Cytokinins and fruit development in the kiwifruit (Actinidia deliciosa). I. Changes during fruit development

The cytokinin content in fruit tissue of the kiwifruit ( Actinidia deliciosa [A. Chev.] C. F. Liang et A. R. Ferguson var. deliciosa cv. Hayward) was monitored during fruit development to identify which cytokinins were present and if they were linked with specific stages of fruit growth. Cytokinins were isolated and purified by column chromatography and high-performance liquid chromatography and quantified by radioimmunoassay. A novel HPLC step utilising an amine column was successfully introduced as a preparative step in the separation of the O - and 9-glucosides from the free bases and ribosides. The radioimmunoassay results were validated, and the different cytokinins identified, by gas chromatography-mass spectrometry. Cytokinins detected in fruit included the cytokinin free bases, zeatin and isopentenyladenine, their ribosides, nucleotides and both O - and 9-glucosides. Both qualitative and quantitative changes of the cytokinins occurred during fruit development. A decrease in cytokinin concentration occurred after anthesis (from 342 pmol g⁻¹ fresh weight at anthesis to 41 pmol g⁻¹ fresh weight 27 days after anthesis). A large increase in cytokinin concentration and content per fruit occurred as the fruit reached commercial maturity (to 1900 pmol g⁻¹ fresh weight). Individual cytokinins showed quite different patterns. Zeatin, in particular, showed a peak in concentration (13 pmol g⁻¹ fresh weight) 11 days after anthesis that correlated with the beginning of the cell division phase of fruit growth. The accumulation of cytokinin (mostly zeatin riboside or zeatin nucleotide) in mature fruit may be of significance for the postharvest storage of kiwifruit fruit.     

Co-purification,co-imniunoprecipitation,and coordinate expression of acetyl-coenzyme A carboxylase activity,biotin carboxylase,and biotin carboxyl carrier protein of higher plants

Acetyl-CoA carboxylase (ACCase; EC 6.4.1.2) is a regulatory enzyme of fatty acid synthesis, and in some higher-plant plastids is a multi-subunit complex consisting of biotin carboxylase (BC), biotin-carboxyl carrier protein (BCCP), and carboxyl transferase (CT). We recently described a Nicotiana tabacum L. (tobacco) cDNA with a deduced amino acid sequence similar to that of prokaryotic BC. We here provide further biochemical and immunological evidence that this higher-plant polypeptide is an authentic BC component of ACCase. The BC protein co-purified with ACCase activity and with BCCP during gel permeation chromatography of Pisum sativum L. (pea) chloroplast proteins. Antibodies to the Ricinus communis L. (castor) BC co-precipitated ACCase activity and BCCP. During castor seed development, ACCase activity and the levels of BC and BCCP increased and subsequently decreased in parallel, indicating their coordinate regulation. The BC protein comprised about 0.8% of the soluble protein in developing castor seed, and less than 0.05% of the protein in young leaf or root. Polypeptides cross-reacting with antibodies to castor BC were detected in several dicotyledons and in the monocotyledons Hemerocallis fulva L. (day lily), Iris L., and Allium cepa L. (onion), but not in the Gramineae species Hordeum vulgare L. (barley) and Panicum virgatum L. (switchgrass). The castor endosperm and pea chloroplast ACCases were not significantly inhibited by long-chain acyl-acyl carrier protein, free fatty acids or acyl carrier protein. The BC polypeptide was detected throughout Brassica napus L. (rapeseed) embryo development, in contrast to the multi-functional ACCase isoenzyme which was only detected early in development. These results firmly establish the identity of the BC polypeptide in plants and provide insight into the structure, regulation and roles of higherplant ACCases.Abbreviations ACCase acetyl-CoA carboxylase - ACP acyl carrier protein - BC biotin carboxylase - BCCP biotin carboxyl carrier protein - CT carboxyl transferase - MF multi-functional - MS multi-subunit We thank our colleagues Nicki Engeseth and Vicki Eccleston for advice on fatty acid analysis and Sarah Hunter for providing the developing Iris seed. This work was supported in part by grant MCB 9406466 from NSF. Acknowledgement is also made to the Michigan Agriculture Experiment Station for its support of this research.     

Thrust reversal by tubular mastigonemes: immunological evidence for a role of mastigonemes in forward motion of zoospores ofPhytophthora cinnamomi

Summary The role of tubular mastigonemes in the reversal of thrust of the anterior flagellum ofPhytophthora cinnamomi was analysed using mastigoneme-specific monoclonal antibodies and immunoflu-orescence and video microscopy. Exposure of live zoospores ofP. cinnamomi to the mastigoneme-specific Zg antibodies caused alterations in the arrangement of mastigonemes on the flagellar surface and at Zg concentrations above 0.3 /ml, mastigonemes became detached from the flagellum. As a consequence of antibody binding to the mastigonemes there were concentration-dependent perturbations in zoospore swimming behaviour and anterior flagellum beat pattern. With increasing antibody concentration zoospores swam more slowly and other parameters of their swimming pattern, such as the wavelength of the swimming helix and the frequency of rotation, were also reduced. The effects of Zg antibodies were specific at two levels: control immunoglobulins or antibodies that bound to other flagellar surface components did not have an effect on motility, and Zg antibodies did not interfere with the motility of zoospores of oomycete species to which they did not bind. The effects of antibody-induced disruption of mastigoneme arrangement strongly support previous hypotheses that tubular mastigonemes are responsible for thrust reversal by the anterior flagellum, enabling it to pull the cell through the surrounding medium.     

The 5′ untranslated region of Arabidopsis thaliana calmodulin cDNA is an independent cDNA containing an open reading frame

A cDNA clone, pAUK1, with an open reading frame (ORF) coding for a hypothetical 164-amino-acid protein was isolated from an Arabidopsis thaliana (L.) Heynh cDNA library. The clone was attached, tail to tail, to the 3′ end of A. thaliana hexokinase cDNA. An almost identical sequence had been previously described as the 5′ untranslated region (5′ UTR) of A. thaliana calmodulin cDNA (ACaM-2). Sequence comparison with three additional A. thaliana truncated cDNA clones which appear in a database (GenBank) supports the conclusion that pAUKl is identical to the 5′ UTR of ACaM-2 and that the 5′ UTR of ACaM-2 is an independent cDNA artificially linked to A. thaliana calmodulin cDNA.     

Subcellular compartmentation of different lipophilic fluorescein derivatives in maize root epidermal cells

Summary Fluorescence microscopy offers some distinct advantages over other techniques for studying ion transport processes in situ with plant cells. However, the use of this technology in plant cells has been limited by our lack of understanding the mechanisms that influence the subcellular distribution of dyes after loading with the lipophilic precursors. In this study, the subcellular distribution of 5-(and 6-)carboxydichlorofluorescein (CDCF), carboxy-SNAFL-1, and carboxy-SNARF-1 was compared to that of 2,7-bis-(2-carboxyethyl)-5-(and 6-)carboxyfluorescein (BCECF) after incubation of maize roots with their respective lipophilic precursors. Previously, we reported that incubation of roots with BCECF-acetomethyl ester (BCECF-AM) led to vacuolar accumulation of this dye. Similar results were found when roots were incubated with CDCF-diacetate. In contrast, carboxy-SNAFL-1 appeared to be confined to the cytoplasm based on the distribution of fluorescence and the excitation spectra of the dye in situ. On the other hand, incubation of roots with carboxy-SNARF-1-acetoxymethyl acetate yielded fluorescence throughout the cell. When the cytoplasm of epidermal cells was loaded with the BCECF acid by incubation at pH 4 in the absence of external Ca, the dye was retained in the cytoplasm at least 3 h after the loading period. This result indicated that vacuolar accumulation of BCECF during loading of BCECF-AM was not due to transport of BCECF from cytoplasm to vacuole. The esterase activities responsible for the production of either carboxy-SNAFL-1 or BCECF from their respective lipophilic precursor by extracts of roots were compared. The characterization of esterase activities was consistent with the subcellular distribution of these dyes in root cells. The results of these experiments suggest that in maize root epidermal cells the subcellular distribution of these fluorescein dyes may be determined by the characteristics of the esterase activities responsible for hydrolysis of the lipophilic precursor.Abbreviations BCECF (BCECF-AM) 2,7-bis-(2-carboxyethyl)-5-(and 6-)carboxyfluorescein (its acetoxymethyl ester) - BTB bis-trispropane - CDCF (CDCF-DA) 5-(and 6-)carboxy-2,7-dichlorofluorescein (its diacetate derivative) - DAPI 4,6-diamidino-2 phenylindole dihydrochloride - DMSO dimethylsulfoxide - HEPES N-[2-hydroxyethyl] piperazine-N-[2-ethanesulfonic acid] - MES 2-[N-morpholino]ethane-sulfonic acid - SNAFL-1 (SNAFL-1-DA) carboxyl SNAFL-1 (its diacetate) - SNARF-1 (SNARF-1-AM) carboxyl SNARF-1 (its acetoxymethyl acetate)     

Reproductive and neonatal outcomes in captive bred baboons (Papio hamadryas)

Abstract: Baboons are widely used in biomedical research. Although it is widely held that Papio hamadryas breed well in captivity, each established colony has a different reproductive success often hypothesised to be due to husbandry practices. The National Baboon Colony in Australia is a unique colony that houses Papio hamadryas to mimic that structure seen in the wild. In this article; we have analysed their reproductive parameters and neonatal outcomes. The success of the colony husbandry practices was demonstrated by lack of maternal mortality, low foetal morbidity, and known maternal and paternal linage.     

Making sense of the combined effect of interleukin-2 and interleukin-4 on lymphocytes using a mathematical model

The cytokines are the information superhighway of the immune system. They are an important component of the integrated behavior of the system. In order to be able to have a good understanding of the immune system, we must be able to model the effect of cytokines and their combined effect. This work is a step in that direction. We study the combined effect of two cytokines: interleukin-2 (IL-2) and interleukin-4 (IL-4) on some cells of the immune system. Interleukin-2 and interleukin-4 are important growth and differentiation factors for B and T cells. Interleukin-4 antagonizes the effect of interleukin-2 on B cells and some T cells while it synergizes with interleukin-2 on other T cells. We build a mathematical model of the interaction of both cytokines on T and B cells as a building block toward a model of the Th1/Th2 cross-regulation. The response of a given cell to the combination of interleukin-2 and interleukin-4 is shown to involve competing dynamical effects which can lead to either antagnostic or synergistic combined effect. Author to whom correspondence should be addressed at Department of Engineering and Public Policy. Work supported by NIH grant nv: Ai31427.     

Fetal ultrasonography: Normal biometric ranges in the baboon (Papio hamadryas)

Normal biometric ranges for fetal growth in a captive breeding baboon (Papio hamadryas) colony are described. Measurements include crown-rump length, biparietal diameter, binocular distance, head circumference, abdominal circumference, femur length and amniotic fluid index. The pattern of fetal growth is compared with other baboon subspecies and man. The uses and limitations of such data for breeding colony management and optimum utilisation of experimentally derived data are discussed.