Ergosterol levels in two l-methionine-enriched mutants of the methylotrophic yeast Candida boidinii ICCF26

Two L-methionine-enriched mutants, SN-78 and SE-57, were isolated in a sulphur-deficient medium from the methylotrophic yeast Candida boidinii ICCF26. No significant differences were detected between the L-cysteine pools of the mutants and the wild-type. In mutant strain SE-57, S-adenosylmethionine and ergosterol levels were higher than in the wild-type strain, while in the other mutant, SN-78, the levels were lower. The evidence presented would suggest that, in both the mutants and the wild-type used in this study, S-adenosylmethionine was of key importance for the accumulation of L-methionine and ergosterol.     

A dinoflagellate mutant with higher frequency of multiple fission

Summary The dinoflagellateCrypthecodinium cohnii Biecheler propagates by both binary and multiple fission. By a newly developed mutagenesis protocol based on using ethyl methanesulfonate and a cell size screening method, a cell cycle mutant,mƒ2, was isolated with giant cells which predominantly divide by multiple fission. The average cell size of the mutantmƒ2 is larger than the controlC. cohnii. Cell cycle synchronization experiments suggest that mutantmƒ2, when compared with the control strain, has a prolonged G₁ phase with a corresponding delay of the G₂+M phase.     

Stability of recombinant protein production by Penicillium chrysogenum in prolonged chemostat culture

Abstract A strain (WKW2) of Penicillium chrysogenum transformed with heterologous fungal acetamidase ( amd S) and bacterial β-galactosidase ( lac Z) was grown at a dilution rate of 0.17 h⁻¹ (doubling time of approx. 4.1 h) for 1600 h in a glucose-limited culture. By the end of the experiment the original strain had been almost completely replaced by spontaneous, morphological mutants, but the acetamidase and β-galactosidase activities of the culture were essentially unaltered. Furthermore, when WKW2 and the non-transformed parental strain (NRRL1951) were grown together in glucose- or NH₄⁺-limited chemostat cultures, neither strain had a selective advantage over the other. Thus, heterologous gene expression does not result in NRRL1951 having a selective advantage over WKW2. These results suggest that continuous flow culture systems could be used for efficient (and cost effective) production of recombinant proteins.     

Dysregulation of Exosome Cargo by Mutant Tau Expressed in Human-induced Pluripotent Stem Cell (iPSC) Neurons Revealed by Proteomics Analyses

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Highlights

• •Mutant Tau dysregulates exosome cargo generated by human iPSC neurons.
• •Expression of P301L and V337M mutations of Tau in human iPSC neurons result in recruitment of distinct proteins to exosomes, and absence of control proteins to exosomes.
• •Tau mutations of FTDP-17 result in up- and downregulation of exosome proteins.
• •Altered proteome cargo of mTau exosomes may be involved in Tau pathogenesis in vivo in brain.

     

Effect of inoculation ofAzospirillum spp. on nitrogen accumulation by field-grown wheat

Summary Two experiments were performed to examine the effects of inoculation of field grown wheat with various Azospirillum strains. In the first experiment the soil was sterilized with methyl bromide to reduce the Azospirillum population and¹⁵N labelled fertilizer was added to all treatments. Two strains ofAzospirillum brasilense isolated from surface sterilized wheat roots and theA. brasilense type strain Sp7 all produced similar increases in grain yield and N content. From the¹⁵N and acetylene reduction data it was apparent that these increases were not due to N₂ fixation. In the second experiment performed in the same (unsterilized) soil, twoA. brasilense strains (Sp245, Sp246) and oneA. amazonense strain (Am YTr), all isolated from wheat roots, produced responses of dry matter and N content while the response to the strain Sp7 was much smaller. These data confirm earlier results which indicate that if natural Azospirillum populations in the soil are high (the normal situation under Brazilian conditions), strains which are isolated from wheat roots are better able to produce inoculation responses than strains isolated from other sources. The inoculation of a nitrate reductase negative mutant of the strain Sp245 produced only a very small inoculation response in wheat. This suggests that the much greater inoculation response of the original strain was not due to N₂ fixation but to an increased nitrate assimilation due to the nitrate reductase activity of the bacteria in the roots. Consultant Inter-American Institute for Cooperation in Agriculture IICA/EMBRAPA World Bank Project.     

Enzymatic activity of atypical oriental types of aldehyde dehydrogenases

Catalytic activity of the atypical Oriental-type aldehyde dehydrogenase-2 (ALDH₂) was considered to be null or severely diminished. Recently it was suggested that the atypical ALDH ₂ ² retained about 30% of the specific activity of the usual ALDH ₂ ¹ . We reexamined the problem by two-dimensional crossed immunoelectrophoresis. The usual Caucasian livers exhibited two distinctive precipitin peaks, one corresponding to the cytosolic ALDH₁ and the other corresponding to the usual mitochondrial ALDH ₂ ¹ , in both protein stain and enzyme activity stain. In contrast, the atypical Oriental livers exhibited two precipitin peaks in protein stain, but only one peak, corresponding to ALDH₁, in enzyme activity stain. These results support the original notion that the atypical ALDH ₂ ² is enzymatically inactive or far less active than the usual enzyme, refuting the idea of the atypical ALDH ₂ ² with substantial enzyme activity.This work was supported by U.S. Public Health Service Grants HL-29515 and AA05763.     

The TGF-beta pseudoreceptor gene Bambi is dispensable for mouse embryonic development and postnatal survival

The Bambi (Bmp and activin membrane-bound inhibitor) gene encodes a transmembrane protein highly similar in amino acid sequence to transforming growth factor-beta (TGF-beta receptors, however, the Bambi intracellular domain is short and lacks a serine/threonine-kinase domain that is essential for transducing TGF beta signaling. Previous biochemical assays showed that Bambi interacts directly with BMP receptors and antagonizes BMP signaling. Interestingly, the expression of Bambi largely overlaps, both temporally and spatially, with that of Bmp4 during early embryonic development in Xenopus, zebrafish, and mice, which led to the hypothesis that Bambi may function to regulate BMP signaling during embryogenesis. To directly analyze the roles of Bambi during embryonic development, we generated mice carrying a conditional allele of Bambi, Bambi(flox), with loxP sequences flanking the first exon that encodes the N-terminus and signal peptide region of the Bambi protein. Mice homozygous for this targeted conditional allele appear normal and fertile. We crossed the Bambi(flox)/+ mice to the EIIa-Cre transgenic mice and generated mice carrying deletion of the first exon of the Bambi gene. Surprisingly, mice homozygous for the deleted allele were viable, fertile and did not exhibit any discernible developmental defect. Our data exclude an essential role for Bambi in mouse embryonic development and postnatal survival.