The high-quality genome of Cryptotaenia japonica and comparative genomics analysis reveals anthocyanin biosynthesis in Apiaceae.

Cryptotaenia japonica, a traditional medicinal and edible vegetable crops, is well-known for its attractive flavors and health care functions. As a member of the Apiaceae family, the evolutionary trajectory and biological properties of C. japonica are not clearly understood. Here, we first reported a high-quality genome of C. japonica with a total length of 427 Mb and N50 length 50.76 Mb, was anchored into 10 chromosomes, which confirmed by chromosome (cytogenetic) analysis. Comparative genomic analysis revealed C. japonica exhibited low genetic redundancy, contained a higher percentage of single-cope gene families. The homoeologous blocks, Ks, and collinearity were analyzed among Apiaceae species contributed to the evidence that C. japonica lacked recent species-specific WGD. Through comparative genomic and transcriptomic analyses of Apiaceae species, we revealed the genetic basis of the production of anthocyanins. Several structural genes encoding enzymes and transcription factor genes of the anthocyanin biosynthesis pathway in different species were also identified. The CjANSa, CjDFRb, and CjF3H gene might be the target of Cjaponica_2.2062 (bHLH) and Cjaponica_1.3743 (MYB). Our findings provided a high-quality reference genome of C. japonica and offered new insights into Apiaceae evolution and biology.

Low-Temperature Regulates the Cell Structure and Chlorophyll in Addition to Cellulose Metabolism of Postharvest Red Toona sinensis Buds across Different Seasons.

Postharvest fibrosis and greening of Toona sinensis buds significantly affect their quality during storage. This study aimed to clarify the effects of low-temperature storage on postharvest red TSB quality harvested in different seasons. Red TSB samples were collected from Guizhou province, China, 21 days after the beginning of spring (Lichun), summer (Lixia), and autumn (Liqiu), and stored at 4 °C in dark conditions. We compared and analyzed the appearance, microstructure, chlorophyll and cellulose content, and expression levels of related genes across different seasons. The results indicated that TSB harvested in spring had a bright, purple-red color, whereas those harvested in summer and autumn were green. All samples lost water and darkened after 1 day of storage. Severe greening occurred in spring-harvested TSB within 3 days, a phenomenon not observed in summer and autumn samples. Microstructural analysis revealed that the cells in the palisade and spongy tissues of spring and autumn TSB settled closely during storage, while summer TSB cells remained loosely aligned. Xylem cells were smallest in spring-harvested TSB and largest in autumn. Prolonged storage led to thickening of the secondary cell walls and pith cell autolysis in the petioles, enlarging the cavity area. Chlorophyll content was higher in leaves than in petioles, while cellulose content was lower in petioles across all seasons. Both chlorophyll and cellulose content increased with storage time. Gene expression analysis showed season-dependent variations and significant increases in the expression of over half of the chlorophyll-related and cellulose-related genes during refrigeration, correlating with the observed changes in chlorophyll and cellulose content. This research provides valuable insights for improving postharvest storage and freshness preservation strategies for red TSB across different seasons.

Interaction between SlMAPK3 and SlASR4 regulates drought resistance in tomato (Solanum lycopersicum L.).

Tomato is a leading vegetable in modern agriculture, and with global warming, drought has become an important factor threatening tomato production. Mitogen-activated protein kinase 3 (MAPK3) plays an important role in plant disease and stress resistance. To clarify the downstream target proteins of SlMAPK3 and the mechanism of stress resistance in tomato, this study was conducted with the SlMAPK3-overexpressing lines OE-1 and OE-2 and the CRISPR/Cas9-mediated mutant lines slmapk3-1 and slmapk3-2 under PEG 6000-simulated drought. The results of yeast two-hybrid (Y2H), pull-down, and coimmunoprecipitation (Co-IP) assays confirmed that SlASR4 (NP_001269248.1) interacted with SlMAPK3. Analyses of the SlASR4 protein structure and SlASR4 expression under PEG 6000 and BTH stress revealed that SlASR4 has a highly conserved protein structural domain involved in the drought stress response under PEG 6000 treatment. The function of the SlASR4 and SlMAPK3 downstream target protein, in drought resistance in tomato plants, was identified by virus-induced gene silencing (VIGS). This study clarified that SlMAPK3 interacts with SlASR4 to positively regulate drought resistance in tomato plants.

Comparative Analysis of the Complete Mitochondrial Genomes of Apium graveolens and Apium leptophyllum Provide Insights into Evolution and Phylogeny Relationships.

The genus Apium, belonging to the family Apiaceae, comprises roughly 20 species. Only two species, Apium graveolens and Apium leptophyllum, are available in China and are both rich in nutrients and have favorable medicinal properties. However, the lack of genomic data has severely constrained the study of genetics and evolution in Apium plants. In this study, Illumina NovaSeq 6000 and Nanopore sequencing platforms were employed to identify the mitochondrial genomes of A. graveolens and A. leptophyllum. The complete lengths of the mitochondrial genomes of A. graveolens and A. leptophyllum were 263,017 bp and 260,164 bp, respectively, and contained 39 and 36 protein-coding genes, five and six rRNA genes, and 19 and 20 tRNA genes. Consistent with most angiosperms, both A. graveolens and A. leptophyllum showed a preference for codons encoding leucine (Leu). In the mitochondrial genome of A. graveolens, 335 SSRs were detected, which is higher than the 196 SSRs found in the mitochondrial genome of A. leptophyllum. Studies have shown that the most common RNA editing type is C-to-U, but, in our study, both A. graveolens and A. leptophyllum exhibited the U-C editing type. Furthermore, the transfer of the mitochondrial genomes of A. graveolens and A. leptophyllum into the chloroplast genomes revealed homologous sequences, accounting for 8.14% and 4.89% of the mitochondrial genome, respectively. Lastly, in comparing the mitochondrial genomes of 29 species, it was found that A. graveolens, A. leptophyllum, and Daucus carota form a sister group with a support rate of 100%. Overall, this investigation furnishes extensive insights into the mitochondrial genomes of A. graveolens and A. leptophyllum, thereby enhancing comprehension of the traits and evolutionary patterns within the Apium genus. Additionally, it offers supplementary data for evolutionary and comparative genomic analyses of other species within the Apiaceae family.

Genome-Wide Analysis of Flax (Linum usitatissimum L.) Growth-Regulating Factor (GRF) Transcription Factors.

Flax is an important cash crop globally with a variety of commercial uses. It has been widely used for fiber, oil, nutrition, feed and in composite materials. Growth regulatory factor (GRF) is a transcription factor family unique to plants, and is involved in regulating many processes of growth and development. Bioinformatics analysis of the GRF family in flax predicted 17 LuGRF genes, which all contained the characteristic QLQ and WRC domains. Equally, 15 of 17 LuGRFs (88%) are predicted to be regulated by lus-miR396 miRNA. Phylogenetic analysis of GRFs from flax and several other well-characterized species defined five clades; LuGRF genes were found in four clades. Most LuGRF gene promoters contained cis-regulatory elements known to be responsive to hormones and stress. The chromosomal locations and collinearity of LuGRF genes were also analyzed. The three-dimensional structure of LuGRF proteins was predicted using homology modeling. The transcript expression data indicated that most LuGRF family members were highly expressed in flax fruit and embryos, whereas LuGRF3, LuGRF12 and LuGRF16 were enriched in response to salt stress. Real-time quantitative fluorescent PCR (qRT-PCR) showed that both LuGRF1 and LuGRF11 were up-regulated under ABA and MeJA stimuli, indicating that these genes were involved in defense. LuGRF1 was demonstrated to be localized to the nucleus as expected for a transcription factor. These results provide a basis for further exploration of the molecular mechanism of LuGRF gene function and obtaining improved flax breeding lines.

Combined Analysis of the Metabolome and Transcriptome to Explore Heat Stress Responses and Adaptation Mechanisms in Celery (Apium graveolens L.).

Celery is an important leafy vegetable that can grow during the cool season and does not tolerate high temperatures. Heat stress is widely acknowledged as one of the main abiotic stresses affecting the growth and yield of celery. The morphological and physiological indices of celery were investigated in the present study to explore the physiological mechanisms in response to high temperatures. Results showed that the antioxidant enzyme activity, proline, relative conductivity, and malondialdehyde were increased, while chlorophyll and the water content of leaves decreased under high-temperature conditions. Short-term heat treatment increased the stomatal conductance to cool off the leaves by transpiration; however, long-term heat treatment led to stomatal closure to prevent leaf dehydration. In addition, high temperature caused a disordered arrangement of palisade tissue and a loose arrangement of spongy tissue in celery leaves. Combined metabolomic and transcriptomic analyses were further used to reveal the regulatory mechanisms in response to heat stress at the molecular level in celery. A total of 1003 differential metabolites were identified and significantly enriched in amino acid metabolism and the tricarboxilic acid (TCA) cycle. Transcriptome sequencing detected 24,264 different genes, including multiple transcription factor families such as HSF, WRKY, MYB, AP2, bZIP, and bHLH family members that were significantly upregulated in response to heat stress, suggesting that these genes were involved in the response to heat stress. In addition, transcriptional and metabolic pathway analyses showed that heat stress inhibited the glycolysis pathway and delayed the TCA cycle but increased the expression of most amino acid synthesis pathways such as proline, arginine, and serine, consistent with the results of physiological indicators. qRT-PCR further showed that the expression pattern was similar to the expression abundance in the transcriptome. The important metabolites and genes in celery that significantly contributed to the response to high temperatures were identified in the present study, which provided the theoretical basis for breeding heat-resistant celery.

Analysis and review of trichomes in plants.

BACKGROUND: Trichomes play a key role in the development of plants and exist in a wide variety of species. RESULTS: In this paper, it was reviewed that the structure and morphology characteristics of trichomes, alongside the biological functions and classical regulatory mechanisms of trichome development in plants. The environment factors, hormones, transcription factor, non-coding RNA, etc., play important roles in regulating the initialization, branching, growth, and development of trichomes. In addition, it was further investigated the atypical regulation mechanism in a non-model plant, found that regulating the growth and development of tea (Camellia sinensis) trichome is mainly affected by hormones and the novel regulation factors. CONCLUSIONS: This review further displayed the complex and differential regulatory networks in trichome initiation and development, provided a reference for basic and applied research on trichomes in plants.

AgNAC1, a celery transcription factor, related to regulation on lignin biosynthesis and salt tolerance.

The NAC transcription factor participates in various biotic and abiotic stress responses and plays a critical role in plant development. Lignin is a water-insoluble dietary fiber, but it is second only to cellulose in abundance. Celery is the main source of dietary fiber, but its quality and production are limited by various abiotic stresses. Here, AgNAC1 containing the NAM domain was identified from celery. AgNAC1 was found to be a nuclear protein. Transgenic Arabidopsis thaliana plants hosting AgNAC1 have longer root lengths and stomatal axis lengths than the wide type (WT). The evidence from lignin determination and expression levels of lignin-related genes indicated that AgNAC1 plays a vital role in lignin biosynthesis. Furthermore, the results of the physiological characterization and the drought and salt treatments indicate that AgNAC1-overexpressing plants are significantly resistive to salt stress. Under drought and salt treatments, the AgNAC1 transgenic Arabidopsis thaliana plants presented increased superoxide dismutase (SOD) and peroxidase (POD) activities and decreased malondialdehyde (MDA) content and size of stomatal apertures relatively to the WT plants. The AgNAC1 served as a positive regulator in inducing the expression of stress-responsive genes. Overall, the overexpressing AgNAC1 enhanced the plants' resistance to salt stress and played a regulatory role in lignin accumulation.

Advances in the research of celery, an important Apiaceae vegetable crop.

Celery (Apium graveolens L.), one of the most important vegetables in Apiaceae family, is cultivated worldwide and utilized in food and cosmetic industries because it is an excellent source of vitamins, phenolic compounds, volatile oils and other nutrients. Celery extracts possess various medicinal properties, such as antibacterial, anti-inflammatory and lowering blood glucose and serum lipid levels. With the rapid advancements in molecular biology and sequencing technology, studies on celery have been performed. Numerous molecular markers and regulatory genes have been discovered and applied to improve celery. Research advances, including genetic breeding, genomics research, function genes and chemical composition, regarding celery are reviewed in this paper. Further exploration and application trends are briefly described. This review provides a reference for basic and applied research on celery, an important Apiaceae vegetable crop.

Distinct transcription profile of genes involved in carotenoid biosynthesis among six different color carrot (Daucus carota L.) cultivars.

Carotenoid, a group of lipophilic molecules, is widely distributed in nature, and is important for plant photosynthesis and photoprotection. In carrot taproot, different types of dominant carotenoid accumulation lead to yellow, orange, and red colors. In this study, six different carrot cultivars were used to simultaneously analyze carotenoid contents by high performance liquid chromatography. The expression levels of genes involved in carotenoid biosynthesis of carrot were also detected by real-time quantitative PCR. It was found that genes involved in xanthophyll formation were expressed at high levels in yellow carrot cultivars. However, these genes were expressed at low levels in orange carrot cultivars. The contents of α- and ß-carotene accounted for a large proportion in total carotenoid contents in orange carrot cultivars. These results indicate that α-carotene accumulation and xanthophyll formation may be related to the expression levels of carotene hydroxylase genes in carrot.

De novo transcriptome assembly, gene annotation, marker development, and miRNA potential target genes validation under abiotic stresses in Oenanthe javanica.

Oenanthe javanica is an aquatic perennial herb with known medicinal properties and an edible vegetable with high vitamin and mineral content. The understanding of the biology of O. javanica is limited by the absence of information on its genome, transcriptome, and small RNA. In this study, transcriptome sequencing and small RNA sequencing were performed to annotate function genes, develop SSR markers and analyze potential target genes of miRNAs in O. javanica. All reads with total nucleotides number of 1,440,321,408 bp were assembled into 58,072 transcripts and 40,208 unigenes. A total of 1,233 SSRs were identified from O. javanica. Generated unigenes were aligned against seven databases and annotated with functions. A total of 29 potential targets were predicted. Expression of 10 miRNAs and their corresponding target genes under abiotic stresses (heat, cold, salinity, and drought) was validated. All ten miRNAs were confirmed to response to abiotic stresses. A pair of miRNA and its target gene was found. This study can serve as a valuable resource for future studies on O. javanica, which may focus on novel gene discovery, SSR development, gene mapping, and miRNA-affected processes and pathways. This can promote the development of the useful medicinal properties of O. javanica in medical science.

High throughput sequencing of two celery varieties small RNAs identifies microRNAs involved in temperature stress response.

BACKGROUND: MicroRNAs (miRNAs) are small, non-coding RNAs of 20 to 24 nucleotides that regulate gene expression and responses to biotic and abiotic stress. Till now, no reports have previously been published concerning miRNAs in celery. RESULTS: Two small RNAs libraries were constructed from two celery varieties, 'Jinnan Shiqin' and 'Ventura', and characterized by deep sequencing. A total of 431 (418 known and 13 novel) and 346 (341 known and five novel) miRNAs were identified in celery varieties 'Jinnan Shiqin' and 'Ventura', respectively. Potential miRNA-target genes were predicted and annotated by screening diverse protein databases, including Gene Ontology, Cluster of Orthologous Groups and Kyoto Encyclopedia of Genes and Genomes. Significant differential expression between the two varieties was seen for 221 miRNAs. qRT-PCR was used to analyze the abundance of six miRNAs under cold and heat stress conditions. The results showed that miRNAs may have important functions in controlling temperature stress in celery. CONCLUSION: A large number of miRNAs were identified in celery, and their target genes, functional annotations, and gene expression patterns have been explored.These findings provide the first information on celery miRNAs and enhance understanding of celery miRNA regulatory mechanisms under extreme temperature stress.

Telomere-to-telomere carrot (Daucus carota) genome assembly reveals carotenoid characteristics.

Carrot (Daucus carota) is an Apiaceae plant with multi-colored fleshy roots that provides a model system for carotenoid research. In this study, we assembled a 430.40 Mb high-quality gapless genome to the telomere-to-telomere (T2T) level of "Kurodagosun" carrot. In total, 36 268 genes were identified and 34 961 of them were functionally annotated. The proportion of repeat sequences in the genome was 55.3%, mainly long terminal repeats. Depending on the coverage of the repeats, 14 telomeres and 9 centromeric regions on the chromosomes were predicted. A phylogenetic analysis showed that carrots evolved early in the family Apiaceae. Based on the T2T genome, we reconstructed the carotenoid metabolic pathway and identified the structural genes that regulate carotenoid biosynthesis. Among the 65 genes that were screened, 9 were newly identified. Additionally, some gene sequences overlapped with transposons, suggesting replication and functional differentiation of carotenoid-related genes during carrot evolution. Given that some gene copies were barely expressed during development, they might be functionally redundant. Comparison of 24 cytochrome P450 genes associated with carotenoid biosynthesis revealed the tandem or proximal duplication resulting in expansion of CYP gene family. These results provided molecular information for carrot carotenoid accumulation and contributed to a new genetic resource.

Advances in engineering the production of the natural red pigment lycopene: A systematic review from a biotechnology perspective.

BACKGROUND: Lycopene is a natural red compound with potent antioxidant activity that can be utilized both as pigment and as a raw material in functional food, and so possesses good commercial prospects. The biosynthetic pathway has already been documented, which provides the foundation for lycopene production using biotechnology. AIM OF REVIEW: Although lycopene production has begun to take shape, there is still an urgent need to alleviate the yield of lycopene. Progress in this area can provide useful reference for metabolic engineering of lycopene production utilizing multiple approaches. KEY SCIENTIFIC CONCEPTS OF REVIEW: Using conventional microbial fermentation approaches, biotechnologists have enhanced the yield of lycopene by selecting suitable host strains, utilizing various additives, and optimizing culture conditions. With the development of modern biotechnology, genetic engineering, protein engineering, and metabolic engineering have been applied for lycopene production. Extraction from natural plants is the main way for lycopene production at present. Based on the molecular mechanism of lycopene accumulation, the production of lycopene by plant bioreactor through genetic engineering has a good prospect. Here we summarized common strategies for optimizing lycopene production engineering from a biotechnology perspective, which are mainly carried out by microbial cultivation. We reviewed the challenges and limitations of this approach, summarized the critical aspects, and provided suggestions with the aim of potential future breakthroughs for lycopene production in plants.

AgGMP encoding GDP-D-mannose pyrophosphorylase from celery enhanced the accumulation of ascorbic acid and resistance to drought stress in Arabidopsis.

Ascorbic acid (AsA) is an important nutrient in celery, the conversion of D-mannose-1-P to GDP-D-mannose catalyzed by GDP-D-mannose pyrophosphorylase (GMPase) represents the first committed step in the biosynthesis of AsA. To clarify the function of the AgGMP gene of celery, the AgGMP gene was cloned from celery cv. 'Jinnan Shiqin' . It contains an open reading frame (ORF) with the length of 1,086 bp, encoding 361 amino acids. AgGMP protein was highly conserved among different plant species. Phylogenetic analysis demonstrated that the GMP proteins from celery and carrot belonged to the same branch. AgGMP protein was mainly composed of three α-helixes and certain random coils. No signal peptide was found in the AgGMP protein. The subcellular localization indicated that the AgGMP protein was located in the cytoplasm. The relative expression levels of AgGMP in 'Jinnan Shiqin' were significantly up-regulated at 2 h and 4 h under drought stress treatments. AsA contents in transgenic Arabidopsis lines hosting AgGMP gene were higher than that in wild type plants, and the root lengths were also longer in the MS medium containing 300 mM mannitol. The present study provides useful evidence for the functional involvement of AgGMP in regulating AsA accumulation and response to drought stress in celery.

Multigene manipulation of photosynthetic carbon metabolism enhances the photosynthetic capacity and biomass yield of cucumber under low-CO2 environment.

Solar greenhouses are important in the vegetable production and widely used for the counter-season production in the world. However, the CO2 consumed by crops for photosynthesis after sunrise is not supplemented and becomes chronically deficient due to the airtight structure of solar greenhouses. Vegetable crops cannot effectively utilize light resources under low-CO2 environment, and this incapability results in reduced photosynthetic efficiency and crop yield. We used cucumber as a model plant and generated several sets of transgenic cucumber plants overexpressing individual genes, including ß-carbonic anhydrase 1 (CsßCA1), ß-carbonic anhydrase 4 (CsßCA4), and sedoheptulose-1,7-bisphosphatase (CsSBP); fructose-1,6-bisphosphate aldolase (CsFBA), and CsßCA1 co-expressing plants; CsßCA4, CsSBP, and CsFBA co-expressing plants (14SF). The results showed that the overexpression of CsßCA1, CsßCA4, and 14SF exhibited higher photosynthetic and biomass yield in transgenic cucumber plants under low-CO2 environment. Further enhancements in photosynthesis and biomass yield were observed in 14SF transgenic plants under low-CO2 environment. The net photosynthesis biomass yield and photosynthetic rate increased by 49% and 79% compared with those of the WT. However, the transgenic cucumbers of overexpressing CsFBA and CsSBP showed insignificant differences in photosynthesis and biomass yield compared with the WT under low-CO2.environment. Photosynthesis, fluorescence parameters, and enzymatic measurements indicated that CsßCA1, CsßCA4, CsSBP, and CsFBA had cumulative effects in photosynthetic carbon assimilation under low-CO2 environment. Co-expression of this four genes (CsßCA1, CsßCA4, CsSBP, and CsFBA) can increase the carboxylation activity of RuBisCO and promote the regeneration of RuBP. As a result, the 14SF transgenic plants showed a higher net photosynthetic rate and biomass yield even under low-CO2environment.These findings demonstrate the possibility of cultivating crops with high photosynthetic efficiency by manipulating genes involved in the photosynthetic carbon assimilation metabolic pathway.

Origin, evolution, breeding, and omics of Apiaceae: a family of vegetables and medicinal plants.

Many of the world's most important vegetables and medicinal crops, including carrot, celery, coriander, fennel, and cumin, belong to the Apiaceae family. In this review, we summarize the complex origins of Apiaceae and the current state of research on the family, including traditional and molecular breeding practices, bioactive compounds, medicinal applications, nanotechnology, and omics research. Numerous molecular markers, regulatory factors, and functional genes have been discovered, studied, and applied to improve vegetable and medicinal crops in Apiaceae. In addition, current trends in Apiaceae application and research are also briefly described, including mining new functional genes and metabolites using omics research, identifying new genetic variants associated with important agronomic traits by population genetics analysis and GWAS, applying genetic transformation, the CRISPR-Cas9 gene editing system, and nanotechnology. This review provides a reference for basic and applied research on Apiaceae vegetable and medicinal plants.

The complete chloroplast genome of Cymbidium dayanum (Orchidaceae).

Cymbidium dayanum, a wild orchid species in the Orchid family (Orchidaceae), is considered highly valuable because of its long flowering period and beautiful plant shape. We sequenced the complete chloroplast genome of C. dayanum using the Illumina Hiseq platform (Illumina, San Diego, CA). The size of the C. dayanum chloroplast genome is 155,408 bp, with an average GC content of 36.76%. This chloroplast genome has containing a large single-copy (LSC) region of 84,189 bp, a small single-copy (SSC) region of 17,991 bp, and two inverted (IRa and IRb) repeat regions of two 26,614 bp. A total of 118 unique genes were annotated, including 76 protein-coding genes, 38 tRNA genes, and 4 rRNA genes. A maximum-likelihood phylogenetic tree indicated that C. dayanum is closely related to C. tracyanum in the genus Cymbidium based on 9 whole chloroplast genome sequences.

Origin, Evolution, Breeding, and Omics of Chayote, an Important Cucurbitaceae Vegetable Crop.

Chayote (Sechium edule), a member of the Cucurbitaceae family, is cultivated throughout tropical and subtropical regions of the world and utilized in pharmaceutical, cosmetic and food industries because it is an excellent source of minerals, dietary fibers, protein, vitamins, carotenoids, polysaccharides, phenolic and flavonoid compounds, and other nutrients. Chayote extracts process various medicinal properties, such as anti-cardiovascular, antidiabetic, antiobesity, antiulcer, and anticancer properties. With the rapid advancements of molecular biology and sequencing technology, studies on chayote have been carried out. Research advances, including molecular makers, breeding, genomic research, chemical composition, and pests and diseases, regarding chayote are reviewed in this paper. Future exploration and application trends are briefly described. This review provides a reference for basic and applied research on chayote, an important Cucurbitaceae vegetable crop.

Effects of simulated drought stress on carotenoid contents and expression of related genes in carrot taproots.

Carotenoids are liposoluble pigments found in plant chromoplasts that are responsible for the yellow, orange, and red colors of carrot taproots. Drought is one of the main stress factors affecting carrot growth. Carotenoids play important roles in drought resistance in higher plants. In the present work, the carotenoid contents in three different-colored carrot cultivars, 'Kurodagosun' (orange), 'Benhongjinshi' (red), and 'Qitouhuang' (yellow), were determined by ultra-high-performance liquid chromatography (UPLC) after 15% polyethylene glycol (PEG) 6000 treatment. Real-time fluorescence quantitative PCR (RT-qPCR) was then used to determine the expression levels of carotenoid synthesis- and degradation-related genes. Increases in ß-carotene content in 'Qitouhuang' taproots under drought stress were found to be related to the expression levels of DcPSY2 and DcLCYB. Increases in lutein and decreases in α-carotene content in 'Qitouhuang' and 'Kurodagosun' under PEG treatment may be related to the expression levels of DcCYP97A3, DcCHXE, and DcCHXB1. The expression levels of DcNCED1 and DcNCED2 in the three cultivars significantly increased, thus suggesting that NCED genes could respond to drought stress. Analysis of the growth status and carotenoid contents of carrots under PEG treatment indicated that the orange cultivar 'Kurodagosun' has better adaptability to drought stress than the other cultivars and that ß-carotene and lutein may be involved in the stress resistance process of carrot.