A clinical comparative study of dual LVIS devices and single flow diversion stenting for the treatment of unruptured V3-V4 vertebral artery dissection.

PURPOSE: This study aims to compare the efficacy and safety of using overlapping low-profile visualized intraluminal support (LVIS) devices and flow diversion (FD) for the treatment of unruptured vertebral artery dissection (VAD) in the V3-V4 segments. METHODS: The clinical and imaging data of 71 patients with unruptured VAD in the V3-V4 segments who underwent either dual LVIS stenting (d-LVIS group) or single FD stenting (FD group) at our center from September 2014 to December 2021 were retrospectively analyzed. RESULTS: Immediate postoperative angiography revealed no significant difference in the degree of occlusion between the two groups in treating vertebral artery dissecting aneurysms (with or without noncompact coiling). However, the d-LVIS group had significantly higher fluoroscopy exposure time and total radiation exposure dose compared to the FD group. During the perioperative period, two cases of pontine infarction and one case of acute thrombosis were encountered. One patient died from subarachnoid hemorrhage during the follow-up period. For dissecting the aneurysm, angiographic follow-up (8.56 ± 1.96 months) showed similar healing outcomes between the two groups (with or without noncompact coiling). However, seven patients (7/40, 17.5%) showed poor healing and one patient showed mild in-stent stenosis. For simple dissection, angiographic follow-up (8.78 ± 1.83 months) showed patent lumens in both groups, with all dissections healing well, and two patients having mild in-stent stenosis. CONCLUSION: Both methods could effectively treat unruptured VAD in V3-V4 segments. Nevertheless, simple FD implantation is relatively easier to perform and involves lower radiation exposure.

Genetic Analyses of Flower Main Traits from Two Pitayas and Their Progenies: A Cactus Plant.

Elucidation of the genetic foundation governing crucial traits in pitaya flowers is imperative for enhancing both the ornamental and economic values. In this study, the dynamic variation in flower genetics, segregation variation patterns, and a mixed inheritance model of the major and multigene flower traits of 'Dahong' and 'Honghuaqinglong' pitayas and their progenies were explored. The results showed that the main traits of flowers exhibited varying degrees of variation among the reciprocal F1 hybrids, with the data exhibiting the characteristics of quantitative traits. The betalain content, petal number, and stigma number exhibited values below the median values of the parents, suggesting a genetic inclination towards lower values. Perianth width, calyx tube width, petal number, and stigma number had the same genetic effects and significant correlation. Stigma-related traits had a clear maternal inheritance tendency. The heritability of flower length, stigma relative to anther distance, and petal betalain content was governed by two pairs of additive-dominant major genes. Perianth width, calyx tube width, petal number, and stigma number all conformed to the model of two pairs of equal-additive-dominant major genes. This study provides valuable information for parental selection, cross-breeding, and the enhancement of pitaya varieties to meet market preferences and environmental conditions.

Identification of HuSWEET Family in Pitaya (Hylocereus undatus) and Key Roles of HuSWEET12a and HuSWEET13d in Sugar Accumulation.

The sugar composition and content of fruit have a significant impact on their flavor and taste. In pitaya, or dragon fruit, sweetness is a crucial determinant of fruit taste and consumer preference. The sugars will eventually be exported transporters (SWEETs), a novel group of sugar transporters that have various physiological functions, including phloem loading, seed filling, nectar secretion, and fruit development. However, the role of SWEETs in sugar accumulation in pitaya fruit is not yet clear. Here, we identified 19 potential members (HuSWEET genes) of the SWEET family in pitaya and analyzed their conserved motifs, physiochemical characteristics, chromosomal distribution, gene structure, and phylogenetic relationship. Seven highly conserved α-helical transmembrane domains (7-TMs) were found, and the HuSWEET proteins can be divided into three clades based on the phylogenetic analysis. Interestingly, we found two HuSWEET genes, HuSWEET12a and HuSWEET13d, that showed strong preferential expressions in fruits and an upward trend during fruit maturation, suggesting they have key roles in sugar accumulation in pitaya. This can be further roughly demonstrated by the fact that transgenic tomato plants overexpressing HuSWEET12a/13d accumulated high levels of sugar in the mature fruit. Together, our result provides new insights into the regulation of sugar accumulation by SWEET family genes in pitaya fruit, which also set a crucial basis for the further functional study of the HuSWEETs.

Massively parallel FMCW lidar with cm range resolution using an electro-optic frequency comb.

Frequency-modulated continuous wave (FMCW) light detection and ranging (lidar) is a promising solution for three-dimensional (3D) imaging and autonomous driving. This technique maps range and velocity measurement to frequency counting via coherent detection. Compared with single-channel FMCW lidar, multi-channel FMCW lidar can greatly improve the measurement rate. A chip-scale soliton micro-comb is currently used in FMCW lidar to enable multi-channel parallel ranging and significantly increase the measurement rate. However, its range resolution is limited due to the soliton comb having only a few-GHz frequency sweep bandwidth. To overcome this limitation, we propose using a cascaded modulator electro-optic (EO) frequency comb for massively parallel FMCW lidar. We demonstrate a 31-channel FMCW lidar with a bulk EO frequency comb and a 19-channel FMCW lidar using an integrated thin-film lithium niobate (TFLN) EO frequency comb. Both systems have a sweep bandwidth of up to 15 GHz for each channel, corresponding to a 1-cm range resolution. We also analyze the limiting factors of the sweep bandwidth in 3D imaging and perform 3D imaging for a specific target. The measurement rate achieved is over 12 megapixels per second, which verifies its feasibility for massively parallel ranging. Our approach has the potential to greatly benefit 3D imaging in fields where high range resolution is required, such as in criminal investigation and precision machining.

Identification of HuSPL family and key role of HuSPL12 in regulation of betalain biosynthesis in pitaya.

The SQUAMOSA promoter binding protein-like (SPL) gene family is a unique family of plant-specific transcription factors (TFs), which plays vital roles in a variety of plant biological processes. Its role in betalain biosynthesis in Hylocereus undantus; however, is still unclear. Here, we report a total of 16 HuSPL genes from the pitaya genome, which were unevenly distributed among nine chromosomes. The HuSPL genes were clustered into seven groups, and most HuSPLs within the same group shared similar exon-intron structures and conserved motifs. Eight segment replication events in the HuSPL gene family were the main driving force behind the gene family expansion. Nine of the HuSPL genes had potential target sites for Hmo-miR156/157b. Hmo-miR156/157b-targeted HuSPLs exhibited differential expression patterns compared with constitutive expression patterns of most Hmo-miR156/157b-nontargeted HuSPLs. The expression of Hmo-miR156/157b gradually increased during fruit maturation, while the expression of Hmo-miR156/157b-targeted HuSPL5/11/14 gradually decreased. In addition, the lowest expression level of Hmo-miR156/157b-targeted HuSPL12 was detected 23rd day after flowering, when the middle pulps started to turn red. HuSPL5, HuSPL11, HuSPL12, and HuSPL14 were nucleus-localized proteins. HuSPL12 could inhibit the expression of HuWRKY40 by binding to its promoter. Results from yeast two-hybrid and bimolecular fluorescence complementation assays showed that HuSPL12 could interact with HuMYB1, HuMYB132, or HuWRKY42 TFs responsible for betalain biosynthesis. The results of the present study provide an essential basis for future regulation of betalain accumulation in pitaya.

Metabolome and transcriptome analyses reveal the molecular mechanisms of LcMYB1 regulating anthocyanin accumulation in litchi hairy roots.

Agrobacterium rhizogenes-mediated hairy root culture offer a promising approach for gene function analysis and production of plant secondary metabolites. Here, we obtained red litchi hairy roots using A. rhizogenes-mediated LcMYB1 transformation. Using high performance liquid chromatography, the main anthocyanins in the red hairy roots were determined to be cyanidin 3-rutinoside and cyanidin 3-glucoside. A total of 164 metabolites were significantly upregulated or downregulated in the red hairy roots, which were mostly involved in flavone and flavonol pathway, and flavonoid pathway. The transcriptome analysis revealed 472 differentially expressed genes (DEGs). Up-regulated genes were considerably enriched in anthocyanin, flavone and flavonol biosynthesis. Integrative metabolite profiling and transcriptome analyses showed that LcF3'H, LcUFGT1, and LcGST4 were key structural genes in anthocyanin biosynthesis. However, the expression of Cinnamyl-alcohol dehydrogenase (CAD) and Peroxidase (POD) leading to the production of lignin were significantly down-regulated, suggesting flavonoids and lignin compete with each other in the phenylpropanoid pathway. A total of 52 DEGs were identified as transcription factors. Correlation analysis showed that 8 transcription factors were positively correlated with LcUFGT1, and LcGST4, involving in anthocyanin biosynthesis. These findings clarify the molecular mechanisms of LcMYB1 regulating anthocyanin accumulation in litchi hairy roots.

Identification of HubHLH family and key role of HubHLH159 in betalain biosynthesis by activating the transcription of HuADH1, HuCYP76AD1-1, and HuDODA1 in pitaya.

Basic helix-loop-helix (bHLH) proteins are dimeric transcription factors (TFs) involved in various plant physiological and biological processes. Despite this, little is known about the molecular properties and roles of bHLH TFs in pitaya betalain biosynthesis. Here we report the identification of 165 HubHLH genes in H. undantus genome, their chromosomal distribution, physiochemical characteristics, conserved motifs, gene structure, phylogeny and synteny of HubHLH genes. Based on phylogenetic relationship analysis, the 165 HubHLHs were divided into 26 subfamilies and unequally distributed on the 11 chromosomes of pitaya. Based on the pitaya transcriptome data, a candidate gene HubHLH159 was obtained, and the real-time quantitative PCR analysis confirmed that HubHLH159 showed a high expression level in 'Guanhuahong' pitaya (red-pulp) at mature stage, indicating its role in betalain biosynthesis. HubHLH159 is a Group II protein and contains a bHLH domain. It is a nuclear protein with transcriptional activation activity. Dual luciferase reporter assays and virus-induced gene silencing (VIGS) experiments showed that HubHLH159 promotes betalain biosynthesis by activating the expression of HuADH1, HuCYP76AD1-1, and HuDODA1. The results of the present study lay a new theoretical reference for the regulation of pitaya betalain biosynthesis and also provides as essential basis for the future analysis of the functions of HubHLH gene family.

Betalain biosynthesis in red pulp pitaya is regulated via HuMYB132: a R-R type MYB transcription factor.

BACKGROUND: Multiple MYB transcription factors (TFs) are involved in the regulation of plant coloring. Betalain is a kind of natural plant pigment and its biosynthesis is regulated by a number of enzymes. Despite this, little is known about the molecular properties and roles of MYB TFs in pitaya betalain biosynthesis. RESULTS: In the present study, we identified a 1R-MYB gene, HuMYB132, which is preferentially expressed in red-pulp pitaya at the mature stage. It was clustered with Arabidopsis R-R-type genes and had two DNA-binding domains and a histidine-rich region. The expression assays in N. benthamiana and yeast indicated that HuMYB132 is a nucleus-localized protein with transcriptional activation activity. Dual luciferase reporter assay and electrophoretic mobility shift assays (EMSA) demonstrated that HuMYB132 could promote the transcriptional activities of HuADH1, HuCYP76AD1-1, and HuDODA1 by binding to their promoters. Silencing HuMYB132 reduced betalain accumulation and the expression levels of betalain biosynthetic genes in pitaya pulps. CONCLUSIONS: According to our findings, HuMYB132, a R-R type member of 1R-MYB TF subfamily, positively regulates pitaya betalain biosynthesis by regulating the expression of HuADH1, HuCYP76AD1-1, and HuDODA1. The present study provides a new theoretical reference for the management of pitaya betalain biosynthesis and also provides an essential basis for future regulation of betalain biosynthesis in Hylocereus.

An Imidazole-Based Triangular Macrocycle for Visual Detection of Formaldehyde.

Highly selective detection of formaldehyde utilizing supramolecules has promising applications in both environmental monitoring and biomonitoring areas. Herein we present a new class of imidazole-based, coordination-driven, self-assembled triangular macrocycles with specific recognition of formaldehyde. The visible fluorescence change to the naked eye from yellow to green-yellow occurs via an unusual reversible hydroxymethylation reaction of imidazole, whereas the corresponding imidazole ligands show no fluorescence change. This study provides a new method for efficient formaldehyde detection by utilizing imidazole-based coordination supramolecules.

Genome-Wide Identification of WRKY Gene Family in Pitaya Reveals the Involvement of HmoWRKY42 in Betalain Biosynthesis.

The WRKY gene family is a plant-specific transcription factor (TF) that regulates many physiological processes and (a) biotic stress responses. Despite this, little is known about the molecular properties and roles of WRKY TFs in pitaya betalain biosynthesis. Here we report the identification of 70 WRKY in Hylocereus undatus, their gene structure, locations on each chromosome, systematic phylogenetic analysis, conserved motif analysis, and synteny of HuWRKY genes. HmoWRKY42 is a Group IIb WRKY protein and contains a coiled-coil motif, a WRKY domain and a C2H2 zinc-finger motif (CX5CX23HXH). Results from yeast one-hybrid and transient dual-luciferase assays showed that HmoWRKY42 was a transcriptional repressor and could repress HmocDOPA5GT1 expression by binding to its promoter. Yeast two-hybrid assays showed that HmoWRKY42 could interact with itself to form homodimers. Knocking out the coiled-coil motif of HmoWRKY42 prevented its self-interaction and prevented it from binding to the HmocDOPA5GT1 promoter. Knocking out the WRKY domain and C2H2 zinc-finger motif sequence of HmoWRKY42 also prevented it from binding to the HmocDOPA5GT1 promoter. The coiled-coil motif, the WRKY domain and the C2H2 zinc finger motif are key motifs for the binding of HmoWRKY42 to the HmocDOPA5GT1 promoter. HmoWRKY42 is localized in the nucleus and possesses trans-activation ability responsible for pitaya betalain biosynthesis by repressing the transcription of HmocDOPA5GT1. As far as we know, no reports are available on the role of HmoWRKY42 in pitaya betalain biosynthesis. The results provide an important foundation for future analyses of the regulation and functions of the HuWRKY gene family.

Pitaya Genome and Multiomics Database (PGMD): A Comprehensive and Integrative Resource of Selenicereus undatus.

Pitaya (Selenicereus) is a kind of novel fruit with a delicious taste and superior horticulture ornamental value. The potential economic impact of the pitaya lies in its diverse uses not only as agricultural produce and processed foods but also in industrial and medicinal products. It is also an excellent plant material for basic and applied biological research. A comprehensive database of pitaya would facilitate studies of pitaya and the other Cactaceae plant species. Here, we constructed pitaya genome and multiomics database, which is a collection of the most updated and high-quality pitaya genomic assemblies. The database contains various information such as genomic variation, gene expression, miRNA profiles, metabolite and proteomic data from various tissues and fruit developmental stages of different pitaya cultivars. In PGMD, we also uploaded videos on the flowering process and planting tutorials for practical usage of pitaya. Overall, these valuable data provided in the PGMD will significantly facilitate future studies on population genetics, molecular breeding and function research of pitaya.

Metabolic Profiling of Sugars and Organic Acids, and Expression Analyses of Metabolism-Associated Genes in Two Yellow-Peel Pitaya Species.

Sugar and organic acids are important factors determining pitaya fruit quality. However, changes in sugars and acids, and expressions of metabolism-associated genes during fruit maturation of yellow-peel pitayas are not well-documented. In this study, metabolic and expression analyses in pulps of different fruit developmental stages of 'Wucihuanglong' ('WCHL', Hylocereus undatus) and 'Youcihuanglong' pitaya ('YCHL', Hylocereus megalanthus) were used to explore the sugar and organic acid metabolic process. Total phenols and flavonoids were mainly accumulated at S1 in pitaya pulps. Ascorbic acid contents of 'WCHL' pitaya were higher than that of 'YCHL' pitaya during fruit maturation. Starch was mainly accumulated at early fruit development stages while soluble sugars were rich in late stages. Sucrose, fructose, and glucose were the main sugar components of 'YCHL' pitaya while glucose was dominant in 'WCHL' pitaya. Malic and citric acids were the main organic acids in 'WCHL' and 'YCHL' pitayas, respectively. Based on the transcriptome analyses, 118 genes involved in pitaya sugar and organic acid metabolism were obtained. Results from the correlation analyses between the expression profiling of candidate genes and the contents of sugar and organic acid showed that 51 genes had a significant correlation relationship and probably perform key role in pitaya sugar and organic acid metabolism processes. The finding of the present study provides new information for quality regulation of pitayas.

HuNAC20 and HuNAC25, Two Novel NAC Genes from Pitaya, Confer Cold Tolerance in Transgenic Arabidopsis.

NAC transcription factors are one of the largest families of transcriptional regulators in plants, and members of the gene family play vital roles in regulating plant growth and development processes including biotic/abiotic stress responses. However, little information is available about the NAC family in pitaya. In this study, we conducted a genome-wide analysis and a total of 64 NACs (named HuNAC1-HuNAC64) were identified in pitaya (Hylocereus). These genes were grouped into fifteen subgroups with diversities in gene proportions, exon-intron structures, and conserved motifs. Genome mapping analysis revealed that HuNAC genes were unevenly scattered on all eleven chromosomes. Synteny analysis indicated that the segmental duplication events played key roles in the expansion of the pitaya NAC gene family. Expression levels of these HuNAC genes were analyzed under cold treatments using qRT-PCR. Four HuNAC genes, i.e., HuNAC7, HuNAC20, HuNAC25, and HuNAC30, were highly induced by cold stress. HuNAC7, HuNAC20, HuNAC25, and HuNAC30 were localized exclusively in the nucleus. HuNAC20, HuNAC25, and HuNAC30 were transcriptional activators while HuNAC7 was a transcriptional repressor. Overexpression of HuNAC20 and HuNAC25 in Arabidopsis thaliana significantly enhanced tolerance to cold stress through decreasing ion leakage, malondialdehyde (MDA), and H2O2 and O2- accumulation, accompanied by upregulating the expression of cold-responsive genes (AtRD29A, AtCOR15A, AtCOR47, and AtKIN1). This study presents comprehensive information on the understanding of the NAC gene family and provides candidate genes to breed new pitaya cultivars with tolerance to cold conditions through genetic transformation.

Sensilla of the Western Flower Thrips, Frankliniella occidentalis (Pergande) (Thysanoptera, Thripidae)

ABSTRACT The sensilla of insects play important roles in odor, taste, the feeling environment, and some sensory functions, which are closely associated with insect host locating, feeding, habitat searching, courtship, mating, and oviposition. In this study, we used a scanning electron microscope to observe the external morphology of nymph and adult Frankliniella occidentalis sensilla on antennae, compound eyes, legs, mouthparts, wings and tail. The results show that three main types of sensilla are located on the antennae: sensilla trichodea, sensilla chaetica, and sensilla basiconica. Among them, sensilla trichodea are the most abundant, followed by sensilla chaetica. Sensilla basiconica on antennae are divided into seven sub-styles, including longer sensilla (L-sensilla basiconica, long sensilla basiconica), shorter sensilla (angle sensilla basiconica, bud sensilla basiconica), and thicker and bigger sensilla (stick sensilla basiconica, fork sensilla basiconica, and finger sensilla basiconica). Only two fork sensilla basiconica were found, located on the dorsal part of the first flagellum subsegment and the ventral part of the second flagellum subsegment, respectively. Seven sensillum types were found on the legs: sensilla trichodea, sensilla chaetica, sensilla basiconica, sensilla ear washing buob-shaped, mamillary sensilla, sensilla campaniform, and Böhm bristle. About 60% of them are sensilla chaetica. Only one sensillum type was found on compound eyes: sensilla chaetica. In addition, some sensillum types were also found on the mouthparts, wings and tail, respectively. In the study, we observed the type, morphology, and distribution of sensilla on antennae, legs, compound eyes, and other regions of nymph and adult F. occidentalis, forming a base for future electrophysiological and behavior experiments on F. occidentalis.

A Genome-Wide Identification Study Reveals That HmoCYP76AD1, HmoDODAα1 and HmocDOPA5GT Involved in Betalain Biosynthesis in Hylocereus.

Betalains are water-soluble nitrogen-containing pigments with multiple bioactivities. Pitayas are the only at large-scale commercially grown fruit containing abundant betalains for consumers. Currently, the key genes involved in betalain biosynthesis remain to be fully elucidated. Moreover, genome-wide analyses of these genes in betalain biosynthesis are not available in betalain-producing plant species. In this study, totally 53 genes related to betalain biosynthesis were identified from the genome data of Hylocereus undatus. Four candidate genes i.e., one cytochrome P-450 R gene (HmoCYP76AD1), two L-DOPA 4,5-dioxygenase genes (HmoDODAα1 and HmoDODAα2), and one cyclo-DOPA 5-O glucosyltransferase gene (HmocDOPA5GT) were initially screened according to bioinformatics and qRT-PCR analyses. Silencing HmoCYP76AD1, HmoDODAα1, HmoDODAα2 or HmocDOPA5GT resulted in loss of red pigment. HmoDODAα1 displayed a high level of L-DOPA 4,5-dioxygenase activity to produce betalamic acid and formed yellow betaxanthin. Co-expression of HmoCYP76AD1, HmoDODAα1 and HmocDOPA5GT in Nicotiana benthamiana and yeast resulted in high abundance of betalain pigments with a red color. These results suggested that HmoCYP76AD1, HmoDODAα1, and HmocDOPA5GT play key roles in betalain biosynthesis in Hylocereus. The results of the present study provide novel genes for molecular breeding programs of pitaya.

Optical coherent dot-product chip for sophisticated deep learning regression.

Optical implementations of neural networks (ONNs) herald the next-generation high-speed and energy-efficient deep learning computing by harnessing the technical advantages of large bandwidth and high parallelism of optics. However, due to the problems of the incomplete numerical domain, limited hardware scale, or inadequate numerical accuracy, the majority of existing ONNs were studied for basic classification tasks. Given that regression is a fundamental form of deep learning and accounts for a large part of current artificial intelligence applications, it is necessary to master deep learning regression for further development and deployment of ONNs. Here, we demonstrate a silicon-based optical coherent dot-product chip (OCDC) capable of completing deep learning regression tasks. The OCDC adopts optical fields to carry out operations in the complete real-value domain instead of in only the positive domain. Via reusing, a single chip conducts matrix multiplications and convolutions in neural networks of any complexity. Also, hardware deviations are compensated via in-situ backpropagation control provided the simplicity of chip architecture. Therefore, the OCDC meets the requirements for sophisticated regression tasks and we successfully demonstrate a representative neural network, the AUTOMAP (a cutting-edge neural network model for image reconstruction). The quality of reconstructed images by the OCDC and a 32-bit digital computer is comparable. To the best of our knowledge, there is no precedent of performing such state-of-the-art regression tasks on ONN chips. It is anticipated that the OCDC can promote the novel accomplishment of ONNs in modern AI applications including autonomous driving, natural language processing, and scientific study.

Agrobacterium rhizogenes-mediated hairy root transformation as an efficient system for gene function analysis in Litchi chinensis.

BACKGROUND: Litchi chinensis Sonn. is an economically important fruit tree in tropical and subtropical regions. However, litchi functional genomics is severely hindered due to its recalcitrance to regeneration and stable transformation. Agrobacterium rhizogenes-mediated hairy root transgenic system provide an alternative to study functional genomics in woody plants. However, the hairy root transgenic system has not been established in litchi. RESULTS: In this study, we report a rapid and highly efficient A. rhizogenes-mediated co-transformation system in L. chinensis using Green Fluorescent Protein (GFP) gene as a marker. Both leaf discs and stem segments of L. chinensis cv. 'Fenhongguiwei' seedlings were able to induce transgenic hairy roots. The optimal procedure involved the use of stem segments as explants, infection by A. rhizogenes strain MSU440 at optical density (OD600) of 0.7 for 10 min and co-cultivation for 3 days, with a co-transformation efficiency of 9.33%. Furthermore, the hairy root transgenic system was successfully used to validate the function of the key anthocyanin regulatory gene LcMYB1 in litchi. Over-expression of LcMYB1 produced red hairy roots, which accumulated higher contents of anthocyanins, proanthocyanins, and flavonols. Additionally, the genes involving in the flavonoid pathway were strongly activated in the red hairy roots. CONCLUSION: We first established a rapid and efficient transformation system for the study of gene function in hairy roots of litchi using A. rhizogenes strain MSU440 by optimizing parameters. This hairy root transgenic system was effective for gene function analysis in litchi using the key anthocyanin regulator gene LcMYB1 as an example.

Genome-Wide Characterization of R2R3-MYB Transcription Factors in Pitaya Reveals a R2R3-MYB Repressor HuMYB1 Involved in Fruit Ripening through Regulation of Betalain Biosynthesis by Repressing Betalain Biosynthesis-Related Genes.

The MYB (myeloblastosis) superfamily constitutes one of the most abundant transcription factors (TFs) regulating various biological processes in plants. However, the molecular characteristics and functions of MYB TFs in pitaya remain unclear. To date, no genome-wide characterization analysis of this gene family has been conducted in the Cactaceae species. In this study, 105 R2R3-MYB members were identified from the genome data of Hylocereus undatus and their conserved motifs, physiological and biochemical characteristics, chromosome locations, synteny relationship, gene structure and phylogeny were further analyzed. Expression analyses suggested that three up-regulated HuMYBs and twenty-two down-regulated HuMYBs were probably involved in fruit ripening of pitaya. Phylogenetic analyses of R2R3-MYB repressors showed that seven HuMYBs (HuMYB1, HuMYB21, HuMYB48, HuMYB49, HuMYB72, HuMYB78 and HuMYB101) were in clades containing R2R3-MYB repressors. HuMYB1 and HuMYB21 were significantly down-regulated with the betalain accumulation during fruit ripening of 'Guanhuahong' pitaya (H. monacanthus). However, only HuMYB1 had R2 and R3 repeats with C1, C2, C3 and C4 motifs. HuMYB1 was localized exclusively to the nucleus and exhibited transcriptional inhibition capacities. Dual luciferase reporter assay demonstrated that HuMYB1 inhibited the expression of betalain-related genes: HuADH1, HuCYP76AD1-1 and HuDODA1. These results suggested that HuMYB1 is a potential repressor of betalain biosynthesis during pitaya fruit ripening. Our results provide the first genome-wide analyses of the R2R3-MYB subfamily involved in pitaya betalain biosynthesis and will facilitate functional analysis of this gene family in the future.