Molecular Mechanism of Different Rooting Capacity between Two Clones of Taxodium hybrid 'Zhongshanshan'.

The conifer Taxodium hybrid 'Zhongshanshan' (T. hybrid 'Zhongshanshan') is characterized by rapid growth, strong stress resistance, and high ornamental value and has significant potential for use in afforestation, landscaping, and wood production. The main method of propagating T. hybrid 'Zhongshanshan' is tender branch cutting, but the cutting rooting abilities of different T. hybrid 'Zhongshanshan' clones differ significantly. To explore the causes of rooting ability differences at a molecular level, we analyzed the transcriptome data of cutting base and root tissues of T. hybrid 'Zhongshanshan 149' with a rooting rate of less than 5% and T. hybrid 'Zhongshanshan 118' with rooting rate greater than 60%, at the developmental time points in this study. The results indicated that differentially expressed genes between the two clones were mainly associated with copper ion binding, peroxidase, and oxidoreductase activity, response to oxidative stress, phenylpropanoid and flavonoid biosynthesis, and plant hormone signal transduction, among others. The expression pattern of ThAP2 was different throughout the development of the adventitive roots of the two clone cuttings. Therefore, this gene was selected for further study. It was shown that ThAP2 was a nuclear-localized transcription factor and demonstrated a positive feedback effect on rooting in transgenic Nicotiana benthamiana cuttings. Thus, the results of this study explain the molecular mechanism of cutting rooting and provide candidate gene resources for developing genetic breeding strategies for optimizing superior clones of T. hybrid 'Zhongshanshan'.

Development of an UV-Resistant Multilayer Film with Enhanced Compatibility between Carboxymethyl Cellulose and Polylactic Acid via Incorporation of Tannin and Ferric Chloride.

Carboxymethyl cellulose (CMC) and polylactic acid (PLA) are recognized for their environmental friendliness. By merging them into a composite film, packaging solutions can be designed with good performance. Nonetheless, the inherent interface disparity between CMC and PLA poses a challenge, and there may be layer separation issues. This study introduces a straightforward approach to mitigate this challenge by incorporating tannin acid and ferric chloride in the fabrication of the CMC-PLA. The interlayer compatibility was improved by the in situ formation of a cohesive interface. The resulting CMC/TA-PLA/Fe multilayer film, devoid of any layer separation, exhibits exceptional mechanical strength, with a tensile strength exceeding 70 MPa, a high contact angle of 105°, and superior thermal stability. Furthermore, the CMC/TA-PLA/Fe film demonstrates remarkable efficacy in blocking ultraviolet light, effectively minimizing the discoloration of various wood surfaces exposed to UV aging.

Extraction and In Vitro Skincare Effect Assessment of Polysaccharides Extract from the Roots of Abelmoschus manihot (L.).

Obtaining high-added value compounds from agricultural waste receives increasing attention, as it can both improve resource utilization efficiency and reduce waste generation. In this study, polysaccharides are extracted from the discarded roots of Abelmoschus manihot (L.) by the high-efficiency ultrasound-assisted extraction (UAE). The optimized condition was determined as solid-liquid ratio SL ratio = 1:20, temperature T = 30 °C and time T = 40 min, achieving an extraction yield of 13.41%. Composition analysis revealed that glucose (Glc, 44.65%), rhamnose (Rha, 26.30%), galacturonic acid (GalA, 12.50%) and galactose (Gal, 9.86%) are the major monosaccharides of the extract. The extract showed a low degree of esterification (DE) value of 40.95%, and its Fourier-transform infrared (FT-IR) spectrum exhibited several characteristic peaks of polysaccharides. Inspired by the wide cosmetic applications of polysaccharides, the skincare effect of the extract was evaluated via the moisture retention, total phenolic content (TPC) quantification, 2,2-Diphenyl-1-picrylhydrazyl (DPPH)-free radical scavenging activity, anti-hyaluronidase and anti-elastase activity experiments. The extract solutions demonstrated a 48 h moisture retention rate of 10.75%, which is superior to that of commercially available moisturizer hyaluronic acid (HA). Moreover, both the TPC value of 16.16 mg GAE/g (dw) and DPPH-free radical scavenging activity of 89.20% at the concentration of 2 mg/mL indicated the strong anti-oxidant properties of the extract. Furthermore, the anti-hyaluronidase activity and moderate anti-elastase activity were determined as 72.16% and 42.02%, respectively. In general, in vitro skincare effect experiments suggest moisturizing, anti-oxidant, anti-radical and anti-aging activities of the A. manihot root extract, indicating its potential applications in the cosmetic industry.

Physiological and transcriptional regulation in Taxodium hybrid 'Zhongshanshan' leaves in acclimation to prolonged partial submergence.

MAIN CONCLUSION: Taxodium 703 leaves activate fermentation, amino acids metabolism and ROS detoxification, and reduce TCA cycle and ABA biosynthesis in acclimation to prolonged partial submergence stress. Taxodium hybrid 'Zhongshanshan 703' (T. mucronatum × T. distichum; Taxodium 703) is a highly flooding-tolerant woody plant. To investigate the physiological and transcriptional regulatory mechanisms underlying its leaves in acclimation to long-term flooding, we exposed cuttings of Taxodium 703 to either non-flooding (control) or partial submergence for 2 months. The leaf tissues above (AL) and below (BL) flooding-water were separately harvested. Partial submergence decreased concentrations of chlorophyll (a + b) and dehydroascorbate (DHA) and lactate dehydrogenase (LDH) activity in AL, and reduced biomass, concentrations of succinic acid, fumaric acid and malic acid, and transcript levels of genes involved in tricarboxylic acid (TCA) cycle in BL. Under partial submergence, concentrations of starch, malondialdehyde and abscisic acid (ABA) decreased, and also mRNA levels of nine-cis-epoxycarotenoid dioxygenases that are involved in ABA biosynthesis in AL and BL of Taxodium 703. Partial submergence increased O2- content in AL, and improved concentrations of pyruvate and soluble sugars and activities of LDH and peroxidase in BL. In addition, partial submergence increased concentrations of ethanol, lactate, alanine, γ-aminobutyric acid, total amino acids and ascorbic acid (ASA), and ASA/DHA, activities of alcohol dehydrogenases (ADH) and ascorbate peroxidase, as well as transcript levels of ADH1A, ADH1B and genes involved in alanine biosynthesis and starch degradation in AL and BL of Taxodium 703. Overall, these results suggest that Taxodium 703 leaves activate fermentation, amino acids metabolism and reactive oxygen species detoxification, and maintain a steady supply of sugars, and reduce TCA cycle and ABA biosynthesis in acclimation to prolonged partial submergence stress.

Genome-Wide Identification and Characterization of NAC Family in Hibiscus hamabo Sieb. et Zucc. under Various Abiotic Stresses.

NAC transcription factor is one of the largest plant gene families, participating in the regulation of plant biological and abiotic stresses. In this study, 182 NAC proteins (HhNACs) were identified based on genomic datasets of Hibiscus hamabo Sieb. et Zucc (H. hamabo). These proteins were divided into 19 subfamilies based on their phylogenetic relationship, motif pattern, and gene structure analysis. Expression analysis with RNA-seq revealed that most HhNACs were expressed in response to drought and salt stress. Research of quantitative real-time PCR analysis of nine selected HhNACs supported the transcriptome data's dependability and suggested that HhNAC54 was significantly upregulated under multiple abiotic stresses. Overexpression of HhNAC54 in Arabidopsis thaliana (A. thaliana) significantly increased its tolerance to salt. This study provides a basis for a comprehensive analysis of NAC transcription factor and insight into the abiotic stress response mechanism in H. hamabo.

Transcriptome Analysis of Salt Stress in Hibiscus hamabo Sieb. et Zucc Based on Pacbio Full-Length Transcriptome Sequencing.

Hibiscus hamabo Sieb. et Zucc is an important semi-mangrove plant with great morphological features and strong salt resistance. In this study, by combining single molecule real time and next-generation sequencing technologies, we explored the transcriptomic changes in the roots of salt stressed H. hamabo. A total of 94,562 unigenes were obtained by clustering the same isoforms using the PacBio RSII platform, and 2269 differentially expressed genes were obtained under salt stress using the Illumina platform. There were 519 differentially expressed genes co-expressed at each treatment time point under salt stress, and these genes were found to be enriched in ion signal transduction and plant hormone signal transduction. We used Arabidopsis thaliana (L.) Heynh. transformation to confirm the function of the HhWRKY79 gene and discovered that overexpression enhanced salt tolerance. The full-length transcripts generated in this study provide a full characterization of the transcriptome of H. hamabo and may be useful in mining new salt stress-related genes specific to this species, while facilitating the understanding of the salt tolerance mechanisms.

Genome-wide Analysis of Basic Helix-Loop-Helix Family Genes and Expression Analysis in Response to Drought and Salt Stresses in Hibiscus hamabo Sieb. et Zucc.

The basic helix-loop-helix (bHLH) family of transcription factors is one of the most significant and biggest in plants. It is involved in the regulation of both growth and development, as well as stress response. Numerous members of the bHLH family have been found and characterized in woody plants in recent years. However, no systematic study of the bHLH gene family has been published for Hibiscus hamabo Sieb. et Zucc. In this research, we identified 162 bHLH proteins (HhbHLHs) from the genomic and transcriptomic datasets of H. hamabo, which were phylogenetically divided into 19 subfamilies. According to a gene structural study, the number of exon-introns in HhbHLHs varied between zero and seventeen. MEME research revealed that the majority of HhbHLH proteins contained three conserved motifs, 1, 4, and 5. The examination of promoter cis-elements revealed that the majority of HhbHLH genes had several cis-elements involved in plant growth and development and abiotic stress responses. In addition, the overexpression of HhbHLH2 increased salt and drought stress tolerance in Arabidopsis.

Comparative chloroplast genomics of the genus Taxodium.

BACKGROUND: Chloroplast (cp) genome information would facilitate the development and utilization of Taxodium resources. However, cp genome characteristics of Taxodium were poorly understood. RESULTS: We determined the complete cp genome sequences of T. distichum, T. mucronatum, and T. ascendens. The cp genomes are 131,947 bp to 132,613 bp in length, encode 120 genes with the same order, and lack typical inverted repeat (IR) regions. The longest small IR, a 282 bp trnQ-containing IR, were involved in the formation of isomers. Comparative analysis of the 3 cp genomes showed that 91.57% of the indels resulted in the periodic variation of tandem repeat (TR) motifs and 72.46% single nucleotide polymorphisms (SNPs) located closely to TRs, suggesting a relationship between TRs and mutational dynamics. Eleven hypervariable regions were identified as candidates for DNA barcode development. Hypothetical cp open reading frame 1(Ycf1) was the only one gene that has an indel in coding DNA sequence, and the indel is composed of a long TR. When extended to cupressophytes, ycf1 genes have undergone a universal insertion of TRs accompanied by extreme length expansion. Meanwhile, ycf1 also located in rearrangement endpoints of cupressophyte cp genomes. All these characteristics highlight the important role of repeats in the evolution of cp genomes. CONCLUSIONS: This study added new evidence for the role of repeats in the dynamics mechanism of cp genome mutation and rearrangement. Moreover, the information of TRs and hypervariable regions would provide reliable molecular resources for future research focusing on the infrageneric taxa identification, phylogenetic resolution, population structure and biodiversity for the genus Taxodium and Cupressophytes.

An Integrated Transcriptome and Proteome Analysis Reveals Putative Regulators of Adventitious Root Formation in Taxodium 'Zhongshanshan'.

Adventitious root (AR) formation from cuttings is the primary manner for the commercial vegetative propagation of trees. Cuttings is also the main method for the vegetative reproduction of Taxodium 'Zhongshanshan', while knowledge of the molecular mechanisms regulating the processes is limited. Here, we used mRNA sequencing and an isobaric tag for relative and absolute quantitation-based quantitative proteomic (iTRAQ) analysis to measure changes in gene and protein expression levels during AR formation in Taxodium 'Zhongshanshan'. Three comparison groups were established to represent the three developmental stages in the AR formation process. At the transcript level, 4743 genes showed an expression difference in the comparison groups as detected by RNA sequencing. At the protein level, 4005 proteins differed in their relative abundance levels, as indicated by the quantitative proteomic analysis. A comparison of the transcriptome and proteome data revealed regulatory aspects of metabolism during AR formation and development. In summary, hormonal signal transduction is different at different developmental stages during AR formation. Other factors related to carbohydrate and energy metabolism and protein degradation and some transcription factor activity levels, were also correlated with AR formation. Studying the identified genes and proteins will provide further insights into the molecular mechanisms controlling AR formation.

High-density genetic map construction and quantitative trait loci identification for growth traits in (Taxodium distichum var. distichum × T. mucronatum) × T. mucronatum.

BACKGROUND: 'Zhongshanshan' is the general designation for the superior interspecific hybrid clones of Taxodium species, which is widely grown for economic and ecological purposes in southern China. Growth is the priority objective in 'Zhongshanshan' tree improvement. A high-density linkage map is vital to efficiently identify key quantitative trait loci (QTLs) that affect growth. RESULTS: In total, 403.16 Gb of data, containing 2016,336 paired-end reads, was obtained after preprocessing. The average sequencing depth was 28.49 in T. distichum var. distichum, 25.18 in T. mucronatum, and 11.12 in each progeny. In total, 524,662 high-quality SLAFs were detected, of which 249,619 were polymorphic, and 6166 of the polymorphic markers met the requirements for use in constructing a genetic map. The final map harbored 6156 SLAF markers on 11 linkage groups, and was 1137.86 cM in length, with an average distance of 0.18 cM between adjacent markers. Separate QTL analyses of traits in different years by CIM detected 7 QTLs. While combining multiple-year data, 13 QTLs were detected by ICIM. 5 QTLs were repeatedly detected by the two methods, and among them, 3 significant QTLs (q6-2, q4-2 and q2-1) were detected in at least two traits. Bioinformatic analysis discoveried a gene annotated as a leucine-rich repeat receptor-like kinase gene within q4-2. CONCLUSIONS: This map is the most saturated one constructed in a Taxodiaceae species to date, and would provide useful information for future comparative mapping, genome assembly, and marker-assisted selection.

De novo sequencing, assembly, and analysis of the Taxodium 'Zhongshansa' roots and shoots transcriptome in response to short-term waterlogging.

BACKGROUND: Taxodium is renowned for its strong tolerance to waterlogging stress, thus it has great ecological and economic potential. However, the scant genomic resources in genus Taxodium have greatly hindered further exploration of its underlying flood-tolerance mechanism. Taxodium 'Zhongshansa' is an interspecies hybrid of T. distichum and T. mucronatum, and has been widely planted in southeastern China. To understand the genetic basis of its flood tolerance, we analyzed the transcriptomes of Taxodium 'Zhongshansa' roots and shoots in response to short-term waterlogging. RESULTS: RNA-seq was used to analyze genome-wide transcriptome changes of Taxodium 'Zhongshansa 406' clone root and shoot treated with 1 h of soil-waterlogging stress. After de novo assembly, 108,692 unigenes were achieved, and 70,260 (64.64%) of them were annotated. There were 2090 differentially expressed genes (DEGs) found in roots and 394 in shoots, with 174 shared by both of them, indicating that the aerial parts were also affected. Under waterlogging stress, the primary reaction of hypoxic-treated root was to activate the antioxidative defense system to prevent cells experiencing reactive oxygen species (ROS) poisoning. As respiration was inhibited and ATP decreased, another quick coping mechanism was repressing the energy-consuming biosynthetic processes through the whole plant. The glycolysis and fermentation pathway was activated to maintain ATP production in the hypoxic root. Constantly, the demand for carbohydrates increased, and carbohydrate metabolism were accumulated in the root as well as the shoot, possibly indicating that systemic communications between waterlogged and non-waterlogged tissues facilated survival. Amino acid metabolism was also greatly influenced, with down-regulation of genes involvedin serine degradation and up-regulation of aspartic acid degradation. Additionally, a non-symbiotic hemoglobin class 1 gene was up-regulated, which may also help the ATP production. Moreover, the gene expression pattern of 5 unigenes involving in the glycolysis pathway revealed by qRT-PCR confirmed the RNA-Seq data. CONCLUSIONS: We conclude that ROS detoxification and energy maintenance were the primary coping mechanisms of 'Zhongshansa' in surviving oxygen deficiency, which may be responsible for its remarkable waterlogging tolerance. Our study not only provided the first large-scale assessment of genomic resources of Taxodium but also guidelines for probing the molecular mechanism underlying 'Zhongshansa' waterlogging tolerance.

Response of underwater photosynthesis to light, CO2, temperature, and submergence time of Taxodium distichum, a flood-tolerant tree.

Introduction: Partial or complete submergence of trees can occur in natural wetlands during times of high waters, but the submergence events have increased in severity and frequency over the past decades. Taxodium distichum is well-known for its waterlogging tolerance, but there are also numerous observations of this species becoming partially or complete submerged for longer periods of time. Consequently, the aims of the present study were to characterize underwater net photosynthesis (PN) and leaf anatomy of T. distichum with time of submergence. Methods: We completely submerged 6 months old seedling of T. distichum and diagnosed underwater (PN), hydrophobicity, gas film thickness, Chlorophyll concentration and needles anatomy at discrete time points during a 30-day submergence event. We also constructed response curves of underwater PN to CO2, light and temperature. Results: During the 30-day submergence period, no growth or formation new leaves were observed, and therefore T. distichum shows a quiescence response to submergence. The hydrophobicity of the needles declined during the submergence event resulting in complete loss of gas films. However, the Chlorophyll concentration of the needles also declined significantly, and it was there not possible to identify the main cause of the corresponding significant decline in underwater PN. Nevertheless, even after 30 days of complete submergence, the needles still retained some capacity for underwater photosynthesis under optimal light and CO2 conditions. Discussion: However, to fully understand the stunning submergence tolerance of T. distichum, we propose that future research concentrate on unravelling the finer details in needle anatomy and biochemistry as these changes occur during submergence.

Integrated metabolomics and transcriptomics reveal that HhERF9 positively regulates salt tolerance in Hibiscus hamabo Siebold & Zuccarini.

Hibiscus hamabo Siebold & Zuccarini is one of the few semi-mangrove plants in the genus Hibiscus that can survive in saline-alkali soil and flooded land, but the mechanism underlying its adaptation to salt soil remains unknown. Here, to uncover this unsolved mystery, we characterized the changes in the accumulation of specific metabolites under salt stress in H. hamabo by integrating physiological, metabolic, and transcriptomic data, and found that osmotic adjustment and abscisic acid (ABA) is highly associated with the salt stress response. Further, a weighted gene co-expression network analysis was performed on the root transcriptome data, which identified three key candidate transcription factors responsive to salt stress. Among them, the expression HhERF9 was significantly upregulated under salt stress and ABA treatment and was involved in regulating the expression of genes related to the salt stress response. Further research indicated that HhERF9 enhances the accumulation of proline and soluble sugars by regulating the expression of genes such as NHX2 and P5CS. These findings provide a reference for improving H. hamabo through targeted genetic engineering and lay a theoretical foundation for its future promotion and cultivation in saline-alkali areas.

Molecular Mechanisms of Chlorophyll Deficiency in Ilex × attenuata 'Sunny Foster' Mutant.

Ilex × attenuata 'Sunny Foster' represents a yellow leaf mutant originating from I. × attenuata 'Foster#2', a popular ornamental woody cultivar. However, the molecular mechanisms underlying this leaf color mutation remain unclear. Using a comprehensive approach encompassing cytological, physiological, and transcriptomic methodologies, notable distinctions were discerned between the mutant specimen and its wild type. The mutant phenotype displayed aberrant chloroplast morphology, diminished chlorophyll content, heightened carotenoid/chlorophyll ratios, and a decelerated rate of plant development. Transcriptome analysis identified differentially expressed genes (DEGs) related to chlorophyll metabolism, carotenoid biosynthesis and photosynthesis. The up-regulation of CHLD and CHLI subunits leads to decreased magnesium chelatase activity, while the up-regulation of COX10 increases heme biosynthesis-both impair chlorophyll synthesis. Conversely, the down-regulation of HEMD hindered chlorophyll synthesis, and the up-regulation of SGR enhanced chlorophyll degradation, resulting in reduced chlorophyll content. Additionally, genes linked to carotenoid biosynthesis, flavonoid metabolism, and photosynthesis were significantly down-regulated. We also identified 311 putative differentially expressed transcription factors, including bHLHs and GLKs. These findings shed light on the molecular mechanisms underlying leaf color mutation in I. × attenuata 'Sunny Foster' and provide a substantial gene reservoir for enhancing leaf color through breeding techniques.

Integrated small RNA, transcriptome and physiological approaches provide insight into Taxodium hybrid 'Zhongshanshan' roots in acclimation to prolonged flooding.

Although Taxodium hybrid 'Zhongshanshan' 406 (Taxodium mucronatum Tenore × Taxodium distichum; Taxodium 406) is an extremely flooding-tolerant woody plant, the physiological and molecular mechanisms underlying acclimation of its roots to long-term flooding remain largely unknown. Thus, we exposed saplings of Taxodium 406 to either non-flooding (control) or flooding for 2 months. Flooding resulted in reduced root biomass, which is in line with lower concentrations of citrate, α-ketoglutaric acid, fumaric acid, malic acid and adenosine triphosphate (ATP) in Taxodium 406 roots. Flooding led to elevated activities of pyruvate decarboxylase, alcohol dehydrogenase and lactate dehydrogenase, which is consistent with higher lactate concentration in the roots of Taxodium 406. Flooding brought about stimulated activities of superoxide dismutase and catalase and elevated reduced glutathione (GSH) concentration and GSH/oxidized glutathione, which is in agreement with reduced concentrations of O2- and H2O2 in Taxodium 406 roots. The levels of starch, soluble protein, indole-3-acetic acid, gibberellin A4 and jasmonate were decreased, whereas the concentrations of glucose, total non-structural carbohydrates, most amino acids and 1-aminocyclopropane-1-carboxylate (ACC) were improved in the roots of flooding-treated Taxodium 406. Underlying these changes in growth and physiological characteristics, 12,420 mRNAs and 42 miRNAs were significantly differentially expressed, and 886 miRNA-mRNA pairs were identified in the roots of flooding-exposed Taxodium 406. For instance, 1-aminocyclopropane-1-carboxylate synthase 8 (ACS8) was a target of Th-miR162-3p and 1-aminocyclopropane-1-carboxylate oxidase 4 (ACO4) was a target of Th-miR166i, and the downregulation of Th-miR162-3p and Th-miR166i results in the upregulation of ACS8 and ACO4, probably bringing about higher ACC content in flooding-treated roots. Overall, these results indicate that differentially expressed mRNA and miRNAs are involved in regulating tricarboxylic acid cycle, ATP production, fermentation, and metabolism of carbohydrates, amino acids and phytohormones, as well as reactive oxygen species detoxification of Taxodium 406 roots. These processes play pivotal roles in acclimation to flooding stress. These results will improve our understanding of the molecular and physiological bases underlying woody plant flooding acclimation and provide valuable insights into breeding-flooding tolerant trees.

Effects of soil type and genotype on lead concentration in rootstalk vegetables and the selection of cultivars for food safety.

Lead (Pb) contamination of soil poses severe health risks to humans through vegetable consumption. The variations of Pb concentration in different parts of rootstalk vegetables (radish, carrot and potato) were investigated by using twelve cultivars grown in acidic Ferralsols and neutral Cambisols under two Pb treatments (125 mg kg(-1) and 250 mg kg(-1) for Ferralsols; 150 mg kg(-1) and 300 mg kg(-1) for Cambisols) in a pot experiment. The Pb concentration in edible parts was higher in Ferralsols under two Pb treatments, with range from 0.28 to 4.14, 0.42-10.66 mg kg(-1) (fresh weight) respectively, and all of them exceeded the food safety standard (0.1 mg kg(-1)) recommended by the Codex Alimentarius Commission of FAO and WHO. The Pb concentration in edible parts was significantly affected by genotype, soil type and the interaction between these two factors. The variation of Pb concentration in different cultivars was partially governed by Pb absorption and the transfer of Pb from aerial to edible part. The results revealed that caution should be paid to the cultivation of rootstalk vegetables in Pb-contaminated Ferralsols without any agronomic management to reduce Pb availability and plant uptake. For Cambisols with slight to moderate Pb contamination, growing potato cultivar Shandong No.1 and Chongqing No.1 was effective in reducing the risk of Pb entering human food chain. The results suggest the possibility of developing cultivar- and soil-specific planting and monitoring guidelines for the cultivation of rootstalk vegetables on slight to moderate Pb-contaminated soils.

Grafting Causes Physiological Changes and Promotes Adventitious Root Formation in Rejuvenated Soft Shoots of Taxodium hybrid 'Zhongshanshan'.

Taxodium hybrid 'Zhongshanshan' has been widely used as a timber tree in river network areas and coastal regions and is mainly propagated by cuttings. However, when trees age, their capacity to form adventitious roots becomes weaker. We successfully enhanced the rooting ability of shoots in T. hybrid 'Zhongshanshan 302' by their rejuvenation based on grafting. We recorded temporal variation in endogenous auxin, abscisic acid (ABA), gibberellins (GAs), trans-zeatin-riboside (TZR), soluble sugar and H2O2 after root induction. Auxin, soluble sugars and H2O2 levels were higher in rejuvenated shoots than in mature shoots, whereas the opposite was true for ABA and GAs. Notably, indole-3-acetic acid (IAA) and GA3 presented higher contents with more obvious differences in T. hybrid 'Zhongshanshan 302' rejuvenated shoots vs. mature shoots compared with other kinds of auxin and GAs. The evident improvement in the rooting ability of rejuvenated shoots after grafting likely resulted from the differential regulation of plant hormones, carbohydrates and redox signaling. In addition to the physiological basis of improved rooting ability by grafting, this study provided a theoretical basis for the optimization of subsequent propagation techniques in T. hybrid 'Zhongshanshan' and potentially other Taxodium spp.

ADH Gene Cloning and Identification of Flooding-Responsive Genes in Taxodium distichum (L.) Rich.

As a flooding-tolerant tree species, Taxodium distichum has been utilized in afforestation projects and proven to have important value in flooding areas. Alcohol dehydrogenase (ADH), which participates in ethanol fermentation, is essential for tolerance to the anaerobic conditions caused by flooding. In a comprehensive analysis of the ADH gene family in T. distichum, TdADHs were cloned on the basis of whole-genome sequencing, and then bioinformatic analysis, subcellular localization, and gene expression level analysis under flooding were conducted. The results show that the putative protein sequences of 15 cloned genes contained seven TdADHs and eight TdADH-like genes (one Class III ADH included) that were divided into five clades. All the sequences had an ADH_N domain, and except for TdADH-likeE2, all the other genes had an ADH_zinc_N domain. Moreover, the TdADHs in clades A, B, C, and D had a similar motif composition. Additionally, the number of TdADH amino acids ranged from 277 to 403, with an average of 370.13. Subcellular localization showed that, except for TdADH-likeD3, which was not expressed in the nucleus, the other genes were predominantly expressed in both the nucleus and cytosol. TdADH-likeC2 was significantly upregulated in all three organs (roots, stems, and leaves), and TdADHA3 was also highly upregulated under 24 h flooding treatment; the two genes might play key roles in ethanol fermentation and flooding tolerance. These findings offer a comprehensive understanding of TdADHs and could provide a foundation for the molecular breeding of T. distichum and current research on the molecular mechanisms driving flooding tolerance.

Transcriptomic and metabolomic analyses unveil the growth advantage mechanism conferred by heterosis of Michelia 'Zhongshanhanxiao'.

Michelia compressa (Maxim.) Sarg. is one of the important timber trees in Taiwan province, P. R. China. Michelia 'Zhongshanhanxiao' is a group of variants found among the progeny of M. compressa that exhibit higher growth rates compared with normal individuals, with a significantly increased stem diameter and height, as well as enlarged leaves and flowers. However, the molecular mechanisms fostering the growth advantage and morphological variations are unknown and deserve further study. Through analysing the transcriptome, metabolome and physiological processes of leaves, we identified remarkable differences in gene expression and metabolic profiles between Michelia 'Zhongshanhanxiao' and both the maternal M. compressa and its normal progeny. These differences were widely associated with a plant-pathogen interaction, phenylpropanoid biosynthesis, cyanoamino acid metabolism, carbon fixation in photosynthetic organisms and plant hormone signal transduction. Additionally, physiological measurements showed that Michelia 'Zhongshanhanxiao' possesses stronger photosynthetic capacity and higher plant hormone content. These results suggest that the heterosis of Michelia 'Zhongshanhanxiao' is regulated by candidates related to cell division, resistance to pathogens and the accumulation of organic compounds. The findings of this study provide crucial information on the molecular mechanisms underlying the growth advantages conferred by heterosis in trees.

The complete chloroplast genome sequence of Hibiscus coccineus.

Hibiscus coccineus is famous for its wide geographical distribution and the showy flowers of scarlet rose mallow. It belongs to the Malvaceae family and has greatly ornamental and ecological value. In this study, high-throughput sequencing and bioinformatics technology were used to assemble the complete chloroplast genome sequence, which will provide more genomic information for studying the genetic diversity and phylogenetic relationship. The full length of chloroplast genome is 160,280 bp, composed of a large single-copy (LSC) region of 89,121 bp, a small single-copy (SSC) region of 18,673 bp, and two inverted repeats (IRs) of 26,243 bp. A total of 113 genes were annotated, including 79 protein-coding genes, 30 tRNA, and four rRNA genes. Phylogenetic tree analysis revealed that the Hibiscus coccineus is closest to Hibiscus mutabilis in the Hibiscus L.