Intracellular communication of genetic information in mammalian cells

Utilising the technique of poly(A)-sepharose affinity chromatography, it has proven possible to isolate a class of RNA from polysomes of Friend leukaemia cells, clone M2, which does not appear to be of ribosomal origin since its synthesis is unaffected by concentrations of actinomycin D (0.04mug/ml) which inhibit rRNA synthesis. Although this class displays messenger-like behaviour in being released from polysomes on treatment with EDTA and in being able to direct polypeptide synthesis in a cell-free system it is nonetheless distinct from the well-known polyadenylated messenger RNAs (poly(A)+mRNAs) as judged by the following properties - (a) A complete lack of poly(A) tracts (b) A different size distribution on denaturing gradients, displaying a mean size of 20s compared to 18s for polyCA)+ RNAs. (c) The presence, close to the 3' terminus, of an "uridylate- rich" region in contrast to the 3'-poly(A) tracts of the poly (A)+RNA. (d) Little sequence homology with poly(A)+RWAs as judged from molecular hybridisation data. (e) A different base composition compared to poly(A)+RNA. (f) In contrast to poly(A)+RNA which is transcribed from both unique and middle-repetitive DNA sequences, this new class of RNA seems to be transcribed solely from unique sequences. (g) A difference in metabolic stability between this class and the poly(A)+RM class was found. (h) The size distribution of polypeptide products pro-duced when this RNA is used as template in a cell-free protein synthesising system appears slightly different to that directed by poly(A)+mRNA. The lack of poly(A) tracts coupled with the presence of "U-rich" region(s) has led to the designation of this class of RM as poly(A)-u+RNA. In addition to detecting these poly(A)-u+RNAs in polysomes, a similar class of RWAs have also been detected in nuclei. The nuclear poly(A)-U+RNAS. elute from poly(A)-sepharose with increasing formamide concentration in a similar fashion to that of the polysomal poly (A)-u+RNAs. Indeed, the "U-rich" region(s) of nuclear and polysomal poly(A)-u+RNAs appear similar. In a further examining of the total nuclear RNA, two other RNA classes having either poly(A) tracts (poly(A)+RNA) or oligo(A) tracts (poly(A)-a+RNA) were also detected. These three RNA classes display distinct size distribution and content of double-stranded regions. When the stability of these nuclear RWA classes were examined, using a "pulse-chase" approach, it was found that the poly(A)-u+RNA class was relatively labile compared to the poly(A)+RNA. Interestingly, the poly(A)+RNA appeared to have at least two distinct metabolic components. The "pulse-chase" approach used, allowed an estimate to be made of the conversion of nuclear poly(A)+ and poly(A)-u+ RNAs into cytoplasmic poly(A)+and poly (A)-u+RNAs . Finally the metabolic behaviour of both the nuclear and cytoplasmic classes of RNA was found to be relatively unaffected by induction of Friend cells using Dimethylsulphoxide

Communication and signal exchange in the Rhizobium bradyrhizobium legume system

A new comprehensive communication concept in the Rhizobium/Bradyrhizobium legume symbiosis was developed. It includes a root zone specific flavonoid exudation, the differential activity of phenylpropane/acetate pathway derivatives on chemotaxis, nod-gene inducing activity and phytoalexin resistance induction on the microsymbiont side (Bradyrhizobium). Nod factor production from the microsymbiont affects the host plant in root hair curling and meristem induction. Phytoalexin production in the host plant is also an early response, however repressed to a low level after a few hours. Another strategy of the microsymbiont to overcome phytoalexin effects is degradation of phytoalexins in Rhizobium leguminosarum bv. vicieae. Competitiveness within the same infection group of the microsymbiont was studied with gus-gene fusion, using the blue coloured nodules to easily discriminate marked strains from unmarked competitors. New exopolysaccharide (EPS) mutants of Bradyrhizobium japonicum were reconstructed homologous with a DNA region to exoB gene of Rhizobium meliloti. Their clearly reduced competitiveness of nodulation, demonstrates that exopolysaccharides of Bradyrhizohium japonicum also have an important function during the early stages of this symbiotic interaction

A cytosolic invertase is required for normal growth and cell development in the model legume, Lotus japonicus

Neutral/alkaline invertases are a subgroup, confined to plants and cyanobacteria, of a diverse family of enzymes. A family of seven closely-related genes, LjINV1–LjINV7, is described here and their expression in the model legume, Lotus japonicus, is examined. LjINV1 previously identified as encoding a nodule-enhanced isoform is the predominant isoform present in all parts of the plant. Mutants for two isoforms, LjINV1 and LjINV2, were isolated using TILLING. A premature stop codon allele of LjINV2 had no effect on enzyme activity nor did it show a visible phenotype. For LjINV1, premature stop codon and missense mutations were obtained and the phenotype of the mutants examined. Recovery of homozygous mutants was problematic, but their phenotype showed a severe reduction in growth of the root and the shoot, a change in cellular development, and impaired flowering. The cellular organization of both roots and leaves was altered; leaves were smaller and thicker with extra layers of cells and roots showed an extended and broader zone of cell division. Moreover, anthers contained no pollen. Both heterozygotes and homozygous mutants showed decreased amounts of enzyme activity in nodules and shoot tips. Shoot tips also contained up to a 9-fold increased level of sucrose. However, mutants were capable of forming functional root nodules. LjINV1 is therefore crucial to whole plant development, but is clearly not essential for nodule formation or function

Low temperature storage affects the ascorbic acid metabolism of cherry tomato fruits

Tomato fruits are an important source of l-Ascorbic acid, which is an essential compound of human diet. The effect of the widespread practice of cold storing (5-10 °C) tomato fruits was monitored to determine its impact on the concentration and redox status of l-Ascorbic acid. Total l-Ascorbic acid levels were well maintained in both attached fruits and cold treated fruits, while in other treatments its levels were considerably reduced. However, low temperature storage conditions enhanced the expression of most genes coding for enzymes involved in l-Ascorbic acid biosynthesis and redox reactions. The findings suggest that the transcriptional up-regulation under chilling stress conditions of most genes coding for l-Ascorbic acid biosynthetic genes galactono-1,4-lactone dehydrogenase, GDP-d-mannose 3,5-epimerase but also for the isoenzymes of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase enzyme, glutathione reductase that are strongly correlated to the l-Ascorbic redox status. Moreover, fruits stored at 10 °C exhibited higher levels of transcript accumulation of MDHAR2, DHAR1, DHAR2, GR1 and GR2 genes, pointing to a better ability to manage chilling stress in comparison to fruits stored at 5 °C

Impact of Elemental Sulfur on the Rhizospheric Bacteria of Durum Wheat Crop Cultivated on a Calcareous Soil

Previous experiments have shown that the application of fertilizer granules containing elemental sulfur (S0) as an ingredient (FBS0) in durum wheat crops produced a higher yield than that produced by conventional ones (F), provided that the soils of the experimental fields (F vs. FBS0) were of comparable quality and with the Olsen P content of the field’s soil above 8 mg kg−1. In this experiment the FBS0 treatment took place in soil with Olsen P at 7.8 mg kg−1, compared with the F treatment’s soil with Olsen P of 16.8 mg kg−1, aiming at reducing the imbalance in soil quality. To assess and evaluate the effect of FBS0 on the dynamics of the rhizospheric bacteria in relation to F, rhizospheric soil at various developmental stages of the crops was collected. The agronomic profile of the rhizospheric cultivable bacteria was characterized and monitored, in connection with the dynamics of phosphorus, iron, organic sulfur, and organic nitrogen, in both the rhizosoil and the aerial part of the plant during development. Both crops were characterized by a comparable dry mass accumulation per plant throughout development, while the yield of the FBS0 crop was 3.4% less compared to the F crop’s one. The FBS0 crop’s aerial part showed a transient higher P and Fe concentration, while its organic N and S concentrations followed the pattern of the F crop. The incorporation of S0 into the conventional fertilizer increased the percentage of arylsulfatase (ARS)-producing bacteria in the total bacterial population, suggesting an enhanced release of sulfate from the soil’s organic S pool, which the plant could readily utilize. The proportion of identified ARS-producing bacteria possessing these traits exhibited a maximum value before and after topdressing. Phylogenetic analysis of the 68 isolated ARS-producing bacterial strains revealed that the majority of the isolates belonged to the Pseudomonas genus. A large fraction also possessed phosphate solubilization, and/or siderophore production, and/or ureolytic traits, thus improving the crop’s P, Fe, S, and N balance. The aforementioned findings imply that the used FBS0 substantially improved the quality of the rhizosoil at the available phosphorus limiting level by modulating the abundance of the bacterial communities in the rhizosphere and effectively enhancing the microbially mediated nutrient mobilization towards improved plant nutritional dynamics