The signals that control the developmental switch from primary to secondary wall synthesis in higher plants are not known. This transition is characterized by a cessation of synthesis of polymers unique to the primary cell wall accompanied by enhanced rates of cellulose deposition and induction of synthesis of specific secondary wall matrix polysaccharides and lignin. The developing fibers of cotton (Gossypium hirsutum) and tracheary elements differentiated from isolated mesophyll cells of zinnia have emerged as two good model systems for studying this transition. In the zinnia system the mesophyll cells are cultured in noninductive medium and differentiation is induced by changes in hormonal balance. Specialized, localized regions of secondary wall formation unique to these tracheary elements have been shown to contain large amounts of cellulose, xylan, and lignin (for reviews, see Fukuda, 1991Fukuda, , 1996. The developing cotton fiber is unique in that the secondary wall consists of nearly pure cellulose and is devoid of hemicellulose and lignin (for reviews of cotton fiber development, see Basra and Malik, 1984;Ryser, 1985). Furthermore, development occurs synchronously for nearly all fibers within a boll, with the transition to secondary wall formation beginning abruptly in varieties of cotton at about 14 to 16 DPA, which is a few days prior to the cessation of fiber elongation (Meinert and Delmer, 1977).Rates of secondary wall cellulose synthesis peak at about 24 DPA; the fibers mature and die sometime after 40 DPA, presumably by a process of programmed cell death. During the transition the rate of cellulose synthesis increases abruptly to about 100-fold (Meinert and Delmer, 1977), and recent evidence indicates that genes that most likely encode the catalytic subunit of cellulose synthase are also strongly induced at this time (Pear et al., 1996). During xylogenesis there is also evidence that expression of genes involved in synthesis of hemicellulose (Bolwell and Northcote, 1981) and lignin (Fukuda, 1991) also undergo induction. The transition in both cotton fibers and tracheary elements is also characterized by a reorganization of the cytoskeleton that directs the specific patterns of cellulose deposition (Seagull, 1990; Fukuda, 1991 Fukuda, , 1996.Our interest in the events regulating this transition was stimulated by our recent characterization of genes that encode two small GTPases of the Rho subfamily in cotton, named Rac13 and Rac9. Rac13 in particular shows highly induced expression at the transition from primary to secondary wall synthesis (Delmer et al., 1995). In animals Rac proteins function in several possibly related signal transduction pathways. Rac has been shown to be involved in regulation of reorganization of the actin cytoskeleton (Symons, 1996) and it plays another role in leukocytes as a specific activator of the plasma membrane NADPH oxidase (Freeman et al., 1996). Activation of the NADPH oxidase leads to generation of the oxidative burst, which serves as a defense against pathoge...

Background Fecal microbiota transplantation (FMT) is a promising new strategy in the treatment of Inflammatory Bowel Disease, but long-term delivery systems are lacking. This randomized study was designed as a safety and feasibility study of long-term FMT in subjects with mild to moderate UC using frozen, encapsulated oral FMT (cFMT). Methods Subjects were randomized 1:1 to receive FMT induction by colonoscopy, followed by 12 weeks of daily oral administration of frozen encapsulated cFMT or sham therpay. Subjects were followed for 36 weeks and longitudenal clinical assessments included multiple subjective and objective markers of disease severity. Ribosomal 16S bacterial sequencing was used to assess donor-induced changes in the gut microbiota. Changes in T regulatory (Treg) and mucosal associated invariant T (MAIT) cell populations were evaluated by flow cytometry as an exploratory endpoint. Results Twelve subjects with active UC were randomized: 6 subjects completed the full 12-week course of FMT plus cFMT, and 6 subjects received sham treatment by colonic installation and longitudinal oral placebo capules. Chronic administration of cFMT was found to be safe and well-tolerated but home storage concerns exist. Protocol adherence was high, and none of the study subjects experienced FMT-associated treatment emergent adverse events. Two subjects that received cFMT achieved clinical remission versus none in the placebo group (95% CI = 0.38-infinity, p = 0.45). cFMT was associated with sustained donor-induced shifts in fecal microbial composition. Changes in MAIT cell cytokine production were observed in cFMT recipients and correlated with treatment response. Conclusion These pilot data suggest that daily encapsulated cFMT may extend the durability of index FMT-induced changes in gut bacterial community structure and that an association between MAIT cell cytokine production and clinical response to FMT may exist in UC populations. Oral frozen encapsulated cFMT is a promising FMT delivery system and may be preferred for longterm treatment strategies in UC and other chronic diseases but further evaluations will have to address home storage concerns. Larger trials should be done to explore the benefits of cFMT and to determine its long-term impacts on the colonic microbiome. Trial registration: ClinicalTrials.gov (NCT02390726). Registered 17 March 2015, https://clinicaltrials.gov/ct2/show/NCT02390726?term=NCT02390726&draw=2&rank=1.

Signal transduction through the Rho family GTPases requires regulated cycling of the GTPases between the active GTP-bound state and the inactive GDP-bound state. Rho family members containing an arginine residue at position 186 in the C-terminal polybasic region were found to possess a self-stimulatory GTPase-activating protein (GAP) activity through homophilic interaction, resulting in significantly enhanced intrinsic GTPase activities. This arginine residue functions effectively as an "arginine finger" in the GTPase activating reaction to confer the catalytic GAP activity but is not essential for the homophilic binding interactions of Rho family proteins. The arginine 186-mediated negative regulation seems to be absent from Cdc42, a Rho family member important for cell-division cycle regulation, of lower eukaryotes, yet appears to be a part of the turn-off machinery of Cdc42 from higher eukaryotes. Introduction of the arginine 186 mutation into S. cerevisiae CDC42 led to phenotypes consistent with down-regulated CDC42 function. Thus, specific Rho family GTPases may utilize a built-in arginine finger, in addition to RhoGAPs, for negative regulation.

There is considerable clinical interest in the utility of probiotic therapy--the feeding of (live) non-pathogenic bacteria, originally derived from the alimentary tract, for disease treatment or health promotion. The microflora of the gastrointestinal tract is essential for mucosal protection, for immune education and for metabolism of fecal residue. Physiological disturbances of these processes, when they occur, result from: i) alteration of a microbial ecosystem, originally conserved by evolution; ii) reduced consumption of microorganisms; iii) invasion of pathogens; or iv) modern interventions. Recent data support the use of proven probiotic organisms in prevention and treatment of flora-related gastrointestinal disorders including inflammatory bowel disease, infectious and antibiotic related diarrheas, and post-resection disorders including pouchitis. Therapeutic activity of probiotic bacteria can be due to competition with pathogens for nutrients and mucosal adherence, production of antimicrobial substances, and modulation of mucosal immune functions. Although a promising treatment, controlled clinical trials are necessary to validate the benefit of probiotics.

The Saccharomyces cerevisiae Cdc42p GTPase is localized to the plasma membrane and involved in signal transduction mechanisms controlling cell polarity. The mechanisms of action of the dominant negative cdc42 D118A mutant and the lethal, gain of function cdc42 G12V mutant were examined. Cdc42 D118A,C188S p and its guanine-nucleotide exchange factor Cdc24p displayed a temperature-dependent interaction in the twohybrid system, which correlated with the temperature dependence of the cdc42 D118A phenotype and supported a Cdc24p sequestration model for the mechanism of cdc42 D118A action. Five cdc42 mutations were isolated that led to decreased interactions with Cdc24p. The isolation of one mutation (V44A) correlated with the observations that the T35A effector domain mutation could interfere with Cdc42 D118A,C188S p-Cdc24p interactions and could suppress the cdc42 D118A mutation, suggesting that Cdc24p may interact with Cdc42p through its effector domain. The cdc42 G12V mutant phenotypes were suppressed by the intragenic T35A and K183-187Q mutations and in skm1⌬ and cla4⌬ cells but not ste20⌬ cells, suggesting that the mechanism of cdc42 G12V action is through the Skm1p and Cla4p protein kinases at the plasma membrane. Two intragenic suppressors of cdc42 G12V were also identified that displayed a dominant negative phenotype at 16°C, which was not suppressed by overexpression of Cdc24p, suggesting an alternate mechanism of action for these dominant negative mutations.The establishment of cell polarity is crucial for the control of many cellular and developmental processes, such as the generation of cell shape, the intracellular movement of organelles, and the secretion and deposition of new cell surface constituents (1). Polarized growth in the yeast Saccharomyces cerevisiae occurs in response to both internal and external signals, resulting in different morphological structures (2-5). The mechanics of cell polarity initiation during the mitotic cell cycle can be divided into three sequential phases: (i) nonrandom bud site selection; (ii) organization of proteins at the bud site; and (iii) bud emergence and polarized growth. Genetic and biochemical studies have identified over 25 proteins, including several GTPases and components of the actin cytoskeleton, that are involved in the regulation of the cell polarity pathway in S. cerevisiae (1, 6, 7).At least six members of the Ras superfamily of GTPases (Rsr1p/Bud1p, Cdc42p, Rho1p, Rho2p, Rho3p, and Rho4p) are involved in controlling cell polarity in S. cerevisiae. These proteins are active when in the GTP-bound state and inactive in the GDP-bound state (8, 9). The activity of these GTPases is controlled by regulatory proteins, such as guanine-nucleotide exchange factors, GTPase-activating proteins, and guanine-nucleotide dissociation inhibitors, as well as by the intracellular localization of the GTPase. Rsr1p/Bud1p is a member of the Ras subfamily and is responsible for bud site selection at one of the two cell poles, but it is not required for bud emergence or polari...

γδ T cells participate in the innate immune response to a variety of infectious microorganisms. They also link to the adaptive immune response through their induction of maturation of dendritic cells (DC) during the early phase of an immune response when the frequency of Ag-specific T cells is very low. We observe that in the presence of Borrelia burgdorferi, synovial Vδ1 T cells from Lyme arthritis synovial fluid potently induce maturation of DC, including production of IL-12, and increased surface expression of CD40 and CD86. The activated DC are then able to stimulate the Vδ1 T cells to up-regulate CD25. Both of these processes are initiated primarily by Fas stimulation rather than CD40 activation of DC via high expression of Fas ligand by the Vδ1 T cells. DC are resistant to Fas-induced death due to expression of high levels of the Fas inhibitor c-FLIP. This effect serves to divert Fas-mediated signals from the caspase cascade to the ERK MAPK and NF-κB pathways. The findings affirm the importance of the interaction of certain T cell populations with DC during the early phases of the innate immune response. They also underscore the view that as levels of c-FLIP increase, Fas signaling can be diverted from induction of apoptosis to pathways leading to cell effector function.

Activation of the innate immune system typically precedes engagement of adaptive immunity. Cells at the interface between these two arms of the immune response are thus critical to provide full engagement of host defense. Among the innate T cells at this interface are γδ T cells. γδ T cells contribute to the defense from a variety of infectious organisms, yet little is understood regarding how they are activated. We have previously observed that human γδ T cells of the Vδ1 subset accumulate in inflamed joints in Lyme arthritis and proliferate in response to stimulation with the causative spirochete, Borrelia burgdorferi. We now observe that murine γδ T cells are also activated by B. burgdorferi and that in both cases the activation is indirect via TLR stimulation on dendritic cells or monocytes. Furthermore, B. burgdorferi stimulation of monocytes via TLR, and secondary activation of γδ T cells, are both caspase-dependent.

Fecal microbiota transplantation (FMT)—transferring fecal microbes from a healthy donor to a sick patient—has shown promise for gut diseases such as inflammatory bowel disease. However, unlike pharmaceuticals, fecal transplants are complex mixtures of living organisms, which must then interact with the microbes and immune system of the recipient.