Role of phytohormones in organogenic ability of elm multiplicated shoots

The study presents the comparative analyses of endogenous contents of auxin (IAA), cytokinins (CKs), polyamines (PAs), and phenolic acids (PhAs) in apical and basal parts of elm multiplicated shoots with regard to the organogenic potential. The shoot-forming capacity was higher in the apical part than in the basal part. However, the timing of root formation was in the apical type of explant significantly delayed (compared with the organogenic potential of basal part). Significantly higher contents of free bases, ribosides and ribotides of isopentenyl adenine, zeatin and dihydrozeatin that were found in the apical segments, might be considered as the most important factor affecting in vitro shoot formation. The content of endogenous free IAA was approximately three times higher in the basal shoot parts than in the apical parts. The amounts of putrescine and spermidine were higher in the apical part which generally contains less differentiated tissues than the basal part of shoot. The predominant PhA in both types of explants was caffeic acid, and concentrations of other PhAs decreased in the following order: p-coumaric, ferulic, sinapic, vanillic, chlorogenic, p-hydroxybenzoic and gallic acids. The contents of all determined PhAs in their free forms and higher contents of glycoside-bound p-coumaric, ferulic and sinapic acids, precursors for lignin biosynthesis, were found in the basal parts.     

T cell-specific negative regulation of transcription of the human cytokine IL-4.

IL-4 secreted by activated T cells is a pleiotropic cytokine affecting growth and differentiation of diverse cell types such as T cells, B cells, and mast cells. We investigated the upstream regulatory elements of the human IL-4 promoter. A novel T cell-specific negative regulatory element (NRE) composed of two protein-binding sites were mapped in the 5' flanking region of the IL-4 gene: -311CTCCCTTCT-303 (NRE-I) and -288CTTTTTGCTT-TGC-300 (NRE-II). A T cell-specific protein Neg-1 and a ubiquitous protein Neg-2 binding to NRE-I and NRE-II, respectively, were identified. Furthermore, a positive regulatory element was found 45 bp downstream of the NRE. The enhancer activity of the PRE was completely suppressed when the NRE was present. These data suggest that IL-4 promoter activity is normally down-regulated by an NRE via repression of the enhancer positive regulatory element. These data may have implications for the stringent control of IL-4 expression in T cells.     

Effect of inhibition of phenylalanine ammonia-lyase activity on growth of alfalfa cell suspension culture: Alterations in mitotic index, ethylene production, and contents of phenolics, cytokinins and polyamines

The effect of inhibition of phenylpropanoid biosynthesis on the growth of Medicago sativa L. suspension culture was studied. 2-Aminoindan-2-phosphonic acid (AIP), a potent inhibitor of phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), caused a marked reduction in the amount of hydroxycinnamic acid derivatives in a few hours after cell inoculation into AIP medium. The treatment of alfalfa suspension culture with this inhibitor increased the extractable PAL activity and elevated ethylene production during the growth cycle. The addition of AIP (10 μ M ) stimulated cell division activity during the growth cycle, although the onset of cell division was slightly delayed. The maxima of cytokinin content as well as of the mitotic index were postponed in AIP-treated cells, however, the unchanged content of cytokinins did not correlate with increased mitotic activity of treated cells. The decreased level of hydroxycinnamic acid derivatives, which represent the phenolic conjugation partners of free polyamines (PAs), influenced the rate of PA conjugation. Consequently, the balance between free and conjugated PAs was shifted in favor of the free PA form. A potential role of the reduction of the pool of phenolic acids in the enhancement of cell division of alfalfa cell suspension culture is discussed.     

Polypeptide composition of rat high density lipoprotein: characterization by SDS-gel electrophoresis

The histones synthesized by three different interspecies hybrid echinoid embryos have been examined. In all three crosses, the species-specific F1 histone of the paternal parent is found in the chromatin of the hybrid. These findings provide direct evidence for the involvement of newly transcribed mRNA in the synthesis of this protein. F1 histone is a unique protein in that it is the only paternal protein detected in these hybrids. The possibility that the synthesis of histones is controlled differently from that of other proteins is discussed.     

Signature lipids and stable carbon isotope analyses of Octopus Spring hyperthermophilic communities compared with those of Aquificales representatives.

The molecular and isotopic compositions of lipid biomarkers of cultured Aquificales genera have been used to study the community and trophic structure of the hyperthermophilic pink streamers and vent biofilm from Octopus Spring. Thermocrinis ruber, Thermocrinis sp. strain HI 11/12, Hydrogenobacter thermophilus TK-6, Aquifex pyrophilus, and Aquifex aeolicus all contained glycerol-ether phospholipids as well as acyl glycerides. The n-C(20:1) and cy-C(21) fatty acids dominated all of the Aquificales, while the alkyl glycerol ethers were mainly C(18:0). These Aquificales biomarkers were major constituents of the lipid extracts of two Octopus Spring samples, a biofilm associated with the siliceous vent walls, and the well-known pink streamer community (PSC). Both the biofilm and the PSC contained mono- and dialkyl glycerol ethers in which C(18) and C(20) alkyl groups were prevalent. Phospholipid fatty acids included both the Aquificales n-C(20:1) and cy-C(21), plus a series of iso-branched fatty acids (i-C(15:0) to i-C(21:0)), indicating an additional bacterial component. Biomass and lipids from the PSC were depleted in (13)C relative to source water CO(2) by 10.9 and 17.2 per thousand, respectively. The C(20-21) fatty acids of the PSC were less depleted than the iso-branched fatty acids, 18.4 and 22.6 per thousand, respectively. The biomass of T. ruber grown on CO(2) was depleted in (13)C by only 3.3 per thousand relative to C source. In contrast, biomass was depleted by 19.7 per thousand when formate was the C source. Independent of carbon source, T. ruber lipids were heavier than biomass (+1.3 per thousand). The depletion in the C(20-21) fatty acids from the PSC indicates that Thermocrinis biomass must be similarly depleted and too light to be explained by growth on CO(2). Accordingly, Thermocrinis in the PSC is likely to have utilized formate, presumably generated in the spring source region.     

Reinitiation of cell division and polyamine and aromatic monoamine levels in alfalfa explants during the induction of somatic embryogenesis

The early cellular events in leaf explants of Medicago sativa L. cultured on somatic embryogenesis- and callogenesis-inducing media (EIM and CIM, respectively) were correlated with the endogenous contents of polyamines (PAs) and aromatic monoamines (AMs). On the second day of culture, replication of DNA occurred in epidermal and subepidermal cells on the edges of explants on EIM and was a prerequisite for proembryonal mass and, later, globular proembryo formation. In explants cultured on CIM, replication occurred at least one day later and in fewer cells, which were randomly spread all over the explant. Transition of leaf explant cells to rapidly dividing meristematic-like cells on EIM or to enlarged, highly vacuolated cells on CIM was observed. The increase in total PA levels in cultured explants was primarily a consequence of increases in putrescine (Put) and spermidine (Spd) contents and was much more pronounced on EIM than on CIM. High Spd levels were characteristic of meristematic cells and might be essential for the development of globular structures. The higher amount of insoluble PA conjugates was determined in explant cells on EIM, as compared with CIM. Proembryogenic cell mass formation was positively correlated with free tyramine and negatively correlated with free phenylethylamine contents.