Designing Heterodiatomic Carbon Hydrangea Superstructures via Machine Learning-Regulated Solvent-Precursor Interactions for Superior Zinc Storage.

Carbon superstructures with exquisite morphologies and functionalities show appealing prospects in energy realms, but the systematic tailoring of their microstructures remains a perplexing topic. Here, hydrangea-shaped heterodiatomic carbon superstructures (CHS) are designed using a solution phase manufacturing route, wherein machine learning workflow is applied to screen precursor-matched solvent for optimizing solvent-precursor interaction. Based on the established solubility parameter model and molecular growth kinetics simulation, ethanol as the optimal solvent stimulates thermodynamic solubilization and growth of polymeric intermediates to evoke CHS. Featured with surface-active motifs and consecutive charge transfer paths, CHS allows high accessibility of zincophilic sites and fast ion migration with low energy barriers. A anion-cation hybrid charge storage mechanism of CHS cathode is disclosed, which entails physical alternate uptake of Zn2+/CF3SO3 - ions at electroactive sites and chemical bipedal redox of Zn2+ ions with carbonyl/pyridine motifs. Such a beneficial electrochemistry contributes to all-round improvement in Zn-ion storage, involving excellent capacities (231 mAh g-1 at 0.5 A g-1; 132 mAh g-1 at 50 A g-1), high energy density (152 Wh kg-1), and long-lasting cyclability (100 000 cycles). This work expands the design versatilities of superstructure materials and will accelerate experimental procedures during carbon manufacturing through machine learning in the future.

Regulation of blue infertile flower pigmentation by WD40 transcription factor HmWDR68 in Hydrangea macrophylla 'forever summer'.

BACKGROUND: WD40 transcription factors are crucial in plant growth and developmental, significantly impacting plant growth regulation. This study investigates the WD40 transcription factor HmWDR68's role in developing the distinctive blue infertile flower colors in Hydrangea macrophylla 'Forever Summer'. METHODS AND RESULTS: The HmWDR68 gene was isolated by PCR, revealing an open reading frame of 1026 base pairs, which encodes 341 amino acids. Characterized by four WD40 motifs, HmWDR68 is a member of the WD40 family. Phylogenetic analysis indicates that HmWDR68 shares high homology with PsWD40 in Camellia sinensis and CsWD40 in Paeonia suffruticosa, both of which are integral in anthocyanin synthesis regulation. Quantitative real-time PCR (qRT-PCR) analysis demonstrated that HmWDR68 expression in the blue infertile flowers of 'Forever Summer' hydrangea was significantly higher compared to other tissues and organs. Additionally, in various hydrangea varieties with differently colored infertile flowers, HmWDR68 expression was markedly elevated in comparison to other hydrangea varieties, correlating with the development of blue infertile flowers. Pearson correlation analysis revealed a significant association between HmWDR68 expression and the concentration of delphinidin 3-O-glucoside, as well as key genes involved in anthocyanin biosynthesis (HmF3H, HmC3'5'H, HmDFR, and HmANS) in the blue infertile flowers of 'Forever Summer' hydrangea (P < 0.01). CONCLUSION: These findings suggest HmWDR68 may specifically regulate blue infertile flower formation in hydrangea by enhancing delphinidin-3-O-glucoside synthesis, modulating expression of HmF3H, HmC3'5'H, HmDFR and HmANS. This study provides insights into HmWDR68's role in hydrangea's blue flowers development, offering a foundation for further research in this field.

Phyllodulcin from the hexane fraction of Hydrangea macrophylla inhibits glucose-induced lipid accumulation and reactive oxygen species generation in Caenorhabditis elegans.

We confirmed that the hexane layer of Hydrangea macrophylla leaf extract (HLH) is rich in phyllodulcin (PD), an alternative sweetener, through high performance liquid chromatography (HPLC) analysis. To investigate in vivo activity of HLH and its PD, acute toxicity and growth rate of Caenorhabditis elegans were tested and there are no clinical abnormalities at 125-500 µg/mL of HLH. HLH decreased the total lipid and triglyceride contents dose-dependently in glucose-induced obese worms. Also, HLH increased survival rates under oxidative and thermal stress and decreased body reactive oxygen species (ROS) contents significantly. Such antioxidant properties of HLH were attributed to the enhanced activity of the antioxidant enzyme catalase. To determine whether the effect of HLH was due to PD, worms were treated with PD (concentration contained in HLH), and inhibitory effects on total lipids and ROS were observed. Our results suggest that HLH and its PD as a natural alternative sweetener can be used as materials to improve metabolic diseases.

First Report of Botrytis cinerea Causing Stem Rot on Hydrangea macrophylla in China.

Hydrangea (Hydrangea macrophylla), commonly referred to as big leaf hydrangea, is a species within the Hydrangeaceae family notable for its ornamental value. Characterized by its vividly colored sepals and lush, striking inflorescences, this species is globally esteemed as both a potted and landscape plant. Notably, in 2022, an alarming incidence of stem rot was observed in approximately 40% of H. macrophylla plants aged between six and twelve months within 16 greenhouses situated in Nanjing City (N 31°14', E 118°22'), Jiangsu Province, China. Initial symptoms of the disease manifested as wet gray-black spots at the base of the seedlings and stems, progressing to a necrotic gray-white discoloration in the stems and accompanied by the growth of gray mold on the affected parts. This infection ultimately led to the wilting of the leaves and the death of the seedlings. For pathogen identification, stem tissues at the interface of diseased and healthy sections were excised, surface-sterilized with 75 % ethanol for 30 s, followed by a 2 - 3 min treatment with 3% sodium hypochlorite, and subsequently rinsed three times with sterile water before air drying. Sections measuring 2 - 3 mm were then cultured on potato dextrose agar (PDA) medium, supplemented with 50 mg/mL rifampicin (RFP), and incubated at 25 ℃ for 3 - 5 d (Zhou et al. 2022). Upon 2 - 3 days of incubation, notable growth of fungal colonies was observed. Mycelial clusters from the periphery of these colonies were subsequently transferred to fresh PDA plates and incubated at 25 ℃ for an additional 5 - 7 d. A particular colony, designated JSNJ2022-2 and now preserved at the Jiangsu Academy of Agricultural Sciences, was selected for detailed examination. This colony exhibited a flocculent texture, with a coloration ranging from grey-white to light brown. It was characterized by the presence of irregularly formed, hard sclerotia within the hyphae. The conidiophores were observed to be slender and erect, featuring dendritic branches at their extremities. The conidia were clustered on the conidiophore like grapes. These conidia were generally colorless or grey, oval in shape, smooth and transparent, and measured between 6.4 - 12.2 × 7.3 - 18.2 µm (n = 50). For genetic analysis, genomic DNA (gDNA) was extracted using the DNA secure Plant Kit (Tiangen Biotech, Beijing, China). Polymerase chain reaction (PCR) amplification was performed using a set of universal primers of ITS1/ITS4 (White et al. 1990), primers corresponding to the specific sequences of glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60), and DNA-dependent RNA polymerase subunit II (RPB2) (Yang et al. 2020). The resultant PCR products were sequenced, and the resulting sequences were submitted to the GenBank database, under the accession numbers OP131597, OP142320, OP142321, and OP142322, respectively. BLAST analysis of the sequences obtained from the isolate JSNJ2022-2 revealed a high degree of genetic similarity, ranging from 99 to 100%, with known sequences of Botrytis cinerea (accessions MK051124.1, MH796662.1, MH479931.1, and KU760986.1). To elucidate the phylogenetic position of the isolate, a phylogenetic tree was constructed using the maximum likelihood method, supported by 1,000 bootstrap replications, in the Mega7 software (Kumar et al. 2016). The results of this analysis confirmed that the strains under study clustered within the same branch as B. cinerea. To establish the pathogenicity of the isolate, Koch's postulates (Falkow 1988) were employed. Healthy potted H. macrophylla seedlings, approximately three months old, were wound inoculated at the base of the seedlings with a 6 mm diameter mycelium plug of JSNJ2002-2 cultivated on PDA for 3 days, which was subsequently covered with moistened degreasing cotton. Control plants were treated with moistened degreasing cloths minus the pathogen. Post-inoculation, these plants were placed in a growth chamber maintained at 25 ℃ with a relative humidity range of 60 - 80%. After a 3-d incubation period, the inoculated plants displayed symptoms identical to those initially observed in the greenhouse. The pathogen was successfully re-isolated from these inoculated plants and was morphologically re-confirmed as B. cinerea, thus satisfying the criteria of Koch's postulates. To our knowledge, this report represents the first documented incidence of B. cinerea causing stem rot in H. macrophylla in China.

First Reports of Cladosporium tenuissimum Causing Leaf spots on Hydrangea macrophylla in Anhui province in China.

Forever Summer Hydrangea (Hydrangea macrophylla) is a common flowering plant in the Yangtze River Valley area of China, and it is widely cultivated globally (Chen et al. 2015). In July 2023, H. macrophylla leaves exhibiting visible diseased lesions were reported in a nursery in Wuhu, Anhui Province, China. The incidence reached 40% in a 0.2 ha area. The primary disease symptom was multiple irregular necrotic spots (0.5 to 1 mm in diameter) appearing on the leaves. These spots on the leaves were faded yellow around the perimeter and grayish brown in the center.). 15 leaf samples were sterilized with 75% alcohol and rinsed three times in sterile distilled water, then transferred to antibiotic-added potato dextrose agar (PDA) for incubation at 27°C. The colonies were fluffy, flocculent, or hairy, dark green, gray-green to gray-brown in color, and spreading or protruding punctate with a colorless halo on PDA. The conidiophores were brown to dark brown, smooth or rough surface, mostly unbranched, clearly differentiated, erect or curved. The conidia displayed a light brown to brown hue, lemon shape, fusiform, elongated ellipsoid or others with obvious spore markings and spore umbilicus. Genomic DNA was extracted from fungal colonies on infected leaves of three collections separately (Braun et al. 2003) and the internal transcribed spacer regions (ITS), actin (ACT) genes and partial translation elongation factor-l-alpha (EF) were amplified and sequenced using the primers ITS1/4 (Yin et al. 2012), ACT-512F/ACT-783R and EF 1-728F/986R (Carbone and Kohn 1999), respectively. DNA sequences of isolates were identical and deposited in GenBank (accession no. OR362754 for ITS, OR611929 for ACT and PP209106 for EF). The consensus sequences from ITS, EF and ACT showed 100%, 98.98% and 100% identical to Cladosporium strains (accession no. OQ186140.1, MT154169.1 and OL322092.1), respectively. To confirm the pathogenicity of the isolates, hydrangeas were planted in 15-cm pots containing commercial potting mix (one plant/pot). Three healthy plants were inoculated at the five to eight leaf stage by spraying 50 µL of the isolate conidial suspension (4 × 106 spores/mL) on healthy leaves. Three plants treated with sterile distilled water were used as controls. After inoculation, all plants were placed in a humidity chamber (>95% relative humidity, 26°C) for 48 h and then transferred to a greenhouse at 22/27°C. All inoculated leaves exhibited symptoms similar to those observed in the nursery 10 days after inoculation, while no symptoms were observed for control leaves. The fungus was re-isolated and confirmed to be C. tenuissimum. Based on the above morphological characterization and molecular identification, the causal agent for this leaf spot disease was identified as C. tenuissimum. Although C. tenuissimum has been reported to cause disease on H. paniculata in northern China (Li et al.2021), this is the first time that C. tenuissimum has been found on H. macrophylla in southern China. This new disease of H. macrophylla caused by C. tenuissimum is a threat to urban greening and is worth further investigation.

Self-powered photochemical cathode aptamer sensor based on ZnIn2S4 photoanode and Cu2O@Ag@Ag3PO4 photocathode for the sensitive detection of Hg2.

A self-powered photoelectrochemical (PEC) aptamer sensor based on ZnIn2S4 as the photoanode and Cu2O@Ag@Ag3PO4 as the sensing cathode is designed for the detection of Hg2+. An indium tin oxide (ITO) electrode modified with ZnIn2S4 was used instead of a platinum (Pt) counter electrode to provide an obviously stable photocurrent signal. The suitable band gap width of ZnIn2S4 can generate photogenerated electrons well. The unique hydrangea structure of ZnIn2S4 can enhance light absorption and accelerate the separation and transfer of photocarriers. At the same time, Cu2O@Ag@Ag3PO4 with excellent electrical conductivity further enhances the photocurrent provided by the ZnIn2S4 photoanode. Because the reducing substances in the biological medium can change the photoanode characteristics of the photoanode interface, the separation of the photoanode and the sensing bicathode is beneficial to improve the anti-interference ability of the sensor. Under optimized conditions, the PEC aptamer sensor realizes the detection of Hg2+ (1 mM-1 fM), and the detection limit is 0.4 fM. In addition, the constructed self-powered PEC sensor has good selectivity, repeatability, and stability, which provides a new idea for the design of the PEC aptamer sensor platform.

Phylogenomics and historical biogeography of Hydrangeeae (Hydrangeaceae) elucidate the effects of geologic and climatic dynamics on diversification.

Demonstrating the process of transregional biogeography and mechanisms underlying evolutionary radiations is crucial to understanding biological evolution. Here, we use Hydrangeeae (Hydrangeaceae), a tribe with a unique disjunct distribution and complex trait variations, using a solid phylogenetic framework, to investigate how geographical and climatic factors interact with functional traits to trigger plant evolutionary radiations. We constructed the first highly supported and dated phylogenetic framework using 79 protein-coding genes obtained from 81 plastomes, representing 63 species and all major clades, and found that most extant species originated from asynchronous diversification of two lineages undergoing repeated expansion and retraction, at middle and high latitudes of the Northern Hemisphere between East Asia and North America, during the Eocene to Pleistocene (driven by geologic and climatic dynamics). In accordance with these drivers, interactions of flora between central-eastern China and Japan occurred frequently after the Late Tertiary. We found that resource limitation and range fragmentation probably accelerated the diversification of Hydrangeeae, which supports the resource-use hypothesis. Our study sheds light on the evolutionary radiation and assembly of flora within East Asia, and the East Asian-North American disjunction, through integration of phylogenomic and biogeographic data with functional trait and ecological data.

Dihydroisocoumarins of Hydrangea macrophylla var. thunbergia inhibit binding of the SARS-CoV-2 spike protein to ACE2.

Binding of the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to the cognate angiotensin-converting enzyme 2 (ACE2) receptor is the initial step in the viral infection process. In this study, we screened an in-house extract library to identify food materials with inhibitory activity against this binding using enzyme-linked immunosorbent assays and attempted to ascertain their active constituents. Hydrangea macrophylla var. thunbergia leaves were identified as candidate materials. Its active compounds were purified using conventional chromatographic methods and identified as naringenin, dihydroisocoumarins, hydrangenol, and phyllodulcin, which have affinities for the ACE2 receptor and inhibit ACE2 receptor-spike S1 binding. Given that boiled water extracts of H. macrophylla leaves are commonly consumed as sweet tea in Japan, we speculated that this tea could be used as a potential natural resource to reduce the risk of SARS-CoV-2 infection.

Production of Dihydroisocoumarins by Callus Induction from Hydrangea macrophylla var. thunbergii Leaves.

Dihydroisocoumarins, hydrangenol 8-O-ß-D-glucopyranoside (1), phyllodulcin 8-O-ß-D-glucopyranoside (2), hydrangenol (3), and phyllodulcin (4), are well-known as the major secondary metabolites in the leaves of Hydrangea macrophylla var. thunbergii. Dihydroisocoumarins are pharmaceutical compounds with diverse bioactivity. Although dihydroisocoumarins are commonly isolated from Hydrangea plants or via organic chemical synthesis, their production via callus induction is considered a promising alternative. In the present study, callus induction and proliferation of H. macrophylla var. thunbergii, and constituents 1-4 were quantified in calluses cultured in 17 different media. We found that the combination of the phytohormones 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BA) was useful for callus proliferation in H. macrophylla var. thunbergii. The balance and concentrations of indole-3-acetic acid (IAA) and BA greatly affected the contents of 1-4. Particularly, 1 (2.03-3.46% yield from the dry callus) was successfully produced from the callus induced by IAA (0.5 mg/L) and BA (1.0 mg/L) at yields comparable to isolated yields from plants. To the best of our knowledge, this is the first study to show that the calluses of H. macrophylla var. thunbergii contained 1. These findings may be useful for producing bioactive dihydroisocoumarins.

Comparison of Growth in Hydrangea macrophylla var. thunbergii Grown in Different Soil pH and Quantitative Analysis of Its Sweetness-Related Constituents.

Dried and fermented (processed) leaves of Hydrangea macrophylla Seringe var. thunbergii Makino (Hydrangeae Dulcis Folium) are currently used as a crude drug with a sweet taste for diabetic patients and as an oral refrigerant. The sweet taste of this crude drug is primarily attributed to phyllodulcin. However, there are currently no standards for the cultivation of H. macrophylla var. thunbergii and the isolation and production of the primary constituents of this crude drug. In the present study, we prepared five types of soils with different pH values (pH 7.5-5.0) and investigated the effects of these soils on the growth of this plant. The contents of phyllodulcin and its glycoside, phyllodulcin 8-O-ß-D-glucopyranoside, in the leaves of plants grown in these soils were quantified. Furthermore, the correlation between the sweetness of Hydrangeae Dulcis Folium and phyllodulcin was investigated. The results showed that soils with pH ranging from 7.0 to 5.5 was not only suitable for plant growth but also increased the content of phyllodulcin and phyllodulcin 8-O-ß-D-glucopyranoside in the leaves. Altogether, these findings could be useful for the development of high-quality Hydrangeae Dulcis Folium.

Evaluation of Hydrangea Cultivars for Tolerance Against Root Rot Caused by Fusarium oxysporum.

Root rot caused by Fusarium oxysporum Schltdl. is a newly identified disease in oakleaf hydrangea. Some cultivars such as Pee Wee and Queen of Hearts grown in pot-in-pot container systems showed root rot symptoms after late spring frost in May 2018 with 40 and 60% incidence in the infected nursery, respectively. This experiment was carried out to evaluate the tolerance among different hydrangea cultivars against root rot caused by F. oxysporum. Fifteen hydrangea cultivars from four different species were selected, and rooted cuttings were prepared from new spring flushes. Twelve plants from each cultivar were transplanted in a 1-gallon pot. Half of transplanted plants (six single plants) were inoculated by drenching 150 ml of F. oxysporum conidial suspension to maintain the concentration of 1 × 106 conidia/ml. Half of the plants remain noninoculated (control) and were drenched with sterile water. After 4 months, root rot was assessed using a scale of 0 to 100% root area affected, and recovery of F. oxysporum was recorded by plating 1-cm root sections in Fusarium selective medium. Fusaric acid (FA) and mannitol were extracted from the roots of inoculated and noninoculated plants to see the effect and role on pathogenesis. Further, mannitol concentration was analyzed using absorption wavelength in a spectrophotometer, and FA was analyzed using high-performance liquid chromatography (HPLC). Results indicated that no cultivars were resistant to F. oxysporum. Cultivars from Hydrangea arborescens, H. macrophylla, and H. paniculata were more tolerant to F. oxysporum compared to cultivars from H. quercifolia. Among H. quercifolia, cultivars Snowflake, John Wayne, and Alice were more tolerant to F. oxysporum.

Identification and Chemical and Biological Management of Fusarium Root and Crown Rot Disease of Oakleaf Hydrangea.

Oakleaf hydrangea (Hydrangea quercifolia) is an important ornamental plant grown in Tennessee. In May 2018, after late spring frost, cultivars Pee Wee and Queen of Hearts showed root and crown rot symptoms and identification and management of the disease was a major concern. The objective of this research was to identify the causal organism of this disease and develop management recommendations for nursery growers. Isolates from the infected root and crown parts were subjected to microscopy, and the morphology of fungi resembled Fusarium. Molecular analysis was conducted by amplifying the internal transcribed spacer of ribosomal DNA, ß-tubulin, and translation elongation factor 1-α regions. Fusarium oxysporum was identified as a causal organism based on molecular analysis. A pathogenicity test was done to complete the Koch's postulates by drenching containerized oakleaf hydrangea with a conidial suspension. Experiments were conducted to evaluate different chemical fungicides and biological products with different rates for Fusarium root and crown rot management in container-grown Queen of Hearts. Plants were inoculated by drenching containerized oakleaf hydrangea with 150-ml conidial suspensions of F. oxysporum, maintaining the concentration of 1 × 106 conidia/ml. Root and crown rot were assessed using a scale of 0 to 100%. Recovery of F. oxysporum was recorded by plating root and crown sections. Chemical fungicides such as mefentrifluconazole (BAS75002F), the low rate (1.09 ml/liter) of difenoconazole + pydiflumetofen (Postiva), and the high rate (1.32 ml/liter) of isofetamid (Astun) and biopesticide were applied; the high rate (1.64 g/liter) of ningnanmycin (SP2700 WP) effectively reduced Fusarium root rot severity and pyraclostrobin effectively reduced Fusarium crown rot severity in both trials.

First Report of Xanthomonas hydrangeae Causing Leaf Spot on Oakleaf Hydrangea (Hydrangea quercifolia) in Tuscany (Italy).

Hydrangeas (Hydrangea L.) are popular ornamental plants used in urban landscapes and gardens worldwide for the beauty of their large flowers. In June 2022, dark brown/purple and irregular water-soaked spots coalescing into large areas of necrosis were observed on the leaves of potted Hydrangea quercifolia Bartr. plants growing in two ornamentals nurseries in Pistoia, Tuscany, Italy. Isolations, using two symptomatic plants/nursery, were performed by excising small portions of leaf tissue from the margin of the lesions, and macerating them in 100 µl of sterile distilled water (SDW). After 15 min of incubation, a loopful of the resulting suspension was streaked on yeast extract-dextrose-CaCO3 agar (YDCA) amended with 60 mg L-1 cycloheximide. Mucoid, convex and yellow colonies appeared on YDCA after incubation at 28°C for 48h. After colony purification on yeast extract-nutrient-agar (YNA), two isolates from each nursery were subject to amplification and sequence analysis of the 16S rRNA using universal primers FD1/RD1, for genus identification (Vauterin et al. 2000; Weisburg et al. 1991). All 16S rRNA sequences (OP441051) were identical and BLASTn searches indicated that the isolates belong to the genus Xanthomonas [99.9% nucleotide identity with X. hydrangeae strain LMG 31885 (LR990741.1) and 99.8% with strain LMG 31884T (NR_181958.1)]. For classification at species level, fragments of the housekeeping genes gyrB, rpoD, dnaK, and fyuA, were amplified according to Young et al. (2008). Both strands were sequenced and the consensus sequences aligned using MUSCLE as implemented in MEGA X (Kumar et al. 2018). Homologous sequences were once again identical between the isolates. A neighbor joining phylogenetic analysis of the concatenated fragments, was carried out, using the Tuscan isolate HyQ-Tu1, the type/pathotype strains of the seven pathovars of X.hortorum, proposed by Morinière et al. (2020), the four X.hydrangeae strains characterized by Dia et al. (2021) and the type strain of X.populi as the outgroup. The analysis indicated that HyQ-Tu1 isolate clusters within the X. hydrangeae branch of the recently described X. hortorum - X. hydrangeae species complex (Morinière et al. 2020; Dia et al. 2021; 2022). In agreement with this result, isolates tested positive to the LAMP assay specific for members of the complex's clade C (X. hydrangeae) (Dia et al. 2022). Based on molecular evidence, the isolates were identified as X. hydrangeae (Dia et al. 2021; Oren and Garrity, 2022). Three healthy H. quercifolia potted plants were inoculated by rubbing a 10 µl droplet of a bacterial suspension of X. hydrangeae HyQ-Tu1 adjusted to an OD600 of 0.3 (approx. 108 CFU/ml) in SDW on the adaxial surface of two leaves per plant. Two control leaves/plant were inoculated with SDW. Each inoculated leaf was enclosed for 24h in a polyethylene bag and all plants were maintained in a greenhouse at 28°C. Nine days post inoculation (DPI), leaf spots similar to those observed on naturally infected plants started to become evident on the bacteria-inoculated leaves while control leaves remained asymptomatic throughout the trial (21 DPI). Koch's postulates were fulfilled by re-isolating the bacterium from the symptomatic tissues, obtaining a positive amplification with the clade C-specific LAMP assay (Dia et al. 2022), and confirming that the gyrB sequence was 100% identical to that of X. hydrangeae HyQ-Tu1. Housekeeping gene sequences were submitted to GenBank (OP456006-9). Members of the X. hortorum - X. hydrangeae species complex have been reported to affect H. quercifolia in the USA (Uddin et al. 1996) and H. quercifolia and H. arborescens L. in Belgium (Cottyn et al. 2021). To the best of our knowledge, this is the first documentation of X. hydrangeae causing disease on H. quercifolia in Italy. Further work is required to verify the presence of the bacterium in other European countries and to assess the economic impact that it causes within and outside nurseries.

Study on the Flower Induction Mechanism of Hydrangea macrophylla.

The flower induction of Hydrangea macrophylla "Endless Summer" is regulated by a complex gene network that involves multiple signaling pathways to ensure continuous flowering throughout the growing season, but the molecular determinants of flower induction are not yet clear. In this study, genes potentially involved in signaling pathway mediating the regulatory mechanism of flower induction were identified through the transcriptomic profiles, and a hypothetical model for this regulatory mechanism was obtained by an analysis of the available transcriptomic data, suggesting that sugar-, hormone-, and flowering-related genes participated in the flower induction process of H. macrophylla "Endless Summer". The expression profiles of the genes involved in the biosynthesis and metabolism of sugar showed that the beta-amylase gene BAM1 displayed a high expression level at the BS2 stage and implied the hydrolysis of starch. It may be a signaling molecule that promotes the transition from vegetative growth to reproductive growth in H. macrophylla "Endless Summer". Complex hormone regulatory networks involved in abscisic acid (ABA), auxin (IAA), zeatin nucleoside (ZR), and gibberellin (GA) also induced flower formation in H. macrophylla. ABA participated in flower induction by regulating flowering genes. The high content of IAA and the high expression level of the auxin influx carrier gene LAX5 at the BS2 stage suggested that the flow of auxin between sources and sinks in H. macrophylla is involved in the regulation of floral induction as a signal. In addition, flowering-related genes were mainly involved in the photoperiodic pathway, the aging pathway, and the gibberellin pathway. As a result, multiple pathways, including the photoperiodic pathway, the aging pathway, and the gibberellin pathway, which were mainly mediated by crosstalk between sugar and hormone signals, regulated the molecular network involved in flower induction in H. macrophylla "Endless Summer".

Comparative physiology and transcriptome analysis reveals that chloroplast development influences silver-white leaf color formation in Hydrangea macrophylla var. maculata.

BACKGROUND: Hydrangea macrophylla var. Maculata 'Yinbianxiuqiu' (YB) is an excellent plant species with beautiful flowers and leaves with silvery white edges. However, there are few reports on its leaf color characteristics and color formation mechanism. RESULTS: The present study compared the phenotypic, physiological and transcriptomic differences between YB and a full-green leaf mutant (YM) obtained from YB. The results showed that YB and YM had similar genetic backgrounds, but photosynthesis was reduced in YB. The contents of pigments were significantly decreased at the edges of YB leaves compared to YM leaves. The ultrastructure of chloroplasts in the YB leaves was irregular. Transcriptome profiling identified 7,023 differentially expressed genes between YB and YM. The expression levels of genes involved in photosynthesis, chloroplast development and division were different between YB and YM. Quantitative real-time PCR showed that the expression trends were generally consistent with the transcriptome data. CONCLUSIONS: Taken together, the formation of the silvery white leaf color of H. macrophylla var. maculata was primarily due to the abnormal development of chloroplasts. This study facilitates the molecular function analysis of key genes involved in chloroplast development and provides new insights into the molecular mechanisms involved in leaf coloration in H. macrophylla.

Physiological and metabolomics responses of Hydrangea macrophylla (Thunb.) Ser. and Hydrangea strigosa Rehd. to lead exposure.

Hydrangea is a potential remediation plant for lead (Pb) pollution. Plant roots communicate with soil through the release of root exudates. It is crucial to study rhizoremediation mechanisms to understand the response of root exudates to contamination stress. Here, we investigated the physiological responses and metabolomic profiling of two Hydrangea species, a horticultural cultivar (Hydrangea macrophylla (Thunb.) Ser.) and a wild type (Hydrangea strigosa Rehd.), under Pb-free and Pb-stressed conditions for 50 days. The results showed that Pb treatment adversely affected the biomass and root growth of the two species. H. strigosa was a Pb-tolerant species with higher superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities and more ascorbic acid (AsA) content in roots. Metabolomic profiling showed that 181 and 169 compounds were identified in H. macrophylla and H. strigosa root exudates, respectively, among which 18 showed significant differences between H. macrophylla and H. strigosa under Pb exposure. H. strigosa showed significantly (P < 0.05) higher secretion of sucrose, glycolic acid, and nonanoic acid than H. macrophylla after Pb treatment. Pb stress promoted fatty acid metabolism in H. strigosa, suppressed amino acid metabolism in H. macrophylla, and promoted a higher carbohydrate metabolism in H. strigosa compared with H. macrophylla. This study provides a possible mechanism for the high Pb absorption potential of Hydrangea.

First Report of Leaf Spot Caused by Alternaria tenuissima on Panicle Hydrangea (Hydrangea paniculata) in China.

Panicle hydrangea (Hydrangea paniculata), belonging to the Saxifragaceae family (Wu et al. 2001), is an ornamental flowering plant which is native to China and Japan. In July 2021, brown leaf spots (diameter ranged from 3 to 5 mm) were observed on panicle hydrangea plants in a 0.1 ha field of Northeast Agriculture University (126.72°E, 45.74°N), Heilongjiang Province. The incidence was approximately 30%. Small circular or irregular brown spots initially appeared on the older leaves, and these lesions gradually expanded with time. In some serious cases, lesions joint together and caused leaf wilting. To identify the causal agent, ten symptomatic leaves from different panicle hydrangea plants were collected, and surface sterilized with 70% ethanol for 30 s, followed by 0.5% NaClO treatment for 4 min, and then rinsed with sterile water three times. Tissues between healthy and necrotic area were cut into 5×5 mm pieces after air drying on sterile filter paper. The pieces were placed on potato dextrose agar (PDA) amended with streptomycin sulfate (50 mg/liter) and incubated at 25°C for 5 days. Fifteen pure isolates were obtained using the hyphal tip technique and cultured on PDA for 7 days at 25°C for morphological and molecular identification. Colonies of all isolates were dark olivaceous with white margin. Conidiophores were septate, singly arising, and light brown, with a size range of 10.2-60.1 × 1.4-5.6 µm (n=50). Conidia were obclavate to obpyriform, brown to dark brown, and in a size range of 15.0-25.2 × 5.1-15.3 µm (n=50). To further identify these isolates, four different genomic DNA regions including ribosomal DNA internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), RNA polymerase II second largest subunit (rpb2), and histone 3 (HIS3) were amplified and sequenced with primers ITS1/ITS4 (White et al. 1990), gpd1/gpd2 (Berbee et al. 1999), RPB2-5F2/RPB2-7R (Sung et al. 2007), and H3-1a/H3-1b (Xu et al. 2022) for three representative isolates (DXQ2-2, DXQ2-3, and DXQ2-4), respectively. The sequences of ITS, GADPH, rpb2, and HIS3 for these three isolates were identical and only sequences of DXQ2-2 were deposited in GenBank (GenBank accession nos. OL305828, OL333601, OL333602, and OL436242). These sequences showed 100%, 100%, 100%, and 99.61% identity with A. tenuissima BJ-CX-1 (GenBank accession nos. MK683974, MK683784, MK684069, and MK683879), respectively. Based on morphological features and DNA sequences analyses, these isolates were identified as Alternaria tenuissima (Simmons 2007). To fulfill Koch's postulates, ten healthy and surface disinfected leaves of one panicle hydrangea plant grown in pot were sprayed with a conidial suspension (1×106 conidia/mL) of isolate DXQ2-2. Meanwhile, ten surface disinfected leaves of another panicle hydrangea plant grown in pot sprayed with sterilize water served as the control. All plants were maintained in a greenhouse at 25℃ and 70% relative humidity. Five days after inoculation, leaves inoculated with conidial suspension showed leaf spot symptoms that were similar to those observed in the field, whereas no symptom was observed on the control leaves. The experiment was conducted twice. The Alternaria tenuissima isolate was successfully re-isolated from the symptomatic leaves and confirmed based on above morphological and molecular methods. To our knowledge, this is the first report of leaf spot on panicle hydrangea caused by A. tenuissima. Leaf spot has a negative effect on the aesthetic value of panicle hydrangea, so further investigation and management is needed to control this disease.

Comparative Transcriptome Analysis Unveils the Molecular Mechanism Underlying Sepal Colour Changes under Acidic pH Substratum in Hydrangea macrophylla

The hydrangea (Hydrangea macrophylla (Thunb). Ser.), an ornamental plant, has good marketing potential and is known for its capacity to change the colour of its inflorescence depending on the pH of the cultivation media. The molecular mechanisms causing these changes are still uncertain. In the present study, transcriptome and targeted metabolic profiling were used to identify molecular changes in the RNAome of hydrangea plants cultured at two different pH levels. De novo assembly yielded 186,477 unigenes. Transcriptomic datasets provided a comprehensive and systemic overview of the dynamic networks of the gene expression underlying flower colour formation in hydrangeas. Weighted analyses of gene co-expression network identified candidate genes and hub genes from the modules linked closely to the hyper accumulation of Al3+ during different stages of flower development. F3'5'H, ANS, FLS, CHS, UA3GT, CHI, DFR, and F3H were enhanced significantly in the modules. In addition, MYB, bHLH, PAL6, PAL9, and WD40 were identified as hub genes. Thus, a hypothesis elucidating the colour change in the flowers of Al3+-treated plants was established. This study identified many potential key regulators of flower pigmentation, providing novel insights into the molecular networks in hydrangea flowers.

Exploring the Molecular Mechanism of Sepal Formation in the Decorative Flowers of Hydrangea macrophylla 'Endless Summer' Based on the ABCDE Model.

With its large inflorescences and colorful flowers, Hydrangea macrophylla has been one of the most popular ornamental plants in recent years. However, the formation mechanism of its major ornamental part, the decorative floret sepals, is still not clear. In this study, we compared the transcriptome data of H. macrophylla 'Endless Summer' from the nutritional stage (BS1) to the blooming stage (BS5) and annotated them into the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases. The 347 identified differentially expressed genes (DEGs) associated with flower development were subjected to a trend analysis and a protein-protein interaction analysis. The combined analysis of the two yielded 60 DEGs, including four MADS-box transcription factors (HmSVP-1, HmSOC1, HmAP1-2, and HmAGL24-3) and genes with strong connectivity (HmLFY and HmUFO). In addition, 17 transcription factors related to the ABCDE model were screened, and key candidate genes related to the development of decorative floret sepals in H. macrophylla were identified by phylogenetic and expression pattern analysis, including HmAP1-1, HmAP1-2, HmAP1-3, HmAP2-3, HmAP2-4, and HmAP2-5. On this basis, a gene regulatory network model of decorative sepal development was also postulated. Our results provide a theoretical basis for the study of the formation mechanism of decorative floret sepals and suggest a new direction for the molecular breeding of H. macrophylla.

Separation of Dihydro-Isocoumarins and Dihydro-Stilbenoids from Hydrangea macrophylla ssp. serrata by Use of Counter-Current Chromatography.

Previously, different Hydrangea macrophylla ssp. serrata cultivars were investigated by untargeted LC-MS analysis. From this, a list of tentatively identified and unknown compounds that differ significantly between these cultivars was obtained. Due to the lack of reference compounds, especially for dihydro-isocoumarins, we aimed to isolate and structurally characterise these compounds from the cultivar 'Yae-no-amacha' using NMR and LC-MS methods. For purification and isolation, counter-current chromatography was used in combination with reversed-phase preparative HPLC as an orthogonal and enhanced purification workflow. Thirteen dihydro-isocoumarins in combination with other metabolites could be isolated and structurally identified. Particularly interesting was the clarification of dihydrostilbenoid glycosides, which were described for the first time in H. macrophylla ssp. serrata. These results will help us in further studies on the biological interpretation of our data.