High-quality and low cost bulk crystals are needed in the field of group III nitride semiconductors in order to develop optical and electrical devices. There are two approaches for the growth of bulk ...GaN crystal by the Na flux method. One is to grow thick GaN crystal on a large seed GaN crystal grown by vapor phase method. The other is to grow GaN crystal on a small seed GaN crystal. 3in diameter GaN crystals were grown on the large GaN seed crystal. In the case of the growth on a small GaN seed, we obtained bulk crystal with a pyramidal shape and its height and diameter were 15mm and >20mm, respectively. We also present the effects of the impurity in the solution on the property and growth habit.
We screened a rice (Oryza sativa L. 'Nipponbare') full-length cDNA expression library through functional complementation in yeast (Saccharomyces cerevisiae) to find novel cation transporters involved ...in salt tolerance. We found that expression of a cDNA clone, encoding the rice homolog of Shaker family K⁺ channel KAT1 (OsKAT1), suppressed the salt-sensitive phenotype of yeast strain G19 (Δena1-4), which lacks a major component of Na⁺ efflux. It also suppressed a K⁺-transport-defective phenotype of yeast strain CY162 (Δtrk1Δtrk2), suggesting the enhancement of K⁺ uptake by OsKAT1. By the expression of OsKAT1, the K⁺ contents of salt-stressed G19 cells increased during the exponential growth phase. At the linear phase, however, OsKAT1-expressing G19 cells accumulated less Na⁺ than nonexpressing cells, but almost the same K⁺. The cellular Na⁺ to K⁺ ratio of OsKAT1-expressing G19 cells remained lower than nonexpressing cells under saline conditions. Rice cells overexpressing OsKAT1 also showed enhanced salt tolerance and increased cellular K⁺ content. These functions of OsKAT1 are likely to be common among Shaker K⁺ channels because OsAKT1 and Arabidopsis (Arabidopsis thaliana) KAT1 were able to complement the salt-sensitive phenotype of G19 as well as OsKAT1. The expression of OsKAT1 was restricted to internodes and rachides of wild-type rice, whereas other Shaker family genes were expressed in various organs. These results suggest that OsKAT1 is involved in salt tolerance of rice in cooperation with other K⁺ channels by participating in maintenance of cytosolic cation homeostasis during salt stress and thus protects cells from Na⁺.
To remove nitrogen efficiently from high-concentration organic wastewater, we studied breeding methods using Saccharomyces cerevisiae as a model yeast with improved nitrogen accumulation ability. By ...DNA microarray analysis under various nitrogen concentrations with two nitrogen sources (peptone and L-asparagine), we obtained 295 commonly overexpressed (over 2-fold) genes and 283 commonly underexpressed (under one-half) genes under nitrogen-starvation conditions. We speculated that overexpression or underexpression recombination of some of these genes might enhance nitrogen uptake. Because a complete collection of nonessential gene deletion strains had been created, we investigated the nitrogen accumulation profiles of underexpressed gene deletion strains. From 256 nonessential gene deletion strains, three (URE2, SNO1, and AVT3) were selected. Strain SUD2 (ure2Δ::kanMX4) improved by 1.2-fold total nitrogen per cell (TN/OD660) as compared to the parent strain, S288c. Positive selection of methylamine-resistant mutants to obtain URE2 mutants was useful for improving nitrogen accumulation ability without recombinant techniques.
Paraphoma-related fungal strain B47-9 secreted a biodegradable plastic (BP)-degrading enzyme which amounted to 68 % (w/w) of the total secreted proteins in a culture medium containing emulsified ...poly(butylene succinate-co-adipate) (PBSA) as sole carbon source. The gene for this enzyme was found to be composed of an open reading frame consisting of 681 nucleotides encoding 227 amino acids and two introns. Southern blot analysis showed that this gene exists as a single copy. The deduced amino acid sequence suggested that this enzyme belongs to the cutinase (E.C.3.1.1.74) family; thus, it was named P araphoma-related fungus cutinase-like enzyme (PCLE). It degraded various types of BP films, such as poly(butylene succinate), PBSA, poly(butylene adipate-co-terephthalate), poly(ε-caprolactone), and poly(DL-lactic acid). It has a molecular mass of 19.7 kDa, and an optimum pH and temperature for degradation of emulsified PBSA of 7.2 and 45 °C, respectively. Ca²⁺ ion at a concentration of about 1.0 mM markedly enhanced the degradation of emulsified PBSA.
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CEKLJ, DOBA, EMUNI, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK
Enzymatic degradation of polyester films by a cutinase-like enzyme from
Pseudozyma antarctica
JCM10317 (PaE) was analyzed by surface plasmon resonance (SPR). The adsorption of PaE and the degradation ...rate for polyester films were quantitatively monitored by a positive and negative SPR signal shifts, respectively. The decrease in SPR signal and the erosion depth of amorphous poly(
l
-lactide) (a-PLLA) film measured by atomic force microscopy (AFM) had a linear relationship, and the weight loss was estimated from the AFM data combined with a density of a-PLLA film. Furthermore, SPR sensorgrams for various polyester films showed that degradation rate of poly(ε-caprolactone) and poly(butylene succinate-
co
-adipate) which contain C6 units was higher than that of other polyesters such as poly(butylene succinate) and a-PLLA. These results suggest that C6 is the preferred chain length as substrates for PaE.
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CEKLJ, DOBA, EMUNI, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK
To improve the biodegradation of biodegradable plastic (BP) mulch films, 1227 fungal strains were isolated from plant surface (phylloplane) and evaluated for BP-degrading ability. Among them, B47-9 a ...strain isolated from the leaf surface of barley showed the strongest ability to degrade poly-(butylene succinate-
co
-butylene adipate) (PBSA) and poly-(butylene succinate) (PBS) films. The strain grew on the surface of soil-mounted BP films, produced breaks along the direction of hyphal growth indicated that it secreted a BP-degrading enzyme, and has directly contributing to accelerating the degradation of film. Treatment with the culture filtrate decomposed 91.2 wt%, 23.7 wt%, and 14.6 wt% of PBSA, PBS, and commercially available BP polymer blended mulch film, respectively, on unsterlized soil within 6 days. The PCR-DGGE analysis of the transition of soil microbial community during film degradation revealed that the process was accompanied with drastic changes in the population of soil fungi and
Acantamoeba
spp., as well as the growth of inoculated strain B47-9. It has a potential for application in the development of an effective method for accelerating degradation of used plastics under actual field conditions.
Two yeast strains, which have the ability to degrade biodegradable plastic films, were isolated from the larval midgut of a stag beetle,
Aegus laevicollis
. Both of them are most closely related to
...Cryptococcus magnus
and could degrade biodegradable plastic (BP) films made of poly(butylene succinate) (PBS) and poly(butylene succinate-
co
-adipate) (PBSA) effectively. A BP-degrading enzyme was purified from the culture broth of one of the isolated strains employing a newly developed affinity purification method based on the binding action of the enzyme to the substrate (emulsified PBSA) and its subsequent degradative action toward the substrate. Partial amino acid sequences of this enzyme suggested that it belongs to the cutinase family, and thus, the enzyme was named CmCut1. It has a molecular mass of 21 kDa and a degradative activity for emulsified PBSA which was significantly enhanced by the simultaneous presence of Ca
2+
or Mg
2+
at a concentration of about 2.5 mM. Its optimal pH was 7.5, and the optimal temperature was 40 °C. It showed a broad substrate specificity for
p
-nitrophenyl (pNP)-fatty acid esters ranging from pNP-acetate (C2) to pNP-stearate (C18) and films of PBSA, PBS, poly(
ε
-caprolactone), and poly(lactic acid).
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CEKLJ, DOBA, EMUNI, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK
The pathway oxoaverantin (OAVN) rightwards arrow averufin (AVR) rightwards arrow hydroxyversicolorone (HVN) rightwards arrow versiconal hemiacetal acetate (VHA) is involved in aflatoxin biosynthesis, ...and the cypX and moxY genes, which are present in the aflatoxin gene cluster, have been previously suggested to be involved in this pathway. To clarify the function of these two genes in more detail, we disrupted the genes in aflatoxigenic Aspergillus parasiticus NRRL 2999. The cypX-deleted mutant lost aflatoxin productivity and accumulated AVR in the mycelia. Although this mutant converted HVN, versicolorone (VONE), VHA, and versiconol acetate (VOAc) to aflatoxins in feeding experiments, it could not produce aflatoxins from either OAVN or AVR. The moxY-deleted mutant also lost aflatoxin productivity, whereas it newly accumulated HVN and VONE. In feeding experiments, this mutant converted either VHA or VOAc to aflatoxins but did not convert OAVN, AVR, HVN, or VONE to aflatoxins. These results demonstrated that cypX encodes AVR monooxygenase, catalyzing the reaction from AVR to HVN, and moxY encodes HVN monooxygenase, catalyzing a Baeyer-Villiger reaction from HVN to VHA as well as from VONE to VOAc. In this work, we devised a simple and rapid method to extract DNA from many fungi for PCR analyses in which cell disruption with a shaker and phenol extraction were combined.
The killer yeast species Pichiaacaciae produces a heteromeric killer protein, PaT, that causes DNA damage and arrests the cell cycle of sensitive Saccharomyces cerevisiae in the S phase. However, the ...mechanism by which DNA damage occurs remains elusive. A previous study has indicated that Orf2p, a subunit of PaT, specifically cleaves an anticodon loop of an S. cerevisiae transfer RNA (tRNA(Gln)mcm5s2UUG). This finding raised a question about whether the DNA damage is a result of the tRNA cleavage or whether Orf2p directly associates with and cleaves the genomic DNA of sensitive yeast cells. We showed that Orf2p cleaves genomic DNA in addition to cleaving tRNA in vitro. This DNA cleavage requires the same Orf2p residue as that needed for tRNA cleavage, His299. The expression of Orf2p, in which His299 was substituted to alanine, abolished the cell cycle arrest of the host cell. Moreover, the translation impairment induced by tRNA cleavage enabled Orf2p to enter the nucleus, thereby inducing histone phosphorylation.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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