Gene expression during tuber development in potato plants

Potato tubers are modified stems that have differentiated into storage organs. Factors such as day-length, nitrogen supply, and levels of the phytohormones cytokinin and gibberellic acid, are known to control tuberization. Morphological changes during tuber initiation are accompanied by the accumulation of a characteristic set of proteins, thought to be involved in N-storage (i.e. patatin) or defense against microbial or insect attack (i.e. proteinase inhibitor II). Additionally, deposition of large amounts of starch occurs during tuber formation, which is paralleled by an increase in sucrose synthase and other enzymes involved in starch biosynthesis (i.e. ADP-glucose pyrophosphorylase, starch synthases, and branching enzyme). Potential controlling mechanisms for genes expressed during tuberization are discussed.     

Members of the alpha-amylase inhibitors family from wheat endosperm are major allergens associated with baker's asthma

We have identified the major antigens or IgE binding components from wheat flour. Thirty-five sera from patients with baker's asthma were used to analyze the reaction with wheat salt-soluble proteins. We found a 15 kDa SDS-PAGE band which reacted with all sera tested. Purified members of the alpha-amylase inhibitor family, which are the main components of the 15 kDa band, were recognized by specific IgE when tested with a pool of reactive sera. Immunodetection after two-dimensional electrophoretic fractionation of crude inhibitor preparations from wheat endosperms also detected several inhibitor subunits as major low-molecular-weight allergens.     

Ecological aspects of Sargassum muticum (Fucales,Phaeophyta) in Baja California,Mexico: reproductive phenology and epiphytes

The reproductive phenology and epiphytic macroalgae of Sargassum muticum were studied through an annual cycle (September 1987 to November 1988) at two sites on the northwestern coast of Baja California, Mexico, which were subjected to different degrees of wave exposure. Sargassum muticum is a brown alga of Japanese origin, now considered a permanent member of the marine flora of Baja California. A similar reproductive development was observed at both sites, with a maximum percentage of reproductive plants from May to July (spring–summer) and minimum from December to March (winter). Reproductive plants were found throughout the year. A total of 48 species of epiphytes were identified and seasonal variation in their diversity was observed. The greatest diversity was found at the more protected site.     

Stir-up effect of wind on a more-or-less stratified shallow lake phytoplankton community,Lake Balaton,Hungary

Microstratification of phytoplankton in the large shallow Lake Balaton (Hungary) was studied during a 24 h period. Dissolved O₂ showed biological stratification; flagellates exhibited a definite circadian rhythm. In the middle of the investigation a heavy storm broke out which was followed by the disappearance of differences between different layers of water. Storm-induced destratification is described by cluster-analysis. Abundances of dominant species changed differently in connection with the storm. Numbers of Nitzschia sp. increased due to stirring up from the sediment surface. Numbers of single-celled or colony-forming species (Cyclotella comta, Crucigenia quadrata, Coelosphaerium kuetzingianum) practically did not change. Numbers of all the three dominant filamentous species (Aphanizomenon fos-aquae f. klebahnii, Lyngbya limnetica, Planctonema lauterbornii) significantly decreased, which might be attributed to an unknown loss process and was followed by a competitive displacement by algae of small cell size.     

Toxic cyanobacteria (blue-green algae) in Finnish fresh and coastal waters

A survey of the occurrence of toxic blooms of cyanobacteria in Finnish fresh and coastal waters was made during 1985 and 1986. Toxicity of the freeze-dried water bloom samples was tested by mouse-bioassay (i.p.). Forty-four per cent (83/188) of the bloom samples were found to be lethally toxic. Hepatotoxic blooms (54) were almost twice as common as neurotoxic ones (29). Anabaena was the most frequently found genus in toxic and non-toxic blooms and it was present in all neurotoxic samples. Statistical associations were found between hepatotoxicity and incidence of Microcystis aeruginosa, M. viridis, M. wesenbergii, Anabaena flos-aquae and Anabaena spiroides. Neurotoxicity was statistically associated with Anabaena lemmermannii, Anabaena flos-aquae and Gomphosphaeria naegeliana. Isolation of strains of cyanobacteria confirmed the occurrence of hepatotoxic and neurotoxic strains of Anabaena, as well as hepatotoxic strains of Microcystis and Oscillatoria species.Toxic blooms caused cattle poisonings at three different lakes during the study period. Toxic blooms also occurred in drinking water sources. Our study shows that toxic cyanobacteria are more common in Finnish lakes than would be expected on the basis of animal poisonings. The results of this study show the existence of toxic cyanobacteria in Finnish water supplies and the need for their continued study as agents of water based disease.     

Studies on the yield and gel strength of agar from Gracilaria domingensis Sonder ex Kuetzing (Gracilariales,Rhodophyta) following the addition of calcium

Studies were carried out on the seasonal variation in yield and gel strength of agar from Gacilaria domingensis with and without the addition of calcium chloride. Extraction was done with and without treatment with 1% hydrochloric acid. The results showed an increase in yield and gel strength when an alkaline solution of calcium was used, but the gel strength was low. For commercial use, Gracilaria domingensis should be mixed with better quality Gracilaria species because of its low gel strength.     

High concentration of neutral endopeptidase (enkephalinase E.C. 3.4.24.11) in a malignant tumor: rat hepatoma 3924A

The activity of the membrane-bound neutral endopeptidase 24.11 was low in the normal liver (21 +/- 3 pmol/h/mg protein, mean +/- SE) but it increased 56-fold in rapidly-growing rat hepatoma 3924A. The identity of the enzyme in the tumor was established by immunoprecipitation and by using a specific inhibitor of neutral endopeptidase. The endopeptidase concentration in the differentiating and regenerating liver was lower than in normal tissue, 39 and 8% of the corresponding control. The activity of a plasma membrane marker enzyme carboxypeptidase M in the normal liver was 1.0 +/- 0.2 nmol/h/mg protein, it increased about 2-fold in the rapidly-growing hepatoma and in the differentiating liver, but was unchanged in regenerating liver. The function of the strikingly increased neutral endopeptidase activity in the rapidly growing hepatoma may relate to activation of autocrine or exocellular growth factors or to inactivation of cell proliferation-inhibitory factors. Such a biochemical change should confer selective advantages to the cancer cells.     

Mastoparan interacts with the carboxyl terminus of the alpha subunit of Gi

Mastoparan, a peptide toxin from wasp venom, stimulates guanine nucleotide binding and hydrolysis by G proteins. To elucidate the site of mastoparan-G protein interaction, we utilized a polyclonal antibody (R16,17) directed against the carboxyl terminus of the Gi alpha subunit to develop a competitive enzyme-linked immunosorbent assay. We investigated the ability of mastoparan to influence R16,17 antibody binding to G protein alpha subunits in a purified preparation of brain Gi and in neutrophil membrane extracts. Mastoparan antagonized the ability of R16,17 to detect G protein alpha subunits with an IC50 of 15 microM in the purified preparation and with an IC50 of 1 microM for the predominant G protein population in membrane extracts. This reduction was not seen when an unrelated peptide or a peptide of similar charge composition to mastoparan was used in place of mastoparan in the assay. Additionally, antibody R16,17 blocked up to 85% of mastoparan-stimulated GTPase activity. Taken together, these data indicate that the interaction of mastoparan with G protein depends in part on the carboxyl terminus of Gi alpha. Pertussis toxin-catalyzed ADP-ribosylation of Gi alpha markedly inhibited mastoparan-stimulated GTPase activity but only slightly attenuated the ability of mastoparan to recognize G protein. These data suggest that ribosylation inhibits mastoparan-induced G protein activation by a mechanism distinct from the ability of mastoparan to physically interact with G protein. Since mastoparan is thought to mimic hormone-liganded receptors, these findings may be applicable to the mechanism of receptor-Gi protein uncoupling that results from ADP-ribosylation of the G protein.     

Use of two-dimensional thin-layer chromatography for the components study of poly(adenosine diphosphate ribose)

Two-dimensional thin-layer chromatography on cellulose plates has been used for separating and quantifying the three adenosine derivatives: AMP, phosphoribosyl AMP (PRAMP), and (PR)2AMP obtained by venom phosphodiesterase digestion of poly(ADP-ribose). In vitro synthesized polymer, up to 300 derivatives in length were studied. Some parameters of the complexity of poly(ADP-ribose) could be deduced from our results: (i) The first branching point appears in fragments of approximately 21 derivatives in length. (ii) The branching points are located at regular distances of approximately 41 derivatives from each other.