Agrobacterium rhizogenes T-DNA genes capable of inducing hairy root phenotype

Summary Segments of the TL-DNA of the agropine type Ri plasmid pRi 1855 encompassing single and groups of open-reading frames were cloned in the Ti plasmid-derived binary vector system Bin 19. Leaf disc infections on Nicotiana tabacum led to transformed plants, some of which showed typical hairy root phenotypes, such as the wrinkled leaf morphology, excessive and partially non geotropic root systems and the ability of leaf explants to differentiate roots in a hormone-free culture medium. Particularly interestingly, most of these traits were shown by plants transformed with a TL-DNA segment encompassing the single ORF 11, corresponding to the rolB locus. Hairy root can be induced by this latter T-DNA segment on wounded stems of tobacco plants; hairy root induction on carrot discs requires, on the contrary, a more complex complement of TL-DNA genes.Abbreviations YMB yeast mannitol broth - MS Murashige and Skoog medium - 6-BAP 6-benzylaminopurine - NAA naphthalene acetic acid - Km kanamycin - Cb carbenicillin     

Thyroid-thymus interactions during development and aging

A good body of experimental and clinical evidences suggests that bidirectional interactions do exist between the neuroendocrine system and the thymus activity. In particular, thymic endocrine activity seems to be strongly influenced by neuroendocrine signals. In this context, studies performed in hyper- and hypothyroid subjects and in the low triiodothyronine (T3) syndrome, which affects premature infants, have clearly shown that thyroid hormones and in particular T3 physiologically modulate thymic peptide secretion. In vitro experiments, with thymic whole-organ cultures, have demonstrated that thyroid hormones exert their action on the epithelial cells of the thymus deputed to synthesize and secrete thymic peptides and that such an effect does not seem to depend on the known permissive action of thyroid hormones.     

Inactivation of skeletal glycogen synthetase by diethylpyrocarbonate

Glycogen synthetase from skeletal muscle is rapidly inactivated by DEPC. In the presence of the substrate UDPG only 50% of the enzyme activity is lost. The concomitant addition of both UDPG and the allosteric activator glucose-6-phosphate almost completely prevents the inactivation by DEPC. Since glucose-6-phosphate alone does not prevent the inactivation by DEPC, it is concluded that it is effective through a potentiation of the effects of UDPG, possibly through a conformational change of the enzyme.     

蚕豆叶片发育与衰老过程中超氧物歧化酶活性与丙二醛含量变化

蚕豆植株叶片随茎节自上而下表现出明显的发育与衰老顺序,可作为衰老特征的是叶绿素和蛋白质含量明显下降。蚕豆叶中SOD活性主要定位于12 000× g离心后所得的上清液和叶绿体组分。衰老叶片的SOD总活性和叶绿体组分的相对活性都有所下降,SOD同工酶谱也发生了改变。O_2~ 产生速率随叶龄增大而稍上升;而MDA含量在叶片外观表现枯黄衰老征兆前就急剧上升。可能因为衰老叶片过氧化氢酶活性大幅度下降与SOD之间的不平衡,致使O_2~ 代谢中间产物累积而引起膜的损伤.     

Changes of the forest-savanna boundary in Brazilian Amazonia during the Holocene revealed by stable isotope ratios of soil organic carbon

The possibility of ecosystem boundary changes in northern Brazilian Amazonia during the Holocene period was investigated using soil organic carbon isotope ratios. Determination of past and present fluctuations of the forest-savanna boundary involved the measurement of natural ¹³C isotope abundance, expressed as ¹³C, in soil organic matter (SOM). SOM ¹³C analyses and radiocarbon dating of charcoal fragments were carried out on samples derived from soil profiles taken along transects perpendicular to the ecotonal boundary. SOM ¹³C values in the upper soil horizons appeared to be in equilibrium with the overlying vegetation types and did not point to a movement of the boundary during the last decades. However, ¹³C values obtained from deeper savanna and forest soil layers indicated that the vegetation type has changed in the past. In current savanna soil profiles, we observed the presence of mid-Holocene charcoals derived from forest species: fire frequency at that time was probably greater, and more extensive savanna may have resulted. Isotope data and the presence of these charcoals thus suggest that the forest-savanna boundary has shifted significantly in the recent Holocene period, forest being more extensive during the early Holocene than today. During the middle Holocene, the forest could have strongly regressed, and fires appeared, with a maximum development of the savanna vegetation. At the beginning of the late Holocene, the forest may have invaded a part of this savanna, and fires occurred again.     

Physical Map of the Malaria Vector Anopheles Gambiae

Random cDNA clones, cosmid clones and RAPD polymorphic fragments have been localized by in situ hybridization to the ovarian nurse cell polytene chromosomes of the malaria vector Anopheles gambiae. We thus established 85 molecular markers for 110 sites within the whole A. gambiae polytene chromosome complement. The cDNA clones analyzed were isolated at random, and their exact localizations were determined by in situ hybridization. For 15 of the cDNA clones, a partial nucleotide sequence has been obtained; for nine of them sequence searches in the GenBank database revealed high degrees of similarity with published sequences. The cosmid clones analyzed were obtained as the result of screening with a few of the aforementioned cDNA clones of particular interest, or taken from a small set of randomly isolated cosmid clones. The RAPD clones are polymorphic fragments, potentially diagnostic for the various chromosomal forms of A. gambiae that are currently being analyzed.     

Chlorsulfuron resistance in Daucus carota cell lines and plants:Involvement of gene amplification

Daucus carota L. cell lines stably resistant to the herbicide chlorsulfuron (CS) have been isolated according to a stepwise selection. Studies carried out during different selection steps show that the specific activity of the target enzyme acetohydroxyacid synthase (AHAS) increases along with CS resistance. Southern hybridization analysis performed with aBrassica napus AHAS probe in a CS highly-resistant cell line reveals the presence of a greatly amplifiedEcoRI fragment of genomic DNA. This indicates that AHAS overproduction induced by stepwise selection is due to gene amplification. Regenerants from some resistant cell lines maintained the CS-resistant trait at the whole plant level.     

Spatial partitioning of the soil water resource between grass and shrub components in a West African humid savanna

Most savanna water balance models assume water partitioning between grasses and shrubs in a two-layer hypothesis, but this hypothesis has not been tested for humid savanna environments. Spatial partitioning of soil water between grasses and shrubs was investigated in a West African humid savanna by comparing the isotopic composition (oxygen-18 and deuterium) of soil water and plant stem water during rainy and dry conditions. Both grass and shrub species acquire most of their water from the top soil layer during both rainy and dry periods. A shift of water uptake pattern towards deeper horizons was observed only at the end of the dry season after shrub defoliation. The mean depth of water uptake, as determined by the isotopic signature of stem water, was consistent with grass and shrub root profiles and with changes in soil water content profiles as surveyed by a neutron probe. This provides evidence for potentially strong competition between shrubs and grasses for soil water in these humid savannas. Limited nutrient availability may explain these competitive interactions. These results enhance our understanding of shrub-grass interactions, and will contribute to models of ecosystem functioning in humid savannas.     

Biosynthesis of lysosomal hydrolases: their synthesis in bound polysomes and the role of co- and post-translational processing in determining their subcellular distribution

By in vitro translation of mRNA’s isolated from free and membrane-bound polysomes, direct evidence was obtained for the synthesis of two lysosomal hydrolases, β-glucuronidase of the rat preputial gland and cathespin D of mouse spleen, on polysomes bound to rough endoplasmic reticulum (ER) membranes. When the mRNA’s for these two proteins were translated in the presence of microsomal membranes, the in vitro synthesized polypeptides were cotranslationally glycosylated and transferred into the microsomal lumen. Polypeptides synthesized in the absence of microsomal membranes were approximately 2,000 daltons larger than the respective unglycosylated microsomal polypeptides found after short times of labeling in cultured rat liver cells treated with tunicamycin. This strongly suggests that nascent chains of the lysosomal enzymes bear transient amino terminal signals which determine synthesis on bound polysomes and are removed during the cotranslational insertion of the polypeptides into the ER membranes. In the line of cultured rat liver cells used for this work, newly synthesized lysosomal hydrolases showed a dual destination; approximately 60 percent of the microsomal polypeptides detected after short times of labeling were subsequently processed proteolytically to lower molecular weight forms characteristic of the mature enzymes. The remainder was secreted from the cells without further proteolytic processing. As previously observed by other investigations in cultured fibroblasts (A. Gonzalez-Noriega, J.H. Grubbs, V. Talkad, and W.S. Sly, 1980, J Cell Biol. 85: 839-852; A. Hasilik and E.F. Neufeld, 1980, J. Biol. Chem., 255:4937-4945.) the lysosomotropic amine chloroquine prevented the proteolytic maturation of newly synthesized hydrolases and enhanced their section. In addition, unglycosylated hydrolases synthesized in cells treated with tunicamycin were exclusively exported from the cells without undergoing proteolytic processing. These results support the notions that modified sugar residues serve as sorting out signals which address the hydrolases to their lysosomal destination and that final proteolytic cleavage of hydrolase precursors take place within lysosome itself. Structural differences in the carbohydrate chains of intracellular and secreted precursors of cathespin D were detected from their differential sensitivity to digestion with endoglycosidases H and D. These observations suggest that the hydrolases exported into the medium follow the normal secretory route and that some of their oligosaccharides are subject to modifications known to affect many secretory glycoproteins during their passage through the Golgi apparatus.     

Orientation of anosmatic pigeons

Summary Test releases performed at five symmetrically arranged sites around the loft, at a distance of 78–99 km from it, showed that 1) anosmatic birds transported without alteration of the earth's magnetic field were completely random-oriented, 2) anosmatic birds transported in a container inside which the intensity of the magnetic field was strongly reduced were unable to orientate homewards and mostly departed according to a preferred compass direction, 3) control birds, which could smell, and were transported without alteration of the magnetic field, were homeward oriented and performed better in homing than both experimental groups. The conclusion is that anosmatic birds are unable to detect home direction at unfamiliar sites and that magnetic stimuli perceived during the outward journey are unable to substitute olfactory cues.Abbreviation PCD preferred compass direction Supported by a grant from the Consiglio Nazionale delle Ricerche