The calcium-dependent protein kinase CPK28 negatively regulates the BIK1-mediated PAMP-induced calcium burst

Plants are protected from microbial infection by a robust immune system. Two of the earliest responses mediated by surface-localized immune receptors include an increase in cytosolic calcium (Ca(2+)) and a burst of apoplastic reactive oxygen species (ROS). The Arabidopsis plasma membrane-associated cytoplasmic kinase BIK1 is an immediate convergent substrate of multiple surface-localized immune receptors that is genetically required for the PAMP-induced Ca(2+) burst and directly regulates ROS production catalyzed by the NADPH oxidase RBOHD. We recently demonstrated that Arabidopsis plants maintain an optimal level of BIK1 through a process of continuous degradation regulated by the Ca(2+)-dependent protein kinase CPK28. cpk28 mutants accumulate more BIK1 protein and display enhanced immune signaling, while plants over-expressing CPK28 accumulate less BIK1 protein and display impaired immune signaling. Here, we show that CPK28 additionally contributes to the PAMP-induced Ca(2+) burst, supporting its role as a negative regulator of BIK1

Modeling Longitudinal Oscillations of Bunched Beams in Synchrotrons

Longitudinal oscillations of bunched beams in synchrotrons have been analyzed by accelerator physicists for decades, and a closed theory is well-known [1]. The first modes of oscillation are the coherent dipole mode, quadrupole mode, and sextupole mode. Of course, these modes of oscillation are included in the general theory, but for developing RF control systems, it is useful to work with simplified models. Therefore, several specific models are analyzed in the paper at hand. They are useful for the design of closed-loop control systems in order to reach an optimum performance with respect to damping the different modes of oscillation. This is shown by the comparison of measurement and simulation results for a specific closed-loop control system.Comment: 14 pages, 14 figure

Receptor-like kinases and pathogen-associated molecular patterns perception in Arabidopsis

Comparable to the innate immune response in mammals and insects, plants possess highly specific and sensitive recognition systems for pathogen-associated molecular patterns (PAMPs), such as bacterial flagellin. In Arabidopsis, perception of flagellin occurs via recognition of the most conserved domain in its N-terminus, represented by the peptide flg22. Perception of this elicitor-active domain depends on the LRR receptor kinase FLS2. Here, using transcriptome analysis in Arabidopsis, we first present evidences that treatment with flg22, bacteria or avirulence proteins are similar, and that virulent bacteria are likely to suppress flg22-induced responses (Chapter 1). Second, we demonstrated that flagellin perception contributes to the basal resistance against bacteria, as fls2 mutants are more susceptible to bacterial infection, proving for the first time that perception of a single PAMP is sufficient to restrict bacterial growth (Chapter 2). This study also showed that PAMPs other than flagellin trigger resistance against virulent bacteria. Wild-type and fls2 mutants both display enhanced resistance when treated with crude bacterial extracts, even devoid of elicitor-active flagellin, indicating the existence of functional perception systems for PAMPs other than flagellin. One of these novel PAMPs was just identified as the elongation factor EF-Tu, and the corresponding active peptidic epitope identified (Appendix 1). FLS2 constituted so far the only PAMP receptor identified in Arabidopsis. Using ATH1 Affymetrix arrays, we identified about 1000 genes whose expression was induced 30 minutes after flg22 treatment (Chapter 2). Strikingly, among these induced genes there were 106 RLK out of the 610 RLK genes present in Arabidopsis. We hypothesize that the perception of a single PAMP (e.g. flg22) could enhance the sensitivity of the plant to microbial stimuli sensing the presence of invading microorganisms. In particular, some of the induced RLKs might be involved in the recognition of other PAMPs. We generated a collection of mutants for the induced LRR-RLKs to test the implication of the corresponding proteins in innate immune responses (Chapter 3.1). This approach led to the discovery of the EF-Tu receptor (Chapter 3.2) and suggested a new role for the previously described BAK1 gene in flg22- and probably elf18-signaling (Chapter 3.3)