Colchicine-mediated in vitro polyploidization in gerbera hybrid

An efficient in vitro protocol for high-frequency polyploidization for the first time in gerbera hybrid (BGC-2019-01) was developed in the present study. Two-week-old in vitro-developed shoots (tips) were treated individually with 0.1%, 0.25% and 0.5% (w/v) colchicine solutions for 4, 6, 8, and 12 h. The colchicine-treated shoot tips were then inoculated on Murashige and Skoog (MS) medium fortified with 1.5 mg/l meta-Topolin for multiple shoot proliferation and later transferred into 1.5 mg/l indole-3-acetic acid-fortified MS medium for rooting of shoots. The ploidy levels of the colchicine-treated and regenerated plantlets along with the non-treated ones were confirmed via flow cytometry analysis and metaphasic chromosome count. The highest frequency of tetraploid plantlets (50%) were obtained when shoot tips were treated with 0.1% colchicine for 4 h. Morphological observations revealed that induced tetraploid plantlets exhibited delayed fresh shoot initiation, fewer but longer shoots, as well as fewer but broader leaves. Likewise, the study of stomata revealed that in comparison to their diploid counterparts, the tetraploid plantlets exhibited less frequent yet significantly larger stomata, and higher number of chloroplasts. The tetraploids were recorded with significantly higher chlorophyll, carotenoid, and anthocyanin content during the photosynthetic pigment analyses. During ex vitro acclimatization and field growth, the tetraploid plants exhibited delayed proliferation but with higher vigor and thickened broad leaves. The genetic uniformity among the diploid and the tetraploid plants was confirmed using conserved DNA-derived polymorphism (CDDP), directed amplification of minisatellite-region DNA (DAMD), inter simple sequence repeats (ISSR), and start codon targeted (SCoT) polymorphism marker systems. The tetraploids developed in the present study would be of immense importance for the genetic improvement of gerbera as far as its ornamental values are concerned.

Effects of nZnS vs. nZnO and ZnCl2 on mungbean [Vigna radiata (L.) R. Wilczek] plant and Bradyrhizobium symbiosis: A life cycle study

Scarce of knowledge of using Zinc (Zn) nanoparticles (NPs) to augment plant growth, Zn availability to plants and its potential toxicity warrants more NPs-plant life cycle studies. The main objectives of this study were to compare nano zinc sulphide (nZnS) with nano zinc oxide (nZnO) and ionic Zn i.e., ZnCl₂, as a source of Zn, as well as to establish physiological impact of NPs on growth, yield and symbiosis of mungbean [Vigna radiata (L.) R. Wilczek] plants at different concentrations (0, 0.01, 0.1, 1 and 10 mg kg^-1 of soil). In this study, mungbean plants were grown for 60 days (life cycle study) in natural soil infested with Bradyrhizobium. Effects of Zn compounds (nZnS, nZnO and ZnCl₂) on plant height, dry biomass, number of nodules per plant, yield and fruit agronomical parameters along with micronutrient assessment were determined. Impact of Zn compounds on Bradyrhizobium-mungbean symbiosis was also unravelled. Results showed that both the NPs, (nZnS and nZnO) were more effective than ZnCl₂ in promoting growth and yield up to a critical concentration and above which phytotoxic effects were observed. Both the NPs were more effective than ZnCl₂ at increasing fruit Zn content also. Whereas, nZnS treatment was found to be better than nZnO in improving overall plant growth. Bradyrhizobium-mungbean symbiosis was not affected at lower NPs concentrations, while higher concentration revealed toxicity by damaging bacterial morphology and nodule formation. There was no nano specific toxicity found while, ZnCl₂ showed relatively more toxicity than both the NPs. The present investigation demonstrated the concept of nano-micronutrient as well as NPs phytotoxicity by understanding NPs-plant interactions in the soil environment.

Cisgenics - a sustainable approach for crop improvement

The implication of molecular biology in crop improvement is now more than three decades old. Not surprisingly, technology has moved on, and there are a number of new techniques that may or may not come under the genetically modified (GM) banner and, therefore, GM regulations. In cisgenic technology, cisgenes from crossable plants are used and it is a single procedure of gene introduction whereby the problem of linkage drag of other genes is overcome. The gene used in cisgenic approach is similar compared with classical breeding and cisgenic plant should be treated equally as classically bred plant and differently from transgenic plants. Therefore, it offers a sturdy reference to treat cisgenic plants similarly as classically bred plants, by exemption of cisgenesis from the current GMO legislations. This review covers the implications of cisgenesis towards the sustainable development in the genetic improvement of crops and considers the prospects for the technology.

Quercetin induces cytochrome-c release and ROS accumulation to promote apoptosis and arrest the cell cycle in G2/M, in cervical carcinoma: signal cascade and drug-DNA interaction

OBJECTIVES

Small aromatic compounds like flavonoids can intercalate with DNA molecules bringing about conformational changes leading to reduced replication and transcription. Here, we have examined one dietary flavonoid, quercetin (found in many fruit and vegetables), for possible anti-cancer effects, on HeLa cells originally derived from a case of human cervical cancer.

MATERIAL AND METHODS

By circular dichroism spectroscopy we tested whether quercetin effectively interacted with DNA to bring about conformational changes that would strongly inhibit proliferation and migration of the HeLa cells. Cytotoxic effects of quercetin on cancer/normal cells, if any, were determined by MTT assay and such depolarization of mitochondrial membrane potential, as a consequence of quercetin treatment, and accumulation of reactive oxygen species (ROS) also were studied, by FACS analysis and expression profiles of different anti- and pro-apoptotic genes and their products were determined.

RESULTS

Quercetin intercalated with calf thymus cell DNA and HeLa cell DNA and inhibition of anti-apoptotic AKT and Bcl-2 expression were observed. Levels of mitochondrial cytochrome-c were elevated and depolarization of mitochondrial membrane potential occurred with increase of ROS; upregulation of expression of p53 and caspase-3 activity were also noted. These alterations in signalling proteins and externalization of phosphotidyl serine residues were involved with initiation of apoptosis. Reduced AKT expression suggested reduction in cell proliferation and metastasis potential, with arrest of the cell cycle at G2/M.

CONCLUSION

Quercetin would have potential for use in cervical cancer chemotherapy.

Unaltered cleavage and secretion of angiotensin-converting enzyme in tumor necrosis factor-alpha-converting enzyme-deficient mice

Mammalian angiotensin-converting enzyme (ACE) is one of several biologically important ectoproteins that exist in both membrane-bound and soluble forms as a result of a post-translational proteolytic cleavage. It has been suggested that a common proteolytic system is responsible for the cleavage of a diverse group of membrane ectoproteins, and tumor necrosis factor-alpha-converting enzyme (TACE), a recently purified disintegrin-metalloprotease, has been implicated in the proteolytic cleavage of several cell surface proteins. Mice devoid of TACE have been developed by gene targeting. Such mice could provide a useful system to determine if TACE is responsible for the cleavage of other ectoproteins. Cultured fibroblasts without TACE activity, when transfected with cDNA encoding for the testicular isozyme of ACE (ACET), synthesized and secreted ACET normally after a proteolytic cleavage near the C terminus. In addition, similar quantities of the soluble, C-terminally truncated somatic isozyme of ACE (ACEP) were present in the serum of wild-type and TACE-deficient mice. These results demonstrate that TACE is not essential in the generation of soluble ACE under physiological conditions. Finally, we also report solubilization of ACE-secretase, the enzyme that cleaves ACE, from mouse ACE89 cells and from rabbit lung. We demonstrate that soluble ACE-secretase from both sources failed to cleave its substrate in solution, suggesting a requirement for anchoring to the membrane.

The distal ectodomain of angiotensin-converting enzyme regulates its cleavage-secretion from the cell surface

Angiotensin-converting enzyme (ACE) is a type I ectoprotein that is cleaved off the cell surface by a plasma membrane-bound metalloprotease. However, CD4, another type I ectoprotein does not undergo such cleavage-secretion. In this study, we investigated the structural determinants of the ACE protein that regulate the cleavage-secretion process. Substitution and deletion mutations revealed that the cytoplasmic domain, the transmembrane domain, and the juxtamembrane region encompassing the major and the minor cleavage sites of ACE do not regulate its cleavage. Moreover, a chimeric protein containing the distal extracellular domain of CD4 and the juxtamembrane, transmembrane, and the cytoplasmic domains of ACE, although transported to the cell surface, was not cleavage-secreted. In contrast, the distal extracellular domain of ACE was shown to be the important determinant: a protein containing the distal extracellular domain of ACE and the juxtamembrane, transmembrane, and cytoplasmic domain of CD4 was efficiently cleaved off the cell surface. The chimeric protein was cleaved within the CD4 sequence and the responsible enzymatic activity was inhibited by Compound 3, a relatively specific inhibitor of the ACE secretase activity. These results demonstrate that, in a chimeric protein, the distal extracellular domain of a cleavable protein, such as ACE, can induce a proteolytic cleavage within the juxtamembrane domain of an uncleaved protein such as CD4.

Synthesis and cleavage- secretion of enzymatically active rabbit angiotensin-converting enzyme in Pichia pastoris

Many biologically important ectoproteins that are anchored in the plasma membrane via a hydrophobic domain undergo a proteolytic cleavage process, which releases the ectodomain to the extracellular milieu in a regulated fashion. Angiotensin-converting enzyme (ACE) is one such protein that is secreted from human and mouse cells by its cleavage at one of two alternative sites in the ectodomain. Here, we report similar cleavage-secretion of ACE in the yeast Pichia pastoris. The cleavage site used in yeasts was identical to one of the two sites used in mouse cells. Moreover, as in mammalian cells, ACE secretion in yeast was inhibited by compound 3, a potent inhibitor of the metzincin family of metalloproteases. ACE proteins cleavage-secreted from yeast and from mammalian cells had identical enzymatic properties. These results demonstrate the existence of a secretase activity in yeast whose properties closely resemble those of the mammalian ACE secretase.

Different glycosylation requirements for the synthesis of enzymatically active angiotensin-converting enzyme in mammalian cells and yeast

For facilitating crystallization and structural studies of the testicular isozyme of angiotensin-converting enzyme (ACE,), we attempted the production of enzymatically active ACET proteins which are unglycosylated or underglycosylated. Expression in Escherichia coli of the rabbit ACET cDNA resulted in the synthesis of an unglycosylated but inactive protein. Similarly, unglycosylated ACET synthesized in HeLa cells, by using a cDNA in which all five potential N-glycosylation sites had been mutated, was inactive and rapidly degraded. Several ACET variants carrying mutations in one or more of the potential N-glycosylation sites were used to examine the role of glycosylation at specific sites on ACET synthesis, transport to the cell surface, cleavage processing, and enzyme activity. These experiments demonstrated that allowing glycosylation only at the first or the second site, as counted from the NH2 terminus, was sufficient for normal synthesis and processing of active ACET. In contrast, ACETg3, which had only the third glycosylation site available, was unglycosylated, enzymatically inactive and rapidly degraded. N-Glycosylated ACET could also be produced in yeast. Surprisingly, the mutant ACETg3 was synthesized, N-glycosylated, and properly transported in yeast. Wild type and mutant ACE proteins were cleavage-secreted from yeast and enzymatically active.

Purification, characterization and antitumor activity of L-asparaginase isolated from Pseudomonas stutzeri MB-405

An L-asparaginase produced by Pseudomonas stutzeri MB-405 was isolated and characterized. After initial ammonium sulfate fractionation, the enzyme was purified by consecutive column chromatography on Sephadex G-100, Ca-hydroxylapatite, and DEAE-Sephadex A-50. The 665.5-fold purified enzyme thus obtained has the specific activity of 732.3 units mg protein-1 with an overall recovery of 27.2%. The apparent M(r) of the enzyme under nondenaturing and denaturing conditions was 34 kDa and 33 kDa respectively, and the isoelectric point was 6.38 +/- 0.02. It displayed optimum activity at pH 9.0 and 37 degrees C. The enzyme was very specific for L-asparagine and did not hydrolyze L-glutaminate. The Km of the L-asparaginase was found to be 1.45 x 10(-4) M towards L-asparagine and was competitively inhibited by 5-diazo-4-oxo-L- norvaline (DONV) with a Ki of 0.03 mM. Metal ions such as Mn2+, Zn2+, Hg2+, Fe3+, Ni2+, and Cd2+ potentially inhibited the enzyme activity. The activity was enhanced in the presence of thiol-protecting reagents such as DTT, 2-ME, and glutathione (reduced), but inhibited by PCMB and iodoacetamide. The tumor inhibition study with Dalton's lymphoma tumor cells in vivo indicated that this enzyme possesses antitumor properties.

Induction and regulation of alpha-amylase synthesis in a cellulolytic thermophilic fungus Myceliophthora thermophila D14 (ATCC 48104)

The alpha-amylase enzyme synthesis was higher when M. thermophila D-14 (ATCC 48104) was grown in culture medium incorporated with starch or other carbohydrates containing maltose units. Maximum enzyme production was attained with 1% starch followed by a gradual decrease with increasing concentration. Marked decrease in alpha-amylase synthesis occurred with the addition of glucose to the culture medium and this decreasing activity was proportional to the concentration of glucose. The enzyme synthesis was resumed as soon as the glucose concentration fell below a critical level. The addition of cAMP did not eliminate the repressive activity of glucose. The findings suggest that extracellular alpha-amylase synthesis in M. thermophila D-14 was inducible and subject to catabolite repression.