Photosynthetic Efficiency and Antioxidant Defense Potential are Key Players in Inducing Drought Tolerance in Transgenic Tobacco Plants Over-Expressing AVP1

Journal of Plant Growth Regulation - Plants have developed a number of physiological, biochemical, and molecular strategies to overcome water deficit conditions. Arabidopsis vacuolar...     

Multiple forms of alkaline phosphatase isoenzymes of Serratia marcescens

Alkaline phosphatase (APase) isoenzymes produced by different strains of Serratia marcescens were examined. Variation of isoenzyme patterns with respect to number and their mobilities in starch gels after electrophoresis were observed. Ten strains gave a 1-isoenzyme pattern with 5 different mobilities; 7 strains gave a 2-isoenzyme pattern with 3 different mobilities; 9 strains gave a 3-isoenzyme pattern with 5 different mobilities; and 3 strains gave a 4-isoenzyme pattern. Three strains synthesized two electrophoretically distinct APases in low phosphate medium. A high concentration of inorganic phosphate induced the synthesis of one of these APase isoenzymes.     

Acritarchs,miospores and correlation of the Ludlovian-Downtonian and Silurian-Devonian boundaries

An attempt is made to use palynomorphs to correlate the Ludlovian-Downtonian and the Silurian-Devonian boudaries in successions from the British Isles, Estonia, Podolia and north Africa. Miospores are found to be of most use for this purpose: (a) the micronatus-newportensis zone can be recognised in the Anglo-Welsh area, in Podolia and in north Africa, and the base of this zone indicates a level above, but close to, the Silurian-Devonian boundary; (b) the Ludlovian-Downtonian boundary is well-defined in the Anglo-Welsh area on the basis of miospores and can be determined approximately in north Africa and Estonia since several miospore species appear at or close to this boundary. The lack of stratigraphically important acritarch and miospore species in the Silurian-Devonian stratotype at Klonk (Czechoslovakia) underlines the importance of the Podolian sequence for the recognition of the Silurian-Devonian boundary in continental sequences. Recognition of the Ludlovian-Downtonian boundary in Podolia is difficult since the miospores below the Borschov Horizon have not been systematically described and are probably rare. Further, there are difficulties in using acritarchs for interregional correlation since they appear to be considerably influenced by provinciality and local environmental factors. From the palynological point of view therefore the Ludlovian-Downtonian boundary should be chosen from a sequence in which miospores are common, since one based on acritarchs would involve two stratotypes, one from the Deunffia-Domasia, and one from the carminae, realms. Finally, some features of current palinspastic continental plate reconstructions are discussed in the light of acritarch provinciality.     

Photoperiodic induction of the pupal diapause in the tobacco hornworm, Manduca sexta

A study was made of photoperiodic induction of the facultative pupal diapause in the tobacco hornworm, Manduca sexta, reared on artificial diet in the laboratory. The species entered a prolonged diapause when the egg and larval feeding stages were reared in daily photoperiods of 13·5 hr or less. Diapause was induced in all insects at photoperiods ranging from 1 to 13 hr, and part of the population entered diapause at only 15 to 30 min of light per day. Photoperiods of 14 hr or more and continous darkness prevented diapause. Duration of diapause varied with the inductive photoperiod in which the hornworms were reared during the sensitive period. Insects reared in longer diapause-inducing photoperiods within a range of 12 to 13·25 hr remained in diapause longer than those reared in shorter photoperiods. There was no difference in the rate of larval development of hornworms reared in diapause-inducing vs diapause-preventing photoperiods. Temperatures of 26 to 30°C were most favourable for the photoperiodic induction of diapause; at 21°C, the critical photoperiod and incidence of diapause were decreased. Diapause induction was suppressed by low (18°C) and higher (33°C) temperatures. The number of inductive 12L:12D (light = 12 hr; dark = 12 hr) cycles required to induce diapause ranged from as few as 5 for some insects to as many as 12 for others when the post-inductive régimen was continuous light, but with insects previously held in continuous dark, as few as 2 12L:12D cycles during the last 2 days of larval feeding induced diapause in 38 per cent of the population. Only 3 to 4 cycles of 15L:9D during the final larval instar reversed inductive effects of 14 to 15 12L:12D cycles. Photoperiodic sensitivity extended from the late embryo to the end of larval feeding but showed considerable fluctuation during development with maximum sensitivity occurring just before egg hatch and during larval growth.Light breaks applied at different times during the dark period of 12L:12D cycles generated different response curves, depending on the number of cycles in which light breaks were repeated. When repeated for 6 cycles, a unimodal response curve was obtained; 10 cycles produced a bimodal curve and light breaks given for 18 cycles throughout the sensitive period averted diapause regardless of time of night applied. It is suggested that diapause is regulated by a photo- and thermolabile substance that accumulates during long nights (11 hr or more) and acts during the early pupal stage to inhibit the translocation and release of development-promoting neurosecretion from the brain.     

Mycorrhizal inoculation in neem (Azadirachta indica) enhances azadirachtin content in seed kernels

In view of the high mycorrhizal dependency of neem trees (Azadirachta indica), an experiment was conducted to study if Arbuscular Mycorrhizal (AM) inoculation can enhance the azadirachtin content in seed kernels of trees grown in the field. Azadirachtin is an important active ingredient in neem seed kernels based on which a large biopesticide industry has emerged in India and few countries in Europe and the USA. Inoculation of neem seedlings in the nursery with Glomus fasciculatum and Glomus mosseae resulted in increased height, dry weight, root colonization and phosphorus (P) content. In a separate experiment, field-grown neem plants inoculated in the nursery and during transplantation with Glomus fasciculatum were evaluated after 5 years. No significant differences were found in the tree height, girth at breast height (GBH) and fruit yield but oil percentage, total triterpenoids and azadirachtin content in kernels increased significantly as a result of AM inoculation. A similar enhancement in azadirachtin was noted with P application. These results open up possibilities of producing quality neem seed with high bioactive ingredients through AM inoculation.     

Carbon-nanotube-modified electrodes for amplified enzyme-based electrical detection of DNA hybridization

Carbon-nanotube-modified glassy carbon (CNT/GC) transducers have been developed for enhancing the sensitivity and stability of enzyme-based electrochemical bioassays of DNA hybridization. The amplified signal reflects the interfacial accumulation of phenolic products of the alkaline-phosphatase tracer onto the CNT layer. In particular, chronopotentiometric measurements (following short accumulation periods) offer a substantial enhancement of the response of enzymatically liberated alpha-naphthol. The CNT modifier also leads to a dramatic improvement in the stability of the amperometric response of alpha-naphthol. These advantages of CNT/GC electrodes are illustrated from comparison to unmodified glassy carbon electrodes. Factors influencing the adsorptive accumulation of alpha-naphthol, and the overall performance of the new DNA assay, are assessed and optimized. The attractive performance characteristics of the new multi-amplification electrochemical detection of DNA hybridization are reported in connection to the detection of nucleic acid sequences related to the breast cancer BRCA1 gene.     

Persulfide properties of thiocystine and related trisulfides

Thiocystine (bis[2-amino-2-carboxyethyl]trisulfide) functions as a persulfide in transferring its sulfane sulfur to thiophilic acceptors. This occurs by formation of a reactive intermediate, thiocysteine (alanine hydrogen disulfide). In the absence of an acceptor sulfur is released in elemental form. Thiocystine is relatively stable in the pH range of 2–9. However, its conversion to unstable thiocysteine is accelerated by sulfhydryl compounds, rhodanese, or reagents that cleave sulfur-sulfur bonds to yield sulfhydryl groups. Since thiocystine has been detected in biological systems, it is proposed that in provides a storage form of sulfane sulfur. Trisulfides related to thiocystine show qualitatively similar properties.     

Detection of l-alanylaminopeptidase activity in microorganisms using chromogenic self-immolative enzyme substrates

Three potential chromogenic enzymatic probes, each possessing a self-immolative spacer unit, were synthesised for the purpose of detecting l-alanylaminopeptidase activity in microorganisms. An Alizarin-based probe was the most effective, allowing several species to generate strongly coloured colonies in the presence of metal ions.