The beautiful bract coloration of Bougainvillea × buttiana 'Miss Manila' renders it significant for both landscaping and as a key source material for betaine extraction. To understand its response to gamma rays irradiation, we exposed cuttings to varying doses of 60Co-γ radiation and integrated physiological assessments and transcriptome profiling. The results demonstrated that radiation significantly altered the physiological and biochemical characteristics of the leaves. The median lethal dose value is 30-38 Gy, with the highest relative mutation rate observed at a radiation dose of 30 Gy. Antioxidant enzyme activities responded differentially: superoxide dismutase (SOD) activity decreased, while catalase (CAT) activity increased with rising radiation dose. Transcriptome analysis revealed 2211 differentially expressed genes, including 1288 up- and 923 down-regulated, enriched in pathways related to antioxidant defense, osmotic regulation, and DNA repair. qRT-PCR results further confirmed the significant upregulation of antioxidant-related gene IMT1 and DNA repair-related genes CARP1, PBP1, among others. These results not only uncover the physiological and molecular mechanisms underpinning radiation tolerance, but also provide a foundational molecular framework for gamma rays mutation breeding in Bougainvillea.

BACKGROUND:The subtribe Malaxidinae encompasses diverse species, many of which possess remarkable medicinal properties that have been employed in traditional Chinese medicine for centuries. Although recent advancements have improved our understanding of the backbone phylogeny of Malaxidinae, clarifying the complex intergeneric relationships remains challenging, largely owing to limited genomic data. To address this gap and further investigate the genetic diversity and evolutionary patterns within this subtribe, we sequenced and assembled complete chloroplast (cp.) genomes from sixteen Malaxidinae species. These newly acquired genomic resources, combined with two previously published cp. genomes from closely related species, were incorporated into a comprehensive comparative genomic and phylogenomic analysis. RESULTS:The complete cp. genomes of all 18 Malaxidinae species were analyzed, revealing lengths ranging from 143,062 bp to 158,785 bp. Each genome contains 123-133 genes, including 74-86 protein-coding genes, 38 tRNA genes, 8 rRNA genes and 1-8 pseudogenes. The chloroplast genomes of Malaxidinae species exhibit significant structural diversity, with particularly pronounced variations observed in the ndhF and ycf1 genes located at the IR/SSC boundary regions. In certain species, the SSC regions showed substantial size reduction, ranging from 10,224 to 15,582 bp. Notable variability in both gene loss and truncation patterns was observed in the ndh gene family across these species, accompanied by diverse modifications affecting the length, position, and pseudogenization of the ycf1 gene. Furthermore, our study identified genomic inversions and rearrangements occurring in both the LSC and SSC regions of specific species. The detection of abundant long dispersed repeats and SSRs provides valuable molecular markers for evaluating both intrageneric and interspecific polymorphism as well as genetic diversity patterns. Through codon usage bias analysis, we established that natural selection serves as the predominant evolutionary force shaping codon usage patterns in most Malaxidinae species. Detailed sequence alignment of the chloroplast genome revealed that structural variants are primarily concentrated within single-copy regions. Ten highly variable cpDNA markers were chosen as mutational hotspots, with the potential for development as DNA barcodes for Malaxidinae species. Our phylogenomic analysis clearly resolved the Malaxidinae into three well-supported major clades. Clade I comprises species of Liparis s.s., Malaxis, and Oberonioides. Clade II includes species of Crepidium, Dienia, Diteilis and Empusa. Clade III consists of species from the genera Blepharoglossum, Cestichis, Oberonia, Platystyliparis and Stichorkis. CONCLUSION:This research provides valuable insights into the unique characteristics of the chloroplast genome in Malaxidinae orchids, significantly advancing our comprehension of their evolutionary mechanisms and phylogenetic architecture. The acquired genomic data establish a crucial foundation to advance medical resources and aid in species differentiation.

Callicarpa peichieniana is an important traditional Chinese medicinal plant with pharmacological benefits for digestive system diseases and wounds, as well as high ornamental value. The goal of this study is to establish an effective in vitro regeneration system in order to satisfy the expanding market demand. Extracts from algae can enhance the proliferation and rooting effect of adventitious buds and can improve the survival rate of transplantation. This study developed an in vitro regeneration system using apical bud explants of C. peichieniana associated with Chlorella sorokiniana (an alga species). Inter simple sequence repeat (ISSR) molecular markers confirmed the genetic fidelity of the regenerated plantlets. The highest number of adventitious buds (5.00 buds) was induced from the apical buds with 0.5 mg/L 6-BA in a Murashige and Skoog (MS) medium, and the highest proliferation coefficient (5.83) was achieved with 2.0 mg/L 6-BA. A rooting rate of 100% was achieved by using 0.1 mg/L NAA, MS with 50% macroelements, and 20 g/L sucrose, averaging 6.36 roots per explant and a root length of 1.32 cm. In all micropropagation stages, C. sorokiniana coexisted and proliferated alongside C. peichieniana materials. ISSR showed that the genetic fidelity of C. peichieniana regenerated plants was 95.45%. Coconut coir/perlite = 1∶1 (v/v) was identified as the optimal transplantation substrate, achieving a 100% survival rate. The “C. peichieniana–C. sorokiniana association” in vitro regeneration system established in this study not only enables the mass production of high-quality regenerated plantlets but provides new ideas and demonstrations for culturing multiple species in the same in vitro system.

Excessive auxin accumulation inhibits protocorm development during germination of Paphiopedilum spicerianum, delaying shoot meristem formation by downregulating boundary genes (CUC1, CUC2, CLV3) and promoting fungal colonization, essential for seedling establishment. Paphiopedilum, possess high horticultural and conservational value. Asymbiotic germination is a common propagation method, but high rates of protocorm developmental arrest hinder seedling establishment. Our study found that the key difference between normally developing protocorm (NDP) and arrested developmental protocorm (ADP) is their capability for continuous cell differentiation. In ADP, cells divide without differentiating, with indole-3-acetic acid (IAA) levels being 20 times higher than that in NDP. This suggests that auxin level plays a role in protocorm cell fate determination. Exogenous application of NAA demonstrated that elevated auxin level can delay the formation of the shoot apical meristem (SAM) inside the protocorm. Gene expression analysis revealed that elevated auxin can inhibit or even halt the SAM formation through down-regulation of SAM-related genes such as CLV3, CUC1 and CUC2. High auxin levels also led to reduced cell wall rigidity by up-regulation of cell wall expanding protein (EXPB15), thereby creating ideal conditions for fungi entry. Inoculation with a compatible orchid mycorrhizal fungus (OMF) resulted in successful cell differentiation of ADP and eventually triggered the conversion of ADP to NDP. Since the protocorm is a distinct structure that facilitates the establishment of symbiotic associations with compatible OMF, we propose that the excessive auxin accumulation inside Paphiopedilum protocorm can pause the further development of protocorm and soften the cell wall. This strategy likely serves to enhance the attraction and colonization by OMFs in the native habitat of Paphiopedilum, facilitating essential symbiotic relationships necessary for their survival and growth.

Phalaenopsis pulcherrima are known for their captivating floral morphology and diverse colors, demonstrate exceptional resilience to adverse environmental conditions, and exhibit significant potential for hybrid breeding. However, current research on flower coloration is still limited. The data from this study indicates that variations in anthocyanin levels are the primary determinants of the difference between white and purple colors. Through RNA-seq, we identified 469 genes that were differentially expressed. Furthermore, our bioinformatics exploration uncovered two potential transcription factors, PpMYB1 and PpbHLH1, which play regulatory roles in anthocyanin accumulation. Y2H assays demonstrated that these two TFs could form heterodimers and interact with each other. Afterwards, transient expression assays were conducted for the first time in P. pulcherrima flowers, revealing that overexpression of PpMYB1 alone or in combination with PpbHLH1 resulted in purple petal pigmentation. Overexpressing PpMYB1 in tobacco resulted in more purple-colored corollas, stamens, pistils, and pods compared to control plants. Y1H and dual-luciferase assays provided further evidence that PpMYB1 and PpbHLH1 interact with the promoters of the structural genes PpF3H, PpDFR, and PpANS in the anthocyanin biosynthesis pathway, thereby driving their robust expression. This study not only enhances our understanding of the molecular mechanisms underlying anthocyanin synthesis but also holds significant practical implications for advancing plant hybrid breeding and genetic engineering applications in flower color regulation.

Paphiopedilum, a high ornamental orchid genus primarily found in tropical Asia and Pacific Islands (Cribb 1998; Liu et al. 2009), is valued for its vibrant flowers, long blooming period, and unique lip structures resembling sacs or helmets (Zhang et al. 2024). However, habitat destruction due to human activities has threatened its survival, leading to the inclusion of all wild species in the Convention on International Trade in Endangered Species Appendix I, which prohibits international trade (Zeng et al. 2012, 2013). Researchers at the South China Botanical Garden (SCBG) have developed more than 100 new Paphiopedilum cultivars, such as SCBG Xia, SCBG Lvfeicui, SCBG Zijun, Yu Yin, and Yuan Chun (Fan et al. 2023; Zhang et al. 2022), among others, to reduce overharvesting and promote sustainable utilization. These efforts reflect SCBG’s commitment to orchid conservation and align with sustainable horticultural practices.

Paphiopedilum orchids have a high ornamental value, and flower abundance is a key horticultural trait. Most Paphiopedilum plants exhibit weak tillering ability, with their tiller buds often entering a dormant state post-formation. Tiller production plays a crucial role in enhancing flower abundance and is potentially regulated by plant hormones. However, the effect of hormones on tillering in Paphiopedilum plants is still unclear. In this study, we investigated the promotion of tillering in P. callosum through exogenous root irrigation of benzylaminopurine (BAP). We observed a dose-dependent promotion of tiller production by BAP, with the strongest effect observed at a concentration of 400 mg/L. By comparing the expression of key genes in P. ‘SCBG Yingchun’ (with strong tiller ability) and P callosum (with weak tiller ability), we found that BAP promotes tillering by interacting with abscisic acid (ABA). This interaction involves down-regulation of the ABA degradation gene PcCYP707A, leading to a reduction in ABA content, and the subsequent down-regulation of dormancy-associated genes (PcDRMH1, PcSVP) to release bud dormancy. Additionally, BAP promotes sustained outgrowth of tiller buds by increasing the level of indole-3-acetic acid (IAA) through up-regulation of the IAA synthesis gene PcYUC2 and the transport gene PcPINIC. Our results indicated that the application of BAP promotes lateral bud outgrowth and increases tiller production in P. callosum. Through transcriptome analysis, we found that the BAP-promotion of tillering involves not only changes in endogenous IAA, ABA, and CTKs content but is also associated with the regulation of metabolism-related genes and dormancy-associated genes. This study presents the first comprehensive report of BAP-promoted tillering in P. callosum, providing a foundational basis for further mechanistic studies on tiller development in Paphiopedilum species and other non-model plants.

Gynura divaricata (L.) DC., a herb with economic, ecological, and medical importance, is widely cultivated in tropical and subtropical areas of Southeast Asia. G. divaricata can bloom and set seeds, but only a small number of seeds form and very few are viable, so seedlings are rarely employed for propagation purposes. In this study, callus and adventitious shoots were induced from leaves. Adventitious shoot propagation is reported for the first time for this species. The optimal medium for direct induction of adventitious shoots from leaf explants was Murashige and Skoog (MS) medium containing 4.0 mg L− 1 thidiazuron (TDZ), forming 7.78 adventitious shoot buds per explant. When 2.0 mg L− 1 TDZ and 0.5 mg L− 1 α-naphthaleneacetic acid (NAA) or 2.0 mg L− 1 6-benzyladenine (BA) and 0.5 mg L− 1 NAA were added to MS medium, callus was induced initially, followed by 9.78 or 8.87 adventitious shoot buds (per explant), which developed from callus. Adventitious shoots could not be induced by 2,4-dichlorophenoxyacetic acid, NAA or kinetin. The addition of L-ascorbic acid (AsA) to MS medium reduced the level of hyperhydricity of shoots and plantlets. The optimal medium for shoot proliferation was MS medium with 4.0 mg L− 1 BA and 50 mg L− 1 AsA. Optimal rooting of G. divaricata was achieved on MS medium with 0.5 mg L− 1 indole-3-butyric acid, with 97.33

Background: Collabieae is a medium-sized group within the orchid subfamily Epidendroideae that is distributed primarily across tropical Asia. Most Collabieae species are known for their considerable ornamental and medicinal merits. However, habitat destruction and overharvesting have led to severe decline in their wild populations. Chloroplast (cp) genomes are highly valued in evolutionary studies, due to comparative conservation and accumulation of genomic variations. Elucidating the structure of chloroplast genome is instrumental in conserving genetic diversity within the Collabieae. Methods: we explored the chloroplast genome characteristics of Collabieae. We incorporated three newly sequenced genomes from species (Acanthophippium sylhetense, Eriodes barbata, and Spathoglottis plicata), along with seven related species. Results: all analyzed cp genomes displayed a typical quadripartite circular structure. The total lengths ranged from 157,036 bp to 158,321 bp. Each genome contained 136 genes: 88 protein-coding genes, 38 tRNA genes, eight rRNA genes, and two pseudogenes. Across the ten Collabieae species, gene number, order, orientation, GC content, and codon usage bias were highly consistent, indicative of strong sequence conservation. However, notable structural divergence was observed at the plastome junctions, alongside variations in SSR and repetitive element frequencies. Moreover, six hypervariable regions were identified. Noncoding regions exhibited higher variability compared to protein-coding regions. Phylogenetic analysis indicated that E. barbata forms a distinct, small branch sister to the rest of the Collabieae members. Genera Acanthophippium and Spathoglottis were sister to the remaining groups within the tribe. Conclusions: this overall phylogenetic framework aligns well with previous findings. Our study provides valuable cp genomic resources and advances evolutionary research in Collabieae.

Callicarpa is an important medicinal plant in China,which has hemostatic,antibacterial,and antioxidant pharmacological effects,and the efficacy of astringing and arresting bleeding,clearing heat and detoxification,activating blood,and resolving stasis is outstanding.At the same time,Callicarpa can be used as an ornamental plant because of its gorgeous flowers and fruits.Callicarpa has good market development prospects,but the long seed reproduction cycle directly limits the large demand for seedlings in its industrial development.Asexual reproduction technology is the basis for the industrialization development of Callicarpa,which is helpful in producing high-quality seedlings and medicinal materials.Although Chinese and foreign scholars have achieved remarkable results in the study of asexual reproduction of Callicarpa,there is no report on the large-scale production of seedlings of Callicarpa.Integrating and improving its asexual reproduction technology can promote the development and utilization of Callicarpa,improve its medicinal value,and create significant economic benefits.Therefore,the authors reviewed the effects of cutting,season,plant growth regulators,substrates,environment,and management measures on the cutting of Callicarpa and the research progress of tissue culture propagation affected by explants,basic media,exogenous additives,subculture cycles,culture conditions,and transplanting substrates.The mechanism of adventitious root formation was reviewed at the cellular,physiological,and biochemical levels,so as to put forward the problems and corresponding solutions in the study of asexual propagation technology and regulatory mechanism of Callicarpa and point out the future research directions.The study aims to provide a reference for in-depth research on the asexual propagation technology of Callicarpa and the commercial production of its high-quality seedlings.

Aquilaria sinensis (Lour.) Spreng. is an economically important tree specie that produces agarwood, a valuable medicinal and aromatic resin, when injured. However, its large-scale cultivation has led to confusion regarding its resources and genetic backgrounds, hindering the conservation and management of A. sinensis accessions. This study systematically developed and validated simple sequence repeat (SSR) molecular markers by using whole-genome resequencing (WGR) data from 60 A. sinensis accessions to elucidate their genetic diversity and population structure. A total of 56,657 SSR sequences (24,430 loci) were identified, which were dominated with dinucleotide repeat motifs (73.59%). After stringent quality control, 46 high-quality SSR loci were obtained, and 93 primer pairs were designed for amplification validation. Ultimately, 20 primer pairs with stable amplification and high polymorphism were selected, of which 11 exhibited high polymorphism (polymorphic information content: 0.554-0.688). These 20 primer pairs identified a total of 121 alleles, with an average of 6 alleles per locus. These primers successfully classified 149 A. sinensis accessions into three subpopulations, achieving a discrimination rate of 95.97%. The analysis of molecular variance revealed that genetic variation within the individuals accounted for 84% of the total variation. This study establishes a rapid and efficient SSR-based method by leveraging resequencing data for large-scale marker discovery in A. sinensis. It further provides a robust technical framework for the conservation and sustainable utilization of this valuable species.

Hippeastrum (Amaryllis) is a bulbous plant valued for its large, showy flowers and distinctive floral morphology. To achieve year-round flowering, Hippeastrum bulbs are typically subjected to low-temperature treatment. However, the physiological and molecular mechanisms underlying this process are still not well understood. In this study, we exposed Hippeastrum 'Alfresco' bulbs to low-temperature treatment (10 °C) for different durations (0, 15, 30, 45, and 60 days) before they were planted in a greenhouse. The results revealed that low-temperature treatment advanced flowering phenology; however, floral bud differentiation occurred before low-temperature treatment. Among all the treatments, 45 days of low-temperature exposure most effectively accelerated scape elongation and flowering and extended the ornamental period. Analysis of non-structural carbohydrates (NSCs) revealed that a 45-day low temperature induced starch breakdown and increased soluble sugars at cylindrical scales. Spatiotemporal analysis of NSCs in the basal plate, cylindrical scales and semicyclic scales of bulbs treated for 45 days revealed significant depletion of starch, sucrose, and fructose accompanied by glucose accumulation during scape elongation. Transcriptome analysis identified a significant enrichment of genes involved in starch and sucrose metabolism in the basal plate during the scape elongation, especially HpSUS1 and HpFRK1. qRT-PCR analysis, which is consistent with the enzyme activity results, confirmed increased expression levels of HpSUS1 and HpFRK1 during scape elongation, which coincides with sucrose depletion in the semicyclic scales adjacent to developing floral buds. To further validate the role of sugars, bulbs treated at 10 °C for 45 days were grown hydroponically and supplemented with sucrose and glucose, resulting in increased flower longevity. Collectively, these findings demonstrate that low temperature influences NSC metabolism through the coordinated activity of HpSUS1 and HpFRK1, which mediate temperature-dependent floral regulation in Hippeastrum. This study provides fundamental insights into ornamental crop physiology and practical strategies for optimizing floral traits.

Background The orchids of the subtribe Coelogyninae are among the most morphologically diverse and economically important groups within the subfamily Epidendroideae. Previous molecular studies have revealed that Coelogyninae is an unambiguously monophyletic group. However, intergeneric and infrageneric relationships within Coelogyninae are largely unresolved. There has been long controversy over the classification among the genera within the subtribe. Results The complete chloroplast (cp.) genomes of 15 species in the subtribe Coelogyninae were newly sequenced and assembled. Together with nine available cp. genomes in GenBank from representative clades of the subtribe, we compared and elucidated the characteristics of 24 Coelogyninae cp. genomes. The results showed that all cp. genomes shared highly conserved structure and contained 135 genes arranged in the same order, including 89 protein-coding genes, 38 tRNAs, and eight rRNAs. Nevertheless, structural variations in relation to particular genes at the IR/SC boundary regions were identified. The diversification pattern of the cp. genomes showed high consistency with the phylogenetic placement of Coelogyninae. The number of different types of SSRs and long repeats exhibited significant differences in the 24 Coelogyninae cp. genomes, wherein mononucleotide repeats (A/T), and palindromic repeats were the most abundant. Four mutation hotspot regions ( ycf1a , ndhF-rp132 , psaC-ndhE , and rp132-trnL ) were determined, which could serve as effective molecular markers. Selection pressure analysis revealed that three genes ( ycf1a , rpoC2 and ycf2 genes) might have experienced apparent positive selection during the evolution. Using the alignments of whole cp. genomes and protein-coding sequences, this study presents a well-resolved phylogenetic framework of Coelogyninae. Conclusion The inclusion of 55 plastid genome data from a nearly complete generic-level sampling provide a comprehensive view of the phylogenetic relationships among genera and species in subtribe Coelogyninae and illustrate the diverse genetic variation patterns of plastid genomes in this species-rich plant group. The inferred relationships and informally recognized major clades within the subtribe are presented. The genetic markers identified here will facilitate future studies on the genetics and phylogeny of subtribe Coelogyninae.

Soil salinity, a major environmental stress, restricts agricultural production worldwide. Gynura divaricata (L.) DC. is widely cultivated on tropical islands in China and has both edible and medicinal value. NaCl stress and growth indicators, antioxidant enzyme activity, as well as MDA, proline, and soluble sugar content, were determined. Based on the transcriptomic data of tissue-cultured G. divaricata plantlets grown in control (0 mM NaCl) and salt stress (50 and 200 mM NaCl) conditions, gene expression patterns were examined. KEGG enrichment analysis of differentially expressed genes indicated significant enrichment of plant hormone signaling, MAPK signaling, and starch and sucrose metabolism pathways. These findings allowed key biological pathways and salt stress-responsive genes to be identified, thus providing a molecular basis for breeding salt-tolerant G. divaricata varieties. This transcriptomic analysis revealed a complex tolerance mechanism of G. divaricata in response to NaCl, laying a foundation for screening and cloning key genes related to NaCl tolerance and studying their interactions. These findings would allow the molecular basis of NaCl tolerance to be explored, with the aim of breeding NaCl-tolerant varieties.

Platycerium wallichii Hook is a rare and endangered tropical epiphytic fern with ornamental and medicinal value. It is usually propagated by spore germination to produce sporophytes. This study established an in vitro protocols for spore germination, leading to filament formation and development of prothallia, and finally development of sporophytes following fertilization. The prothallia could be proliferated by 8.7 time within 30 days. The development of archegonia and antheridia on prothallia was asynchronous and prothallia were mainly dioecious (over 90

MeFtsZ2-1 is a key gene for plant plastid division, but the mechanism by which MeFtsZ2-1 affects pigment accumulation in cassava ( Manihot esculenta Crantz) through plastids remains unclear. We found that MeFtsZ2-1 overexpression in cassava (OE) exhibited darker colors of leaves, with increased levels of anthocyanins and carotenoids. Further observation via Transmission Electron Microscopy (TEM) revealed no apparent defects in chloroplast structure but an increase in the number of plastoglobule in OE leaves. RNA-seq results showed 1582 differentially expressed genes (DEGs) in leaves of OE. KEGG pathway analysis indicated that these DEGs were enriched in pathways related to flavonoid, anthocyanin, and carotenoid biosynthesis. This study reveals the role of MeFtsZ2-1 in cassava pigment accumulation from a physiological and transcriptomic perspective, providing a theoretical basis for improving cassava quality.

Phalaenopsis orchids, with their unique appearance and extended flowering period, are among the most commercially valuable Orchidaceae worldwide. Particularly, the variegation in leaf color of Phalaenopsis significantly enhances the ornamental and economic value and knowledge of the molecular mechanism of leaf-color variegation in Phalaenopsis is lacking. In this study, an integrative analysis of the physiology, cytology, and transcriptome profiles was performed on Phalaenopsis Chia E Yenlin Variegata leaves between the green region (GR) and yellow region (YR) within the same leaf. The total chlorophyll and carotenoid contents in the YR exhibited a marked decrease of 72.18% and 90.21%, respectively, relative to the GR. Examination of the ultrastructure showed that the chloroplasts of the YR were fewer and smaller and exhibited indistinct stromal lamellae, ruptured thylakoids, and irregularly arranged plastoglobuli. The transcriptome sequencing between the GR and YR led to a total of 3793 differentially expressed genes, consisting of 1769 upregulated genes and 2024 downregulated genes. Among these, the chlorophyll-biosynthesis-related genes HEMA, CHLH, CRD, and CAO showed downregulation, while the chlorophyll-degradation-related gene SGR had an upregulated expression in the YR. Plant-hormone-related genes and transcription factors MYBs (37), NACs (21), ERFs (20), bHLH (13), and GLK (2), with a significant difference, were also analyzed. Furthermore, qRT-PCR experiments validated the above results. The present work establishes a genetic foundation for future studies of leaf-pigment mutations and may help to improve the economic and breeding values of Phalaenopsis.

Bougainvillea, an evergreen climbing shrub of the Nyctaginaceae family, holds significant ornamental, economic, and medicinal value. Bougainvillea glabra ‘New River’ is widely used in landscapes due to its strong adaptability to the environment, abundance of flowers, and frequent flowering. Traditionally, Bougainvillea glabra ‘New River’ cultivation has relied on methods such as cuttings or grafting, with limited research on in vitro tissue culture propagation. This study aimed to optimize the tissue culture system, exploring a combination of plant growth regulators (PGRs) for Bougainvillea regeneration from in vitro stem segments. The Murashige and Skoog (MS) medium supplemented with indole-3-butyric acid (IBA), 6-benzylaminopurine (6-BA), and 1-naphthlcetic acid (NAA) was employed. The optimal sterilization of Bougainvillea stem segments involved a 30 s treatment with 75% alcohol and 10 min with 1% NaClO. The synergistic effect of 0.1 mg·L−1 of NAA and 2.5 mg·L−1 of 6-BA maximized the shoot sprouting frequency, while 2.5 mg·L−1 of 6-BA and 0.1 mg·L−1 of NAA produced the maximum shoots. Furthermore, 1.5 mg·L−1 of IBA and 0.1 mg·L−1 of NAA induced the highest rooting levels. This work demonstrates the successful adaptation of a greenhouse environment to efficiently regenerate plants in vitro from stem segments. This approach allows for the mass production of Bougainvillea glabra ‘New River’.

Tetrastigma hemsleyanum is a perennial evergreen vine of the Vitaceae. The entire herb is used in traditional Chinese medicine as a broad-spectrum plant-based antibiotic, so it has high economic and social value. Wild T. hemsleyanum resources are scarce, so it has been declared an endangered and rare medicinal plant. Seed yield is low and vegetative propagation by cuttings results in limited plant production, so development of the T. hemsleyanum industry requires optimized propagation protocols and the development of new biotechnologies to proliferate this plant in commercial quantities. In this study, shoot organogenesis was successfully induced from leaves and petioles. Two plant growth regulators, 6-benzyladenine (BA) and thidiazuron, induced callus and adventitious shoots, but the ideal adventitious shoot induction medium was Murashige and Skoog (MS) medium containing 1.0 mg L−1 BA and 0.1 mg L−1 α-naphthaleneacetic acid (NAA). This resulted in a shoot proliferation coefficient (SPC) of 6.73 within 30 d at a light intensity of 100 µmol m−2 s−1. When light intensity was increased from 50 to 200 µmol m−2 s−1, SPC (7.35), chlorophyll a (Chl a), Chl b, and total Chl (a + b) content increased. On MS medium containing 0.1–2.0 mg L−1 NAA or indole-3-butyric acid, 100

Camellia hainanica is one of the camellia plants distributed in tropical regions, and its regeneration system and genetic transformation are affected by callus browning. However, the underlying mechanism of Camellia hainanica callus browning formation remains largely unknown. To investigate the metabolic basis and molecular mechanism of the callus browning of Camellia hainanica, histological staining, high-throughput metabolomics, and transcriptomic assays were performed on calli with different browning degrees (T1, T2, and T3). The results of histological staining revealed that the brown callus cells had obvious lignification and accumulation of polyphenols. Widely targeted metabolomics revealed 1190 differentially accumulated metabolites (DAMs), with 53 DAMs annotated as phenylpropanoids and flavonoids. Comparative transcriptomics revealed differentially expressed genes (DEGs) of the T2 vs. T1 associated with the biosynthesis and regulation of flavonoids and transcription factors in Camellia hainanica. Among them, forty-four enzyme genes associated with flavonoid biosynthesis were identified, including phenylalaninase (PAL), 4-coumaroyl CoA ligase (4CL), naringenin via flavanone 3-hydroxylase (F3H), flavonol synthase (FLS), Chalcone synthase (CHS), Chalcone isomerase (CHI), hydroxycinnamoyl-CoA shikimate transferase (HCT), Dihydroflavonol reductase (DFR), anthocyanin reductase (LAR), anthocyanin synthetase (ANS), and anthocyanin reductase (ANR). Related transcription factors R2R3-MYB, basic helix-loop-helix (bHLH), and WRKY genes also presented different expression patterns in T2 vs. T1. These results indicate that the browning of calli in Camellia hainanica is regulated at both the transcriptional and metabolic levels. The oxidation of flavonoids and the regulation of related structural genes and transcription factors are crucial decisive factors. This study preliminarily revealed the molecular mechanism of the browning of the callus of Camellia hainanensis, and the results can provide a reference for the anti-browning culture of Camellia hainanica callus.