NaCl as a physiological modulator of proline metabolism and antioxidant potential in Phyllanthus amarus

Some medicinal plants need to be cultivated commercially in order to meet the ever-increasing demand for medicinal plants for the indigenous systems of medicine as well as for the pharmaceutical industry; in this regard, it seems significant to test the important medicinal plants for their salt-tolerance capacity, with a view to exploiting the saline lands for medicinal plant cultivation. Phyllanthus amarus plants were grown in the presence of NaCl in order to study the effect of NaCl (80 mM NaCl) in the induction of oxidative stress in terms of lipid peroxidation (TBARS content), H2O2 content, osmolyte concentration, proline(PRO)-metabolizing enzymes, and antioxidant enzyme activities. Groundwater was used for irrigation of control plants. Plants were uprooted randomly on 90 days after sowing (DAS). NaCl-stressed plants showed increased TBARS, H2O2, glycine betaine (GB), and PRO contents, whereas NaCl uptake decreased proline oxidase (PROX) activity and increased gamma-glutamyl kinase (gamma-GK) activity when compared to control. The antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased under salinity.     

Changes in antioxidant potential and sink-organ dry matter with pigment accumulation induced by hexaconazole in Plectranthus forskholii Briq

An investigation was conducted in Plectranthus forskholii by giving it different concentrations (10, 15, 20, 25, and 30 mg L(-1)) of hexaconazole, a fungicide cum plant-growth regulator, in order to find out its effects on growth, pigment composition, and antioxidant potential. The treatments were given as soil drenching on different growth stages. All the concentrations of hexaconazole used significantly decreased the stem length and leaf area, whereas side branches, fresh and dry matter content, photosynthetic pigments, and antioxidant potential were increased. The number of tubers, length and girth of tubers, fresh and dry weight of tubers and tuber pigments were found to be the highest at a 25 mg L(-1) concentration of hexaconazole. Hexaconazole application at 25 mg L(-1) concentration was found to be more effective than 10, 15, 20, 25, and 30 mg L(-1) in promoting fresh and dry weight of root tuber over 165 days after planting. The pigments like chlorophyll, carotenoid; anthocyanins, xanthophylls and antioxidants such as ascorbic acid, reduced glutathione and total phenol were significantly increased under hexaconazole treatment when compared to untreated control plants.     

Are Prorocentrum hoffmannianum and Prorocentrum belizeanum (DINOPHYCEAE,PROROCENTRALES), the same species? An integration of morphological and molecular data

The taxonomic assignment of Prorocentrum species is based on morphological characteristics; however, morphological variability has been found for several taxa isolated from different geographical regions. In this study, we evaluated species boundaries of Prorocentrum hoffmannianum and Prorocentrum belizeanum based on morphological and molecular data. A detailed morphological analysis was done, concentrating on the periflagellar architecture. Molecular analyses were performed on partial Small Sub‐Unit (SSU) rDNA, partial Large Sub‐Unit (LSU) rDNA, complete Internal Transcribed Spacer Regions (ITS1‐5.8S‐ITS2), and partial cytochrome b (cob) sequences. We concatenated the SSU‐ITS‐LSU fragments and constructed a phylogenetic tree using Bayesian Inference (BI) and maximum likelihood (ML) methods. Morphological analyses indicated that the main characters, such as cell size and number of depressions per valve, normally used to distinguish P. hoffmannianum from P. belizeanum, overlapped. No clear differences were found in the periflagellar area architecture. Prorocentrum hoffmannianum and P. belizeanum were a highly supported monophyletic clade separated into three subclades, which broadly corresponded to the sample collection regions. Subtle morphological overlaps found in cell shape, size, and ornamentation lead us to conclude that P. hoffmanianum and P. belizeanum might be considered conspecific. The molecular data analyses did not separate P. hoffmannianum and P. belizeanum into two morphospecies, and thus, we considered them to be the P. hoffmannianum species complex because their clades are separated by their geographic origin. These geographic and genetically distinct clades could be referred to as ribotypes: (A) Belize, (B) Florida‐Cuba, (C1) India, and (C2) Australia.     

Short- and long-day responses in the pre-adult developmental duration of two species of Camponotus ants

We assessed the effect of different day/night lengths on the pre-adult developmental time of two species of Camponotus ants that normally develop in dark underground nests. We assayed larval (egg-to-pupal formation), pupal (pupal formation-to-adult emergence), and pre-adult (egg-to-adult emergence) durations in these ants under three different light/dark (LD) cycles of 12:12 h, 10:14 h, and 14:10 h. We observed that the pre-adult development time of ants under these day lengths was significantly different. Although both species developed fastest under 12:12 h LD, when asymmetric LD cycles were compared, night-active species (Camponotus compressus) developed faster under short days (10:14 h) and day-active species (C. paria) developed faster under long days (14:10 h). This day/night-length-mediated difference in pre-adult developmental duration was mostly due to modulation of larval duration; however, in day-active species it was also via altered pupal duration. These results thus indicate that the two species of Camponotus ants respond differently to short and long days, suggesting that seasonal timers regulate pre-adult development time in tropical ant species living in dark underground nests.     

An efficient protocol for large-scale plantlet production from male floral meristems of <Emphasis Type="Italic">Musa</Emphasis> spp. cultivars Virupakshi and Sirumalai

In vitro propagation has played a key role for obtaining large numbers of virus free, homogenous plants, and for breeding of plantains and bananas (Musa spp.). Explant sources utilized for banana micropropagation include suckers, shoot tips, and floral buds. The present study employed male floral meristems as explant material for micropropagation of hill banana ecotypes (AAB) ‘Virupakshi’ and ‘Sirumalai.’ Immature male floral buds were collected from healthy plants from hill banana growing areas. Exposure of explants to ethyl alcohol (70%, v/v) for 30 s, then mercuric chloride (0.1%, w/v) for 30 s, followed by three independent rinses of 5 min each in autoclaved, double-distilled water satisfactorily reduced the contamination. Male floral bud explants were cultured on Murashige and Skoog (MS) basal medium supplemented with different combinations of 6-benzylaminopurine (BAP), coconut water, naphthaleneacetic acid, gibberellic acid, and additional supplements. MS medium supplemented with 5 mg l⁻¹ BAP and coconut water (15%) was the most efficient media for shoot initiation and multiple shoot formation (15 shoots from a single part of a floral bud). The best response for shoot elongation was obtained using the combination of basal MS, 5 mg l⁻¹ BAP, 1 mg l⁻¹ naphthaleneacetic acid and 1.5 mg l⁻¹ gibberellic acid. Regenerated shoots were rooted in basal MS medium within 15–20 d. The rooted plantlets were transferred to a soil mixture and maintained at a temperature of 25 ± 2°C for 10 d and then at room temperature (30–32°C) for 2 wk, before transferring to a greenhouse. The regenerated plantlets showed 100% survival.     

Sphingomyelin synthases regulate protein trafficking and secretion

Sphingomyelin synthases (SMS1 and 2) represent a class of enzymes that transfer a phosphocholine moiety from phosphatidylcholine onto ceramide thus producing sphingomyelin and diacylglycerol (DAG). SMS1 localizes at the Golgi while SMS2 localizes both at the Golgi and the plasma membrane. Previous studies from our laboratory showed that modulation of SMS1 and, to a lesser extent, of SMS2 affected the formation of DAG at the Golgi apparatus. As a consequence, down-regulation of SMS1 and SMS2 reduced the localization of the DAG-binding protein, protein kinase D (PKD), to the Golgi. Since PKD recruitment to the Golgi has been implicated in cellular secretion through the trans golgi network (TGN), the effect of down-regulation of SMSs on TGN-to-plasma membrane trafficking was studied. Down regulation of either SMS1 or SMS2 significantly retarded trafficking of the reporter protein vesicular stomatitis virus G protein tagged with GFP (VSVG-GFP) from the TGN to the cell surface. Inhibition of SMSs also induced tubular protrusions from the trans Golgi network reminiscent of inhibited TGN membrane fission. Since a recent study demonstrated the requirement of PKD activity for insulin secretion in beta cells, we tested the function of SMS in this model. Inhibition of SMS significantly reduced insulin secretion in rat INS-1 cells. Taken together these results provide the first direct evidence that both enzymes (SMS1 and 2) are capable of regulating TGN-mediated protein trafficking and secretion, functions that are compatible with PKD being a down-stream target for SMSs in the Golgi.