Plant-based anticancer molecules: a chemical and biological profile of some important leads

A number of natural products, with diverse chemical structures, have been isolated as anticancer agents. Several potential lead molecules such as camptothecin, vincristine, vinblastine, taxol, podophyllotoxin, combretastatins, etc. have been isolated from plants and many of them have been modified to yield better analogues for activity, toxicity or solubility. Several successful molecules like topotecan, irinotecan, taxotere, etoposide, teniposide, etc. also have emerged as drugs upon modification of these natural leads and many more are yet to come. In this review, the authors have focused on four important anticancer leads, that is, camptothecin, taxol, combretastatin A-4 and podophyllotoxin. Their chemistry, structure and activity relationships, biological activities, modes of action, analogue synthesis and future prospects have been discussed.     

Effect of trifluralin on growth, morphology, and nucleic Acid synthesis

Roots and shoots of corn seedlings (Zea mays L. var. Dixie 18) germinated in trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) solutions are characterized by radial enlargement of the cortical cells and by multinucleate cells in the meristematic regions. Trifluralin inhibits elongation of Avena coleoptile sections at concentrations of 0.1 μm to 10 μm. Synthesis of DNA, RNA, and protein is suppressed in the root tips while no significant effect is noticeable in the shoots of corn germinated in trifluralin. A ³²P time-course study of 48, 72, and 96 hours utilizing phenol extraction and MAK column separation of corn root and shoot nucleic acids showed suppression of ³²P incorporation in the treated roots; however, the 72 and 96 hour treated shoots incorporated a much greater amount than the control with most of the increased incorporation found in the sRNA and DNA fractions. The increased activity in the DNA may be due to a high G-C type DNA. No selective suppression or enhancement of any particular RNA species was noticed in the treated plants.     

Improvements in algal lipid production: a systems biology and gene editing approach

Background: In the wake of rising energy demands, microalgae have emerged as potential sources of sustainable and renewable carbon-neutral fuels, such as bio-hydrogen and bio-oil.

Purpose: For rational metabolic engineering, the elucidation of metabolic pathways in fine detail and their manipulation according to requirements is the key to exploiting the use of microalgae. Emergence of site-specific nucleases have revolutionized applied research leading to biotechnological gains. Genome engineering as well as modulation of the endogenous genome with high precision using CRISPR systems is being gradually employed in microalgal research. Further, to optimize and produce better algal platforms, use of systems biology network analysis and integration of omics data is required. This review discusses two important approaches: systems biology and gene editing strategies used on microalgal systems with a focus on biofuel production and sustainable solutions. It also emphasizes that the integration of such systems would contribute and compliment applied research on microalgae.

Conclusions: Recent advances in microalgae are discussed, including systems biology, gene editing approaches in lipid bio-synthesis, and antenna engineering. Lastly, it has been attempted here to showcase how CRISPR/Cas systems are a better editing tool than existing techniques that can be utilized for gene modulation and engineering during biofuel production.     

Pituitary gland of the exotic carp, Carassius carassius Linn., with reference to the histocytology of the adenohypophysis in conjunction to male and female rhythms of reproduction

The pituitaries of the exotic carp (Carassius carassius) are studied at the light microscopic level, for the characterization of the adenohypophysial cell-types with particular emphasis to the gonadotropic potency of the pituitary in relation to the annual reproductive patterns. The gland in the fish is of the cranioleptobasic type. Based on the classical staining methods and localization of the differential cell-types, the adenohypophysis of the fish can be subdivided into the rostral (RPD) and proximal (PPD) pars distalis and the pars intermedia (PI). The pars nervosa (PN) of the fish consists of the neurosecretory (NS) fibres which show varied accumulations of the NS material in concert with the seasonal reproductive cycle. The NS tract is constituted of AF--ve nucleus praeopticus and AF + ve nucleus lateralis tuberis. 2 tinctorially different cell-types, corresponding to corticotrops and lactotrops of other teleosts, are identifiable in the RPD of the present species. In the PPD, 3 cell-types can be distinguished with various granule-staining procedures: they represent somatotrops, thyrotrops, and gonadotrops. Further, 2 gonadotropic cells with apparently different staining properties are discernible. In the PI are dispersed besides a few agranular cells, islets of 2 kinds of cells separable with combined PAS-PbH technique. Seasonal changes in the gonadosomatic index and diameter of the testicular lobules and egg diameter as indices of gonadal maturation are found to be closely interwoven with the morphometric alterations in the basophilic cell area (BCA) chosen as criterion of gonadotropic potency of the PPD. The maximum BCA values are preceded with the time of greatest atresia of the eggs indicating the influence of the pituitary gonadotropins in the follicular resorption in the test fish.     

Phosphorus uptake from different sources of phosphatic fertilizers by maize and wheat at two stages of growth

The results of pot experiments on wheat and maize with³²P labelled phosphatic fertilizers showed that P uptake after one month of sowing and at ear emergence in case of wheat has significant positive correlations with dry matter yield where as P uptake after one month of sowing has only significant positive correlation with dry matter yield and P uptake at tasseling has no correlation with dry matter yield in case of maize. P uptake and P concentration have significant correlation at both the stages of growth in case of wheat but P uptake from fertilizer and its respective concentration has only significant correlation at both the stages in case of maize.     

Study on the Trace Elements in <Emphasis Type="Italic">Swertia chirayita</Emphasis> (Roxb.) H. Karsten

An attempt has been made to analyze some trace elements and electrolytes like Zn, Cu, Mn, Fe, Co, Na, K, Ca, and Li present in the Swertia chirayita roots and leaves. The concentration of Ca in all the samples was more than 1,346.0 mg/kg and the concentration of other elements was found in the order K > Ca > Fe > Na > Mn > Zn > Co > Cu > Li in different samples of S. chirayita.     

Genetic variation and relationship among and within Withania species as revealed by AFLP markers.

Withania somnifera is an important medicinal plant, and its anticancerous properties have been attributed to various classes of withanolide compounds. The objective of the present study was to investigate the inter- and intraspecific genetic variation present in 35 individuals of W. somnifera and 5 individuals of W. coagulans using AFLP (amplified fragment length polymorphism) marker technique. The information about genetic variation determined from AFLP data for 40 individuals was employed to estimate similarity matrix value based on Jaccard's coefficient. The similarity values were further used to construct a phenetic dendrogram revealing the genetic relationships. The dendrogram generated by UPGMA (unweighted pair group method of arithmetic averages) distinguished W. somnifera from W. coagulans and formed two major clusters. These two main clusters shared a similarity coefficient of 0.3, correlating with the high level of polymorphism detected. The dendrogram further separated W. somnifera into three subclasses corresponding to Kashmiri and Nagori groups and an intermediate type. The AFLP profile of Kashmiri individuals was distinct from that of the Nagori group of plants. The intermediate genotype was distinct as it shared bands with both the Kashmiri and Nagori individuals, even though it was identified as a Kashmiri morphotype. Furthermore, the intermediate type shared a similarity coefficient of 0.8 with the Kashmiri individuals. The present work revealed low levels of variation within a population though high levels of polymorphism were detected between Nagori and Kashmiri populations. The ability of AFLP markers for efficient and rapid detection of genetic variations at the species as well as intraspecific level qualifies it as an efficient tool for estimating genetic similarity in plant species and effective management of genetic resources.     

A Carbon-Nitrogen Lyase from Leucaena leucocephala Catalyzes the First Step of Mimosine Degradation

The tree legume Leucaena leucocephala contains a large amount of a toxic nonprotein aromatic amino acid, mimosine, and also an enzyme, mimosinase, for mimosine degradation. In this study, we isolated a 1,520-bp complementary DNA (cDNA) for mimosinase from L. leucocephala and characterized the encoded enzyme for mimosine-degrading activity. The deduced amino acid sequence of the coding region of the cDNA was predicted to have a chloroplast transit peptide. The nucleotide sequence, excluding the sequence for the chloroplast transit peptide, was codon optimized and expressed in Escherichia coli. The purified recombinant enzyme was used in mimosine degradation assays, and the chromatogram of the major product was found to be identical to that of 3-hydroxy-4-pyridone (3H4P), which was further verified by electrospray ionization-tandem mass spectrometry. The enzyme activity requires pyridoxal 5′-phosphate but not α-keto acid; therefore, the enzyme is not an aminotransferase. In addition to 3H4P, we also identified pyruvate and ammonia as other degradation products. The dependence of the enzyme on pyridoxal 5′-phosphate and the production of 3H4P with the release of ammonia indicate that it is a carbon-nitrogen lyase. It was found to be highly efficient and specific in catalyzing mimosine degradation, with apparent K_m and V_max values of 1.16 × 10⁻⁴ m and 5.05 × 10⁻⁵ mol s⁻¹ mg⁻¹, respectively. The presence of other aromatic amino acids, including l-tyrosine, l-phenylalanine, and l-tryptophan, in the reaction did not show any competitive inhibition. The isolation of the mimosinase cDNA and the biochemical characterization of the recombinant enzyme will be useful in developing transgenic L. leucocephala with reduced mimosine content in the future.Leucaena leucocephala is an important agroforestry tree legume of the tropics, and its foliage can be used as a protein-rich fodder (Garcia et al., 1996; Soedarjo and Borthakur, 1998). L. leucocephala is highly tolerant to drought (Shelton and Brewbaker, 1994) and resistant to many pests and diseases. The protein-rich foliage and tolerance to various abiotic and biotic stresses make L. leucocephala a promising legume for use as a fodder. In spite of these desirable attributes, the use of L. leucocephala as a fodder is rather limited because its foliage also contains an N-heterocyclic nonprotein amino acid, known as mimosine, which is toxic to both prokaryotic cells (Soedarjo et al., 1994) and eukaryotic cells (Lalande, 1990). Mimosine inactivates a variety of enzymes either by chelating bivalent metallic ions and thereby limiting their availability for use as cofactors by several metallic ion-dependent enzymes, such as ribonucleotide reductase, alkaline phosphatase, and dopamine β-hydroxylase (Chang, 1960; Hashiguchi and Takahashi, 1977; Dai et al., 1994), or by forming a stable complex with pyridoxal-5′-phosphate (PLP), leading to the inactivation of PLP-dependent enzymes, such as cystathionine synthetase, cystathionase, Asp-Glu transaminase, Tyr decarboxylase, tyrosinase, and l-dopa decarboxylase (Crounse et al., 1962; Lin et al., 1962, 1963; Hylin, 1969). The inactivation of important enzymes by mimosine causes various physiological abnormalities, including enlarged thyroid glands, infertility, birth defects, and loss of hairs (Crounse et al., 1962; Hamilton et al., 1968; Joshi, 1968; Dewreede and Wayman, 1970; Reis et al., 1975; Jones et al., 1976).Mimosine is abundant in all parts of L. leucocephala, and on a dry weight basis, L. leucocephala leaves contain approximately 5% mimosine (Soedarjo and Borthakur, 1998). Such high mimosine content in the foliage indicates that mimosine may have some functional role in the plant. Previously, mimosine has been shown to inhibit DNA synthesis in many DNA viruses by chelating iron required by ribonucleotide reductase (Dai et al., 1994), suggesting its role in defense against virus attacks. Besides this, other possible roles of mimosine in L. leucocephala are not well established. Considering its biochemical properties of inactivating various enzymes that require either bivalent metallic ions or PLP as cofactors, mimosine may have a role in plant defense, and based on its chemical composition, it may serve as a reservoir of carbon and nitrogen for survival and growth under nutrient-limiting conditions. But the utilization of mimosine as a source of carbon and nitrogen is possible only if the plant has specific enzymes to catabolize it. Interestingly, the presence of such mimosine-degrading enzymes has been reported from seedling extracts of L. leucocephala and Mimosa pudica, another mimosine-containing plant (Suda, 1960; Smith and Fowden, 1966). Smith and Fowden (1966) identified the mimosine-degrading enzyme from L. leucocephala seedling extracts as a carbon-nitrogen (C-N) lyase that converted mimosine into 3,4-dihydroxypyridine (3,4DHP), pyruvic acid, and ammonia (Fig. 1). Additionally, a mimosine-degrading enzyme, mimosinase, was purified from L. leucocephala leaves (Tangendjaja et al., 1986) and was found to degrade mimosine into 3-hydroxy-4-pyridone (3H4P; Fig. 1). However, the genes encoding the mimosine-degrading enzymes from L. leucocephala have not been isolated and characterized.Open in a separate windowFigure 1.Chemical structures of mimosine (A), 3H4P (B), 3,4DHP (C), pyruvate (D), and ammonium (E).The goals of this study were to isolate complementary DNA (cDNA) for a mimosine-degrading enzyme from L. leucocephala and to determine the biochemical and kinetic properties of the encoded enzyme. This will help us to understand roles of mimosine and mimosine-degrading enzymes in L. leucocephala. Additionally, it may be useful in developing transgenic L. leucocephala with reduced mimosine content, which will make this tree legume suitable for use as a nutritious fodder for animals in the future.     

Ni<Superscript>+2</Superscript>-inhibited radicle growth in germinating wheat seeds involves alterations in sugar metabolism

Nickel (Ni) is a trace element essential for the growth and development of plants. Conversely, when in excess, Ni inhibits seed germination and reduces seedling growth. Therefore, we investigated the effect of Ni⁺² (5–50 μM; supplied as nickel sulfate: NiSO₄·6H₂O) on the activity of enzymes involved in sugar metabolism of wheat (Triticum aestivum L.) seedlings after 96 h of exposure to the metal. Ni⁺² treatment reduced root and coleoptile length of emerging wheat seedlings and the effect was more pronounced on the root length. Ni⁺² (5–50 μM) treatment significantly enhanced carbohydrate content by 21–100 % over that of the control. In contrast, protein and reducing sugar contents declined by 17–43 and 22–69 %, respectively. The reduction in total protein content was confirmed by SDS-PAGE analysis. The activities of starch-metabolizing enzymes declined upon Ni⁺² stress in a concentration-dependent manner. Activities of α- and β-amylases, acid and alkaline invertases, acid and alkaline phosphatases, and starch phosphorylase declined by 18–74 and 24–85 %, 42–76 and 21–73 %, 15–54 and 28–72 %, and 50–83 %, respectively, when compared to the control. The study concludes that Ni⁺² impairs sugar metabolism as indicated by decline in the activity of sucrose and starch hydrolyzing enzymes. It resulted in decrease in the availability of biochemical energy and sugars required for the synthesis, leading to inhibition of radicle growth in germinating wheat seeds.