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Articles by M Kubota
Total Records ( 2 ) for M Kubota
  Y Kawamura , S Takenaka , S Hase , M Kubota , Y Ichinose , Y Kanayama , K Nakaho , D. F Klessig and H. Takahashi
 

The cell wall protein fraction (CWP) is purified from the non-pathogenic biocontrol agent Pythium oligandrum and is composed of two glycoproteins (POD-1 and POD-2), which are structurally similar to class III elicitins. In tomato plants treated with CWP, jasmonic acid (JA)- and ethylene (ET)-dependent signaling pathways are activated, and resistance to Ralstonia solanaceraum is enhanced. To dissect CWP-induced defense mechanisms, we investigated defense gene expression and resistance to bacterial pathogens in Arabidopsis thaliana ecotype Col-0 treated with CWP. When the leaves of Col-0 were infiltrated with CWP, neither visible necrosis nor salicylic acid (SA)-responsive gene (PR-1 and PR-5) expression was induced. In contrast, JA-responsive gene (PDF1.2 and JR2) expression was up-regulated and the resistance to R. solanaceraum and Pseudomonas syringae pv. tomato DC3000 was enhanced in response to CWP. Such CWP-induced defense responses were completely compromised in CWP-treated coi1-1 and jar1-1 mutants with an impaired JA signaling pathway. The induction of defense-related gene expression after CWP treatment was partially compromised in ET-insensitive ein2-1 mutants, but not in SA signaling mutants or nahG transgenic plants. Global gene expression analysis using cDNA array also suggested that several other JA- and ET-responsive genes, but not SA-responsive genes, were up-regulated in response to CWP. Further analysis of CWP-induced defense responses using another eight mutants with impaired defense signaling pathways indicated that, interestingly, the induction of JA-responsive gene expression and enhanced resistance to two bacterial pathogens in response to CWP were completely compromised in rar1-1, rar1-21, sgt1a-1, sgt1b (edm1) and npr1-1 mutants. Thus, the CWP-induced defense system appears to be regulated by JA-mediated and SGT1-, RAR1- and NPR1-dependent signaling pathways.

  M Kubota , T Tanaka , T Kohno and K. Wakamatsu
 

Although detergents have been widely used in G-protein studies to increase solubility and stability of the protein, we noticed that detergents modulate the nucleotide-binding properties of G-proteins. Hence, we analysed the effects of detergents on guanine nucleotide exchange reactions of Gi1. Lubrol PX, a non-ionic detergent, which has been widely used in nucleotide dissociation/binding assays, was found to accelerate both GDP dissociation and GTPS binding from/to G in parallel at above its critical micelle concentration (cmc). Sodium cholate, an anionic detergent, which have been used to extract G-proteins from animal tissues, decelerated and accelerated GDP dissociation below and above its cmc, respectively. Surprisingly, micellar cholate decelerated GTPS binding, and the binding rate constant was decreased by three orders of magnitude in the presence of 2% cholate. These results demonstrate that the guanine nucleotide exchange reactions of Gi1 are drastically modulated by detergents differently depending on the type and the state (monomeric or micellar) of the detergents and that dissociation of GDP from Gi1 does not necessarily lead to immediate binding of GTP to Gi1 in some cases. These effects of detergents on G-proteins must be taken into account in G-protein experiments.

 
 
 
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