Arbuscular mycorrhizas amplify the risk of heavy metal transfer to human food chain from fly ash ameliorated agricultural soils.

Soil contaminants threaten global food security by posing threats to food safety through food chain pollution. Fly ash is a potential agent of soil contamination that contains heavy metals and hazardous pollutants. However, being rich in macro- and micronutrients that have direct beneficial effects on plant growth, fly ash has been recommended as a low-cost soil ameliorant in agriculture in countries of the Global South. Arbuscular mycorrhizal fungi (AMF), ubiquitous in agricultural soils, enhance efficiency of plant nutrient uptake from soils but can equally increase uptake of toxic pollutants from fly ash ameliorated soils to edible crop tissues. We investigated AMF-mediated amplification of nutrient and heavy metal uptake from fly ash amended soils to shoots, roots and grains of barley. We used a microcosm-based experiment to analyse the impacts of fly ash amendments to soil in concentrations of 0 (control), 15, 30 or 50% respectively, on root colonization by AMF Rhizophagus irregularis and AMF-mediated transfer of N, P and heavy metals: Ni, Co, Pb and Cr to barley tissues. These concentrations of fly ash are equivalent to 0, 137, 275 and 458 t ha-1 respectively, in soil. Root AMF colonization correlated negatively with fly ash concentration and was not detected at 50% fly ash amendment. Shoots, roots and grains of mycorrhizal barley grown with 15, 30 and 50% fly ash amendments had significantly higher concentrations of Ni, Co, Pb and Cr compared to the control and their respective non-mycorrhizal counterparts. Presence of heavy metals in barley plants grown with fly ash amended soil and their increased AMF-mediated translocation to edible grains may significantly enhance the volume of heavy metals entering the human food chain. We recommend careful assessment of manipulation of agricultural soils with fly ash as heavy metal accumulation in agricultural soils and human tissues may cause irreversible damage.

Arbuscular mycorrhizas accelerate the degradation of colour containing organic pollutants present in distillery spent wash leachates.

Distillery spent wash (DSW) from molasses-based distilleries is being used as a low-cost alternative to chemical fertilizers in countries like India and Brazil. However, using DSW as a fertilizer substitute causes organic pollutant leaching, including melanoidins and caramel colourants that turn bodies of water dark brown. This study investigated the arbuscular mycorrhiza (AM) mediated degradation of organic pollutants in DSW. Mycorrhizal and non-mycorrhizal Sorghum bicolor were grown in microcosms for 16 weeks. The plants were fertilized with either raw DSW or Hoagland solution. Leachates draining from the microcosms after fertilization were collected three times in 30-day intervals. Each 30-day collection was preceded by two fertilizations. A gas chromatography-mass spectrometry comparative analyses of raw DSW with leachates of the third collection from mycorrhizal and non-mycorrhizal microcosms was made. Sixty-five and 42 complex organic compounds were detected in raw DSW and leachate collected from the non-mycorrhizal pots respectively. Only 26 compounds were detected in leachate collected from mycorrhizal pots. Absent from leachate of the mycorrhizal pots were: colour-containing organic compounds diacetone alcohol; 3-amino-2-cyano-6-methyl-6,7-dihydrothieno[2,3-b]pyrazine S-oxide; cyclohexane; 1,2-benzenedicarboxylic acid, butyl 8-methylnonyl ester; 2-pyrrolidinone; and acetic acid, dodecyl ester present in raw DSW. The results indicate that AM fungi can degrade organic pollutants in DSW.

Plant hosts may influence arbuscular mycorrhizal fungal community composition in mangrove estuaries.

We investigated the role of plant host and soil variables in determining arbuscular mycorrhizal fungi (AMF) community composition in plant roots of two spatially separated mangrove estuaries on the rivers Aghanashini (14° 30' 30″ N-74° 22' 44″ E) and Gangavali (14° 35' 26″ N-74° 17' 51″ E) on the west coast of India. Both mangrove estuaries had similar plant species composition but differed in soil chemistries.We amplified a 550-bp portion of 18S small subunit (SSU) rDNA from mangrove plant roots and analysed it by restriction fragment length polymorphism (RFLP). Clones representing unique RFLP patterns were sequenced. A total of 736 clones were obtained from roots of seven and five plant species sampled at Aghanashini and Gangavali, respectively. AMF phylotype numbers in plant roots at Aghanashini (12) were higher than at Gangavali (9) indicating quantitative differences in the AMF community composition in plant roots at the two mangrove estuaries. Because both estuaries had similar plant species composition, the quantitative difference in AMF communities between the estuaries could be an attribute of the differences in rhizospheric chemistry between the two sites.Non-metric multidimensional scaling (NMDS) revealed overlap in the AMF communities of the two sites. Three and two AMF phylotypes had significant indicator value indices with specific hosts at Aghanashini and Gangavali, respectively. Environmental vector fitting to NMDS ordination did not reveal a significant effect of any soil variable on AMF composition at the two sites. However, significant effects of both plant hosts and sites were observed on rhizospheric P. Our results indicate that root AMF community composition may be an outcome of plant response to rhizospheric variables. This suggests that plant identity may have a primary role in shaping AMF communities in mangroves.

HCN-producing Pseudomonas protegens CHA0 affects intraradical viability of Rhizophagus irregularis in Sorghum vulgare roots.

Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria inhabit the plant rhizosphere. Both functional groups can influence plant community structures, and interactions between them can vary from being synergistic to antagonistic. HCN-producing Pseudomonas protegens CHA0 is a plant growth-promoting rhizobacterium. P. protegens CHA0 has been shown to weakly attach to AMF hyphae. Here, we analyze the effect of P. protegens CHA0 on the viability of intraradical AMF hyphae. Using pot experiments, we have grown mycorrhizal and nonmycorrhizal Sorghum vulgare var. M35 with P. protegens CHA0 or HCN- mutant P. protegens CHA77, which did not produce HCN. Mycorrhizal and nonmycorrhizal Sorghum grown without CHA0 or CHA77 served as the control. While metabolically active AMF was not detected in mycorrhizal plants grown with HCN+ CHA0, the percentage of root colonization of metabolically active AMF in plants grown with HCN- CHA77 was lower than in the control. Root phosphorus was highest in mycorrhizal plants grown with HCN+ CHA0, but root Fe was higher in plants grown with the bacterial strains. Our results indicate that HCN-producing P. protegens can affect the viability of intraradical AMF.

Blockade of Deubiquitylating Enzyme USP1 Inhibits DNA Repair and Triggers Apoptosis in Multiple Myeloma Cells.

Purpose: The ubiquitin proteasome pathway is a validated therapeutic target in multiple myeloma. Deubiquitylating enzyme USP1 participates in DNA damage response and cellular differentiation pathways. To date, the role of USP1 in multiple myeloma biology is not defined. In the present study, we investigated the functional significance of USP1 in multiple myeloma using genetic and biochemical approaches.Experimental Design: To investigate the role of USP1 in myeloma, we utilized USP1 inhibitor SJB3-019A (SJB) for studies in myeloma cell lines and patient multiple myeloma cells.Results: USP1-siRNA knockdown decreases multiple myeloma cell viability. USP1 inhibitor SJB selectively blocks USP1 enzymatic activity without blocking other DUBs. SJB also decreases the viability of multiple myeloma cell lines and patient tumor cells, inhibits bone marrow plasmacytoid dendritic cell-induced multiple myeloma cell growth, and overcomes bortezomib resistance. SJB triggers apoptosis in multiple myeloma cells via activation of caspase-3, caspase-8, and caspase-9. Moreover, SJB degrades USP1 and downstream inhibitor of DNA-binding proteins as well as inhibits DNA repair via blockade of Fanconi anemia pathway and homologous recombination. SJB also downregulates multiple myeloma stem cell renewal/survival-associated proteins Notch-1, Notch-2, SOX-4, and SOX-2. Moreover, SJB induced generation of more mature and differentiated plasma cells. Combination of SJB and HDACi ACY-1215, bortezomib, lenalidomide, or pomalidomide triggers synergistic cytotoxicity.Conclusions: Our preclinical studies provide the framework for clinical evaluation of USP1 inhibitors, alone or in combination, as a potential novel multiple myeloma therapy. Clin Cancer Res; 23(15); 4280-9. ©2017 AACR.

Soil moisture--a regulator of arbuscular mycorrhizal fungal community assembly and symbiotic phosphorus uptake.

Multiple species of arbuscular mycorrhizal fungi (AMF) can colonize roots of an individual plant species but factors which determine the selection of a particular AMF species in a plant root are largely unknown. The present work analysed the effects of drought, flooding and optimal soil moisture (15-20 %) on AMF community composition and structure in Sorghum vulgare roots, using PCR-RFLP. Rhizophagus irregularis (isolate BEG 21), and rhizosphere soil (mixed inoculum) of Heteropogon contortus, a perennial C4 grass, collected from the semi-arid Delhi ridge, were used as AMF inocula. Soil moisture functioned as an abiotic filter and affected AMF community assembly inside plant roots by regulating AMF colonization and phylotype diversity. Roots of plants in flooded soils had lowest AMF diversity whilst root AMF diversity was highest under the soil moisture regime of 15-20 %. Although plant biomass was not affected, root P uptake was significantly influenced by soil moisture. Plants colonized with R. irregularis or mixed AMF inoculum showed higher root P uptake than non-mycorrhizal plants in drought and control treatments. No differences in root P levels were found in the flooded treatment between plants colonized with R. irregularis and non-mycorrhizal plants, whilst under the same treatment, root P uptake was lower in plants colonized with mixed AMF inoculum than in non-mycorrhizal plants.

Dickkopf homolog 3 (DKK3) plays a crucial role upstream of WNT/ß-CATENIN signaling for Sertoli cell mediated regulation of spermatogenesis.

Testicular Sertoli cells (Sc) are main somatic component of seminiferous tubules that govern the differentiation of germ cells (Gc) and provide them physical support. Sc are the target of follicle stimulating hormone (FSH) and testosterone (T) which are known to regulate spermatogenesis. FSH and T levels in human and sub-human male primates remain high during infancy (4-6 months post birth), similar to those during puberty. Subsequently, juvenile phase is marked with low levels of these hormones. In spite of prolonged hormonal exposure, spermatogenesis is not discerned during infancy unlike that during puberty. Situation during infancy is similar to certain idiopathic male infertility, where prolonged hormone supplementation fails to initiate spermatogenesis. In our quest to determine non hormonal causes of idiopathic infertility which may reside within the Sc, we investigated the association between spermatogenesis and Sc specific gene(s) expressed differentially during puberty and infancy. Although products of several genes may be necessary for quantitatively normal spermatogenesis, one needs to investigate their roles one by one. Differential display and real time PCR analysis revealed higher expression of a known tumor suppressor, Dickkopf homolog 3 (DKK3), by pubertal monkey Sc as compared to infant Sc. To evaluate role of DKK3 in spermatogenesis, we generated DKK3 knock down mice (DKDM) using shRNA construct targeted to DKK3. In testis of adult DKDM, expression of DKK3 mRNA and protein were significantly (p<0.05) low and was associated with elevated WNT-4/ß-CATENIN activity. Elevated ß-CATENIN activity is known to restrict Sc maturation. Abundant expression of infant Sc marker, Mullerian inhibiting substance (MIS), in the testes of adult DKDM confirmed lack of Sc maturation in DKDM. Gc differentiation and fertility was severely compromised in DKDM. This is the first report of role of DKK3 in the testis and DKK3 mediated regulation of spermatogenesis via WNT-4/ß-CATENIN modulation.

A role for apoptosis-inducing factor in T cell development.

Apoptosis-inducing factor (Aif) is a mitochondrial flavoprotein that regulates cell metabolism and survival in many tissues. We report that aif-hypomorphic harlequin (Hq) mice show thymic hypocellularity and a cell-autonomous thymocyte developmental block associated with apoptosis at the ß-selection stage, independent of T cell receptor ß recombination. No abnormalities are observed in the B cell lineage. Transgenes encoding wild-type or DNA-binding-deficient mutant Aif rectify the thymic defect, but a transgene encoding oxidoreductase activity-deficient mutant Aif does not. The Hq thymic block is reversed in vivo by antioxidant treatment, and Hq T but not B lineage cells show enhanced oxidative stress. Thus, Aif, a ubiquitous protein, serves a lineage-specific nonredundant antiapoptotic role in the T cell lineage by regulating reactive oxygen species during thymic ß-selection.