Ketoacyl synthase domain is a major determinant for fatty acyl chain length in Saccharomyces cerevisiae

Yeast fatty acid synthase (Fas) comprises two subunits, α₆ and β₆, encoded by FAS2 and FAS1, respectively. To determine features of yeast Fas that control fatty acyl chain length, chimeric genes were constructed by combining FAS sequences from Saccharomyces cerevisiae (ScFAS) and Hansenula polymorpha (HpFAS), which mostly produces C16 and C18 fatty acids, respectively. The C16/C18 ratios decreased from 2.2 ± 0.1 in wild-type S. cerevisiae to 1.0 ± 0.1, 0.5 ± 0.2 and 0.8 ± 0.1 by replacement of ScFAS1, ScFAS2 and ScFAS1 ScFAS2 with HpFAS1, HpFAS2 and HpFAS1 HpFAS2, respectively, suggesting that the α, but not β subunits play a major role in determining fatty acyl chain length. Replacement of phosphopantetheinyl transferase (PPT) domain with the equivalent region from HpFAS2 did not affect C16/C18 ratio. Chimeric Fas2 containing half N-terminal ScFas2 and half C-terminal HpFas2 carrying H. polymorpha ketoacyl synthase (KS) and PPT gave a remarkable decrease in C16/C18 ratio (0.6 ± 0.1), indicating that KS plays a major role in determining chain length.     

Development of surface‐engineered yeast cells displaying phytochelatin synthase and their application to cadmium biosensors by the combined use of pyrene‐excimer fluorescence

The development of simple, portable, inexpensive, and rapid analytical methods for detecting and monitoring toxic heavy metals are important for the safety and security of humans and their environment. Herein, we describe the application of phytochelatin (PC) synthase, which plays a critical role in heavy metal responses in higher plants and green algae, in a novel fluorescent sensing platform for cadmium (Cd). We first created surface‐engineered yeast cells on which the PC synthase from Arabidopsis (AtPCS1) was displayed with retention of enzymatic activity. The general concept for the sensor is based on the Cd level‐dependent synthesis of PC₂ from glutathiones by AtPCS1‐displaying yeast cells, followed by simple discriminative detection of PC₂ via sensing of excimer fluorescence of thiol‐labeling pyrene probes. The intensity of excimer fluorescence increased in the presence of Cd up to 1.0 μM in an approximately dose‐dependent manner. This novel biosensor achieved a detection limit of as low as 0.2 μM (22.5 μg/L) for Cd. Although its use may be limited by the fact that Cu and Pb can induce cross‐reaction, the proposed simple biosensor holds promise as a method useful for cost‐effective screening of Cd contamination in environmental and food samples. The AtPCS1‐displaying yeast cells also might be attractive tools for dissection of the catalytic mechanisms of PCS. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1197–1202, 2013     

Asymmetric cell division in human leukemic promyelocytic cells (HL-60).

Small cells accounted for 8-9% of the human leukemic promyelocytic cells (HL-60). The diameter of the small cells was 8.44 μm, whereas that of the large cells, which were heterogeneous in cell size, was 11.0 μm. The small cells were produced from the large cells through asymmetric cell division, which was demonstrated by cloning experiments and by microscopy.     

Japanese marine algae: New combinations, new names and new species

Several new species, combinations and names are described or proposed for the following species of algae reported from Japan: Gloiocladia japonica comb. nov. (=Gloioderma japonicum Okamura), Mazzaella hemisphaerica comb. nov. (=Rhodoglos-sum hemisphaericum Mikami), Melanamansia mitsuii comb. nov. (=Amansia mitsuii Segawa), Ptilo-cladia divaricata comb. nov. (=Crouania divaricata Okamura), Analipus gunjii comb. nov. (=Chordaria gunjii Yendo), Elachista okarnurae nom. nov. (=Elachista globosa Takamatsu), Gelidium inagakii nom. nov. (=Gelidium nanum Inagaki), Mastocarpus yendoisp. nov. (=Gigartina mamillosa sensu Yendo), Melobesia masakii nom. nov. (=Metobesia pacifica Masaki) and Porphyra yamadae sp. nov. (=Porphyra crispata sensu Okamura and Ueda).     

Plasma Membrane Permeability of Root-Tip Cells Following Temporary Exposure to Al Ions Is a Rapid Measure of Al Tolerance among Plant Species

No correlations were recognized between Al tolerance among fourplant species, rice (Oryza sativa L.), maize (Zea mays L.),pea (Pisum sativum L.), and barley (Hordeum vulgare L.), inrank order of Al tolerance, and cation exchange capacities ofroot-tip (0-1 cm) cells or of their cell walls. The plasma membraneof root-tip of Al sensitive plant species (pea and barley) wasconsiderably permeabilized with elongation of root in Al-freesolution following 0.5 h pretreatment with Al. K⁺ release fromand Al permeation into the protoplasts isolated from the root-tipof Al-sensitive plant species were more significant than thosefor Al-tolerant plant species (rice and maize) on 10 or 30 mintreatment with Al. The permeability of the plasma membrane forprotoplasts isolated from Al sensitive plant species was considerablyincreased by treatment with hy-potonic Al-free control solutionfollowing 10 min pretreatment with Al. To our knowlege, theseare the most rapid responses to Al ions reported to date, i.e.,within 0.5 h in whole plant and within 10 min in protoplast.These results suggest that a temporary contact with Al ionsirreversibly alters the plasma membrane of root-tip cells ofAl-sensitive plant species: the cells become more leaky andrigid due to binding of Al ions to the plasma membrane. (Received January 5, 1998; Accepted February 26, 1998)