Project description:Phosphatidylinositol-4-kinases β1 and β2 (PI4Kβ1/PI4Kβ2), which are responsible for phosphorylation of phosphoinositol to phosphatidylinositol-4-phosphate, have an important role in vesicular trafficking in plants. Moreover, PI4Kβ1/PI4β2 negatively regulate biosynthesis of phytohormone salicylic acid (SA). SA plays crucial role in plant immune responses and its endogenous concentration strongly affects plant transcriptome. In this study we were focused on the effect of the PI4Kβ1/PI4Kβ2 and SA on the abundance of membrane proteins. For this purpose, we performed proteomic analysis on isolated microsomal fractions from leaves of four Arabidopsis thaliana genotypes: wild type ecotype Columbia-0; double mutant impaired in function of PI4Kβ1/PI4Kβ2 (pi4kβ1/pi4kβ2) exhibiting high SA level; sid2 mutant with impaired SA biosynthesis depending on the isochorismate synthase 1 and triple mutant sid2/pi4kβ1/pi4kβ2. In total, we identified 4534 proteins from which 1696 proteins differed in abundance between the mutants and WT. We showed that SA has a big impact on membrane proteome, because among hundreds of the identified affected proteins typical proteins associated with SA triggered pathway occurred. Our data thus point out new connections between SA pathway and clathrin independent endocytosis (flotillins) and exocytosis/protein secretion (syntaxins, tertraspanin) to be investigated in future. In contrast to SA, presence/absence of PI4Kβ1/PI4Kβ2 itself affected only 27 proteins. Nevertheless, among them we identified CERK1, plasma membrane receptor for chitin. Although PI4Kβ1/PI4Kβ2 itself did not have strong impact on A. thaliana microsomal proteome, our data clearly shows that PI4Kβ1/PI4Kβ2 enhance the proteome changes when SA pathway is modulated in parallel
Project description:In this study we show the comparative transcriptome of constitutive subtilisin3 (csb3) plants, an Arabidopsis mutant showing strikingly enhanced resistance to biotrophic pathogens. CSB3 encodes a 1-hydroxy-2-methyl-2-butenyl 4-diphosphate synthase, the enzyme controlling the penultimate step of the biosynthesis of isopentenyl diphosphate via the 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway in the chloroplast. It has been proposed that CSB3 represents a point of metabolic convergence modulating the magnitude of SA-mediated disease resistance to biotrophic pathogens. We show that csb3 have increased expression of a set of genes encoding defense-related proteins and enzymes, which includes two subtilisins. In essence our results substantiates an important role of these two subtilases in the activation of defense-related signaling pathways against biotrophic pathogens.