Taxodin A, a Cytotoxic C30 Terpenoid from Taxodium mucronatum with a Unique Skeleton.

Taxodin A (1), a unique C30 terpenoid featuring an unprecedented skeleton composed of an abietane-type diterpene and a menthane-type monoterpene, was obtained from the leaves and branches of Taxodium mucronatum. The structure and absolute configuration of compound 1 was unequivocally established by the combination of extensive spectroscopic analyses and X-ray single-crystal diffraction analysis. Compound 1 exhibited potent cytotoxic activities against A549, SMMC-7721, MDA-MB-231, and SW480 cell lines with IC50 values of 15.35±0.73, 8.49±0.35, 17.53±0.79, 18.93±0.60 µM, respectively.

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.

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'.

Reconstrucción de precipitación y temperatura con anillos de crecimiento anual del ciprés Taxodium mucronatum (Taxodiaceae) en Coahuila, México / Reconstruction of precipitation and temperature with annual growth rings of the cypress Taxodium mucronatum (Taxodiaceae) in Coahuila, Mexico

Introducción: La determinación del clima en cuencas productoras de agua, como la del río Sabinas, Coahuila, donde no existe información de su variabilidad, se puede estimar mediante anillos de crecimiento de ahuehuete (Taxodium mucronatum Ten.), especie longeva con anillos bien definidos, presente en las zonas ribereñas, constituye un "proxy" o método indirecto de la variabilidad climática interanual y multianual. Objetivo: Desarrollar una reconstrucción estacional de precipitación y temperatura máxima y analizar la influencia que ejercen fenómenos de circulación global en el crecimiento de la especie. Métodos: Los núcleos de crecimiento de T. mucronatum fueron datados a través de técnicas dendrocronológicas para producir una serie de ancho de anillo. Se utilizaron datos de mallas del clima de dos bases de datos para desarrollar el análisis de la función de respuesta con fines de reconstrucción climática. Resultados: Una cronología de anillo total de 218 años (1808-2018) se desarrolló con especímenes de T. mucronatum en parajes del Río Sabinas, con la que se generó una reconstrucción estacional de precipitación abril-junio y de temperatura máxima junio-julio. El periodo detectado más seco se presentó de 1815 a 1818 con una precipitación de 27.39 mm y una temperatura máxima de 41.16 °C; mientras que el año más húmedo fue 1828 con 393.72 mm. La cronología de anillo total se correlacionó con los índices de sequía SPEI y PDSI, y con índices de fenómenos atmosféricos como El Niño Oscilación del Sur, a través del Índice de Oscilación del Sur (SOI) y el índice Multivariado (MEI); Oscilación Decadal del Pacífico (PDO) y Oscilación Multidecadal del Atlántico (AMO). La relación entre el índice de anillo total y el del Índice Estandarizado de Precipitación Evaporación (SPEI) mostró significancia en el mes de junio (r = 0.52, P < 0.01), al igual que el Índice de Severidad de Sequía del Palmer (PDSI), PDSI anual (r = 0.38, P < 0.05). El SOI reconstruido noviembre-febrero, se asoció significativamente con la serie dendrocronológica (r = -0.41, P < 0.01). La Oscilación Decadal del Pacífico y la Oscilación Multidecadal del Atlántico, no mostraron significancia. Conclusiones: En este estudio, desarrollamos una función de respuesta climática y reconstruimos variables climáticas estacionales (precipitación, temperatura máxima) de importancia para desarrollar estrategias de manejo para la conservación de T. mucronatum en esta cuenca, e implementar acciones de mitigación para la presencia de eventos climáticos extremos que se pueden presentar en los próximos años.

Introduction: Dendroclimatic reconstructions in water-yield basins lacking hydroclimatic data, such as the Rio Sabinas is important to analyze its interannual and multiannual climatic variability. One of the species useful for this purpose is the Montezuma baldcypress (Taxodium mucronatum Ten.), a long-lived species with well-defined annual rings, present along the riparian zone of the Rio Sabinas that constitutes a "proxy" of interannual and multiannual climate variability. Objective: Develop a seasonal precipitation and maximum temperature reconstructions, and to analyze the influence of global circulatory modes on the species annual radial increase. Methods: Increment cores of the Montezuma baldcypress specimens were dated through dendrochronological techniques to produce a ring-width series. Climate gridded data from two databases were used to develop a response function analysis for climate reconstruction purposes. Results: A ring-width chronology extending from 1808 to 2018 (211 years) was developed and used to develop a seasonal April-June precipitation and a mean June-July maximum temperature reconstruction. The driest period detected on the rainfall reconstruction occurred from 1815 to 1818 with 27.4 mm and a maximum temperature of 41.2 °C; while the wettest year was 1828 with 393.72 mm. The ring-width chronology was correlated with the Standardized Precipitation Evaporation Index (SPEI) and the Palmer Drought Severity Index (PDSI), and with indices of atmospheric phenomena such as El Niño Southern Oscillation (ENSO), through the Southern Oscillation Index (SOI) and the Multivariate Index (MEI); Pacific Decadal Oscillation (PDO), and the Atlantic Multidecadal Oscillation (AMO). The relationship between the ring-width series and drought indices (SPEI, PDSI) was significant in June (r = 0.52, P < 0.01), and June-August (r = 0.38, P < 0.05) for the SPEI and reconstructed PDSI, respectively. It was found a significant association between the ring-width chronology and the reconstructed November-February SOI (r = -0.41, P < 0.01). The Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation were not significant. Conclusions: On this study, we developed a climatic response function and reconstructed seasonal climatic variables (precipitation, maximum temperature) of importance to develop management strategies for conservation of the Montezuma bald cypress on this basin, and to implement mitigation actions for the presence of extreme climatic events that may occur in coming years.

Effects of cadmium stress on the antioxidant system and chlorophyll fluorescence characteristics of two Taxodium clones.

KEY MESSAGE: The T.118 and T.406 seedlings showed strong adaptability under Cd concentrations ≤ 50 µM. The mechanisms of photoprotection in T.118 and T.406 differed in high-Cd concentrations. To explore the physiological response characteristics of Taxodium hybrids to cadmium (Cd) stress and provide basis for screening of Cd-tolerant species, the hydroponic cultivation of T.118 and T.406 seedlings was conducted to demonstrate the effects of Cd stress on seedling growth, antioxidant system, and chlorophyll fluorescence parameters. After 35 days of Cd stress at a concentration ≤ 50 µM, the dry weight biomass of the two clones did not significantly differ from that of the control. T.406 exhibited a significant increase in POD activity compared to T.118 and maintained high SOD activity after exposure to high concentrations of Cd, whereas MDA levels showed little changes. Under low-Cd stress, chlorophyll content and fluorescence parameters remained stable, especially for T.406. Under high-Cd concentration stress, the above parameters were lower than the control, with a more significant decrease in T.118 than in T.406. The non-photochemical quenching coefficient (NPQ) of both clones increased with increasing Cd concentration. T.118 showed a greater increase than T.406, particularly under high-Cd concentration stress. The T.118 and T.406 seedlings adapted to low-Cd concentration stress by enhancing their antioxidant enzyme activity to maintain the balance of reactive oxygen metabolism and reduce cellular damage. The photochemical activity of mesophyll cells remained high to maintain photosynthetic capacity and normal seedling growth. T.406 showed stronger resistance to Cd than T.118. T.406 prevented photodamage by promoting the photochemical utilization of the excitation energy and maintaining a strong antioxidant stress ability. Enhancement of heat dissipation capability may be the main photoprotection mechanism of T.118.

Taxodione induces apoptosis in BCR-ABL-positive cells through ROS generation.

Chronic myeloid leukemia (CML) and acute lymphoblastic leukemia (ALL) are hematopoietic malignancies caused by the constitutive activation of BCR-ABL tyrosine kinase. Although direct BCR-ABL inhibitors, such as imatinib, were initially successful in the treatment of leukemia, many patients developed drug resistance over time due to the gatekeeper mutation of BCR-ABL T315I. In the present study, we found that taxodione, a quinone methide diterpene isolated from Taxodium distichum, significantly induced apoptosis in human myelogenous leukemia-derived K562 cells, which were transformed by BCR-ABL. Taxodione reduced the activities of mitochondrial respiratory chain (MRC) complexes III and V, which appeared to induce the production of reactive oxygen species (ROS). N-acetylcysteine (NAC), an antioxidant agent, canceled taxodione-induced ROS production, reductions in MRC activities, particularly complex V, and apoptotic cell death. Furthermore, in K562 cells treated with taxodione, BCR-ABL and its major signaling molecules, such as STAT5 and Akt were sequestered in mitochondrial fraction, and their localization changes decrease their abilities to stimulate cell proliferation, suggesting that these actions seem to be a mechanism how taxodione functions as an anti-tumor drug. Strikingly, NAC canceled these taxodione-caused anti-cancer effects. Taxodione induced apoptosis in transformed Ba/F3 cells induced not only by BCR-ABL, but also T315I-mutated BCR-ABL through the generation of ROS. Collectively, the present results suggest that in the treatment of leukemia, taxodione has potential as a compound with high efficacy to overcome BCR-ABL T315I mutation-mediated resistance in leukemia cells.

In vitro and in vivo antitumor effects of the diterpene-enriched extract from Taxodium ascendens through the mitochondrial-dependent apoptosis pathway.

Extracts and components of Taxodium ascendens Brongn, an excellent afforestation tree, have exhibited several activities, including antibacterial activity and inhibitory activity on carbonic anhydrase II. However, the anti-hepatocellular carcinoma (anti-HCC) activity of extracts from the leaves of T. ascendens (TALE) remains unclear. In the present study, six diterpenoid compounds were isolated from a TALE extract. Here, the pro-apoptotic activities and the molecular mechanisms of TALE and the compounds 1-6 on HepG2 and Hep3B HCC cells were evaluated. Results show that the TALE and compounds 1-6 were able to induce apoptosis in the HepG2 and Hep3B HCC cells, particularly ferruginol (3). Mechanistically, the application of TALE and ferruginol (3) resulted in a significant decrease in mitochondria membrane potential, which was coupled with an increase in the Bax/Bcl-2 ratio and caspase-3/-9 activity. In vivo experiments showed that oral administration of TALE inhibited the proliferation of transplanted H22 cells in Kunming mice. However, TALE toxicity in KM mice was undetectable. The study provides strong evidence for the anti-HCC capacity of TALE.

Compositional and Enantiomeric Analysis of the Essential Oil of Taxodium distichum from India.

The leaf essential oil composition of Taxodium distichum L., collected from the foothills of Uttarakhand, India was analyzed using gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS) equipped with DB-5 (5% diphenyl-95% dimethyl polysiloxane) and ß-cyclodextrin (6-tertiarybutyldimethylsiliyl-2,3-diethyl-ß-cyclodextrin) capillary columns. Seventeen constituents, representing 90.3 to 99.4% of composition were identified in the essential oils from different seasons, viz. spring, summer, rainy, autumn and winter. The essential oil composition was mainly dominated by monoterpene hydrocarbons, represented mainly by α-pinene (81.9-94.3%). Other constituents of the oil were myrcene (0.5-4.7%), ß-pinene (2.2-2.9%), limonene (0.5-1.5%), camphene (≤ 0.03-1.5%), and α-terpineol (upto 1.6%). Chiral analysis of T. distichum essential oil on an ethyl substituted ß-cyclodextrin capillary column revealed the presence of a-pinene in racemic form, with an enantiomeric ratio of 49.3% for (1R)-(+)- and 50.7% for (1S)-(-)-α-pinene.

Taxodione, a DNA-binding compound from Taxodium distichum L. (Rich.).

8-beta-Hydroxypimar-15-en-19-oic acid (1), taxodione (2), 6,7-dehydro-8-hydrotaxodone (3), quercetin-3-O-beta-D-glucopyranoside (4), and shikimic acid (5) were isolated from the leaves of Taxodium distichum L. (Rich.) for the first time. Previously reported compounds [beta-sitosterol (6), isorhamnetin (7), quercetin (8), isorhamnetin-3-O-alpha-arabinofuranoside (9), quercetin-3-O-a-arabinofuranoside (10)] have also been isolated. The activity of taxodione as an inhibitor for hepatic stellate cells was determined. The antitumour activity of 2, 3, and 5 using a DNA affinity probe was examined.

Taxodistines A and B, abietane-type diterpenes from Taxodium distichum.

Two new abietane-type diterpenes, taxodistines A (1) and B (2), have been isolated by the guidance of inhibitory effect of tubulin polymerization from the fruits of Taxodium distichum and the structures were elucidated by using 2D NMR data. Taxodistine B (2) showed inhibition of tubulin polymerization.

Natural biflavones as novel inhibitors of cathepsin B and K.

Cathepsin B and K, two important members in lysosomal proteases, involve in many serious human diseases, such as tumor and osteoporosis. In order to find their novel inhibitors, we performed the inhibition assays of cathepsin B and cathepsin K in vitro, randomly screened compounds from plants, and found six biflavones, named AMF1-5 and HIF, can potently inhibit cathepsin B and cathepsin K, especially AMF4 and HIF with IC(50) of 0.62 and 0.58 microM against cathepsin B. They are novel inhibitors for cathepsin B and K. Inhibition and flexible docking studies indicated that these biflavones are reversible inhibitors of cathepsin B, and their binding patterns and interaction modes with cathepsin B made them more specific to cathepsin B endopeptidase.