Effects of seed manganese concentration on lupin emergence

Seed of narrow-leafed lupin (Lupinus angustifolius L.) produced in Western Australia often has low manganese (Mn) concentration because of low Mn availability in the soil during grain filling. A major problem of lupin production is poor seedling establishment. We tested the hypothesis that low Mn concentration in lupin seeds decreases emergence.The experiment was a factorial design comparing emergence of lupins (cv. Gungurru) grown under glasshouse conditions from seed with 2 different internal Mn concentrations (7 or 35 mg Mn kg^–1 DW) and with 2 external Mn fertiliser treatments (0 or 10 mg MnSO₄.H₂O kg^–1 soil). There were no visible differences between the seeds. Emergence was monitored and plants were harvested 17 days after sowing.Emergence was approximately 60% in all pots sown with low Mn compared to 100% in pots sown with high Mn seed. Application of Mn did not increase the final emergence of low Mn seed. Seed viability was assessed by staining with tetrazolium chloride, a common test used in seed testing laboratories. All high Mn seed were viable while 34% of low Mn seed were completely or partly unstained and therefore were non-viable. We have shown that low Mn supply during seed filling may lead to production of non-viable seed that cannot be visually distinguished from viable seed..     

Chromosome walking with YAC clones in Arabidopsis: isolation of 1700 kb of contiguous DNA on chromosome 5, including a 300 kb region containing the flowering-time gene CO

The co mutation of Arabidopsis thaliana causes a late-flowering phenotype that is insensitive to day-ength. The mutation was mapped previously to the upper arm of chromosome 5, approximately 1.6 cM from the chalcone synthase gene (CHS). We were provided with five yeast artificial chromosome (YAC) libraries and used these to perform a chromosome walk from CHS to the CO gene. In this paper we report the isolation of 1700 kb of contiguous Arabidopsis DNA, which represents approximately 1%–2% of the genome, inserted in YACs. This required the detailed analysis of 67 YACs, from which 87 end probes were isolated and examined in hybridisation experiments. This analysis showed that approximately 40% of the YACs presented problems in chromosome walking experiments because they contained repetitive sequence at one of their termini, were chimaeric or because part of the plant DNA was deleted. DNA fragments isolated from YACs were used as restriction fragment length polymorphism (RFLP) markers to localize CO to a 300 kb region within the cloned DNA. We compare the physical distance between CHS and CO with the genetic distance and find that in this region 1 cM is equivalent to approximately 200 kb.     

Vitamin B6 deficiency and the lymphoid system. II. Effects of vitamin B6 deficiency in utero on the immunological competence of the offspring.

Results of this study indicated that an absence of vitamin B₆ from the diet of pregnant rats led to reduced immunological competence in the offspring. While the numbers of cells in the thoracic duct lymph (TDL) of rats approximately 3 months old and progeny of vitamin B₆-deficient mothers were nearly equivalent to control values, such cells had a reduced capacity to respond in the mixed lymphocyte and normal lymphocyte transfer reactions. It is suggested that this reduction may have reflected (i) an alteration in the capacity of TDL cells or their precursors to give rise to immunologically competent cells, (ii) a shift in the proportions of T and B cells in the TDL, and/or (iii) an absence or ineffectiveness of a humoral factor required for the development of immunologically competent lymphocytes.     

Serum and Urinary Fibrin/Fibrinogen Degradation Products in Glomerulonephritis

The serum and urine concentrations of fibrin/fibrinogen degradation products (F.D.P.) were estimated in 172 patients with glomerulonephritis. In each case the diagnosis was established on the basis of clinical, renal histological, and ultrastructural findings. Serum F.D.P. concentrations were often raised in all types of glomerulonephritis, though more consistently in active proliferative forms. The urinary concentration provided a reliable and sensitive index of activity, progression, and natural history in proliferative glomerulonephritis. In these forms the urinary F.D.P. content was thought to reflect predominantly lysis of intraglomerular fibrin deposits. In minimal lesion and membranous glomerulonephritis low but abnormal concentrations of urinary F.D.P. were consistently found. It is suggested that in these cases the products are derived from limited proteolysis of fibrinogen filtered through an abnormally permeable basement membrane.Daily measurement of urinary F.D.P. concentration is of potential value in the differential diagnosis of patients with glomerulonephritis and at the same time provides a sensitive assessment of the activity and natural history of proliferative disease.     

Mobilization of granulose in Clostridium pasteurianum. Purification and properties of granulose phosphorylase

1. The granulose of Clostridium pasteurianum ATCC 6013 is degraded when the organism is incubated in a medium containing no utilizable source of carbon and energy. 2. Mobilization of the polyglucan does not occur in the presence of exogenous glucose. 3. Breakdown of granulose is effected by a constitutively synthesized alpha-1,4-polyglucan phosphorylase. 4. Partial (530-fold) purification of this granulose phosphorylase was facilitated by its being loosely bound to the native granules of its substrate polyglucan. 5. The enzyme (pH optimum 6.4) was assayed both (a) in the degradative direction, K(m) for P(i)=2.2mm, and (b) in the synthetic direction, K(m) for glucose 1-phosphate=0.05mm. No requirement for bivalent cations was evidenced. 6. Granulose phosphorylase was inhibited by various nucleotide sugars; GDP-glucose, ADP-glucose (K(i)=20mum) and UDP-glucose (K(i)=60mum) were particularly potent competitive inhibitors. ATP, NADP(+) and NADPH (at 1mm) were less effective inhibitors, whereas AMP was slightly stimulatory. 7. It would appear that granulose mobilization is favoured under conditions of low adenylate energy charge, but is prevented under conditions of ;glucose excess' chiefly by ADP-glucose-mediated inhibition of granulose phosphorylase.     

Effect of alpha-actinin on actin structure. Actin ATPase activity

The accumulation of low molecular weight RNAs in Escherichia coli cells following amino acid or energy source starvation was examined using two-dimensional polyacrylamide gel electrophoresis. 32P-labeled small RNA prepared from serine- or isoleucine-starved stringent strain (relA+) cells was shown to display gel patterns that were grossly different from that of unstarved cells. It appears that the deprivation of serine or isoleucine has little or no inhibitory effect on the accumulation of transfer RNA cognate to the deprived amino acid. This is demonstrated by a relative increase in the concentrations of small RNAs that can be charged with serine or isoleucine following starvation of these amino acids. However, small RNAs labeled during starvation of phenylalanine or energy source showed gel patterns similar to that of control cells. This suggested a heterogenous response in the accumulation of some low molecular weight RNAs, presumably transfer RNAs, following starvation of different amino acids.     

Structural properties of signal peptides and their membrane insertion

Structural properties of the amino acid sequences from 22 signal peptides have been analyzed and compared with peptides known to interact with biological membranes and liposomes, melittin, a lytic peptide of bee venom, and the non-polar C-terminal segment of cytochrome b5. All these peptides evidence a double amphipatic structure with an hydrophobic core of 9 to 24 amino acid residues and two charged polar ends. They all exhibit a high potential for making alpha-helix and, to a lesser degree, extended or beta-sheet conformation with low or negative potentials for making reverse turns or aperiodic conformation. A model of spontaneous insertion of these peptides into the lipid bilayer without specific surface receptor protein is proposed, where the two polar ends interact with each polar face of the lipid bilayer and the hydrophobic core inserts into the non-hydrogen bonding environment of the fatty acid side chains. This insertion could be the molecular trigger for ribophorin assembly around the signal peptide and subsequent attachment to the ribosome prior to the transfer of the polypeptide chain through the endoplasmic reticulum membrane.