Rhizobia enhance acquisition of phosphorus from different sources by soybean plants

Aims

Some rhizobia can convert insoluble P into available forms for plant growth but the underlying mechanisms for this are not understood. In this study, the function of rhizobia in P acquisition from P sources for soybean was studied.

Methods

Four rhizobial strains were employed to evaluate their phosphate-solubilizing (PS) activity, their ability to mediate pH changes in growth medium for different P sources, and IAA production. A sand culture experiment using different P sources was carried out to characterize P acquisition changes of soybean plants with or without rhizobium inoculation. Rhizospheric acidification in soybean was further analyzed in hydroponics.

Results

Our results showed that all the tested rhizobial strains exhibited significant PS activity for different P sources in the order of Ca-P>Al-P>Phy-P??Fe-P as indicated by the halo/colony ratio technique and increased Pi percentage in the solid and liquid phases, respectively. Furthermore, all of the rhizobial strains could acidify the growth medium for all P sources except Phy-P, but only three of them produced IAA. Compared to non-nodulated plants, the nodulated plants had greater plant biomass and P content in sand culture for all the tested P sources, especially for Ca-P. Moreover, H⁺ and total acid exudation was more significantly enhanced in the nodulated plants in hydroponics.

Conclusions

Our results suggested that the PS ability of rhizobia is more related to acidification of the growth medium than IAA production. Rhizobium inoculation could enhance P acquisition in soybean, especially on soils where Ca-P is the primary P source, and the primary mechanism for rhizobial-mediated P solubilization appears to be via Pi remobilization of nodulated roots through rhizospheric acidification.     

Fe binding properties of two soybean (Glycine max L.) LEA4 proteins associated with antioxidant activity

Late embryogenesis abundant (LEA) group 4 (LEA4) proteins play an important role in the water stress tolerance of plants. Although they have been hypothesized to stabilize macromolecules in stressed cells, the protective functions and mechanisms of LEA4 proteins are still not clear. In this study, the metal binding properties of two related soybean LEA4 proteins, GmPM1 and GmPM9, were tested using immobilized metal ion affinity chromatography (IMAC). The metal ions Fe(3+), Ni(2+), Cu(2+) and Zn(2+) were observed to bind these two proteins, while Ca(2+), Mg(2+) or Mn(2+) did not. Results from isothermal titration calorimetry (ITC) indicated that the binding affinity of GmPM1 for Fe(3+) was stronger than that of GmPM9. Hydroxyl radicals generated by the Fe(3+)/H(2)O(2) system were scavenged by both GmPM1 and GmPM9 in the absence or the presence of high ionic conditions (100 mM NaCl), although the scavenging activity of GmPM1 was significantly greater than that of GmPM9. These results suggest that GmPM1 and GmPM9 are metal-binding proteins which may function in reducing oxidative damage induced by abiotic stress in plants.     

A chimeric peptide that binds to titanium and mediates MC3T3-E1 cell adhesion

Purpose of work  

Our study provides a promising alternative of biomimetic coating which functionalizes the dental implant with adhesion peptides and may be useful for enhancing the bone remodeling around Ti implants.     

Functional identification of hyoscyamine 6β-hydroxylase from <Emphasis Type="Italic">Anisodus acutangulus</Emphasis> and overproduction of scopolamine in genetically-engineered <Emphasis Type="Italic">Escherichia coli</Emphasis>

Hyoscyamine 6β-hydroxylase (H6H; EC 1.14.11.11) converts hyoscyamine to scopolamine in the last step of scopolamine biosynthetic pathway. The gene encoding H6H in Anisodus acutangulus was cloned and expressed in Escherichia coli and the recombinant proteins fused with His-tag or GST-tag at its N-terminal were purified and then confirmed by Western bolt analysis. The biofunctional assay revealed that the His-AaH6H and GST-AaH6H converted hyoscyamine (40 mg/l) to scopolamine at 32 and 31 mg/l, respectively. This is the first report on AaH6H expression, purification and functional characterization facilitates further genetic improvement of scopolamine yield in A. acutangulus.     

Characteristics of Cd uptake, translocation and accumulation in a novel Cd-accumulating tree, star fruit (Averrhoa carambola L., Oxalidaceae)

Cadmium (Cd) accumulation by terrestrial higher plants is an intriguing phenomenon that may be exploited for phytoextraction of Cd-contaminated soils. Characterizing the physiological processes responsible for elevated concentrations of Cd in shoots is a first step towards a comprehensive understanding of the mechanisms underlying Cd accumulation in plants and may eventually improve the efficiency of phytoextraction. Woody species that can accumulate Cd have been recently recommended as good candidates for phytoextraction of Cd-contaminated soils. However, little is known about the mechanisms of Cd accumulation by woody species. In an attempt to understand the physiological processes contributing to Cd accumulation in woody species, Cd uptake and translocation by a novel tropical Cd-accumulating tree, star fruit (Averrhoa carambola) were characterized and compared with those of a non-Cd-accumulating tree (Clausena lansium). Our results showed that A. carambola had higher Cd uptake and root-to-shoot translocation efficiencies than C. lansium, which might account for its greater Cd-accumulating capacity. Furthermore, Cd accumulation by A. carambola was not significantly affected by zinc (Zn), whereas Zn accumulation was greatly lowered by Cd. This phenomenon could not be fully explained by a simple competition between Cd²⁺ and Zn²⁺, implying the existence of a transport system with a preference for Cd over Zn. Collectively, our results indicate that A. carambola has noteworthy physiological traits associated with accumulation of Cd to high levels.     

Cloning, expression, and characterization of a new beta-agarase from Vibrio sp. strain CN41

A new agarase, AgaA(CN41), cloned from Vibrio sp. strain CN41, consists of 990 amino acids, with only 49% amino acid sequence identity with known β-agarases. AgaA(CN41) belongs to the GH50 (glycoside hydrolase 50) family but yields neoagarotetraose as the end product. AgaA(CN41) was expressed and characterized.     

Paroxetine-induced Ca2+ movement and death in OC2 human oral cancer cells

The effect of the antidepressant paroxetine on cytosolic free Ca2+ concentrations ([Ca2+]i) in OC2 human oral cancer cells is unclear. This study explored whether paroxetine changed basal [Ca2+]i levels in suspended OC2 cells by using fura-2 as a Ca2+-sensitive fluorescent dye. Paroxetine at concentrations between 100-1,000 microM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced by 50% by removing extracellular Ca2+. Paroxetine-induced Ca2+ influx was inhibited by the store-operated Ca2+ channel blockers nifedipine, econazole and SK&F96365, and protein kinase C modulators. In Ca2+-free medium, pretreatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin abolished paroxetine-induced [Ca2+]i rise. Inhibition of phospholipase C with U73122 did not alter paroxetine-induced [Ca2+]i rise. Paroxetine at 10-50 microM induced cell death in a concentration-dependent manner. The death was not reversed when cytosolic Ca2+ was chelated with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Propidium iodide staining suggests that apoptosis plays a role in the death. Collectively, in OC2 cells, paroxetine induced [Ca2+]i rise by causing phospholipase C-independent Ca2+ release from the endoplasmic reticulum and Ca2+ influx via store-operated Ca2+ channels in a manner regulated by protein kinase C and phospholipase A2. Paroxetine (up to 50 microM) induced cell death in a Ca2+-independent manner.     

The association of CLOCK gene T3111C polymorphism and hPER3 gene 54-nucleotide repeat polymorphism with Chinese Han people schizophrenics

Many reports have shown that the biologic rhythm could be altered due to mutations of circadian gene hClock or hPeriod, and the mutations of circadian genes have some relationship with psychosis according to recent studies. A preliminary study has been conducted to examine wether the T3111C single nucleotide polymorphism of the hClock gene or the length polymorphism of the hPer3 gene is associated with the development of schizophrenia. The samples from schizophrenics (n = 148, male: 57.4%, female: 42.6%) and normal controls (n = 199, male: 59.3%, female: 40.7%) were examined. Allele frequencies of T3111C SNP of hClock were significantly different between schizophrenics and controls (χ² = 19.738, P < 0.05). Schizophrenics had a significantly higher frequency of the C allele compared with controls (OR = 2.613, 95% CI = 1.693–4.034). On the other hand, there is no significant difference of allele frequencies of 18 exon of hper3 between schizophrenics and controls (χ² = 0.192, P > 0.05). Our results suggest that the T3111C (RS1801260) polymorphism of hClock gene is associated with schizophrenia, but it seems that the length polymorphism of 18 exon of hPer3 may not be associated with schizophrenia. It is important to address of the relationship between circadian gene polymorphisms and dopamine functions in further study.     

<Emphasis Type="Italic">BRAF</Emphasis> V600E mutation and resistance to anti-EGFR monoclonal antibodies in patients with metastatic colorectal cancer: a meta-analysis

Epidemiologic studies have evaluated the association between BRAF mutations and resistance to the treatment of anti-EGFR monoclonal antibodies (MoAb) in patients with metastatic colorectal cancer (mCRC). However, the results are still inconclusive. To derive a more precise estimation of the relationship, we performed this meta-analysis. A total of 11 studies were included in the final meta-analysis. There were seven studies for unselected mCRC patients and four studies for patients with wild type KRAS mCRC. Among unselected mCRC patients, BRAF V600E mutation was detected in 48 of 546 primary tumors (8.8%). The objective response rate (ORR) of patients with mutant BRAF was 29.2% (14/48), whereas the ORR of patients with wild-type BRAF was 33.5% (158/472).The overall RR for ORR of mutant BRAF patients over wild-type BRAF patients was 0.86 (95% CI = 0.57–1.30; P = 0.48). For patients with KRAS wild-type mCRC, BRAF V600E mutation was detected in 40 of 376 primary tumors (10.6%). The ORR of patients with mutant BRAF was 0.0% (0/40), whereas the ORR of patients with wild-type BRAF was 36.3% (122/336). The pooled RR of mutant BRAF patients over wild-type BRAF patients was 0.14 (95% CI = 0.04–0.53; P = 0.004). In conclusion, this meta-analysis provides evidence that BRAF V600E mutation is associated with lack of response in wild-type KRAS mCRC treated with anti-EGFR MoAbs. BRAF mutation may be used as an additional biomarker for the selection of mCRC patients who might benefit from anti-EGFR MoAbs therapy.