.

The Dataset of Camellia Cultivars Names in the World.

BACKGROUND: Camellias are popular ornamental, tea and woody-oil plants that have been cultivated throughout the world for centuries. To date, over 23,000 cultivars, with more than 45,000 cultivar names including synonyms, have been registered or published. A global digital dataset of Camellia names will provide a validated reference which can then serve to prevent further duplication when selecting names for new cultivars and assist in clearing up some of the confusion that still clings to a few of the old cultivar names. This comprehensive compendium is our review of camellia cultivars through history. NEW INFORMATION: The camellia cultivar names were collected from books and journals, as well as new registrations. These were then reviewed by experts in the online working platform, the Database of International Camellia Register (DICR). After treating and correcting important issues that existed in camellia names, especially those with many re-used names and diacritical marks etc. in Japanese cultivars, a dataset of camellia names from sources throughout the world was summarised from the year 1253 to 2019. To date, a total of 45,210 cultivar names were released by different countries, including 23,887 accepted names and 21,323 synonyms. Excluding 3,944 names believed extinct, a total of 19,944 cultivar names are still in use. Amongst camellia cultivars, most (23,449) were for ornamental use, 429 were additionally used for tea and 228 for oil. Camellia japonica and its hybrids represent 18,141 or 74.10%, followed by those of C. reticulata and its hybrids (1,432 or 5.85%) and C. sasanqua and its hybrids (1,291 or 5.27%). The top five countries of origin are USA (7,502 cultivars), Japan (6,592), Italy (2,833), China (2,066) and Australia (1,216). The data showed the number of camellia cultivars per country is somewhat related to each country's economic prosperity. Managed by the International Camellia Registration team, this is the most comprehensive dataset in the genus Camellia. It will facilitate quick reference and scientific naming for breeders.

Blue genome: chromosome-scale genome reveals the evolutionary and molecular basis of indigo biosynthesis in Strobilanthes cusia.

Natural plant dyes have been developed and used across many traditional societies worldwide. The blue pigment indigo has seen widespread usage across South America, Egypt, Europe, India and China for thousands of years, mainly extracted from indigo-rich plants. The utilization and genetic engineering of indigo in industries and ethnobotanical studies on the effects of cultural selection on plant domestication are limited due to lack of relevant genetic and genomic information of dye plants. Strobilanthes cusia (Acanthaceae) is a typical indigo-rich plant important to diverse ethnic cultures in many regions of Asia. Here we present a chromosome-scale genome for S. cusia with a genome size of approximately 865 Mb. About 79% of the sequences were identified as repetitive sequences and 32 148 protein-coding genes were annotated. Metabolic analysis showed that the main indigoid pigments (indican, indigo and indirubin) were mainly synthesized in the leaves and stems of S. cusia. Transcriptomic analysis revealed that the expression level of genes encoding metabolic enzymes such as monooxygenase, uridine diphosphate-glycosyltransferase and ß-glucosidase were significantly changed in leaves and stems compared with root tissues, implying their participation in indigo biosynthesis. We found that several gene families involved in indigo biosynthesis had undergone an expansion in number, with functional differentiation likely facilitating indigo biosynthesis in S. cusia. This study provides insight into the physiological and molecular bases of indigo biosynthesis, as well as providing genomic data that provide the basis for further study of S. cusia cultivation by Asia's traditional textile producers.

Selecting flagship species to solve a biodiversity conservation conundrum.

The difficulty of effectively monitoring and managing the environment to conserve biodiversity is as yet an unsolved conundrum. A project of the Chinese Academy of Sciences has concluded that progress can be made through the use of flagship species selected using criteria drawn from conservation biology, ecosystem function, socio-economics, and cultural importance. Inclusion of the latter three criteria will help attract and maintain the commitment of the public to play full parts in carrying out any conservation measures needed. A system is proposed for scoring species to select those that are most suitable as flagships. This method can be used regardless of the size of the area chosen for attention, whether it is a region, a country, or a particular protected area.

Dodder-transmitted mobile signals prime host plants for enhanced salt tolerance.

The dodders (Cuscuta spp.) are a genus of shoot parasites. In nature, a dodder often simultaneously parasitizes two or more neighboring hosts. Salt stress is a common abiotic stress for plants. It is unclear whether dodder transmits physiologically relevant salt stress-induced systemic signals among its hosts and whether these systemic signals affect the hosts' tolerance to salt stress. Here, we simultaneously parasitized two or more cucumber plants with dodder. We found that salt treatment of one host highly primed the connected host, which showed strong decreases in the extent of leaf withering and cell death in response to subsequent salt stress. Transcriptomic analysis indicated that 24 h after salt treatment of one cucumber, the transcriptome of the other dodder-connected cucumber largely resembled that of the salt-treated one, indicating that inter-plant systemic signals primed these dodder-connected cucumbers at least partly through transcriptomic reconfiguration. Furthermore, salt treatment of one of the cucumbers induced physiological changes, including altered proline contents, stomatal conductance, and photosynthetic rates, in both of the dodder-connected cucumbers. This study reveals a role of dodder in mediating salt-induced inter-plant signaling among dodder-connected hosts and highlights the physiological function of these mobile signals in plant-plant interactions under salt stress.

Plants for health: An ethnobotanical 25-year repeat survey of traditional medicine sold in a major marketplace in North-west Yunnan, China.

ETHNOPHARMACOLOGICAL RELEVANCE: Although quantitative surveys of traditional medicine markets are widely used to gain insights into the economic value, popularity or conservation status of traditional medicinal species, there have been very few repeat surveys. This study is an exception. The research was carried out in Sanyuejie Market in North-west Yunnan Province in China for three reasons. Firstly, Sanyuejie Market is large and historically significant, having operated since the Tang Dynasty (794 CE). Secondly, Sanyuejie Market is located along the "Tea-Horse Road" and "Southern Silk Road", and as such the trade from this market radiates widely throughout China and into neighboring countries such as Myanmar, Nepal and India. Thirdly, a comprehensive and systematic survey of the market was completed in 1987/88 and so this provided a unique opportunity to conduct a repeat quantitative survey. The findings, highlighting changes in species sold and the reasons why the changes have occurred, are highly relevant to ethnopharmacology at a time of substantial socio-economic and cultural change throughout China. AIM OF THE STUDY: To understand the changes in the medicinal plants trade at Sanyuejie Market between 1987/88 and 2012/13. MATERIALS AND METHODS: A quantitative ethnobotanical re-surveying involving literature review, key informant interviews and visual observations of vendor booths at the market and village investigations, was carried out in Sanyuejie. RESULTS: In 1987/88, 401 types of herbal preparations derived from 505 species in 111 families and 315 genera were sold in the market. In 2012/13, 623 herbal preparations derived from 709 species in 173 families and 451 genera were being sold. There were 105 types of herbal preparations originating from 115 species that were recorded in 1987/88 but are no longer sold at the market 25 years later. In addition, 326 types of herbal medicine preparations originating from 336 species have been added to the market since the original survey. Labor divisions have also appeared in the market. CONCLUSION: This study validates that the diversity of herbal medicines sold at Sanyuejie Market has increased and changed greatly. The growing demands for traditional herbal medicines combined with government initiatives to develop the local economy are drivers of the observed changes.

Aphid (Myzus persicae) feeding on the parasitic plant dodder (Cuscuta australis) activates defense responses in both the parasite and soybean host.

Dodders (Cuscuta spp.) are shoot holoparasites, whose haustoria penetrate host tissues to enable fusion between the parasite and host vascular systems, allowing Cuscuta to extract water, nutrients and other molecules from hosts. Aphids are piercing-sucking herbivores that use specialized stylets to feed on phloem sap. Aphids are known to feed on Cuscuta, but how Cuscuta and its host plant respond to aphids attacking the parasite was unknown. Phytohormone quantification, transcriptomic analysis and bioassays were performed to determine the responses of Cuscuta australis and its soybean (Glycine max) hosts to the feeding of green peach aphid (GPA; Myzus persicae) on C. australis. Decreased salicylic acid levels and 172 differentially expressed genes (DEGs) were found in GPA-attacked C. australis, and the soybean hosts exhibited increased jasmonic acid contents and 1015 DEGs, including > 100 transcription factor genes. Importantly, GPA feeding on C. australis increased the resistance of the soybean host to subsequent feeding by the leafworm Spodoptera litura and soybean aphid Aphis glycines, resulting in 21% decreased leafworm mass and 41% reduced aphid survival rate. These data strongly suggest that GPA feeding on Cuscuta induces a systemic signal, which is translocated to hosts and activates defense against herbivores.

Transcriptomics and Alternative Splicing Analyses Reveal Large Differences between Maize Lines B73 and Mo17 in Response to Aphid Rhopalosiphum padi Infestation.

Maize (Zea mays L.) is a staple crop worldwide with extensive genetic variations. Various insects attack maize plants causing large yield loss. Here, we investigated the responses of maize B73, a susceptible line, and Mo17, a resistant line, to the aphid Rhopalosiphum padi on metabolite and transcriptome levels. R. padi feeding had no effect on the levels of the defensive metabolites benzoxazinoids (Bxs) in either line, and Mo17 contained substantially greater levels of Bxs than did B73. Profiling of the differentially expressed genes revealed that B73 and Mo17 responded to R. padi infestation specifically, and importantly, these two lines showed large gene expression differences even without R. padi herbivory. Correlation analysis identified four transcription factors (TFs) that might account for the high Bx levels in Mo17. Similarly, genome-wide alternative splicing (AS) analyses indicated that both B73 and Mo17 had temporally specific responses to R. padi infestation, and these two lines also exhibited large differences of AS regulation under normal condition, and 340 genes, including 10 TFs, were constantly differentially spliced. This study provides large-scale resource datasets for further studies on the mechanisms underlying maize-aphid interactions, and highlights the phenotypic divergence in defense against aphids among maize varieties.

Genome-wide RAD sequencing data provide unprecedented resolution of the phylogeny of temperate bamboos (Poaceae: Bambusoideae).

The temperate bamboos (tribe Arundinarieae, Poaceae) are strongly supported as monophyly in recent molecular studies, but taxonomic delineation and phylogenetic relationships within the tribe lack resolution. Here, we sampled 39 species (36 temperate bamboos and 3 outgroups) for restriction-site associated DNA sequencing (RAD-seq) with an emphasis on Phyllostachys clade and related clades. Using the largest data matrix for the bamboos to date, we were able to infer phylogenetic relationships with unparalleled resolution. The Phyllostachys, Shibataea, and Arundinaria clades defined from plastid phylogeny, were not supported as monophyletic group. However, the RAD-seq phylogeny largely agreed with the morphology-based taxonomy, with two clades having leptomorph rhizomes strongly supported as monophyletic group. We also explored two approaches, BWA-GATK (a mapping system) and Stacks (a grouping system), for differences in SNP calling and phylogeny inference. For the same level of missing data, the BWA-GATK pipeline produced much more SNPs in comparison with Stacks. Phylogenetic analyses of the largest data matrices from both pipelines, using concatenation and coalescent methods provided similar tree topologies, despite the presence of missing data. Our study demonstrates the utility of RAD-seq data for elucidating phylogenetic relationships between genera and higher taxonomic levels in this important but phylogenetically challenging group.

Stem parasitic plant Cuscuta australis (dodder) transfers herbivory-induced signals among plants.

Cuscuta spp. (i.e., dodders) are stem parasites that naturally graft to their host plants to extract water and nutrients; multiple adjacent hosts are often parasitized by one or more Cuscuta plants simultaneously, forming connected plant clusters. Metabolites, proteins, and mRNAs are known to be transferred from hosts to Cuscuta, and Cuscuta bridges even facilitate host-to-host virus movement. Whether Cuscuta bridges transmit ecologically meaningful signals remains unknown. Here we show that, when host plants are connected by Cuscuta bridges, systemic herbivory signals are transmitted from attacked plants to unattacked plants, as revealed by the large transcriptomic changes in the attacked local leaves, undamaged systemic leaves of the attacked plants, and leaves of unattacked but connected hosts. The interplant signaling is largely dependent on the jasmonic acid pathway of the damaged local plants, and can be found among conspecific or heterospecific hosts of different families. Importantly, herbivore attack of one host plant elevates defensive metabolites in the other systemic Cuscuta bridge-connected hosts, resulting in enhanced resistance against insects even in several consecutively Cuscuta-connected host plants over long distances (> 100 cm). By facilitating plant-to-plant signaling, Cuscuta provides an information-based means of countering the resource-based fitness costs to their hosts.

Evolutionary dynamics of triosephosphate isomerase gene intron location pattern in Metazoa: A new perspective on intron evolution in animals.

Intron evolution, including its dynamics in the evolutionary transitions and diversification of eukaryotes, remains elusive. Inadequate taxon sampling due to data shortage, unclear phylogenetic framework, and inappropriate outgroup application might be among the causes. Besides, the integrity of all the introns within a gene was often neglected previously. Taking advantage of the ancient conserved triosephosphate isomerase gene (tim), the relatively robust phylogeny of Metazoa, and choanoflagellates as outgroup, the evolutionary dynamics of tim intron location pattern (ILP) in Metazoa was investigated. From 133 representative species of ten phyla, 30 types of ILPs were identified. A most common one, which harbors the maximum six intron positions, is deduced to be the common ancestral tim ILP of Metazoa, which almost had formed in their protozoan ancestor and was surprisingly retained and passed down till to each ancestors of metazoan phyla. In the subsequent animal diversification, it underwent different evolutionary trajectories: within Deuterostomia, it was almost completely retained only with changes in a few species with relatively recently fast-evolving histories, while within the rapidly radiating Protostomia, besides few but remarkable retention, it usually displayed extensive intron losses and a few gains. Therefore, a common ancestral exon-intron arrangement pattern of an animal gene is definitely discovered; besides the 'intron-rich view' of early animal genes being confirmed, the novel insight that high exon-intron re-arrangements of genes seem to be associated with the relatively recently rapid evolution of lineages/species/genomes but have no correlation with the ancient major evolutionary transitions in animal evolution, is revealed.

Genome-wide identification of calcium-dependent protein kinases in soybean and analyses of their transcriptional responses to insect herbivory and drought stress.

Calcium-dependent protein kinases (CDPKs) are plant-specific calcium sensors that play important roles in various aspects of plant physiology. Here, we investigated phylogenic relationships, chromosomal locations, gene structures, and tissue-specific, herbivory- and drought-induced expression profiles of soybean (Glycine max) GmCDPKs. Fifty GmCDPK genes were identified, which phylogenetically grouped into 4 distinct clusters and distributed across 13 sub-clusters. Individual classes of GmCDPKs harbor highly conserved mRNA splicing sites, and their exon numbers and lengths were consistent with the phylogenetic relationships, suggesting that at least 13 ancestral CDPK genes had emerged before the split of monocots and eudicots. Gene expression analysis indicated that several GmCDPKs were tissue-specific expressed. GmCDPKs' transcript levels changed after wounding, exhibited specific expression patterns after simulated Spodoptera exigua feeding or soybean aphid (Aphis glycines) herbivory, and were largely independent of the phytohormones jasmonic acid and salicylic acid. The most pronounced transcriptional responses were detected after drought and abscisic acid treatments with more than half of all GmCDPKs being upregulated, suggesting their important roles during abiotic stress responses in soybean. Our data provide an important foundation for further functional dissection of GmCDPKs, especially in the context of soybean-insect interactions and drought stress adaptation.

An acyltransferase gene that putatively functions in anthocyanin modification was horizontally transferred from Fabaceae into the genus Cuscuta.

Horizontal gene transfer (HGT) refers to the flow of genetic materials to non-offspring, and occasionally HGT in plants can improve the adaptation of organisms in new niches due to expanded metabolic capability. Anthocyanins are an important group of water-soluble red, purple, or blue secondary metabolites, whose diversity results from modification after the main skeleton biosynthesis. Cuscuta is a stem holoparasitic genus, whose members form direct connection with hosts to withdraw water, nutrients, and macromolecules. Such intimate association is thought to increase the frequency of HGT. By transcriptome screening for foreign genes in Cuscuta australis, we discovered that one gene encoding a putative anthocyanin acyltransferase gene of the BAHD family, which is likely to be involved in anthocyanin modification, was acquired by C. australis from Fabaceae through HGT. The anthocyanin acyltransferase-like (AT-like) gene was confirmed to be present in the genome assembly of C. australis and the transcriptomes of Cuscuta pentagona. The higher transcriptional level in old stems is consistent with its putative function in secondary metabolism by stabilizing anthocyanin at neutral pH and thus HGT of this AT-like gene may have improved biotic and abiotic resistance of Cuscuta.

The parasitic plant Cuscuta australis is highly insensitive to abscisic acid-induced suppression of hypocotyl elongation and seed germination.

Around 1% of angiosperms are parasitic plants. Their growth and development solely or partly depend on host plants from which they extract water, nutrients, and other molecules using a parasitic plant-specific organ, the haustorium. Strong depletion of nutrients can result in serious growth retardation and in some cases, death of the hosts. The genus Cuscuta (dodder) comprises about 200 holoparasitic species occurring on all continents. Their seedlings have no roots and cotyledons but are only string-like hypocotyls. When they contact suitable host plants, haustoria are formed and thereafter seedlings rapidly develop into vigorously growing branches without roots and leaves. This highly specialized lifestyle suggests that Cuscuta plants likely have unique physiology in development and stress responses. Using germination and seedling growth assays, we show that C. australis seeds and seedlings are highly insensitive to abscisic acid (ABA). Transcriptome analysis and protein sequence alignment with Arabidopsis, tomato, and rice homologs revealed that C. australis most likely consists of only four functional ABA receptors. Given that Cuscuta plants are no longer severely challenged by drought stress, we hypothesize that the ABA-mediated drought resistance pathway in Cuscuta spp. might have had degenerated over time during evolution.

Root parasitic plant Orobanche aegyptiaca and shoot parasitic plant Cuscuta australis obtained Brassicaceae-specific strictosidine synthase-like genes by horizontal gene transfer.

BACKGROUND: Besides gene duplication and de novo gene generation, horizontal gene transfer (HGT) is another important way of acquiring new genes. HGT may endow the recipients with novel phenotypic traits that are important for species evolution and adaption to new ecological niches. Parasitic systems expectedly allow the occurrence of HGT at relatively high frequencies due to their long-term physical contact. In plants, a number of HGT events have been reported between the organelles of parasites and the hosts, but HGT between host and parasite nuclear genomes has rarely been found. RESULTS: A thorough transcriptome screening revealed that a strictosidine synthase-like (SSL) gene in the root parasitic plant Orobanche aegyptiaca and the shoot parasitic plant Cuscuta australis showed much higher sequence similarities with those in Brassicaceae than with those in their close relatives, suggesting independent gene horizontal transfer events from Brassicaceae to these parasites. These findings were strongly supported by phylogenetic analysis and their identical unique amino acid residues and deletions. Intriguingly, the nucleus-located SSL genes in Brassicaceae belonged to a new member of SSL gene family, which were originated from gene duplication. The presence of introns indicated that the transfer occurred directly by DNA integration in both parasites. Furthermore, positive selection was detected in the foreign SSL gene in O. aegyptiaca but not in C. australis. The expression of the foreign SSL genes in these two parasitic plants was detected in multiple development stages and tissues, and the foreign SSL gene was induced after wounding treatment in C. australis stems. These data imply that the foreign genes may still retain certain functions in the recipient species. CONCLUSIONS: Our study strongly supports that parasitic plants can gain novel nuclear genes from distantly related host species by HGT and the foreign genes may execute certain functions in the new hosts.