Attenuated innate immune responses to the intestinal microbiota have been linked to the pathogenesis of Crohn’s disease (CD). Recent genetic studies have revealed that hypofunctional mutations of NLRP3, a member of the NOD-like receptor (NLR) superfamily, are associated with an increased risk of developing CD. NLRP3 is a key component of the inflammasome, an intracellular danger sensor of the innate immune system. When activated, the inflammasome triggers caspase-1-dependent processing of inflammatory mediators, such as IL-1β and IL-18. In the current study we sought to assess the role of the NLRP3 inflammasome in the maintenance of intestinal homeostasis through its regulation of innate protective processes. To investigate this role, Nlrp3−/− and wild-type (WT) mice were assessed in the DSS- and TNBS-models of experimental colitis. Nlrp3−/− mice were found to be more susceptible to experimental colitis, an observation that was associated with reduced IL-1β reduced anti-inflammatory cytokine IL-10, and reduced protective growth factor TGF-β. Macrophages isolated from Nlrp3−/− mice failed to respond to bacterial muramyl dipeptide. Furthermore, Nlrp3-deficient neutrophils exhibited reduced chemotaxis and enhanced spontaneous apoptosis, but no change in oxidative burst. Lastly, Nlrp3−/− mice displayed altered colonic β-defensin expression, reduced colonic antimicrobial secretions and a unique intestinal microbiota. Our data confirm an essential role for the NLRP3 inflammasome in the regulation of intestinal homeostasis and provide biological insight into disease mechanisms associated with increased risk of CD in individuals with NLRP3 mutations.

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Seed development ends with a maturation phase that imparts desiccation tolerance, nutrient reserves, and dormancy degree. Here, we report the functional analysis of an Arabidopsis thaliana C2H2 zinc finger protein INDETERMINATE DOMAIN1 (IDD1)/ENHYDROUS (ENY). Ectopic expression of IDD1/ENY (2x35S:ENY) disrupted seed development, delaying endosperm depletion and testa senescence, resulting in an abbreviated maturation program. Consequently, mature 2x35S: ENY seeds had increased endosperm-specific fatty acids, starch retention, and defective mucilage extrusion. Using RAB18 promoter ENY lines (RAB18:ENY) to confine expression to maturation, when native ENY expression increased and peaked, resulted in mature seed with lower abscisic acid (ABA) content and decreased germination sensitivity to applied ABA. Furthermore, results of far-red and red light treatments of 2x35S:ENY and RAB18:ENY germinating seeds, and of artificial microRNA knockdown lines, suggest that ENY acts to promote germination. After using RAB18:ENY seedlings to induce ENY during ABA application, key genes in gibberellin (GA) metabolism and signaling were differentially regulated in a manner suggesting negative feedback regulation. Furthermore, GA treatment resulted in a skotomorphogenic-like phenotype in light-grown 2x35S:ENY and RAB18:ENY seedlings. The physical interaction of ENY with DELLAs and an ENYtriggered accumulation of DELLA transcripts during maturation support the conclusion that ENY mediates GA effects to balance ABA-promoted maturation during late seed development.

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