• The Plant Pathology Journal
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• v.35 no.2
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• pp.91-99
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• 2019

Mitogen-activated protein kinase (MAPK) cascades in fungi are ubiquitously conserved signaling pathways that regulate stress responses, vegetative growth, pathogenicity, and many other developmental processes. Previously, we reported that the AbSte7 gene, which encodes a mitogen-activated protein kinase kinase (MAPKK) in Alternaria brassicicola, plays a central role in pathogenicity against host cabbage plants. In this research, we further characterized the role of AbSte7 in the pathogenicity of this fungus using ${\Delta}AbSte7$ mutants. Disruption of the AbSte7 gene of A. brassicicola reduced accumulation of metabolites toxic to the host plant in liquid culture media. The ${\Delta}AbSte7$ mutants could not efficiently detoxify cruciferous phytoalexin brassinin, possibly due to reduced expression of the brassinin hydrolase gene involved in detoxifying brassinin. Disruption of the AbSte7 gene also severely impaired fungal detoxification of reactive oxygen species. AbSte7 gene disruption reduced the enzymatic activity of cell walldegrading enzymes, including cellulase, ${\beta}$-glucosidase, pectin methylesterase, polymethyl-galacturonase, and polygalacturonic acid transeliminase, during host plant infection. Altogether, the data strongly suggest the MAPKK gene AbSte7 plays a pivotal role in A. brassicicola during host infection by regulating multiple steps, and thus increasing pathogenicity and inhibiting host defenses.

• Molecules and Cells
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• v.38 no.7
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• pp.651-656
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• 2015

Plant growth and development are coordinately orchestrated by environmental cues and phytohormones. Light acts as a key environmental factor for fundamental plant growth and physiology through photosensory phytochromes and underlying molecular mechanisms. Although phytochromes are known to possess serine/threonine protein kinase activities, whether they trigger a signal transduction pathway via an intracellular protein kinase network remains unknown. In analyses of mitogen-activated protein kinase kinase (MAPKK, also called MKK) mutants, the mkk3 mutant has shown both a hypersensitive response in plant hormone gibberellin (GA) and a less sensitive response in red light signaling. Surprisingly, light-induced MAPK activation in wild-type (WT) seedlings and constitutive MAPK phosphorylation in dark-grown mkk3 mutant seedlings have also been found, respectively. Therefore, this study suggests that MKK3 acts in negative regulation in darkness and in light-induced MAPK activation during dark-light transition.

• Journal of Microbiology and Biotechnology
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• v.26 no.7
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• pp.1311-1319
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• 2016

Alternaria brassicicola (Schwein.) invades Brassicaceae and causes black spot disease, significantly lowering productivity. Mitogen-activated protein kinases (MAPKs) and their upstream kinases, including MAPK kinases (MAPKKs) and MAPKK kinases (MAPKKK), comprise one of the most important signaling pathways determining the pathogenicity of diverse plant pathogens. The AbSte7 gene in the genome of A. brassicicola was predicted to be a homolog of yeast Ste7, a MAPKK; therefore, the function was characterized by generating null mutant strains with a gene replacement method. AbSte7 replacement mutants (RMs) had a slower growth rate and altered colony morphology compared with the wild-type strain. Disruption of the AbSte7 gene resulted in defects in conidiation and melanin accumulation. AbSte7 was also involved in the resistance pathways in salt and oxidative stress, working to negatively regulate salt tolerance and positively regulate oxidative stress. Pathogenicity assays revealed that AbSte7 RMs could not infect intact cabbage leaves, but only formed very small lesions in wounded leaves, whereas typical lesions appeared on both intact and wounded leaves inoculated with the wild-type strain. As the first studied MAPKK in A. brassicicola, these data strongly suggest that the AbSte7 gene is an essential element for the growth, development, and pathogenicity of A. brassicicola.

• Journal of The Korean Society of Grassland and Forage Science
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• v.25 no.4
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• pp.287-296
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• 2005

To investigation protein expression pattern in rice leaves exposed to cold stress, the soluble proteins extracted from leaf tissue were fractionated with $15\%$ PEG and separated by two-dimensional polyacrylamide gel electrophoresis (2-DE). Differentially expressed proteins were identified by peptide mass fingerprinting using matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). Eight proteins up-regulated and 10 down-regulated were found in $15\%$ PEG supernatant fraction. In addition, 13 proteins up-regulated and 14 down-regulated were found in $15\%$ PEG pellet fraction. It was identified the differentially expressed proteins in $15\%$ PEG supernatant fraction as pimerase/dehydratase fructokinase, ribose-5-phosphate isomerase (Rpi), chaperonin 21 precursor, probable photosystem II oxygen-envolving complex (PS II OEC) protein 2 precursor and thioredoxin h-type (Trx-h) and those in $15\%$ PEG pellet fraction as OSINBb0059K02.15, hypothetical protein, putative mitogen-activated protein kinase kinase (MAPKK), beta 7 subunit of 205 proteasome, ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit. These proteins are involved in metabolism, energy, protein synthesis, disease/defense and signal transduction-related proteins.

• YAKHAK HOEJI
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• v.47 no.1
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• pp.31-36
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• 2003

To investigate the effect of protein kinase on melanin production via cAMP-dependent pathway, we measured the melanin amount and tyrosinase activity in B16 melanoma cells stimulated by alpha-melanocyte stimulating hormone (MSH), forskolin and 8-Br-cAMP. MSH, forskolin and 8-Br-cAMP significantly increased both melanin production and tyrosinase activity in B16 cells. Melanin production and tyrosinase activity by MSH are significantly inhibited by cyclic AMP-dependent protein kinase inhibitor (KT5720) and protein kinase C down-regulation treated with PMA. Bisindolmaleimide (1$\mu$M), protein kinase C inhibitor, significantly inhibited melanin production and tyrosinase activity stimulated by MSH, forskolin and 8-Br-cAMP with the following order of potency: MSH＞forskolin＞8-Br-cAMP. Tyrosine kinase inhibitor, genistein and DHC, significantly inhibited both, but the inhibitory effect was more potent in 8-Br-cAMP-stimulated B16 cells than MSH-stimulated cells. NFkB inhibitor (parthenolide) significantly inhibited melanin production and tyrosinase activity. Neither melanin production nor tyrosinase activity induced by MSH, forskolin and 8-Br-cAMP were affected by KN-62 (calmodulin-dependent protein kinase II inhibitor), PD098059 (mitogen-activated protein kinase inhibitor, MAPKK) and worthmannin (phosphatidylinositol 3-kinase inhibitor). These results suggest that both protein kinase C and tyrosine kinase are involved in melanin production by cyclic AMP-dependent pathway and NFkB pathway may play an important role in cyclic AMP-dependent melanin production in B16 melanoma cells.

• Molecules and Cells
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• v.23 no.1
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• pp.108-114
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• 2007

The mitogen-activated protein kinase (MAPK) signaling cascade is critical for regulating plant defense systems against various kinds of pathogen and environmental stresses. One component of this cascade, the MAP kinase kinases (MAPKK), has not yet been shown to be induced in plants following biotic attacks, such as those by insects and fungi. We describe here a gene coding for a blast (Magnaporthe grisea)- and insect (Nilaparvata lugens)-responsive putative MAPK kinase, OmMKK1 (Oryza minuta MAPKK 1), which was identified in a library of O. minuta expressed sequence tags (ESTs). Two copies of OmMKK1 are present in the O. minuta genome. They encode a predicted protein with molecular mass 39 kDa and pI of 6.2. Transcript patterns following imbibition of plant hormones such as methyl jasmonic acid (MeJA), ethephone, salicylic acid (SA) and abscisic acid (ABA), as well as exposure to methyl viologen (MV), revealed that the expression of OmMKK1 is related to defense response signaling pathways. A comparative analysis of OmMKK1 and its O. sativa ortholog OsMKK1 showed that both were induced by stress-related hormones and biotic stresses, but that the kinetics of their responses differed despite their high amino acid sequence identity (96%).

• Tuberculosis and Respiratory Diseases
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• v.58 no.6
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• pp.590-599
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• 2005

Object : Cigarette smoking is a major cause of mucus hypersecretion, which is a pathophysiological feature of many inflammatory airway diseases. Mucins, which are an important part of the airway mucus, are synthesized from the Muc gene in airway epithelial cells. However, the signaling pathways for cigarette smoke-induced mucin synthesis are unknown. The aim of this study was to determine the signal pathway for smoking induced Muc5ac gene expression. Methods : A549 cells were cultured and transiently transfected with the Muc5ac promoter fragment. These cells were stimulated with 5% cigarette smoke extract (CSE) alone or with CSE after a pretreatment with various signal transduction pathway inhibitors (AG1478, PD98059 and SB203580). The Muc5ac promoter activity was examined using the luciferase reporter system, and the level of phosphorylated EGFR, ERK1/2, p38 MAPK and JNK were all examined using Western blot analysis. Muc5ac mRNA expression was also examined using reverse transcriptase polymerase chain reactions (RT-PCR). Results : 1. The peak level of luciferase activity of the Muc5ac promoter was observed at 5% concentration and after 3 hours of incubation with the CSE. The level of EGFR phosphorylation and the luciferase activity of the transfected cells caused by the CSE were significantly suppressed by AG1478 or PD98059 (P<0.01). 2. CSE phosphorylated ERK1/2 or p38 MAPK but not JNK. The Muc5ac mRNA expression level was increased by the CSE but that was suppressed by PD98059 or AG1478. 3. The CSE-induced phosphorylation of ERK1/2 was blocked by PD98059 and that of p38 MAPK was blocked by either PD98059 or SB203580. Either PD98059 or SB203580 suppressed the luciferase activity of the transfected cells (P<0.0001). Conclusion : The Muc5ac mRNA expression level was increased by the CSE. The increased CSE-induced transcriptional activity was mediated via EGF receptor activation, which led to ERK1/2 and p38 MAPK phosphorylation.