In vitro protocols and field performance of elites of an important bamboo Dendrocalamus hamiltonii Nees et Arn. Ex Munro*

Seedling raised elites of Dendrocalamus hamiltoniiNees et Arn. Ex Munro were chosen as the source of nodal explants from precocious branches. While axillary bud break was accomplished in hormone free 1/2MS medium containing sucrose (3%, w/v), BA supplementation was required for shoot proliferation. A variety of hormonal combinations induced rooting in clumps of shoots. Somatic embryogenesis was also obtained in callus cultures raised in 2,4-D supplemented MS medium and plantlets derived from somatic embryos were hardened for field transfer. Comparative growth performances of plants raised from nodal cuttings of field-grown plants, those from single node cuttings of precocious branches and from somatic embryos indicated that growth performance of the tissue culture raised plants was relatively better than those from nodal cuttings. Improved protocols for efficient micropropagation are visualized to provide an impetus to raising of bamboo nurseries of elite genotypes in bamboo growing areas of western Himalayas.     

4-thio-U cross-linking identifies the active site of the VS ribozyme

To identify nucleotides in or near the active site, we have used a circularly permuted version of the VS ribozyme capable of cleavage and ligation to incorporate a single photoactive nucleotide analog, 4-thio- uridine, immediately downstream of the scissile bond. Exposure to UV light produced two cross-linked RNAs, in which the 4-thio-uridine was cross-linked to A756 in the 730 loop of helix VI. The cross-links formed only under conditions that support catalytic activity, suggesting that they reflect functionally relevant conformations of the RNA. One of the cross-linked RNAs contains a lariat, indicative of intramolecular cross-linking in the ligated RNA; the other is a branched molecule in which the scissile phosphodiester bond is cleaved, but occupies the same site in the ribozyme-substrate complex. These are the two forms of the RNA expected to be the ground state structures on either side of the transition state. This localization of the active site is consistent with previous mutational, biochemical and biophysical data, and provides direct evidence that the cleavage site in helix I interacts with the 730 loop in helix VI.     

Peripheral nerve connections influence the appearance of neurosecretary material in neural sheath of ventral ganglion of the fly Sarcophaga bullata: an immunocytochemical study

This study examined the role of the brain and peripheral connections with the target organs in the appearance of neurosecretary material within the dorsal neural sheath of the ventral ganglion of the fly S. bullata. Specifically, the accumulation of the neuropeptide FMRFamide (the neurosecretary material) was examined by immunocytochemistry. Immunoreactions were performed on: (1) a normal intact ventral ganglion, (2) an isolated ventral ganglion that was cultured in vivo, and (3) a ventral ganglion that was isolated by transection from the brain, but retained its peripheral nerve connections. The results demonstrate that (a) the neurons of the ganglia survive and exhibit FMRFamide immune reaction independent of their peripheral connections, and (b) the accumulation of neuropeptide in the dorsal neural sheath is controlled by intact peripheral nerve connections with the ganglion. It is suggested that in the absence of their peripheral connections, the axons of FMRFamide immunoreactive neurons fail to invade the neural sheath resulting in the accumulation of neurosecretary material.     

Identification and Characterization of Pancreatic Eukaryotic Initiation Factor 2 α-Subunit Kinase, PEK, Involved in Translational Control

In response to various environmental stresses, eukaryotic cells down-regulate protein synthesis by phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF-2α). In mammals, the phosphorylation was shown to be carried out by eIF-2α kinases PKR and HRI. We report the identification and characterization of a cDNA from rat pancreatic islet cells that encodes a new related kinase, which we term pancreatic eIF-2α kinase, or PEK. In addition to a catalytic domain with sequence and structural features conserved among eIF-2α kinases, PEK contains a distinctive amino-terminal region 550 residues in length. Using recombinant PEK produced in Escherichia coli or Sf-9 insect cells, we demonstrate that PEK is autophosphorylated on both serine and threonine residues and that the recombinant enzyme can specifically phosphorylate eIF-2α on serine-51. Northern blot analyses indicate that PEK mRNA is expressed in all tissues examined, with highest levels in pancreas cells. Consistent with our mRNA assays, PEK activity was predominantly detected in pancreas and pancreatic islet cells. The regulatory role of PEK in protein synthesis was demonstrated both in vitro and in vivo. The addition of recombinant PEK to reticulocyte lysates caused a dose-dependent inhibition of translation. In the Saccharomyces model system, PEK functionally substituted for the endogenous yeast eIF-2α kinase, GCN2, by a process requiring the serine-51 phosphorylation site in eIF-2α. We also identified PEK homologs from both Caenorhabditis elegans and the puffer fish Fugu rubripes, suggesting that this eIF-2α kinase plays an important role in translational control from nematodes to mammals.     

Effect of plant growth regulators and different nitrogen sources on NADP-isocitrate dehydrogenase activity of radish cotyledons

NADP-isocitrate dehydrogenase (NADP-ICDH) activity of radish (Raphanus sativus L.) seedlings pretreated with various plant growth regulators: KiN, GA, and ABA and different nitrogen sources viz. KNO₃, NH₄Cl and NH₄NO₃ in light and dark was investigated. ICDH activity was significantly higher in light than in dark; addition of different nitrogen sources reduced it to a greater extent in NO₃ supplementation. Among hormonal treatment only KiN showed slight promotion with KNO₃ and NH₄NO₃. On the other hand in light KNO₃ and/or NH₄NO₃ promoted ICDH activity and among hormones, KiN significantly promoted the activity in KNO₃ and NH₄NO₃ supplemented seedlings while ABA was effective in NH₄CL. It is suggested that in non-photosynthetic tissues, NADP-ICDH provides both reductant and carbon skeleton for glutamate synthesis.     

Allatostatin-like immunoreactivity in the optic lobe of the fly Sarcophaga bullata.

An antiserum against Diploptera allastostain 1 (Dip-AST1) was used to map the distribution of allatostain containing neurons in the optic lobes of the fly Saccrophaga bullata. Strongly immunoreacting neurons were found in two areas of the optic ganglia, namely, the medulla and the area between medulla and lobula. These cells were generally interneurons arborizing the base of the medulla. The positive reaction of specific populations of the optic lobe neurons against allatostain antiserum suggests some role for this neuropeptide in the visual physiology of the fly.     

Characterization of the autophosphorylation of Era, an essential Escherichia coli GTPase

Era is an essential protein in Escherichia coli which binds both GTP and GDP and has an intrinsic GTPase activity. Studies on the role of GTP/GDP binding and GTPase activity in an attempt to understand its function lead to the observation that Era is autophosphorylated. The autophosphorylated reaction is specific for GTP and cannot use ATP as a phosphoryl group donor. The reaction velocity is of first order with respect to protein concentration, suggesting an intramolecular mechanism. Autophosphorylation occurs at serine and threonine residues. The major phosphorylated tryptic peptide isolated after autophosphorylation has been identified as ISITSR, from residue 33 to 38. The peptide contains the site of phosphorylation and two potential sites for serine and threonine phosphorylation. Subsequently, both the threonine residue at position 36 and the serine residue at position 37 were altered to alanine. The double mutant Era, but not individual single mutants, was unable to functionally complement the growth of an E. coli strain which cannot produce wild-type Era protein at high temperature. This suggests that either threonine 36 or serine 37 has to exist for the function of Era In vivo. phosphorylation of Era was also examined by two-dimensional gel electrophoresis. Era has been previously assigned two distinct positions having two different X-Y co-ordinates: one of the spots (H032.0) was identified as phosphorylated Era, indicating that a substantial portion of Era in the cell is indeed phosphorylated. Therefore, Era autophosphorylation is likely to play an important physiological role in the cell. The sequence encoding the C-terminus previously published had a missing C between A900 and GgO1. As a resuit of the frameshift, Era consists of 301 residues, 15 fewer than originaiiy reported.     

Histochemical studies on the body wall of nematodes: Haemonchus contortus (Rud., 1803) and Xiphinema insigne Loos, 1949.

Histochemical studies on the body wall of Haemonchus contortus (Rud.) and Xiphinema insigne Loos have been made. In H. contortus, the cuticle is mainly proteinous in nature. The lipids and PAS-postive materials are only present in cortical layers. In addition, haemoglobin and acid phosphatase are also present. The hypodermis shows the presence of glycogen, lipids, RNA, acid and alkaline phosphatases. The oval dense body is composed of keratinous and collagenous proteins associated with acid mucopolysaccharides. Muscles carry a greater concentration of glycogen granules and phospholipids. In X. insigne, the cuticle is rich in sudanophilic lipids. The cuticle also consists of weakly acidic mucopolysaccharides. Hypodermis and muscles contain lipids and glycogen. In addition, hypodermis also consists of acidic mucopolysaccharides. The functional significance of these components has been fully discussed.     

Effect of adenosine monophosphates on the flowering of Impatients balsamina L., a qualitative short-day plant

Summary Adenosine monophosphates (AMPs) cause the induction of floral buds in Impatients balsamina L. under strictly non-inductive photoperiods and hasten it under inductive photoperiods, cyclic AMP being more effective than 3- or 5-AMPs in this regard.Abbreviations cyclic AMP cyclic 3,5-adenosine monophosphate