SummaryCoronatine (COR) is a phytotoxin produced by several pathovars of Pseudomonas syringae and consists of coronafacic acid (CFA), an analog of methyl jasmonic acid (MeJA), and coronamic acid (CMA), which resembles 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor to ethylene. An understanding of how COR functions, is perceived by different plant tissues, and the extent to which it mimics MeJA remain unclear. In this study, COR and related compounds were examined with respect to structure and function. The results indicate that conjugation of CFA to an amino acid is required for optimal activity in tomato, including chlorosis, changes in chloroplast structure, cell wall thickening, accumulation of proteinase inhibitors, induction of anthocyanins, and root growth inhibition. cDNA microarrays were utilized to understand the molecular processes that are regulated by MeJA, COR, CFA and CMA in tomato leaves. A comparison of COR-and MeJAregulated transcriptomes revealed that COR regulated 35% of the MeJA-induced genes. There was significant overlap in the number of COR and CFA-regulated genes with CFA impacting the expression of 39.4% of the COR-regulated genes. Taken together, the results of biological assays, ultrastructural studies, and gene expression profiling demonstrate that: (1) the intact COR molecule impacts signaling in tomato via the jasmonic acid, ethylene, and auxin pathways; (2) CMA does not function as a structural analog of ACC; (3) COR has a broader range of functions than either CFA or CMA; and (4) COR and MeJA share similar, but not identical activities and impact multiple phytohormone pathways in tomato.

The phloem-feeding by greenbug (Schizaphis graminum) elicits unique interactions with their host plants. To investigate the expression profiles of sorghum genes responsive to greenbug feeding, two subtractive cDNA libraries were constructed through different combinatorial subtractions in a strong greenbug resistance sorghum M627 line and a susceptible Tx7000 line with or without greenbug infestation. A total of 3,508 cDNAs were selected from the two cDNA libraries, and subsequent cDNA microarray and northern blot analyses were performed for identification of sorghum genes responsive to greenbugs. In total, 157 sorghum transcripts were identified to be differentially expressed by greenbug feeding. The greenbug responsive genes were isolated and classified into nine categories according to the functional roles in plant metabolic pathways, such as defense, signal transduction, cell wall fortification, oxidative burst/stress, photosynthesis, development, cell maintenance, abiotic stress, and unknown function. Overall, the profiles of sorghum genes, responsive to greenbug phloem-feeding shared common identities with other expression profiles known to be elicited by diverse stresses, including pathogenesis, abiotic stress, and wounding. In addition to well-known defense related regulators such as salicylic acid, jasmonic acid, and abscisic acid, auxin and gibberellic acid were also involved in mediation of the defense responses against greenbug phloem-feeding in sorghum.

that the conjugative transfer of all these elements shares a common mechanism, as the elements are derived from an ancestral element with transfer properties.Tn5253, formerly called the fl(cat tet) element (36), was originally detected as a heterologous insertion in the chromosome of the plasmid-free clinical isolate S. pneumoniae BM6001 (3, 9). By inserting the Escherichia coli vector plasmid pVA891 (22) (which is incapable of autonomous replication in streptococci) at many sites specifically within Tn5253, we were able to clone and recover parts of the element in E. coli (37). Physical analysis of the passenger DNAs from these plasmids made it possible to construct a detailed restriction map of this 65.5-kb element, to localize the drug resistance determinants, and to identify its junction and target regions in the pneumococcal chromosome (36), (Fig. 1)

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SummaryAnaplasma phagocytophilum (Rickettsiales: Anaplasmataceae) causes human, equine and canine granulocytic anaplasmosis and tick-borne fever of ruminants. The rickettsia parasitizes granulocytes and bone marrow progenitor cells, and can be propagated in human promyelocytic and tick cell lines. In this study, microarrays of synthetic polynucleotides of 21 329 human genes were used to identify genes that are differentially expressed in HL-60 human promyelocytic cells in response to infection with A. phagocytophilum . Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) of selected genes confirmed the results of the microarray analysis. Six genes in the A. phagocytophiluminfected cells were found to be upregulated greater than 30-fold, while expression of downregulated genes most often did not change more than sixfold. Genes that were found to be differentially regulated in infected cells were those essential for cellular mechanisms including growth and differentiation, cell transport, signalling and communication and protective response against infection, some of which are most likely necessary for infection and multiplication of A. phagocytophilum in host cells. The differentially regulated genes described herein provide new information on the gene expression profiles in A. phagocytophilum -infected HL-60 cells, thus expanding in a global manner the existing information on the response of mammalian cells to A. phagocytophilum infection.

We are using acute ozone as an elicitor of endogenous reactive oxygen species (ROS) to understand oxidative signalling in Arabidopsis . Temporal patterns of ROS following a 6 h exposure to 300 nL L -1 of ozone in ozone-sensitive Wassilewskija (Ws-0) ecotype showed a biphasic ROS burst with a smaller peak at 4 h and a larger peak at 16 h. This was accompanied by a nitric oxide (NO) burst that peaked at 9 h. An analysis of antioxidant levels showed that both ascorbate (AsA) and glutathione (GSH) were at their lowest levels, when ROS levels were high in ozone-stressed plants. Whole genome expression profiling analysis at 1, 4, 8, 12 and 24 h after initiation of ozone treatment identified 371 differentially expressed genes. Early induction of proteolysis and hormone-responsive genes indicated that an oxidative cell death pathway was triggered rapidly. Downregulation of genes involved in carbon utilization, energy pathways and signalling suggested an inefficient defense response. Comparisons with other large-scale expression profiling studies indicated some overlap between genes induced by ethylene and ozone, and a significant overlap between genes repressed by ozone and methyl jasmonate treatment. Further, analysis of cis elements in the promoters of ozone-responsive genes also supports the view that phytohormones play a significant role in ozone-induced cell death.

Fusarium head blight (FHB), primarily caused by Fusarium graminearum Schw., is a destructive disease of wheat (Triticum aestivum L.). Although several genes related to FHB resistance have been reported, global analysis of gene expression in response to FHB infection remains to be explored. The expression patterns of transcriptomes from wheat spikes of FHB-resistant cultivar Ning 7840 and susceptible cultivar Clark were monitored during a period of 72 h after inoculation (hai) with F. graminearum. Microarray analysis, coupled with suppression subtractive hybridization technique, identified 44 significantly differentially expressed genes between cv. Ning 7840 and cv. Clark. More differentially expressed genes were identified from susceptible libraries than from resistance libraries. The up-regulation of defense-related genes in Ning 7840 relative to cultivar Clark occurred during early fungal stress (3-12 hai). Three genes, with unknown function that were up-regulated in cv. Ning 7840 at most time points investigated, might play an important role in enhancing FHB resistance.

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