GmMYB183, a R2R3-MYB Transcription Factor in Tamba Black Soybean (Glycine max. cv. Tamba), Conferred Aluminum Tolerance in Arabidopsis and Soybean.

Aluminum (Al) toxicity is one of the environmental stress factors that affects crop growth, development, and productivity. MYB transcription factors play crucial roles in responding to biotic or abiotic stresses. However, the roles of MYB transcription factors in Al tolerance have not been clearly elucidated. Here, we found that GmMYB183, a gene encoding a R2R3 MYB transcription factor, is involved in Al tolerance. Subcellular localization studies revealed that GmMYB183 protein is located in the nucleus, cytoplasm and cell membrane. Overexpression of GmMYB183 in Arabidopsis and soybean hairy roots enhanced plant tolerance towards Al stress compared to the wild type, with higher citrate secretion and less Al accumulation. Furthermore, we showed that GmMYB183 binds the GmMATE75 gene promoter encoding for a plasma-membrane-localized citrate transporter. Through a dual-luciferase reporter system and yeast one hybrid, the GmMYB183 protein was shown to directly activate the transcription of GmMATE75. Furthermore, the expression of GmMATE75 may depend on phosphorylation of Ser36 residues in GmMYB183 and two MYB sites in P3 segment of the GmMATE75 promoter. In conclusion, GmMYB183 conferred Al tolerance by promoting the secretion of citrate, which provides a scientific basis for further elucidating the mechanism of plant Al resistance.

Identification of MATE Family and Characterization of GmMATE13 and GmMATE75 in Soybean's Response to Aluminum Stress.

The multidrug and toxic compound extrusion (MATE) proteins are coding by a secondary transporter gene family, and have been identified to participate in the modulation of organic acid exudation for aluminum (Al) resistance. The soybean variety Glycine max "Tamba" (TBS) exhibits high Al tolerance. The expression patterns of MATE genes in response to Al stress in TBS and their specific functions in the context of Al stress remain elusive. In this study, 124 MATE genes were identified from the soybean genome. The RNA-Seq results revealed significant upregulation of GmMATE13 and GmMATE75 in TBS upon exposure to high-dose Al3+ treatment and both genes demonstrated sequence homology to citrate transporters of other plants. Subcellular localization showed that both proteins were located in the cell membrane. Transgenic complementation experiments of Arabidopsis mutants, atmate, with GmMATE13 or GmMATE75 genes enhanced the Al tolerance of the plant due to citrate secretion. Taken together, this study identified GmMATE13 and GmMATE75 as citrate transporter genes in TBS, which could improve citrate secretion and enhance Al tolerance. Our findings provide genetic resources for the development of plant varieties that are resistant to Al toxicity.

The formate dehydrogenase enhances aluminum tolerance of tobacco.

The formate dehydrogenase (FDH) is regarded as a universal stress protein involved in various plant abiotic stress responses. This study aims to ascertain GmFDH function in conferring tolerance to aluminum (Al) stress. The bioinformatics analysis demonstrates that GmFDH from Tamba black soybean (TBS) encodes FDH. Quantitative reverse transcription-PCR (qRT-PCR) showed that GmFDH expression was induced by Al stress with a concentration-time-specific pattern. Moreover, Al stress promotes formate content and activates FDH activity. Further studies revealed that GmFDH overexpression alleviated root growth of tobacco under Al stress inhibition and reduced Al and ROS accumulation in roots. In addition, transgenic tobacco had much more root citrate exudation and much higher activity of antioxidant enzymes than wild type. Moreover, under Al stress, NtMATE and NtALS3 expression showed no changes in wild type and overexpression lines, suggesting that here the known Al-resistant mechanisms are not involved. However citrate synthase activity is higher in transgenic tobaccos than that of wild type, which might be the reason for citrate secretion increase. Thus, the increased Al tolerance of GmFDH overexpression lines is likely attributable to enhanced activities of antioxidant enzymes and promoting citrate secretion. Taken together, our findings advance understanding of higher plant Al toxicity mechanisms and suggest a possible new route towards the improvement of plant growth under Al stress.

Anti-inflammation of isoliquiritigenin via the inhibition of NF-κB and MAPK in LPS-stimulated MAC-T cells.

BACKGROUND: The application of plant extracts has received great interest for the treatment of bovine mastitis. Isoliquiritigenin (ISL) is a rich dietary flavonoid that has significant antioxidative, anti-inflammatory and anticancer activities. This study was conducted to explore the protective efficacy and related mechanism of ISL against lipopolysaccharide (LPS)-stimulated oxidation and inflammation in bovine mammary epithelial cells (MAC-T) by in vitro experiments. RESULTS: Real-time PCR and ELISA assays indicated that ISL treatment at 2.5, 5 and 10 µg/mL significantly reduced the mRNA and protein expression of the oxidative indicators cyclooxygenase-2 and inducible nitric oxide synthase (P < 0.01), and of the inflammatory cytokines interleukin-6 (P < 0.05), interleukin-1ß (P < 0.01) and tumor necrosis factor-α (P < 0.01) in LPS-stimulated MAC-T cells. Moreover, Western blotting and immunofluorescence tests indicated that the phosphorylation levels of nuclear factor kappa (NF-κB) p65 and the inhibitor of NF-κB were significantly decreased by ISL treatment, thus blocking the nuclear transfer of NF-κB p65. In addition, ISL attenuated the phosphorylation levels of p38, extracellular signal-regulated kinase and c-jun NH2 terminal kinase. CONCLUSIONS: Our data demonstrated that ISL downregulated the LPS-induced inflammatory response in MAC-T cells. The anti-inflammatory and antioxidative activity of ISL involves the NF-κB and MAPK cascades.

Anti-inflammation of epicatechin mediated by TMEM35A and TMPO in bovine mammary epithelial cell line cells and mouse mammary gland.

Epicatechin (EC) has significant antiinflammation, antioxidation, and anticancer activities. It also provides a new alternative treatment for mastitis, which can result in great economic losses in the dairy industry if left untreated. The purpose of this study was to investigate the anti-inflammatory effects of EC on mastitis and the underlying mechanism using in vivo and in vitro systems. The use of ELISA and immunohistochemistry assays showed that EC treatment at 1.5, 7.5, 15, and 30 mg/mL decreased protein expression of inflammatory mediators, including cyclooxygenase-2 and inducible nitric oxide synthase; inflammatory cytokines, which were composed of IL-1ß, TNF-α, and IL-6 in lipopolysaccharide (LPS)-stimulated bovine mammary epithelial cell line (MAC-T); and mouse mammary gland, together with reduced filtration of T lymphocytes in the mouse mammary gland. Furthermore, EC treatment reduced LPS-induced phosphorylation levels of p65 and inhibitor of NF-κB, and blocked nuclear translocation of p65 as revealed by western blot and immunofluorescence test in MAC-T cells and the mouse mammary gland. Epicatechin also attenuated LPS-induced phosphorylation levels of mitogen-activated protein kinase members (i.e., p38, c-Jun N-terminal kinase 1/2 and extracellular regulated protein kinases 1/2). Using RNA-seq and tandem mass tag analyses, upregulation of TMEM35A and TMPO proteins was disclosed in MAC-T cells cotreated with LPS and EC. Although clustered regularly interspaced short palindromic repeats/Cas9-based knockdown of TMEM35A and TMPO attenuated abundance of phosphorylated (p)-p65, p-p38, TNF-α, and iNOS, overexpression of TMEM35A reversed EC-mediated effects in TMPO knockdown cells. Moreover, interaction between TMEM35A and TMPO was detected using the co-immunoprecipitation method. In conclusion, our data demonstrated that EC inhibited LPS-induced inflammatory response in MAC-T cells and the mouse mammary gland. Importantly, TMEM35A mediated the transmembrane transport of EC, and the interaction between TMEM35A and TMPO inhibited MAPK and NF-κB pathways.

Apigenin Ameliorates Insulin Resistance and Lipid Accumulation by Endoplasmic Reticulum Stress and SREBP-1c/SREBP-2 Pathway in Palmitate-Induced HepG2 Cells and High-Fat Diet-Fed Mice.

Insulin resistance (IR) is the common basis of diabetes and cardiovascular diseases, and its development is closely associated with lipid metabolism disorder. Flavonoids have definite chemical defense effects, including anti-inflammatory effects, anticancer effects, and antimutation effects. However, the function and mechanism of apigenin (AP, a kind of flavonoid) in IR are still unclear. In our study, intracellular fat accumulation model cells and high-fat diet (HFD)-fed model mice were established using palmitate (PA) and HFD. Mechanistically, we first demonstrated that AP could notably downregulate sterol regulatory element-binding protein 1c (SREBP-1c), sterol regulatory element-binding protein 2 (SREBP-2), fatty acid synthase, stearyl-CoA desaturase 1, and 3-hydroxy-3-methyl-glutaryl-CoA reductase in PA-induced hyperlipidemic cells and mice. Functionally, we verified that AP could markedly reduce lipid accumulation in PA-induced hyperlipidemic cells and decrease the body weight, visceral fat weight, IR, and lipid accumulation in HFD-induced hyperlipidemic mice. Besides, we showed that PA could significantly downregulate endoplasmic reticulum stress (ERS)-related proteins and inhibit ERS. Furthermore, we proved that AP could reduce blood lipids by inhibiting ERS in PA-induced hyperlipidemic cells. Meanwhile, 4-phenyl butyric acid (also called ERS alleviator), like AP, could significantly reduce blood lipids and alleviate IR in HFD-fed model mice. Therefore, we concluded that AP could substantially improve the disorder of lipid metabolism, and its mechanism might be related to the decrease of SREBP-1c, SREBP-2, and downstream genes, the inhibition of ERS, and the reduction of blood lipids and IR. SIGNIFICANCE STATEMENT: Apigenin, a nontoxic and naturally sourced flavonoid, has antihyperlipidemic properties in mice and hepatocyte. This study highlights a new mechanism of apigenin and proposes that these hypolipidemic effects are associated with the mitigation of endoplasmic reticulum stress and insulin resistance in diet-induced obesity. This study might provide translational insight into the prevention and treatment of apigenin in hyperlipidemia-related diseases.

Anti-Inflammatory Activity of Oligomeric Proanthocyanidins Via Inhibition of NF-κB and MAPK in LPS-Stimulated MAC-T Cells.

Oligomeric proanthocyanidins (OPCs), classified as condensed tannins, have significant antioxidation, anti-inflammation and anti-cancer effects. This study was performed to investigate the anti-inflammatory effects of OPCs and the mechanism underlying these effects in lipopolysaccharide (LPS)-stimulated bovine mammary epithelial cells (MAC-T). Real-time PCR and ELISA assays indicated that OPC treatment at 1, 3 and 5 µg/ml significantly reduced the mRNA and protein, respectively, of oxidant indicators cyclooxygenase-2 (COX-2) (p < 0.05) and inducible nitric oxide synthase (iNOS) (p < 0.01) as well as inflammation cytokines interleukin (IL)-6 (p < 0.01), IL-1ß (p < 0.01) and tumor necrosis factor-α (TNF-α) (p < 0.05) in LPS-induced MAC-T cells. Moreover, OPCs downregulated LPSinduced phosphorylation of p65 and inhibitor of nuclear factor kappa B (NF-κB) (IκB) in the NF-κB signaling pathway (p < 0.01), and they inhibited p65 translocation from the cytoplasm to the nucleus as revealed by immunofluorescence test and western blot. Additionally, OPCs decreased phosphorylation of p38, extracellular signal regulated kinase and c-jun NH2-terminal kinase in the MAPK signaling pathway (p < 0.01). In conclusion, the anti-inflammatory and antioxidant activities of OPCs involve NF-κB and MAPK signaling pathways, thus inhibiting expression of pro-inflammatory factors and oxidation indicators. These findings provide novel experimental evidence for the further practical application of OPCs in prevention and treatment of bovine mastitis.

Quantitative phosphoproteomic analysis provides insights into the aluminum-responsiveness of Tamba black soybean.

Aluminum (Al3+) toxicity is one of the most important limitations to agricultural production worldwide. The overall response of plants to Al3+ stress has been documented, but the contribution of protein phosphorylation to Al3+ detoxicity and tolerance in plants is unclear. Using a combination of tandem mass tag (TMT) labeling, immobilized metal affinity chromatography (IMAC) enrichment and liquid chromatography-tandem mass spectrometry (LC-MS/MS), Al3+-induced phosphoproteomic changes in roots of Tamba black soybean (TBS) were investigated in this study. The Data collected in this study are available via ProteomeXchange with the identifier PXD019807. After the Al3+ treatment, 189 proteins harboring 278 phosphosites were significantly changed (fold change > 1.2 or < 0.83, p < 0.05), with 88 upregulated, 96 downregulated and 5 up-/downregulated. Enrichment and protein interaction analyses revealed that differentially phosphorylated proteins (DPPs) under the Al3+ treatment were mainly related to G-protein-mediated signaling, transcription and translation, transporters and carbohydrate metabolism. Particularly, DPPs associated with root growth inhibition or citric acid synthesis were identified. The results of this study provide novel insights into the molecular mechanisms of TBS post-translational modifications in response to Al3+ stress.

Plasma membrane proteomic analysis by TMT-PRM provides insight into mechanisms of aluminum resistance in tamba black soybean roots tips.

Aluminum (Al) toxicity in acid soil is a worldwide agricultural problem that inhibits crop growth and productivity. However, the signal pathways associated with Al tolerance in plants remain largely unclear. In this study, tandem mass tag (TMT)-based quantitative proteomic methods were used to identify the differentially expressed plasma membrane (PM) proteins in Tamba black soybean (TBS) root tips under Al stress. Data are available via ProteomeXchange with identifier PXD017160. In addition, parallel reaction monitoring (PRM) was used to verify the protein quantitative data. The results showed that 907 PM proteins were identified in Al-treated plants. Among them, compared to untreated plants, 90 proteins were differentially expressed (DEPs) with 46 up-regulated and 44 down-regulated (fold change > 1.3 or < 0.77, p < 0.05). Functional enrichment based on GO, KEGG and protein domain revealed that the DEPs were associated with membrane trafficking and transporters, modifying cell wall composition, defense response and signal transduction. In conclusion, our results highlight the involvement of GmMATE13, GmMATE75, GmMATE87 and H+-ATPase in Al-induced citrate secretion in PM of TBS roots, and ABC transporters and Ca2+ have been implicated in internal detoxification and signaling of Al, respectively. Importantly, our data provides six receptor-like protein kinases (RLKs) as candidate proteins for further investigating Al signal transmembrane mechanisms.

Inhibition of PHLDA2 transcription by DNA methylation and YY1 in goat placenta.

Pleckstrin homology-like domain family A member 2 (PHLDA2) is essential for placental development in mammals. This study was conducted to investigate transcriptional regulation of goat PHLDA2 in the placenta. Real-time PCR and Western blot analyses showed different expression of the PHLDA2 in goat placentas during gestation with highest expression at 30 and 45 days post coitus (P < 0.05). Luciferase reporter assays demonstrated the highest promoter activity in the region of -1023/+20 (P < 0.05). A CpG island was defined within -631/+379 region, where lower level of CpG-methylation was detected with bisulfite sequencing PCR in the placenta than that in the spleen and liver (P < 0.05). Meanwhile, in vitro experiments showed that 5-AzaC enhanced the gene expression in a dose-dependent manner. Site-directed mutation in vitro demonstrated that transcription factor Ying-yang 1 (YY1) had an inhibitory effect on the PHLDA2 expression, and the inhibition was further confirmed with overexpression and siRNA constructs of YY1. ChIP and RE-ChIP analyses further identified the binding of YY1 to the PHLDA2 promoter by interaction with histone deacetylase 1 (HDAC1) and HDAC3. This study uncovers the negative regulation of the CpG-methylation and YY1 on goat PHLDA2 expression. YY1 prefers binding to CpG-methylation sequences, and inhibits goat PHLDA2 expression via recruiting HDAC1 and 3.

Insights into aluminum-tolerance pathways in Stylosanthes as revealed by RNA-Seq analysis.

Stylo has a great potential for Al3+ resistance in acidic soils through secretion of citrate from the roots. To get insight into the molecular mechanisms responsible, transcriptomic changes were investigated in the roots after treatment with T01 (-Al3+, pH6.0), T02 (-Al3+, pH4.3) and T03 (50 µM AlCl3, pH4.3). In total, 83,197 unigenes generated from 130,933 contigs were obtained. Of them, 282, 148 and 816 differentially expressed unigenes (DEGs) were revealed in T01_vs_T02, T02_vs_T03 and T01_vs_T03 comparison, respectively (FDR < 0.001, log2FC > 2). DEGs by Al3+ were related to G-proteins, diacyglycerol and inositol metabolism, calcium-signaling, transcription regulation, protein modification and transporters for detoxification of Al3+. Additionally, Al3+ facilitates citrate synthesis via modifying gene expression of pathways responsible for citrate metabolism. Overall, Al3+ resistance in stylo involves multiple strategies and enhancement of citrate anabolism. The Al3+ signal transmits through heterotrimeric G-proteins, phospholipase C, inositol triphosphate, diacylglycerol, Ca2+ and protein kinases, thereby activating transcription and anion channels in plasma membrane, and resulting in citrate secretion from stylo roots.

Aluminium-inhibited NO3- uptake is related to Al-increased H2O2 content and Al-decreased plasma membrane ATPase activity in the root tips of Al-sensitive black soybean.

In this study, Al-sensitive black soybean (Glycine max (L.) Merr.) specimens were treated in Hoagland solutions containing 50-400µM Al for 1-4 days. The measurement for NO3- uptake showed that the NO3- uptake decreased gradually as the Al concentration and treatment time increased, suggesting that Al stress significantly reduced the NO3- uptake by soybean. Under 100-µM Al stress for 4 days, the plasma membrane (PM) ATPase activity (inorganic phosphate (Pi) release), H+ pump activity, phosphorylation of PM ATPase and its interaction with 14-3-3 protein in soybean root tips were all smaller than those in the root tips of control plants. The addition of 150µM Mg2+ in Al treatment solutions significantly alleviated the Al inhibition of NO3- uptake in soybean. The presence of Mg2+ in a 100-µM Al solution pronouncedly enhanced PM ATPase activity, H+ pump activity, phosphorylation of PM ATPase and its interaction with 14-3-3 protein in soybean root tips. The application of 2mM ascorbic acid (AsA, an H2O2 scavenger) in Al treatment solutions significantly decreased Al-inhibited NO3- uptake in soybean. The cotreatment of soybeans with 2mM AsA and 100µM Al significantly reduced H2O2 accumulation and increased the PM ATPase activity, H+ pump activity, phosphorylation of PM H+-ATPase and its interaction with 14-3-3 protein in soybean root tips. The evidence suggested that Al-inhibited NO3- uptake is related to Al-increased H2O2 content and Al-decreased phosphorylation of PM ATPase and its interaction with 14-3-3 protein as well as PM ATPase activity in the root tips of soybean.

Auxin enhances aluminium-induced citrate exudation through upregulation of GmMATE and activation of the plasma membrane H+-ATPase in soybean roots.

Background and Aims Aluminium (Al) toxicity is a limiting factor for plant growth and crop production in acidic soils. Citrate exudation and activation of the plasma membrane H+-ATPase are involved in soybean responses to Al stress. Auxin has crucial functions in plant growth and stress responses. However, little is known about possible interactions between auxin and citrate exudation under Al stress. In this study, we elucidated the regulatory roles of IAA in Al-induced citrate exudation in soybean roots. Methods We measured IAA content, Al concentration, citrate exudation, plasma membrane H+-ATPase activity, expression of the relevant genes and phosphorylation of the plasma membrane H+-ATPase by integrating physiological characterization and molecular analysis using hydroponically grown soybean. Key Results The concentration of IAA was increased by 25 and 50 µm Al, but decreased to the control level at 200 µm Al. External addition of 50 µm IAA to the root medium containing 25, 50 or 200 µm Al decreased root Al concentration and stimulated Al-induced citrate exudation and the plasma membrane H+-ATPase activity. Reverse transcription-PCR analysis showed that exogenous IAA enhanced the expression of citrate exudation transporter (GmMATE) but not the plasma membrane H+-ATPase gene. The western blot results suggested that IAA enhanced phosphorylation of the plasma membrane H+-ATPase under Al stress. Conclusions Auxin enhanced Al-induced citrate exudation through upregulation of GmMATE and an increase in phosphorylation of the plasma membrane H+-ATPase in soybean roots.

Phosphorylation and Interaction with the 14-3-3 Protein of the Plasma Membrane H+-ATPase are Involved in the Regulation of Magnesium-Mediated Increases in Aluminum-Induced Citrate Exudation in Broad Bean (Vicia faba. L).

Several studies have shown that external application of micromolar magnesium (Mg) can increase the resistance of legumes to aluminum (Al) stress by enhancing Al-induced citrate exudation. However, the exact mechanism underlying this regulation remains unknown. In this study, the physiological and molecular mechanisms by which Mg enhances Al-induced citrate exudation to alleviate Al toxicity were investigated in broad bean. Micromolar concentrations of Mg that alleviated Al toxicity paralleled the stimulation of Al-induced citrate exudation and increased the activity of the plasma membrane (PM) H(+)-ATPase. Northern blot analysis shows that a putative MATE-like gene (multidrug and toxic compound extrusion) was induced after treatment with Al for 4, 8 and 12 h, whereas the mRNA abundance of the MATE-like gene showed no significant difference between Al plus Mg and Al-only treatments during the entire treatment period. Real-time reverse transcription-PCR (RT-PCR) and Western blot analyses suggest that the transcription and translation of the PM H(+)-ATPase were induced by Al but not by Mg. In contrast, immunoprecipitation suggests that Mg enhanced the phosphorylation levels of VHA2 and its interaction with the vf14-3-3b protein under Al stress. Taken together, our results suggest that micromolar concentrations of Mg can alleviate the Al rhizotoxicity by increasing PM H(+)-ATPase activity and Al-induced citrate exudation in YD roots. This enhancement is likely to be attributable to Al-induced increases in the expression of the MATE-like gene and vha2 and Mg-induced changes in the phosphorylation levels of VHA2, thus changing its interaction with the vf14-3-3b protein.

Up-regulation and interaction of the plasma membrane H(+)-ATPase and the 14-3-3 protein are involved in the regulation of citrate exudation from the broad bean (Vicia faba L.) under Al stress.

Our previous study showed that citrate excretion coupled with a concomitant release of protons was involved in aluminum (Al) resistance in the broad bean. Furthermore, genes encoding plasma membrane (PM) H(+)-ATPase (vha2) and the 14-3-3 protein (vf14-3-3b) were up-regulated by Al in Al-resistant (YD) broad bean roots. In this study, the roles of PM H(+)-ATPase (E.C. 3.6.3.6) and the 14-3-3 protein in the regulation of citrate secretion were further investigated in Al-resistant (YD) and Al-sensitive (AD) broad bean cultivars under Al stress. The results showed that greater citrate exudation was positively correlated with higher activities of PM H(+)-ATPase in roots of YD than AD. Real-time RT-PCR analysis revealed that vha2 was clearly up-regulated by Al in YD but not in AD roots, whereas the transcription levels of vf14-3-3b were elevated in a time-dependent manner in both YD and AD roots. Immunoprecipitation and Western analysis suggested that phosphorylation and interaction with the vf14-3-3b protein of the VHA2 were enhanced in YD roots but not in AD roots with increasing Al treatment time. Fusicoccin or adenosine 5'-monophosphate increased or decreased the interaction between the phosphorylated VHA2 and the vf14-3-3b protein, followed by an enhancement or reduction of the PM H(+)-ATPase activity and citrate exudation in both cultivars under Al stress conditions, respectively. Taken together, these results suggested that Al enhanced the expression and interaction of the PM H(+)-ATPase and the 14-3-3 protein, which thereby led to higher activity of the PM H(+)-ATPase and more citrate exudation from YD plants.

[Determination of total flavonoids in Abrus cantoniensis and its dynamic changes].

OBJECTIVE: To develop a method for ultrasonic extraction and determination of total flavonoids in Abrus cantoniensis, and to analyze its dynamic changes. METHOD: The optimized condition of extraction of total flavonoids was studied with orthogonal design. The contents of total flavonoids in different organs and of different growth stages were determined by UV-visible spectrophotometer. RESULT: The ethanol volume and extraction times were the main factors impacting the effects of ultrasonic extraction. The content of total flavonoids in stems were higher than in roots and the lowest in leaves. The dynamic changes of total flavonoids contents in roots and stems of A. cantoniensis were in similar trends. Its total flavonoids content in the two parts of plant increased gradually with the growth and reached the maximum in October, and the content decreased significantly in Feburay of next year. The content of total flavonoids in leaves reached also to the highest value before leaves fell off. CONCLUSION: The optimized extraction method of total flavonoids in Abrus contoniensis was obtained with three times with 80% ethanol at 20 times of volume for 30 min. The results implied that the best yield and quality may be obtained before leaves fall.

[Isolation and biological characteristics of rhizobia strains from Abrus cantoniensis].

OBJECTIVE: The research aimed at studying the biological characteristics of rhizobia isolated from Abrus cantoniensis. METHOD: The rhizobia strains, isolated from different environments in Guangxi, were studied for their growing characters and the generation time. They were also compared for survival capabilities under stresses caused by NaCl, pH, temperature, and different kinds and concentration of antibiotics. RESULT: The strains obtained from A. cantoniensis in subtropical zone produced alkali in YMA medium, the average generation time was 14.8 hours, and thus they belong to slow-growing rhizobia. Rhizobia strains differed greatly in respect to tolerance of high temperature, adaptability of acidic environment and sensitivity to four antibiotics, but they had the same abilities of using different carbon and nitrogen sources. After 70 days from inoculated strains, the seedling formed nodules on the root (85.0%), and the dry matter of vine was increased by 51.1%. CONCLUSION: The rhizobia strains isolated from different ecological environments are good germplasm resources of tolerances to high temperature and acidic environment. The research will greatly help utilize the rhizobia resources and enhance the quality of crude drugs of medicinal leguminosae.

[Effects of different nitrogenous compounds on growth and nodulation of Abrus cantoniensis].

OBJECTIVE: The research aimed at the effects of different nitrogenous compounds on growth and nodulation of Abrus cantoniensis. METHOD: After the seedlings of the herb were inoculated with rhizobia in potted culture, they were supplied with nutrition solutions which contained the three nitrogenous compounds, KNO3, NH4NO3, (NH4)2SO4 of different nitrogen concentration. The growth and nodulation of seedlings was determined after 70 days. RESULT: Different nitrogenous compounds were able to enhance the vegetable growth of seedlings variously. The effect of (NH4)2SO4 and NH4NO3 on growth was better than that of KNO3. Seedlings nodulation was obviously inhibited by these nitrogenous compounds. Their inhibitory effects ranked NH4NO3 > (NH4)2SO4 > KNO3. The treatments of KNO3 and the lower concentration treatments of NH4NO3 and (NH4)2 SO4 didn't inhibit the nodulation of seedlings, but the higher concentration treatment of NH4NO3 and (NH4)2SO4 severely inhibited nodulation or even made a no formation of nodule. CONCLUSION: The results showed that ammonium nitrogen the higher inhibitory ability to the nodulation of seedlings of A. cantoniensis than nitrate nitrogen. Therefore, the application of ammonium nitrogen fertilizer should be controlled in culture of the herb, which is in favor of increasing the function of biological nitrogen fixation and the quality of the medicinal materials of A. cantoniensis.