The Pti4, Pti5, and Pti6 proteins from tomato were identified based on their interaction with the product of the Pto disease resistance gene, a Ser-Thr protein kinase. They belong to the ethylene-response factor (ERF) family of plantunique transcription factors and bind specifically to the GCC-box cis element present in the promoters of many pathogenesis-related ( PR ) genes. Here, we show that these tomato ERFs are localized to the nucleus and function in vivo as transcription activators that regulate the expression of GCC box-containing PR genes. Expression of Pti4 , Pti5 , or Pti 6 in Arabidopsis activated the expression of the salicylic acid-regulated genes PR1 and PR2 . Expression of jasmonic acid-and ethylene-regulated genes, such as PR3 , PR4 , PDF1.2 , and Thi2.1 , was affected differently by each of the three tomato ERFs, with Arabidopsis -Pti4 plants having very high levels of PDF1.2 transcripts. Exogenous application of salicylic acid to Arabidopsis-Pti4 plants suppressed the increased expression of PDF1.2 but further stimulated PR1 expression. Arabidopsis plants expressing Pti4 displayed increased resistance to the fungal pathogen Erysiphe orontii and increased tolerance to the bacterial pathogen Pseudomonas syringae pv tomato . These results indicate that Pti4, Pti5, and Pti6 activate the expression of a wide array of PR genes and play important and distinct roles in plant defense. INTRODUCTIONPlants respond to pathogen attack by activating multiple defense mechanisms to protect themselves from infection. These rapid cellular responses often are triggered by the recognition of specific pathogens and the activation of highly regulated signal transduction pathways. A major target of these pathways is the cell nucleus, where signals lead to the transcriptional activation of a large array of defense genes (Maleck et al., 2000;Schenk et al., 2000). The products of these genes include pathogenesis-related (PR) proteins as well as enzymes involved in the biosynthesis of protective secondary metabolites. Although the functions of many PR proteins remain unknown, some PR proteins, such as ␤ -1,3-glucanase (PR2) and chitinase (PR3), are hydrolytic enzymes that have been shown to degrade fungal cell walls and to inhibit fungal growth both in vivo and in vitro (Broglie et al., 1991;Sela-Buurlage et al., 1993; Zhu et al., 1994). It was shown recently that osmotin (PR5) induces apoptosis in yeast, and it may act similarly toward plant fungal pathogens (Narasimhan et al., 2001).Several signaling molecules, such as salicylic acid (SA), ethylene (ET), and jasmonic acid (JA), have been shown to be important components of defense response pathways (Dong, 1998;Reymond and Farmer, 1998; Dempsey et al., 1999;Pieterse and van Loon, 1999). Infection by microbial pathogens results in an increase in the levels of these molecules in plants, and many PR genes that are induced upon pathogen infection also are upregulated by one or more of these signaling molecules (Malamy et al., 1990; Dempsey et al., 1999). The SA-dependent...

Castor (Ricinus communis L.) is one of the oldest cultivated crops, but currently it represents only 0.15% of the vegetable oil produced in the world. Castor oil is of continuing importance to the global specialty chemical industry because it is the only commercial source of a hydroxylated fatty acid. Castor also has tremendous future potential as an industrial oilseed crop because of its high seed oil content (more than 480 g kg−1), unique fatty acid composition (900 g kg−1 of ricinoleic acid), potentially high oil yields (1250–2500 L ha−1), and ability to be grown under drought and saline conditions. The scientific literature on castor has been generated by a relatively small global community of researchers over the past century. Much of this work was published in dozens of languages in journals that are not easily accessible to the scientific community. This review was conducted to provide a compilation of the most relevant historic research information and define the tremendous future potential of castor. The article was prepared by a group of 22 scientists from 16 institutions and eight countries. Topics discussed in this review include: (i) germplasm, genetics, breeding, biotic stresses, genome sequencing, and biotechnology; (ii) agronomic production practices, diseases, and abiotic stresses; (iii) management and reduction of toxins for the use of castor meal as both an animal feed and an organic fertilizer; (iv) future industrial uses of castor including renewable fuels; (v) world production, consumption, and prices; and (vi) potential and challenges for increased castor production.

Outer membrane vesicles (OMVs) are important tools in bacterial virulence but their role in the pathogenesis of infections caused by enterohemorrhagic Escherichia coli (EHEC) O157, the leading cause of life-threatening hemolytic uremic syndrome, is poorly understood. Using proteomics, electron and confocal laser scanning microscopy, immunoblotting, and bioassays, we investigated OMVs secreted by EHEC O157 clinical isolates for virulence factors cargoes, interactions with pathogenetically relevant human cells, and mechanisms of cell injury. We demonstrate that O157 OMVs carry a cocktail of key virulence factors of EHEC O157 including Shiga toxin 2a (Stx2a), cytolethal distending toxin V (CdtV), EHEC hemolysin, and flagellin. The toxins are internalized by cells via dynamin-dependent endocytosis of OMVs and differentially separate from vesicles during intracellular trafficking. Stx2a and CdtV-B, the DNase-like CdtV subunit, separate from OMVs in early endosomes. Stx2a is trafficked, in association with its receptor globotriaosylceramide within detergent-resistant membranes, to the Golgi complex and the endoplasmic reticulum from where the catalytic Stx2a A1 fragment is translocated to the cytosol. CdtV-B is, after its retrograde transport to the endoplasmic reticulum, translocated to the nucleus to reach DNA. CdtV-A and CdtV-C subunits remain OMV-associated and are sorted with OMVs to lysosomes. EHEC hemolysin separates from OMVs in lysosomes and targets mitochondria. The OMV-delivered CdtV-B causes cellular DNA damage, which activates DNA damage responses leading to G2 cell cycle arrest. The arrested cells ultimately die of apoptosis induced by Stx2a and CdtV via caspase-9 activation. By demonstrating that naturally secreted EHEC O157 OMVs carry and deliver into cells a cocktail of biologically active virulence factors, thereby causing cell death, and by performing first comprehensive analysis of intracellular trafficking of OMVs and OMV-delivered virulence factors, we provide new insights into the pathogenesis of EHEC O157 infections. Our data have implications for considering O157 OMVs as vaccine candidates.