Downregulation of Chloroplast RPS1 Negatively Modulates Nuclear Heat-Responsive Expression of HsfA2 and Its Target Genes in Arabidopsis

Heat stress commonly leads to inhibition of photosynthesis in higher plants. The transcriptional induction of heat stress-responsive genes represents the first line of inducible defense against imbalances in cellular homeostasis. Although heat stress transcription factor HsfA2 and its downstream target genes are well studied, the regulatory mechanisms by which HsfA2 is activated in response to heat stress remain elusive. Here, we show that chloroplast ribosomal protein S1 (RPS1) is a heat-responsive protein and functions in protein biosynthesis in chloroplast. Knockdown of RPS1 expression in the rps1 mutant nearly eliminates the heat stress-activated expression of HsfA2 and its target genes, leading to a considerable loss of heat tolerance. We further confirm the relationship existed between the downregulation of RPS1 expression and the loss of heat tolerance by generating RNA interference-transgenic lines of RPS1. Consistent with the notion that the inhibited activation of HsfA2 in response to heat stress in the rps1 mutant causes heat-susceptibility, we further demonstrate that overexpression of HsfA2 with a viral promoter leads to constitutive expressions of its target genes in the rps1 mutant, which is sufficient to reestablish lost heat tolerance and recovers heat-susceptible thylakoid stability to wild-type levels. Our findings reveal a heat-responsive retrograde pathway in which chloroplast translation capacity is a critical factor in heat-responsive activation of HsfA2 and its target genes required for cellular homeostasis under heat stress. Thus, RPS1 is an essential yet previously unknown determinant involved in retrograde activation of heat stress responses in higher plants

Limit-point criteria for the matrix Sturm-Liouville operator and its powers

We consider matrix Sturm-Liouville operators generated by the formal expression [formula] in the space [formula]. Let the matrix functions P := P(x), Q := Q(x) and R := R(x) of order n (n ∈ N) be defined on I, P is a nondegenerate matrix, P and Q are Hermitian matrices for x ∈ I and the entries of the matrix functions[formula], Q and R are measurable on I and integrable on each of its closed finite subintervals. The main purpose of this paper is to find conditions on the matrices P, Q and R that ensure the realization of the limit-point case for the minimal closed symmetric operator generated by [formula]. In particular, we obtain limit-point conditions for Sturm-Liouville operators with matrix-valued distributional coefficients

Sauerstoffeintrag ueber semipermeable Membranen in Abwasserreinigungsanlagen Schlussbericht

With 137 refs., 35 tabs., 116 figs.SIGLETIB: FR 1204 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Competition in the Post-Trade Markets: A Network Economic Analysis of the Securities Business

In order to analyse the role of competition in the post-trade markets a normative network economic analysis of the securities business is provided. The theory of monopolistic bottlenecks constitutes the theoretical reference point for this analysis in order to identify stable network specific market power. It is shown that clearing and settlement are competitive value-added telecommunications services and therefore do not justify ex ante market power regulation. Precondition for competition on the markets for clearing and settlement is non-discriminatory access to the complementary technical regulatory function-the notary function (authenticity, registry, links between competing end custodians). Copyright Springer Science + Business Media, Inc. 2006post-trade markets, network economics, competition policy,