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In this experiment, seedlings as sources for shoot tips was assembled from the coconut research institute (CRI) of Chinese Academy of tropical agricultural sciences germplasm, Wenchang, Hainan, China. The shoot tips were cultured on Y3 medium to study the impact of ten concentrations of 2, 4-D and three vitamin mixtures on survival, death and development % on in vitro culture establishment stage of coconut (Cocos nucifera L.). The obtained results revealed that all 2,4-D concentrations 4,7, 75, 100, 120 and 140 mg/L + any vitamin mixture did not give any development and high concentrations of 2, 4-D increased the death %. In any case, it can be concluded that the rate of differences in survival, death and development percentages exhibited by 2, 4-D concentrations was more pronounced than the analogous ones resulted by vitamin mixtures. At any rate, utilizing of (2, 4-D at concentration 25 mg/L+ vitamin mixture 1 or 2) exhibited the greatest values of survival percentage and reduced death percentage. Just as, increased the percentages of development in in vitro culture establishment stage of coconut (Cocos nucifera L.) through seedlings shoot tip.

Elaeis guineensis is a tropical oil crop and has the highest oil yield per unit area. Palm oil has high palmitic acid content and is also rich in vitamins, including vitamin E. We conducted genome-wide association studies in a diversity panel of 161 E. guineensis accessions to identify single-nucleotide polymorphisms (SNPs) linked with vitamin E and validated candidate genes in these marker-associated intervals. Based on the SNPs reported in our previous research, 47 SNP markers were detected to be significantly associated with the variation of tocopherol and tocotrienol content at a cutoff P value of 6.3 × 10-7. A total of 656 candidate genes in the flanking regions of the 47 SNPs were identified, followed by pathway enrichment analysis. Of these candidate genes, EgHGGT (homogentisate geranylgeranyl transferase) involved in the biosynthesis of tocotrienols had a higher expression level in the mesocarp compared to other tissues. Expression of the EgHGGT gene was positively correlated with the variation in α-tocotrienol content. Induced overexpression of the gene in Arabidopsis caused a significant increase in vitamin E content and production of α-tocotrienols compared to wild Arabidopsis.

BackgroundCoconut is an important tropical oil and fruit crop whose evolutionary position renders it a fantastic species for the investigation of the evolution of monocot chromosomes and the subsequent differentiation of ancient plants.ResultsHere, we report the assembly and annotation of reference-grade genomes ofCn. tallandCn. dwarf, whose genome sizes are 2.40 Gb and 2.39 Gb, respectively. The comparative analysis reveals that the two coconut subspecies diverge about 2–8 Mya while the conserved Arecaceae-specific whole-genome duplication (ω WGD) occurs approximately 47–53 Mya. It additionally allows us to reconstruct the ancestral karyotypes of the ten ancient monocot chromosomes and the evolutionary trajectories of the 16 modern coconut chromosomes. Fiber synthesis genes inCn. tall, related to lignin and cellulose synthesis, are found at a higher copy number and expression level than dwarf coconuts. Integrated multi-omics analysis reveals that the difference in coconut plant height is the result of altered gibberellin metabolism, with both the GA20ox copy number and a single-nucleotide change in the promoter together leading to the difference in plant height betweenCn. tallandCn. dwarf.ConclusionWe provide high-quality coconut genomes and reveal the genetic basis of trait differences between two coconuts through multi-omics analysis. We also reveal that the selection of plant height has been targeted for the same gene for millions of years, not only in natural selection of ancient plant as illustrated in coconut, but also for artificial selection in cultivated crops such as rice and maize.

Vitamin E is essential for human health and plays positive roles in anti-oxidation. Previously, we detected large variation in vitamin E content among 161 oil palm accessions. In this study, twenty oil palm accessions with distinct variation in vitamin E contents (171.30 to 1 258.50 ppm) were selected for genetic variation analysis and developing functional markers associated with vitamin E contents. Thirty-seven homologous genes in oil palm belonging to vitamin E biosynthesis pathway were identified via BLASTP analysis, the lengths of which ranged from 426 to 25 717 bp (average 7 089 bp). Multiplex PCR sequencing for the 37 genes found 1 703 SNPs and 85 indels among the 20 oil palm accessions, with 226 SNPs locating in the coding regions. Clustering analysis for these polymorphic loci showed that the 20 oil palm accessions could be divided into five groups. Among these groups, group I included eight oil palm accessions whose vitamin E content (mean value: 893.50 ppm) was far higher than other groups (mean value 256.29 to 532.94 ppm). Correlation analysis between the markers and vitamin E traits showed that 134 SNP and 7 indel markers were significantly (p < 0.05) related with total vitamin E content. Among these functional markers, the indel EgTMT-1-24 was highly correlated with variation in vitamin E content, especially tocotrienol content. Our study identified a number of candidate function associated markers and provided clues for further research into molecular breeding for high vitamin E content oil palm.

Coconut is an important tropical fruit and oil crop. Its long generation time, low multiplication rate and recalcitrant seeds make coconut more difficult for breeding and selection. New technologies and extensive resources to evaluate coconut breeding strategies are the demand of today. Molecular markers had the potential to dramatically increase the efficiency and efficacy in the areas of germplasm management, genotype identification and marker-assisted selection of economically important traits of coconut. However, the lack of relevant molecular techniques impedes the development of a new strategy for the genetic improvement of the coconut. In this study, we have successfully developed 84 SSR markers by Selectively Amplified Microsatellite from coconut genome and more than 90% of these SSR showed good transferability to the palm family. The study will enrich the genomic-SSR pool for coconut and also for the other palm tree. Besides, it will provide the scientists with more options for coconut germplasm evaluation, constructing a coconut genetic linkage map and designing the breeding programs for producing superior cultivars of coconut.

The NAC gene family encode transcriptional regulator that contain a conserved NAM domain near the N-terminus and participate in the regulation of plant development and response to different abiotic stresses. In this study, 129 EgNAC genes were identified from the genome sequence of Elaeis guineensis and 97 EgNAC located on the chromsomes with an average of 4.56 EgNAC genes per chromosome. About 60% of EgNACs contained three exons and the gene sizes varied from 541 bp to 37,294 bp. Genomic duplication analysis showed that 10 EgNAC genes were involved in segmental duplication events and two genes were from tandem duplication. The gene expression profiles of EgNACs based on transcriptome database for different oil palm tissues showed that 30 EgNACs with low or no expression and 24 EgNACs were specifically expressed in one tissue. The trancriptome comparison between the control and cold stress samples demonstrated that thirty-seven EgNACs were down-regulated and 82 EgNACs were up-regulated under cold stress. Further RT-qPCR showed that the expression for 24 out of 32 validated EgNACs were induced under both cold, drought and salt stresses. Our comprehensive analysis of EgNAC genes has provided clues for candidate genes involved in abiotic stress tolerance.

Coconut (Cocos nucifera) is the emblematic palm of tropical coastal areas all around the globe. It provides vital resources to millions of farmers. In an effort to better understand its evolutionary history and to develop genomic tools for its improvement, a sequence draft was recently released. Here, we present a dense linkage map (8402 SNPs) aiming to assemble the large genome of coconut (2.42 Gbp, 2n = 32) into 16 pseudomolecules. As a result, 47% of the sequences (representing 77% of the genes) were assigned to 16 linkage groups and ordered. We observed segregation distortion in chromosome Cn15, which is a signature of strong selection among pollen grains, favouring the maternal allele. Comparing our results with the genome of the oil palm Elaeis guineensis allowed us to identify major events in the evolutionary history of palms. We find that coconut underwent a massive transposable element invasion in the last million years, which could be related to the fluctuations of sea level during the glaciations at Pleistocene that would have triggered a population bottleneck. Finally, to better understand the facultative halophyte trait of coconut, we conducted an RNA-seq experiment on leaves to identify key players of signaling pathways involved in salt stress response. Altogether, our findings represent a valuable resource for the coconut breeding community., Yaodong Yang et al. report a chromosome-scale genome assembly of the coconut and transcriptome analysis of coconut leaves. Their analysis reveals important steps along the evolutionary trajectory of palms and identifies genes that may play a key role in tolerance to salt stress.

Predominant gene isoforms and expression bias in lipid metabolism pathways are highly conserved between oil-producing Arecaceae crop species coconut and oil palm, but diverge in non-oil-producing species date palm. Coconut (Cocos nucifera), African oil palm (Elaeis guineensis) and date palm (Phoenix dactylifera) are three major crop species in the Arecaceae family for which genome sequences have recently become available. Coconut and African oil palm both store oil in their endosperms, while date palm fruits contain very little oil. We analyzed fatty acid composition in three coconut tissues (leaf, endosperm and embryo) and in two African oil palm tissues (leaf and mesocarp), and identified 806, 840 and 848 lipid-related genes in 22 lipid metabolism pathways from the coconut, African oil palm and date palm genomes, respectively. The majority of lipid-related genes were highly homologous and retained in homologous segments between the three species. Genes involved in the conversion of pyruvate to fatty acid had a five-to-sixfold higher expression in the coconut endosperm and oil palm mesocarp than in the leaf or embryo tissues based on Fragments Per Kilobase of transcript per Million mapped reads values. A close evolutionary relationship between predominant gene isoforms and high conservation of gene expression bias in the lipid and carbohydrate gene metabolism pathways was observed for the two oil-producing species coconut and oil palm, differing from that of date palm, a non-oil-producing species. Our results elucidate the similarities and differences in lipid metabolism between the three major Arecaceae crop species, providing important information for physiology studies as well as breeding for fatty acid composition and oil content in these crops.

Coconut palm has two distinct types—“tall” and “dwarf”—which differ morphologically. Tall coconut varieties need 8–10 years to start flowering, while dwarf coconut varieties only require 3–5 years. We compared seedling and reproductive stage transcriptomes for both coconut types to determine potential molecular mechanisms underlying control of flowering time in coconut. Several key genes in the photoperiod pathway were differentially expressed between seedling and reproductive leaf samples in both tall and dwarf coconut. These genes included suppressor of overexpression of constans (SOC1), flowering locus T (FT), and Apetala 1 (AP1). Alternative splicing analysis of genes in the photoperiod pathway further revealed that the FT gene produces different transcripts in tall compared to dwarf coconut. The shorter alternative splice variant of FT [which included a 6 bp deletion, alternative 3′ splicing sites (A3SS)] was found to be exclusively present in dwarf coconut varieties but absent in most tall coconut varieties. Our results provide a valuable information resource as well as suggesting a probable mechanism for differentiation of flowering time onset in coconut, providing a target for future breeding work in accelerating time to flowering in this crop species.

Coconut (Cocos nucifera L.) is an important economic fruit and oil crop largely cultivated in humid and sub-humid tropical coastal zones worldwide. To date proteomic profile analysis of coconut under cold stress yet not been conducted. In order to understand the cold stress tolerance in coconut, the iTRAQ approach was employed to dissect proteomic response of two coconut varieties Hainan Tall, BenDi (BD) and Aromatic coconut, XiangShui (XS) under cold stress. Under cold treatment at (8 °C) for 2 days, 193 up and 134 down-regulated in BD (Cn-DB-0_VS_Cn-DB-2) and 140 up and 155 down-regulated DEPs in XS (Cn-XS-0_VS_Cn-XS-2) were identified. The 5 days post cold treatment also identified increased abundance of up-regulated proteins in BD compared to XS. The 5 days post treatment (dpt) depicted 172-up/127-down and 108-up/134-down accumulated proteins for BD (Cn-DB-0_VS_Cn-DB-5) and XS (Cn-XS-0_VS_Cn-XS-5) respectively. A total of 22, 12 and 14 DEP categories were enriched in biological process, cellular component and molecular function respectively in Gene Ontology (GO) analysis of two coconut varieties. Metabolic and biosynthesis of secondary metabolites pathways were highly enriched in KEGG pathway analysis of DEPs between two varieties. Twenty-two different functional classes revealed differentially expressed proteins in two varieties. Among those, four major categories involved in metabolism, stress response, photosynthesis and respiration related DEPs increased abundance in two varieties. However, general function perdition only (GFPO) and stress-responsive proteins were greatly up-regulated in BD than XS. Increased abundance of stress response related proteins up-regulation under cold stress suggested that BD is cold-tolerant variety. Collectively, iTRAQ-based coconut leaf proteomic analysis showed that XS (aromatic) coconut variety is cold-sensitive compared to BD (Hainan Tall) variety. This study provided a basis for further functional analyses to understand the molecular mechanisms of tropical crops adapting to cold stress. Significance Leaf proteomic approach determines the role of differentially expressed proteins (DEPs) under cold stress in crops. However, cold stress could damage the coconut fruit lead to decrease in crop yield during winter in China. Here, we report the first ever iTRAQ-based proteomic analysis of two coconut varieties in response to cold stress. The study identified the proteins involved in biosynthesis of secondary metabolites, photosynthesis, respiration, biotic and abiotic stresses under cold stress in two coconut varieties. Moreover, the increased abundance of stress-responsive and general function proteins in BD under cold stress suggested that Hainan Tall is cold-tolerant compared to aromatic coconut variety. Inhibition abundance of photosynthesis related proteins may reduce photodamage owing to the over energized state of thylakoid membrane lead to ROS generation during oxidative stress. This could be the reason for adaption of BD to low temperature stress. Nonetheless, further research may insight the mechanism involved in cold tolerance/sensitive in coconut in response to low temperature.

Hainan Tall coconut (Cocos nucifera L.), which show the advantageous characteristics of high yield, hardiness, and wind resistance, is the dominant coconut population in Hainan Island, the main area of coconut production in China. An understanding of the genetic diversities and origins of the Hainan Tall population is essential to effective breeding. To achieve this aim, we used dozens of inter-simple sequence repeat molecular markers to characterize the genetic diversity among Hainan Tall and other coconut accessions outside China. Results revealed that Hainan Tall consisted of two main subgroups reflecting different geographic distributions (such as northern vs. southern parts of Hainan Island), and other accessions lacking clear location trends because of human activities. Diversity analysis revealed that the Hainan Tall population exhibits a higher genetic diversity than that of exotic populations mostly collected from Southeast Asia. The phylogenetic clustering results indicated that the Hainan Tall population is domesticated separately from (and earlier than) other coconut accessions, and the differentiation existed within the Hainan Tall population. Among other causes, this notion may explain the high diversity within the Hainan Tall population. Overall, these findings provide a preliminary scenario of the genetic diversities and origins of the Hainan Tall population.

Oil palm (Elaeis guineensis Jacq.) is a representative tropical oil crop that is sensitive to low temperature. Oil palm can experience cold damage when exposed to low temperatures for a long period. During these unfavorable conditions, a series of gene induction/repression and physico-chemical changes occur in oil palm. To better understand the link between these events, we investigated the expression levels of various genes (including COR410, COR413, CBF1, CBF2, CBF3, ICE1-1, ICE1-2, ICE1-4, SIZ1-1, SIZ1-2, ZAT10, ZAT12) and the accumulation of osmolytes (proline, malondialdehyde and sucrose). Likewise, the activity of superoxide dismutase (SOD) in oil palm under cold stress (4°C, 8°C and 12°C) was examined. The results showed a clear link among the expression of CBFs (especially CBF1 and CBF3) and the all genes examined under cold stress (12°C). The expression of CBF1 and CBF2 also exhibited a positive link with the accumulation of sucrose and proline under cold stress in oil palm. At 4°C, the proline content exhibited a very significant correlation with electrolyte leakage in oil palm. The results of this study provide necessary information regarding the mechanism of the response and adaption of oil palm to cold stress. Additionally, they offer clues for the selection or development of cold-tolerant cultivars from the available germplasms of oil palm.

International audience; Coconut palm (Cocos nucifera, 2n = 32), a member of genus Cocos and family Arecaceae (Palmaceae), is an important tropical fruit and oil crop. Currently, coconut palm is cultivated in 93 countries, including Central and South America, East and West Africa, Southeast Asia and the Pacific Islands, with a total growth area of more than 12 million hectares [1]. Coconut palm is generally classified into 2 main categories: "Tall" (flowering 8-10 years after planting) and " Dwarf" (flowering 4-6 years after planting), based on morphological characteristics and breeding habits. This Palmae species has a long growth period before reproductive years, which hinders conventional breeding progress. In spite of initial successes, improvements made by conventional breeding have been very slow. In the present study, we obtained de novo sequences of the Cocos nucifera genome: a major genomic resource that could be used to facilitate molecular breeding in Cocos nucifera and accelerate the breeding process in this important crop. A total of 419.67 gigabases (Gb) of raw reads were generated by the Illumina HiSeq 2000 platform using a series of paired-end and mate-pair libraries, covering the predicted Cocos nucifera genome length (2.42 Gb, variety " Hainan Tall") to an estimated x173.32 read depth. A total scaffold length of 2.20 Gb was generated (N50 = 418 Kb), representing 90.91% of the genome. The coconut genome was predicted to harbor 28 039 protein-coding genes, which is less than in Phoenix dactylifera (PDK30: 28 889), Phoenix dactylifera (DPV01: 41 660), and Elaeis guineensis (EG5: 34 802). BUSCO evaluation demonstrated that the obtained scaffold sequences covered 90.8% of the coconut genome and that the genome annotation was 74.1% complete. Genome annotation results revealed that 72.75% of the coconut genome consisted of transposable elements, of which long-terminal repeat retrotransposons elements (LTRs) accounted for the largest proportion (92.23%). Comparative analysis of the antiporter gene family and ion channel gene families between C. nucifera and Arabidopsis thaliana indicated that significant gene expansion may have occurred in the coconut involving Na+/H+ antiporter, carnitine/acylcarnitine translocase, potassium-dependent sodium-calcium exchanger, and potassium channel genes. Despite its agronomic importance, C. nucifera is still under-studied. In this report, we present a draft genome of C. nucifera and provide genomic information that will facilitate future functional genomics and molecular-assisted breeding in this crop species.

Simple sequence repeat (SSR) markers have been widely used to evaluate genetic resources and assist crop breeding in plant systems: they are codominant, easy to score and have abundant polymorphisms. In this study, we used coconut transcriptome sequences to determine the distribution characteristics of gene-based microsatellite loci in Cocos nucifera L. and to develop a series of polymorphic SSR markers. A total of 6,608 SSRs were identified across 57,304 unigenes from coconut transcripts: approximately one expressed sequence tag-derived SSR locus per 10 unigenes. We developed 309 primer pairs and characterized 191 polymorphic gene-based SSR markers across a set of ten coconut accessions from different countries. A total of 615 alleles were identified from the 191 polymorphic SSR loci, with an average of 3.22 alleles per locus. These gene-based SSR markers displayed moderate levels of polymorphism, with observed heterozygosity ranging from 0.18 to 0.695 (mean = 0.385 ± 0.14). Subsequently, 80 polymorphic markers were selected to assay genotypes of 82 coconut accessions collected from different regions in Asia. Association analysis found a total of nine markers significantly associated with coconut height (P < 0.05) using general linear models in a selective unstructured population and mixed linear models in a mixed-structure population. Two SSR markers (from Unigene9331 and Unigene3350) were significantly associated with coconut height using both statistical methods.

The Palmae family contains 202 genera and approximately 2800 species. Except for Elaeis guineensis and Phoenix dactylifera, almost no genetic and genomic information is available for Palmae species. Therefore, this is an obstacle to the conservation and genetic assessment of Palmae species, especially those that are currently endangered. The study was performed to develop a large number of microsatellite markers which can be used for genetic analysis in different Palmae species. Based on the assembled genome of Elaeis guineensis and Phoenix dactylifera, a total of 814 383 and 371 629 microsatellites were identified. Among these microsatellites identified in Elaeis guineensis, 734 509 primer pairs could be designed from the flanking sequences of these microsatellites. The majority (618 762) of these designed primer pairs had in silico products in the genome of Elaeis guineensis. These 618 762 primer pairs were subsequently used to in silico amplify the genome of Phoenix dactylifera. A total of 7 265 conserved microsatellites were identified between Elaeis guineensis and Phoenix dactylifera. One hundred and thirty-five primer pairs flanking the conserved SSRs were stochastically selected and validated to have high cross-genera transferability, varying from 16.7% to 93.3% with an average of 73.7%. These genome-wide conserved microsatellite markers will provide a useful tool for genetic assessment and conservation of different Palmae species in the future.

BackgroundCocos nucifera (coconut), a member of the Arecaceae family, is an economically important woody palm grown in tropical regions. Despite its agronomic importance, previous germplasm assessment studies have relied solely on morphological and agronomical traits. Molecular biology techniques have been scarcely used in assessment of genetic resources and for improvement of important agronomic and quality traits in Cocos nucifera, mostly due to the absence of available sequence information.Methodology/principal findingsTo provide basic information for molecular breeding and further molecular biological analysis in Cocos nucifera, we applied RNA-seq technology and de novo assembly to gain a global overview of the Cocos nucifera transcriptome from mixed tissue samples. Using Illumina sequencing, we obtained 54.9 million short reads and conducted de novo assembly to obtain 57,304 unigenes with an average length of 752 base pairs. Sequence comparison between assembled unigenes and released cDNA sequences of Cocos nucifera and Elaeis guineensis indicated that the assembled sequences were of high quality. Approximately 99.9% of unigenes were novel compared to the released coconut EST sequences. Using BLASTX, 68.2% of unigenes were successfully annotated based on the Genbank non-redundant (Nr) protein database. The annotated unigenes were then further classified using the Gene Ontology (GO), Clusters of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases.Conclusions/significanceOur study provides a large quantity of novel genetic information for Cocos nucifera. This information will act as a valuable resource for further molecular genetic studies and breeding in coconut, as well as for isolation and characterization of functional genes involved in different biochemical pathways in this important tropical crop species.