• Mycobiology
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• v.38 no.1
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• pp.26-32
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• 2010

The cyclic AMP (cAMP) pathway plays a major role in growth, sexual differentiation, and virulence factor synthesis of pathogenic fungi. In Cryptococcus neoformans, perturbation of the cAMP pathway, such as a deletion in the gene encoding adenylyl cyclase (CAC1), causes defects in the production of virulence factors, including capsule and melanin production, as well as mating. Previously, we performed a comparative transcriptome analysis of the Ras- and cAMP- pathway mutants, which revealed 163 potential cAMP-regulated genes (38 genes at a 2-fold cutoff). The present study characterized the role of one of the cAMP pathway-dependent genes (serotype A identification number CNAG_ 06576.2). The expression patterns were confirmed by Northern blot analysis and the gene was designated cAMP-regulated gene 1 (CAR1). Interestingly, deletion of CAR1 did not affect biosynthesis of any virulence factors and the mating process, unlike the cAMP-signaling deficient cac1$\Delta$ mutant. Furthermore, the car1$\Delta$ mutant exhibited wild-type levels of the stress-response phenotype against diverse environmental cues, indicating that Car1, albeit regulated by the cAMP-pathway, is not essential to confer a cAMP-dependent phenotype in C. neoformans.

• BMB Reports
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• v.32 no.1
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• pp.6-11
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• 1999

To understand the function of phospholipids and their fatty acid composition on the morphological changes in the amp 1-4 mutant of Arabidopsis, the mutant was compared to the wild-type Arabidopsis by TLC, HPTLC, phosphorous assay, HPLC, and GC. In the mutant, phosphatidylethanolamine (PE) was increased 5-fold and phosphatidylglycerol (PG) was decreased 1.2-fold (nmol phosphorous/g tissue). Inositol phospholipids showed a generally increased trend ranging from 1.4-to 3.0-fold (nmol inositol/g tissue). When fatty acid composition of the mutant was compared to the wild-type, linoleic (18:2) and linolenic (18:3) acids of phosphatidylcholine (PC) and PG were decreased but palmitoleic acid (16:1) and oleic acid (18:1) of PC was increased 2.5- and 2.1-fold (mol%), respectively. In galactolipids, myristic acid (14:0) of monogalactosyl-diacylglycerol (MGDG) were increased 5.8-fold (mol%). Among the inositol phospholipids, lysophosphatidylinositol (L-PI) and phosphatidylinositol 4,5-bisphosphate ($PIP_2$) showed 4-and 1.9-fold (mol%) increase of 16:1, respectively. These results suggest that the increase of PE, the decrease of PG, the increase of inositol phospholipids, and the altered fatty acid composition are related to the phenotypic changes affecting the morphological features, and might cause different physiological changes in the amp 1-4 mutant compared to wild-type Arabidopsis.

• Journal of Animal Reproduction and Biotechnology
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• v.34 no.4
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• pp.267-271
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• 2019

This study aimed to investigate the function of the constitutively activating mutation D540G on eel FSHR activity by in vitro functional studies. Site-directed mutagenesis was carried out to generate the D-to-G mutation at position 540 of the pcDNA3-eel FSHR construct. Vectors expressing either wild type or mutant receptor were transfected into Chinese hamster ovary (CHO-K1) cells. The functional characteristics of both the wild type and mutant receptors were analyzed by a cAMP assay. cAMP accumulation was highly increased in cells transfected with the D540G mutant receptor in a dose-dependent manner. Of note, basal cAMP levels were remarkably increased (~13.1-fold) with expression of this mutant when compared to wild type receptor. These findings suggest that the D540G mutation in the eel FSHR may contribute to ovulation during eel sex maturation as well as play a pivotal role in inducing FSHR activity.

• Animal cells and systems
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• v.10 no.4
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• pp.237-241
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• 2006

Chemotactic behavior is essential for the survival of animals. However, the mechanism by which animals carry out chemotaxis is poorly understood. To explore the biochemical events underlying chemotaxis, we isolated C. elegans mutants that displayed abnormal chemotactic responses to cAMP, a strong attractant for C. elegans. Based on their responses to other chemoattractants, the mutant animals could be classified into five groups: (1) animals with defective chemotaxis to cAMP only; (2) animals with defective chemotaxis to both cAMP and cGMP; (3) animals with defective chemotaxis to water-soluble attractants; (4) animals with defective chemotaxis to both water-soluble and volatile attractants; and (5) animals with enhanced chemotactic responses. We expect that analyses of these mutants will help understand the molecular mechanisms underlying chemotaxis in C. elegans.

• Journal of Microbiology and Biotechnology
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• v.19 no.6
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• pp.542-546
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• 2009

Leaves are the major biomass-producing organs in herbaceous plants and mainly develop during vegetative stage by activities of shoot apical meristem. There is a strong correlation between leaf number and bolting, a characteristic phenotype during the transition to reproductive phase in Arabidopsis thaliana. In order to study interactions between leaf number and bolting, we isolated a Landsberg erecta-derived mutant named multifolial (mfo1) that produces increased number of leaves and bolts at the same time as the wild type. Through positional cloning and allelism test, mfo1 was found to be an allele of a previously reported mutant, altered meristem program1-1 (amp1-1) that is defective in a glutamate carboxypeptidase and bolts earlier than its wild type, Columbia ecotype, with the increased number of leaves. The bolting time differences between mfo1 and amp1, despite the same phenotype of many leaves, suggest the existence of genetic factor(s) differently function in each ecotype in the presence of mfo1/amp1 mutation.

• Korean Journal of Animal Reproduction
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• v.24 no.1
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• pp.41-47
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• 2000

Gonadotropin receptors are members of the seven-transmembrane (TM) receptor family, Point mutations in the lutropin/choriogonadotropin receptor (LH/CGR) have been shown to cause constitutive activation which results in precocious puberty in affected males, We introduced one of the mutation, D556Y, into the LH/CG receptor and the same high affinity binding mutant (D556Y) receptor clone cell for wild type LH/CGR (LH/CGR-wt) was chosen for further analysis, In contrast to cells expressing LH/CGR-wt, it was demonstrated that the mutant receptor exhibited markedly increased basal cAMP production in the absence of agonist, suggesting that autonomous Leydig cell activity in familial male-precocious puberty (FMPP) is caused by a constitutively activating LH/CGR.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1202-1206
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• 1998

We have explored the impact of altering the Ras-cAMP pathway on cell survival upon oxidative exposures. A hyperactivated Ras mutant of Saccharomyces cerevisiae, intrinsically more sensitive to heat shock than the wild type, was investigated with regard to oxidative stress. In this paper we report that the response of iral, ira2-deleted mutant (IR2.53) to an oxidant, such as hydrogen peroxide (H2O2) or menadione is more sensitive than that of the wild type. IR2.53 showed a dramatic decrease in survival rate when challenged with 0.1 mM H2O2 for 30 min. The greater sensitivity of IR2.53 was also noticed with treatment of 0.01 mM menadione. Prior to oxidative stresses by these oxidants, both the wild type and the mutant were preconditioned with a mild heat shock (37 ℃, 30 min), resulting in improved survivals against oxidative stresses. Rescue of IR2.53 from menadione stress by heat pretreatment was more clearly demonstrated than that from H2O2 treatment. On the other hand, no significant difference was observed between the wild type and the IR2.53 mutant in their survival rates upon paraquat treatments. These findings imply that the mechanism by which H2O2 and menadione put forth their oxidative effects may be closely associated with the cAMP-Ras pathway whereas that of paraquat is independent of the Ras pathway. Finally, the level of glutathione (GSH) was measured enzymatically as an indicator of antioxidation and compared with the survival rate. Taken all these together, this study provides an insight into a mechanism of the Ras pathway regulated by several oxidants and suggests that the Ras pathway plays a crucial role in protection of cell damage following oxidative stress.

• Journal of The Korean Society of Grassland and Forage Science
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• v.27 no.4
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• pp.241-248
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• 2007

Cytokinins are essential plant hormones that play crucial roles in various aspects of plant growth and development. By using mRNA differential display, we isolated a cytokinine-inducible cDNA encoding pathogenesis-related (PR) 4 from Arabidopsis amp1 mutant. The full-length PR4 cDNA, designated AtPR4, contains an open reading frame of 212 amino acids with calculated molecular mass of 22,900 Da and isoelectric point (pI) of 7.89. Genomic DNA blotting showed that the Arabidopsis genome has one copy of AtPR4. AtPR4 mRNA was induced by cytokinin and NaCl, but decreased by SA or JA treatment. PR proteins are induced in response to pathogen attack. Thus the AtPR4 gene isolated in this study may be a useful candidate for genetic engineering of forage crops for increased tolerance against pathogen.

• The Korean Journal of Mycology
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• v.21 no.4
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• pp.285-292
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• 1993

For the enzymatic conversion of 5'-XMP to 5'-GMP, partially purified XMP aminase from Escherichia coli was coupled with the yeast, Saccharomycrs cerevisiae, capable of ATP regeneration through glycolytic pathway. In order to elevate the level of XMP aminase in E. coli, $guaB^{-}(IMP\;dehydrogenase-less)$ mutant were introduced, and the yeast used as ATP supplier was treated by some method to increase its membrane permeability. The optimum conditions for efficient conversion reaction by energy-coupled system were investigated. As the results, a CH 41, $guaB^-$ mutant of E. coli K-12, showed 2.75 fold increase in the level of XMP aminase, compared with its parent cell. And the lyophylized yeast was the most effective at the ATP supplier. The optimum temperature and pH of conversion reaction were $40{\circ]C$ and pH 7.4, and the highest conversion ratio was shown under the reaction condition of 100 mM glucose, 100 mM inorganic phosphate and 6 mM AMP. When 36 units/ml XMP aminase used under the above conditions, the amount of 60 mg/ml yeast was sufficient to be used. Under the optimum condition, 71% of 1.8 mM(65.6 mg/100 ml) 5'-XMP was converted to 5'-GMP within 8 hr.

• Development and Reproduction
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• v.25 no.3
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• pp.133-143
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• 2021

In contrast to the human lutropin receptor (hLHR) and rat LHR (rLHR), very few naturally occurring mutants in other mammalian species have been identified. The present study aimed to delineate the mechanism of signal transduction by three constitutively activating mutants (designated M410T, L469R, and D590Y) and two inactivating mutants (D383N and Y546F) of the eel LHR, known to be naturally occurring in human LHR transmembrane domains. The mutants were constructed and measured cyclic adenosine monophosphate (cAMP) accumulation via homogeneous time-resolved fluorescence assays in Chinese hamster ovary (CHO)-K1 cells. The activating mutant cells expressing eel LHR-M410T, L469R, and D590Y exhibited a 4.0-, 19.1-, and 7.8-fold increase in basal cAMP response without agonist treatment, respectively. However, inactivating mutant cells expressing D417N and Y558F did not completely impaired signal transduction. Specifically, signal transduction in the cells expressing activating mutant L469R was not occurred with a further ligand stimulation, showing that the maximal response exhibited approximately 53% of those of wild type receptor. Our results suggested that the constitutively activating mutants of the eel LHR consistently occurred without agonist treatment. These results provide important information of LHR function in fish and regulation with regard to mutations of highly conserved amino acids in glycoprotein hormone receptors.