In vitro plant regeneration via somatic embryogenesis from root culture of some rhizomatous irises

A method for plant regeneration of Iris via somatic embryogenesis is described. Root and leaf pieces from in vitro-grown plants of several genotypes of rhizomatous Iris sp. were cultured in vitro. Callus induction occurred only on root cultures incubated under low light intensity (35 mol m^-2 s^-1) on two induction media containing 2,4-D (4.5 or 22.5 M), NAA (5.4 M) and kinetin (0.5 M). Somatic embryos developed after transfer of callus onto four regeneration media containing 9 or 22 M BA, or 5 M kinetin and 2 M TIBA or 9 M BA and 4 M TIBA. Plantlets could be obtained from these somatic embryos. Genotypic differences were found both in callus induction and somatic embryo formation, with I. pseudacorus responding better than I. versicolor or I. setosa. Cytological analysis performed on root tips of 80 regenerated plants revealed that two of the I. pseudacorus regenerants were tetraploid.Abbreviations 2,4-D dichlorophenoxy acetic acid - NAA naphthaleneacetic acid - BA 6-benzyladenine - TIBA 2,3,5-triiodobenzoic acid - IBA indolebutyric acid     

Leakage of electrolytes and phenols and altered activity profile of peroxidase and its isoenzymes from wheat leaves inoculated withPuccinia recondita

Second and third leaves of 25-day old wheat (Triticum aestivum L.) planta, cultivar WL-711, were inoculated with three races of the brown rust pathogen,Puccinia recondita f. sp.tritici. The host reflected a differential interaction response towards these races, viz., susceptible reaction to race 77 (reaction type 4) intermediate reaction to race 104 (reaction type 1 - 3) and resistant reaction to race 63 (reaction type 0). Post-inoculation mutual interaction brought about observable changes in peroxidase activity along with leakage of electrolytes and phenolic constituents indicating altered permeability of host tissue. Differential increase in leakage of electrolytes and phenols occurred with increase of peroxidase activity during 12 h and 24 h post-inoculation, however, during 36 h, 48 h and 72 h post-inoculation, electrolyte leakage increased continuously with corresponding increases in peroxidase activity in all three interactions, while leakage of phenols showed a differential pattern. The differential changes in isoenzymic pattern of peroxidase activity were also noted during the progressive infection process which may also be an indication of altered permeability of the host issue at the very onset of brown rust infection.     

Biosurfactant production by Pseudomonas sp. and its role in aqueous phase partitioning and biodegradation of chlorpyrifos

Aim:  To study the effect of biosurfactant on aqueous phase solubility and biodegradation of chlorpyrifos.
Methods and Results:  A Pseudomonas sp. (ChlD), isolated from agricultural soil by enrichment culture technique in the presence of chlorpyrifos, was capable of producing biosurfactant (rhamnolipids) and degrading chlorpyrifos (0·01 g l⁻¹). The partially purified rhamnolipid biosurfactant preparation, having a CMC of 0·2 g l⁻¹, was evaluated for its ability to enhance aqueous phase partitioning and degradation of chlorpyrifos (0·01 g l⁻¹) by ChlD strain. The best degradation efficiency was observed at 0·1 g l⁻¹ supplement of biosurfactant, as validated by GC and HPLC studies.
Conclusion:  The addition of biosurfactant at 0·1 g l⁻¹ resulted in more than 98% degradation of chlorpyrifos when compared to 84% in the absence of biosurfactant after 120-h incubation.
Significance and Impact of the Study:  This first report, to the best of our knowledge, on enhanced degradation of chlorpyrifos in the presence of biosurfactant(s), would help in developing bioremediation protocols to counter accumulation of organophosphates to toxic/carcinogenic levels in environment.     

Neuroendocrine control of oocyte development in Poecilocera picta (Insecta: Orthoptera)

The neuroendocrine control of oocyte development in Poecilocera picta Fab. has been described. The secretory activity of the A type of neurosecretory cells has been correlated with ovarian development. In P. picta during the first four days after emergence the neurosecretory material is seen passing down the axons but the cells are largely devoid of neurosecretory material. When the oocytes are developed the A type cells are with stored neurosecretory material.
In P. picta the mature males do not appear to accelerate the process of maturation in females. The females which are reared without males or with castrated males also mature at the same time as the females which are reared with males. The corpus allatum also enlarges and decreases at the same period. The number of resorptive bodies is much more in the females which are reared with castrated males or without males. There appears to be some correlation in the secretion of the neurosecretory material, copulation, and the appearance of resorptive bodies. In P. picta the role of the mature male is only in copulation which very likely allows the cell to synthesize and secrete and release a large amount of neurosecretory material whose discharge in the haemolymph enables a successful development of the oocyte. Corpus allatum appears to be controlled by a precursor from the brain.
Cautery of the cerebral neurosecretory cells, allatectomy and sectioning of the nerves have been done to find out the role of neurosecretory material.     

Characterization of hygromycin-resistant transformants of thermophilic fungus Thermomyces lanuginosus

Hygromycin-resistant stable transformants of the thermophilic fungus, Thermomyces lanuginosus, were obtained by electroporation of germinating aleurospores with a plasmid pMP6, coding for hygromycin resistance. Southern hybridization analysis revealed that the gene is integrated into the chromosome. The hygromycin-resistant transformants were characterized for morphological changes, growth response towards the presence of antagonistic metabolites (hygromycin, 2-deoxy-D-glucose, cylcoheximide, benlate and acriflavine) on plates and enzyme production (amylases, pectinases and xylanase) in shake flask cultures. A hygromycin-resistant transformant hyg 33 was characterized as non-sporulating, 2-deoxy-D-glucose-resistant, acriflavine-sensitive and xylanase hypo-producer and is being used as parental strain for breeding strains through protoplast fusion.     

Mechanisms of low Na+-induced increase in intracellular calcium in KCl-depolarized rat cardiomyocytes

Although low Na⁺ is known to increase the intracellular Ca²⁺ concentration ([Ca²⁺]_i) in cardiac muscle, the exact mechanisms of low Na⁺-induced increases in [Ca²⁺]_i are not completely defined. To gain information in this regard, we examined the effects of low Na⁺ (35 mM) on freshly isolated cardiomyocytes from rat heart in the absence and presence of different interventions. The [Ca²⁺]_i in cardiomyocytes was measured fluorometrically with Fura-2 AM. Following a 10 min incubation, the low Na⁺-induced increase in [Ca²⁺]_i was only observed in cardiomyocytes depolarized with 30 mM KCl, but not in quiescent cardiomyocytes. In contrast, low Na⁺ did not alter the ATP-induced increase in [Ca²⁺]_i in the cardiomyocytes. This increase in [Ca²⁺]_i due to low Na⁺ and elevated KCl was dependent on the extracellular concentration of Ca²⁺ (0.25–2.0 mM). The L-type Ca²⁺-channel blockers, verapamil and diltiazem, at low concentrations (1 M) depressed the low Na⁺, KCl-induced increase in [Ca²⁺]_i without significantly affecting the response to low Na⁺ alone. The low Na⁺, high KCl-induced increase in [Ca²⁺]_i was attenuated by treatments of cardiomyocytes with high concentrations of both verapamil (5 and 10 M), and diltiazem (5 and 10 M) as well as with amiloride (5–20 M), nickel (1.25–5.0 mM), cyclopiazonic acid (25 and 50 M) and thapsigargin (10 and 20 M). On the other hand, this response was augmented by ouabain (1 and 2 mM) and unaltered by 5-(N-methyl-N-isobutyl) amiloride (5 and 10 M). These data suggest that in addition to the sarcolemmal Na⁺–Ca²⁺ exchanger, both sarcolemmal Na⁺–K⁺ATPase, as well as the sarcoplasmic reticulum Ca²⁺-pump play prominent roles in the low Na⁺-induced increase in [Ca²⁺]_i. (Mol Cell Biochem 263: 151–162, 2004)