No abstract

In Saccharomyces cerevisiae, external high osmolarity activates the Hog1 mitogen-activated protein kinase (MAPK), which controls various aspects of osmoadaptation. Ssk1 is a homolog of bacterial two-component response regulators and activates the Ssk2 MAPK kinase kinase upstream of Hog1. It has been proposed that unphosphorylated Ssk1 (Ssk1-OH) is the active form and that Ssk1 phosphorylated (Ssk1ϳP) at Asp554 by the Sln1-Ypd1-Ssk1 multistep phosphorelay mechanism is the inactive form. In this study, we show that constitutive activation of Ssk2 occurs when Ssk1 phosphorylation is blocked by either an Ssk1 mutation at the phosphorylation site or an Ssk1 mutation that inhibits its interaction with Ypd1, the donor of phosphate to Ssk1. Thus, Ssk1-OH is indeed necessary for Ssk2 activation. However, overexpression of wild-type Ssk1 or of an Ssk1 mutant that cannot bind Ssk2 prevents constitutively active Ssk1 mutants from activating Ssk2. Therefore, Ssk1 has a dual function as both an activator of Ssk2 and an inhibitor of Ssk1 itself. We also found that Ssk1 exists mostly as a dimer within cells. From mutant phenotypes, we deduce that only the Ssk1-OH/ Ssk1-OH dimer can activate Ssk2 efficiently. Hence, because Ssk1ϳP binds to and inhibits Ssk1-OH, moderate fluctuation of the level of Ssk1-OH does not lead to nonphysiological and detrimental activation of Hog1.

Zinc (Zn) is an essential micronutrient for plant growth. Accordingly, Zn deficiency (2Zn) in agricultural fields is a serious problem, especially in developing regions. Autophagy, a major intracellular degradation system in eukaryotes, plays important roles in nutrient recycling under nitrogen and carbon starvation. However, the relationship between autophagy and deficiencies of other essential elements remains poorly understood, especially in plants. In this study, we focused on Zn due to the property that within cells most Zn is tightly bound to proteins, which can be targets of autophagy. We found that autophagy plays a critical role during 2Zn in Arabidopsis (Arabidopsis thaliana). Autophagy-defective plants (atg mutants) failed to grow and developed accelerated chlorosis under 2Zn. As expected, 2Zn induced autophagy in wild-type plants, whereas in atg mutants, various organelle proteins accumulated to high levels. Additionally, the amount of free Zn 21 was lower in atg mutants than in control plants. Interestingly, 2Zn symptoms in atg mutants recovered under low-light, iron-limited conditions. The levels of hydroxyl radicals in chloroplasts were elevated, and the levels of superoxide were reduced in 2Zn atg mutants. These results imply that the photosynthesis-mediated Fenton-like reaction, which is responsible for the chlorotic symptom of 2Zn, is accelerated in atg mutants. Together, our data indicate that autophagic degradation plays important functions in maintaining Zn pools to increase Zn bioavailability and maintain reactive oxygen species homeostasis under 2Zn in plants.

Background Chronic periodontitis (CP) is a multifactorial inflammatory disease. For the diagnosis of CP, it is necessary to investigate molecular biomarkers and the biological pathway of CP. Although analysis of mRNA expression profiling with microarray is useful to elucidate pathological mechanisms of multifactorial diseases, it is expensive. Therefore, we utilized pooled microarray gene expression data on the basis of data sharing to reduce hybridization costs and compensate for insufficient mRNA sampling. The aim of the present study was to identify molecular biomarker candidates and biological pathways of CP using pooled datasets in the Gene Expression Omnibus (GEO) database. Methods Three pooled transcriptomic datasets (GSE10334, GSE16134, and GSE23586) of gingival tissue with CP in the GEO database were analyzed for differentially expressed genes (DEGs) using GEO2R, functional analysis and biological pathways with the Database of Annotation Visualization and Integrated Discovery database, Protein-Protein Interaction (PPI) network and hub gene with the Search Tool for the Retrieval of Interaction Genes database, and biomarker candidates for diagnosis and prognosis and upstream regulators of dominant biomarker candidates with the Ingenuity Pathway Analysis database. Results We shared pooled microarray datasets in the GEO database. One hundred and twenty-three common DEGs were found in gingival tissue with CP, including 81 upregulated genes and 42 downregulated genes. Upregulated genes in Gene Ontology were significantly enriched in immune responses, and those in the Kyoto Encyclopedia of Genes and Genomes pathway were significantly enriched in the cytokine-cytokine receptor interaction pathway, cell adhesion molecules, and hematopoietic cell lineage. From the PPI network, the 12 nodes with the highest degree were screened as hub genes. Additionally, six biomarker candidates for CP diagnosis and prognosis were screened. Conclusions We identified several potential biomarkers for CP diagnosis and prognosis (e.g., CSF3, CXCL12 , IL1B , MS4A1 , PECAM1 , and TAGLN ) and upstream regulators of biomarker candidates for CP diagnosis ( TNF and TGF2 ). We also confirmed key genes of CP pathogenesis such as CD19 , IL8 , CD79A , FCGR3B , SELL , CSF3 , IL1B , FCGR2B , CXCL12 , C3 , CD53 , and IL10RA . To our knowledge, this is the first report to reveal associations of CD53 , ...