The transcription factor Stat3 is required for proliferation and pluripotency of embryonic stem cells; we have prepared and characterized fluorescent Stat3-reporter zebrafish based on repeats of minimal responsive elements. These transgenic lines mimic in vivo Stat3 expression patterns and are responsive to exogenous Stat3; notably, fluorescence is inhibited by both stat3 knockout and IL6/Jak/ STAT inhibitors. At larval stages, Stat3 reporter activity correlates with proliferating regions of the brain, haematopoietic tissue and intestine. In the adult gut, the reporter is active in sparse proliferating cells, located at the base of intestinal folds, expressing the stemness marker sox9b and having the morphology of mammalian crypt base columnar cells; noteworthy, zebrafish stat3 mutants show defects in intestinal folding. Stat3 reporter activity in the gut is abolished with mutation of T cell factor 4 (Tcf7l2), the intestinal mediator of Wnt/βcatenin-dependent transcription. The Wnt/β-catenin dependence of Stat3 activity in the gut is confirmed by abrupt expansion of Stat3positive cells in intestinal adenomas of apc heterozygotes. Our findings indicate that Jak/Stat3 signalling is needed for intestinal stem cell maintenance and possibly crucial in controlling Wnt/β-catenindependent colorectal cancer cell proliferation.
Glucocorticoids (GCs) are steroid hormones that contribute to the regulation of many physiological processes, such as inflammation, metabolism and stress response, mainly through binding to their cognate receptor, GR, which works as a ligand-activated transcription factor. Due to their pleiotropy and the common medical use of these steroids to treat patients affected by different pathologies, the investigation of their mechanisms of action is extremely important in biology and clinical research. The evolutionary conservation of GCs’ physiological functions, biosynthesis pathways as well as sequence and structure of their nuclear receptor, in the last 20 years has stimulated the use of zebrafish (a teleost of Ciprinidae family) as a reliable model organism to investigate the topic. In this review, we wanted to collect many of the most important discoveries that the scientific community has obtained using zebrafish to study GCs and their receptors. The paper begins by describing the experiments with transient knockdown of zebrafish gr to gain information mainly during development and continues with the discoveries provided by the generation of transgenic reporter lines. Finally, we discuss how the generation of mutant lines for either gr or the enzymes involved in GCs’ synthesis has significantly advanced our knowledge on GCs’ biology.
Complex microbial communities are associated with plants and can improve their resilience under harsh environmental conditions. In particular, plants and their associated communities have developed complex adaptation strategies against cold stress. Although changes in plant-associated microbial community structure have been analyzed in different cold regions, scarce information is available on possible common taxonomic and functional features of microbial communities across cold environments. In this review, we discuss recent advances in taxonomic and functional characterization of plant-associated microbial communities in three main cold regions, such as alpine, Arctic, and Antarctica environments. Culture-independent and culture-dependent approaches are analyzed, in order to highlight main factors affecting the taxonomic structure of plant-associated communities in cold environments. Moreover, biotechnological applications of plant-associated microorganisms from cold environments are proposed for agriculture, industry, and medicine, according to biological functions and cold adaptation strategies of bacteria and fungi. Although further functional studies may improve our knowledge, the existing literature suggest that plants growing in cold environments harbor complex, host specific, and cold adapted microbial communities, which may play key functional roles in plant growth and survival under cold conditions.
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