A 126 bp fragment of a plant histone gene promoter confers preferential expression in meristems of transgenic Arabidopsis

The tissue-specific pattern of expression directed by the H4A748 Arabidopsis histone promoter was investigated by analysis of beta-glucuronidase (GUS) activity in transgenic Arabidopsis containing H4A748-GUS gene fusions. As determined by fluorimetric and histochemical tests, the H4A748 promoter directs preferential expression in meristems of young seedlings and adult plants. The low activity found in nonproliferating tissues may relate to basal constitutive expression of the histone promoter and/or to endoreduplication occurring in some tissues. The endogenous histone mRNA levels parallel the GUS activity found in different tissues. Analysis of the regulatory properties of 5' deleted promoters showed that multiple positive elements exist between -900 and -219 and that the proximal region of the promoter to -219 is sufficient to establish the full tissue-specific pattern of expression. Further deletion to -93 nearly abolished the promoter activity thus suggesting that the 126 bp fragment located between -219 and -93 contains the elements responsible for the specific expression pattern. The presence of several remarkable sequences within this fragment is discussed.     

Analysis of wheat resistance to the cereal aphidSitobion avenae using electrical penetration graphs and flow charts combined with correspondence analysis

The behaviour ofSitobion avenae (F.), was compared on resistant wheat lines ofTriticum monococcum (L.) and a susceptible variety ofTriticum aestivum (L.). Firstly, stylet penetration activities were monitored with the Electrical Penetration Graph (EPG) technique and subsequently analysed using flow charts combined with correspondence analysis. Plant resistance was shown to be associated with repeated penetrations without access to either the xylem or the phloem, and with numerous failures in starting a sustained sap ingestion (as represented by pattern E2). Access to sieve elements of the phloem did not seem to be much affected on resistant plants but it took the aphid three times as long to produce a sap ingestion pattern when maintained on the resistant lineT. monococcum n^o 44 (Tm44) as compared with aphids maintained on susceptible plants. As a result the total time spent in ingesting from sieve elements was reduced by 72% on Tm44. Secondly, direct observations of freely-moving apterous adults were performed. Aphids did not discriminate between resistant and susceptible wheat during the first 30 min of access to test leaves, but only 4 out of 25 aphids were still probing after eight hours on resistant Tm44. The relevance of these results to possible location of the resistance factor(s) are discussed. Although detection of plant resistance before sieve elements are reached can not be rigorously excluded, the factors involved inT. monococcum resistance toS. avenae undoubtedly occur within the phloem vessels.     

Genes encoding a histone H3.3-like variant in Arabidopsis contain intervening sequences.

Two genes encoding a particular H3 histone variant were isolated from Arabidopsis thaliana. These genes differ from the H3 genes previously cloned from Arabidopsis and other plants by several interesting properties: (1) the two genes are located close to each other; (2) their coding regions are interrupted by two or three small introns, the two closest to the initiation codon being located at the same place in the two genes; (3) another, long intron is located in the 5'-untranslated region just before the initiation codon of gene I as deduced from the sequence of several corresponding cDNAs, and very likely also of gene II; (4) these genes do not show preferential expression in organs containing meristematic tissues contrary to the classical intronless replication-dependent histone genes, thus suggesting that their expression is not replication-dependent; (5) the protein encoded by both genes is the same and corresponds to a minor H3 variant highly conserved among all the plant species studied up to now. All these characteristics are common with the animal replication-independent H3.3 histone genes and it is assumed that the genes described here are the first example of the equivalent H3.3 gene family in plants. Interestingly, the promoter regions of the two genes have the same general structure as the Arabidopsis intronless genes. Possible implications on the regulation of H3 genes expression are discussed.     

Anticoagulant properties of dextranmethylcarboxylate benzylamide sulfate (DMCBSu); a new generation of bioactive functionalized dextran

Dextranmethylcarboxylate benzylamide sulfate (DMCBSu), a functionalized dextran, exhibits anticoagulant properties. Its synthesis involves three steps: a carboxymethylation with monochloroacetic acid in alkaline water-iso-propanol, a benzylamidification of some of the methylcarboxylate groups with benzylamine in the presence of a water soluble carbodiimide and a partial sulfation of the remaining hydroxyl groups with SO3-pyridine in dimethylformamide. This procedure yields reproducibly DMCBSu with degrees of substitution in methylcarboxylate (MC), benzylamide (B) and sulfate (Su) groups, respectively, up to 1.61, 0.35 and 1.5, each obtained in one step. For a degree of substitution of methylcarboxylate ca. 1, the presence of sulfate groups is absolutely necessary to confer anticoagulant activities to the samples. In addition, the anticoagulant ability is higher for derivatives bearing benzylamide groups. The anticoagulant ability of DMCBSu increases with the degree of sulfation, reaching 20% of heparin activity for a degree of substitution of Su groups about 1.3.     

Low-molecular-weight dextran derivatives (f-CMDB) enter the nucleus and are better cell-growth inhibitors compared with parent CMDB polymers

Carboxymethyldextrans-benzylamide (CMDB) are dextran derivatives that are statistically substituted with carboxymethyl and benzylamide groups. These molecules display a variety of biological effects, one of which is their inhibitory activity against mammary tumor cell growth, both in vitro and in vivo. We and others have previously shown that the effects of CMDB on cell growth are related to their ability to interact with the growth factor FGF-2. The binding modifies the conformation of FGF-2, leading to the suppression of its mitogenic activity. Here, the method previously reported to fragment natural polysaccharide fucans has been applied to CMDB (80,000 g/mol). f-CMDB (fragmented CMDB) of molecular weights from 6000 to 20,000 g/mol were found to be more potent inhibitors of MCF7 mammary tumor cell growth than high-molecular-weight CMDB. Confocal microscopy experiments using CMDB and f-CMDB labeled with the fluorophore DTAF (5-([4,6-dichlorotriazine-2-yl]amino) fluorescein) indicate that only low-molecular-weight f-CMDB penetrate into the nucleus of MCF7 cells. It is thus assumed that the better inhibitory properties demonstrated by f-CMDB, compared with CMDB, are related to their better ability to penetrate the nucleus and interact with nuclear targets, including topoisomerase II. The DNA relaxation properties of the latter are inhibited in vitro by both CMDB and f-CMDB. These findings could help us to develop models of low-molecular-weight oligosaccharide derivatives exhibiting better antiproliferative and antitumor properties.     

Genomic organization and nucleotide sequences of two corn histone H4 genes

The sea urchin histone H4 gene has been used as a probe to clone two corn histone H4 genes from a lambda gtWES X lambda B corn genomic library. The nucleotide (nt) sequences of both genes showed that the encoded amino acid sequences were identical to that of the H4 of pea and one variant of wheat. The nt sequences of the coding regions showed 92% homology. 5'- and 3'-flanking regions do not show extensive nt sequence analogies. Southern blotting of the EcoRI digested genomic DNA suggests the existence of multiple H4 genes dispersed throughout the genome.     

Subfamilies of histone H3 and H4 genes are located on most,possibly all of the chromosomes in maize

Summary It has been previously shown that in the genome of maize the multiple copies of the histone H3 and H4 multigenic families are organized into eight to ten subfamilies each containing a variable number of copies. Each subfamily is characterized by a specific proximal environment and thus can be revealed by blot-hybridization with its specific 5 probe. Restriction fragment length polymorphism (RFLP) combined with monosomic analysis was used to localize several H3 and H4 subfamilies on maize chromosomes. H3 and H4 genes were found to be located on most, possibly all of the chromosomes, revealing a remarkably dispersed organization of these multigenic families.     

Growth kinetics of Apple plant cell cultures

Summary Aerobic batch cultures of Apple fruit cells were carried out using sucrose as the sole carbon source. The determination of the growth parameters was used in order to estimate the maintenance coefficient m and the maximum growth yield Y_G; their values at 25°C are respectively 0.32. 10^-2 g sugar/g cell dry weight.h and 0.57 g cell dry weight/g sugar. Then, a mathematical expression of the cell growth is discussed, with respect to the specific growth rate evolution during cultivation.