Cow dung extract: a medium for the growth of pseudomonads enhancing their efficiency as biofertilizer and biocontrol agent in rice

Some pseudomands are being utilized as biofertilizers and biopesticides because of their role in plant growth promotion and plant protection against root parasites, respectively. Two strains of Pseudomonas, P. jessenii LHRE62 and P. synxantha HHRE81, recovered from wheat rhizosphere, have shown their potential in field bioinoculation tests under rice-wheat and pulse-wheat rotation systems. Normally, pseudomonads are cultivated on synthetic media-like King’s B and used for inoculation on seeds/soil drench with talcum or charcoal as carrier material. Cow dung is being used for different purposes from the ancient time and has a significant role in crop growth because of the content in humic compounds and fertilizing bioelements available in it. Here, cow dung extract was tested as a growth medium for strains LHRE62 and HHRE81, in comparison with growth in King’s B medium. The log phase was delayed by 2 h as compared to growth in King’s B medium. The bacterial growth yield, lower in plain cow dung extract as compared to King’s B medium, was improved upon addition of different carbon substrates. Growth of rice var. Pant Dhan 4 in pot cultures was increased using liquid formulation of cow dung extract and bacteria as foliar spray, compared to their respective controls. Biocontrol efficacy of the bioagents was assessed by challenging rice crop with Rhizoctonia solani, a sheath blight pathogen. The growth promotion and biocontrol efficiencies were more pronounced in the case of mixed inocula of strains LHRE62 and HHRE81.     

Effect of estrogen and its antagonist on the expression of arginine vasotocin (AVT) and its oxytocic-like receptor VT3 in the shell gland of Japanese quail, Coturnix coturnix japonica

Avian neurohypophysial hormone arginine vasotocin (AVT) is known to regulate shell gland contractility during oviposition. While studying the role of estrogen in the expression and regulation of AVT and its oxytocic-like receptor VT3, using in situ hybridization and immunohistochemistry, it was observed that the expression of AVT and its receptor was not detected in the shell gland of sexually immature Japanese quail. However, administration of estrogen to these birds not only stimulates the growth and activity (as assessed by increased mucosal fold length, total protein content and alkaline phosphatase level) of the shell gland but also upregulates the expression of AVT and VT3. Further, administration of estrogen antagonist tamoxifen to sexually mature bird shows opposite results. On the other hand, localization of ir-AVT, observed in the ovary of sexually mature bird, was not detected in the estrogen treated sexually immature quail. It is concluded that estrogen not only affects the growth and differentiation of avian oviduct, but also regulates the expression of shell gland AVT and its receptor VT3. Present findings suggest that the locally synthesized AVT acts in a paracrine way to upregulate VT3 receptor and thus facilitates the endocrine function of neurohypophysial AVT during oviposition.     

Identification of genetically diverse genotypes for photoperiod insensitivity in soybean using RAPD markers

Most of the Indian soybean varieties were found to be highly sensitive to photoperiod, which limits their cultivation in only localized area. Identification of genetically diverse source of photoperiod insensitive would help to broaden the genetic base for this trait. Present study was undertaken with RAPD markers for genetic diversity estimation in 44 accessions of soybean differing in response to photoperiod sensitivity. The selected twenty-five RAPD primers produced a total of 199 amplicons, which generated 89.9 % polymorphism. The number of amplification products ranged from 2 to 13 for different primers. The polymorphism information content ranged from 0.0 for monomorphic loci to 0.5 with an average of 0.289. Genetic diversity between pairs of genotypes was 37.7% with a range of 3.9 to 71.6%. UPGMA cluster analysis placed all the accessions of soybean into four major clusters. No discernable geographical patterns were observed in clustering however; the smaller groups corresponded well with pedigree. Mantel’s test (r = 0.915) indicates very good fit for clustering pattern. Two genotypes, MACS 330 and 111/2/1939 made a very divergent group from other accessions of soybean and highly photoperiod insensitive that may be potential source for broadening the genetic base of soybean for this trait.Key words: Genetic diversity, Photoperiod, RAPD, Soybean, UPGMA     

Construction of a recF deletion mutant of Azotobacter vinelandii and its characterization

A deletion was engineered in the cloned recF gene by digestion with suitable restriction endonucleases and a tetracycline resistance gene cartridge was inserted. The mutation was subsequently transferred to the Azotobacter vinelandii chromosome by double cross-over under pressure of tetracycline selection. A recF recA mutant was also constructed in a similar manner. The mutations were found to be stable and mutation of the wild-type recF gene was confirmed by Southern blot hybridization. Both the mutants were UV sensitive and recombination deficient. Mutations in genes involved in nitrogen fixation in A. vinelandii are rather frequent and obtained comparatively easily despite of the presence of multiple identical chromosomes in A. vinelandii. It has been speculated that some kind of `homogenotization' process operates which is responsible for the `transmission' of mutation from one chromosome to all the chromosomes. This process is not affected by a mutation in recF or recA or in both recF and recA.     

Effect of cadmium and zinc on antioxidant enzyme activity in the gastropod, Achatina fulica

Heavy metal stress results in the production of O(2)(.-), H(2)O(2) and (.)OH, which affect various cellular processes, mostly the functioning of membrane systems. Cells are normally protected against free oxyradicals by the operation of intricate antioxidant systems. The aim of the present work is to examine the effect of CdCl(2) and ZnSO(4) on antioxidative enzyme activity in the gastropod, Achatina fulica. The concentrations of antioxidant enzymes--superoxide dismutase (SOD), catalase (Cat) and glutathione peroxidase (GPx)--and nonenzymatic antioxidants--glutathione and vitamin-C--were found to be decreased in both digestive gland and kidney of the gastropod, Achatina fulica treated with individual concentrations of 0.5 ppm and 1ppm of CdCl(2) and ZnSO(4), compared to that of control animals. Based on the above study, it is evident that Achatina fulica can be used as a bioindicator to monitor the environmental heavy metal pollution.     

A new tyrosine phosphorylation site in PLC gamma 1: the role of tyrosine 775 in immune receptor signaling

Phospholipase Cgamma (PLCgamma) is a ubiquitous gatekeeper of calcium mobilization and diacylglycerol-mediated events induced by the activation of Ag and growth factor receptors. The activity of PLCgamma is regulated through its controlled membrane translocation and tyrosine (Y) phosphorylation. Four activation-induced tyrosine phosphorylation sites have been previously described (Y472, Y771, Y783, and Y1254), but their specific roles in Ag receptor-induced PLCgamma1 activation are not fully elucidated. Unexpectedly, we found that the phosphorylation of a PLCgamma1 construct with all four sites mutated to phenylalanine was comparable with that observed with wild-type PLCgamma1, suggesting the existence of an unidentified site(s). Sequence alignment with known phosphorylation sites in PLCgamma2 indicated homology of PLCgamma1 tyrosine residue 775 (Y775) with PLCgamma2 Y753, a characterized phosphorylation site. Tyrosine 775 was characterized as a phosphorylation site using phospho-specific anti-Y775 antiserum, and by mutational analysis. Phosphorylation of Y775 did not depend on the other tyrosines, and point mutation of PLCgamma1 Y775, or the previously described Y783, substantially reduced AgR-induced calcium, NF-AT, and AP-1 activation. Mutation of Y472, Y771, and Y1254 had no effect on overall PLCgamma1 phosphorylation or activation. Although the concomitant mutation of Y775 and Y783 abolished downstream PLCgamma1 signaling, these two tyrosines were sufficient to reconstitute the wild-type response in the absence of functional Y472, Y771, and Y1254. These data establish Y775 as a critical phosphorylation site for PLCgamma1 activation and confirm the functional importance of Y783.     

Regulation of protein kinase Cnu by the B-cell antigen receptor

Diacylglycerol-dependent signaling plays an important role in signal transduction through T- and B-lymphocyte antigen receptors. Recently, a novel serine-threonine kinase of the protein kinase C (PKC) family has been described and designated as PKCnu. PKCnu has two putative diacylglycerol binding C1 domains, suggesting that it may participate in a novel diacylglycerol-mediated signaling pathway. Here we show that both endogenous and recombinant PKCnu are trans-located to the plasma membrane and activated by the diacylglycerol mimic phorbol 12-myristate 13-acetate. Mutational analysis demonstrates that PKCnu activation is dependent on trans-phosphorylation of two conserved activation loop serine residues. We also find that PKCnu is an important physiologic target of the B-cell receptor (BCR), because PKCnu is found to be abundantly expressed in chicken and human B-cell lines and, in addition, exhibits robust activation after BCR engagement. Genetic and pharmacologic analyses of BCR-mediated PKCnu activation indicate that it requires intact phospholipase Cgamma and PKC signaling pathways. Furthermore, in co-transfection assays, PKCnu can be trans-phosphorylated by the novel PKC isozymes PKCepsilon, PKCeta, or PKCtheta but not the classical PKC enzyme, PKCalpha. Taken together, these results suggest that PKCnu is an important component of signaling pathways downstream from novel PKC enzymes after B-cell receptor engagement.     

Differentiation potential of primary myogenic cells derived from skeletal muscle of dystonia musculorum mice

The dystonia musculorum (dt) mouse has a mutation in the gene encoding the cytoskeletal crosslinker protein bullous pemphigoid antigen 1 (Bpag1). These mice have perturbations in the cytoarchitecture of skeletal muscle. Bpag1 has been hypothesized to be involved in the maintenance rather than the establishment of the muscle cell architecture given that cytoskeletal disruptions are observed in the muscle tissue of post-natal dt mice. Not known is whether Bpag1-deficiency affects the proliferative and differentiation potential of myogenic cells. In the present investigation, we show that the growth rate of cultured primary myogenic cells derived from dt mice, as assessed by BrdU incorporation, is similar to that of myogenic cells derived from wild-type littermates. The myogenic differentiation potential of dt versus wild-type cells was monitored by examining the expression of myosin heavy chain by immunofluorescence, and by analyzing the expression profiles of myogenic regulatory factors and myogenic differentiation markers by RT-PCR. In all instances, both dt and wild-type myogenic cells displayed a similar differentiation profile. Furthermore, the absence of any observable differences in the proliferation and differentiation rates of dt and wild-type cells was not due to an overexpression of plectin, another crosslinker protein, in dt cells. Together, these findings demonstrate that the early phases of myogenic differentiation occur independently of Bpag1.     

In vitro somatic embryogenesis and plant regeneration in Acacia arabica

In vitro somatic embryogenesis and subsequent plant regeneration was achieved in callus cultures derived from immature zygotic embryos of Acacia arabica on semi-solid Murashige and Skoog (MS) basal salts and vitamins supplemented with 8.88 MBA, 6.78 M2,4-D and 30 g l^–1 (w/v) sucrose. Somatic embryos proliferated rapidly by secondary somatic embryogenesis after transfer to MS medium supplemented with 6.66 M BA, 6.78 M 2,4-D. The maximum number of somatic embryos per callus was 72.6 after 8 weeks of culture on medium containing 6.66 M BA and 6.78 M 2,4-D. The isolated somatic embryos germinated on half-strength basal MS salts and vitamins supplemented with 0.04 M BA, 0.94 M ABA and 2% (w/v) sucrose. The embryo-derived plantlets were acclimatized in the greenhouse and subsequently showed normal growth.