Project description:Auxin and cytokinin can regulate callus formation from developed plant organs and shoot regeneration from callus. The regulation of dedifferentiation and regeneration of plant cells by auxin and cytokinin stimulation was considered to be caused by the regulation of reprograming of callus cells, but the hypothesis had been argued still in now. Although elucidation of the regulatory mechanisms of callus formation and shoot regeneration has helped advance plant biotechnology research, many plant species are intractable to transformation because of difficulties with callus regulation. In this study, we identified the compound Fipexide (FPX) as a useful regulatory compound through chemical biology-based screening. Compared with the activity of auxin and cytokinin, FPX showed higher efficiency as a chemical inducer in callus formation, shoot regeneration, and Agrobacterium infection. In regards to morphology, the cellular organization of FPX-induced callus differed from that produced under auxin/cytokinin conditions. According to a microarray analysis, the expressions of approximately 971 genes were two-fold up-regulated by FPX treatment for 2 days. Among these genes, 598 genes were also induced by auxin/cytokinin, while 373 genes, including metabolic regulation-related genes, were specifically expressed only under FPX treatment. FPX can promote callus formations in rice, poplar, and several vegetables. FPX should be a useful tool to reveal unknown mechanisms of plant development and to increase the number of transgenic plant species.
Project description:Auxin and cytokinin can regulate callus formation from developed plant organs and shoot regeneration from callus. The regulation of dedifferentiation and regeneration of plant cells by auxin and cytokinin stimulation was considered to be caused by the regulation of reprograming of callus cells, but the hypothesis had been argued still in now. Although elucidation of the regulatory mechanisms of callus formation and shoot regeneration has helped advance plant biotechnology research, many plant species are intractable to transformation because of difficulties with callus regulation. In this study, we identified the compound Fipexide (FPX) as a useful regulatory compound through chemical biology-based screening. Compared with the activity of auxin and cytokinin, FPX showed higher efficiency as a chemical inducer in callus formation, shoot regeneration, and Agrobacterium infection. In regards to morphology, the cellular organization of FPX-induced callus differed from that produced under auxin/cytokinin conditions. According to a microarray analysis, the expressions of approximately 971 genes were two-fold up-regulated by FPX treatment for 2 days. Among these genes, 598 genes were also induced by auxin/cytokinin, while 373 genes, including metabolic regulation-related genes, were specifically expressed only under FPX treatment. FPX can promote callus formations in rice, poplar, and several vegetables. FPX should be a useful tool to reveal unknown mechanisms of plant development and to increase the number of transgenic plant species.
Project description:Unlike most animal cells, plant cells can easily regenerate new tissues from a wide variety of organs when properly cultured. The common elements that provide varied plant cells with their remarkable regeneration ability are still largely unknown. Here we describe the initial process of Arabidopsis in vitro regeneration, where a pluripotent cell mass termed callus is induced. We demonstrate that callus resembles the tip of a root meristem, even if it is derived from aerial organs such as petals, which clearly shows that callus formation is not a simple reprogramming process backwards to an undifferentiated state as widely believed. Furthermore, callus formation in roots, cotyledons and petals is blocked in mutant plants incapable of lateral root initiation. It thus appears that the ectopic activation of a lateral root development program is a common mechanism in callus formation from multiple organs.
Project description:In plants, multiple detached tissues are capable of forming a pluripotent cell mass, termed callus, when cultured with appropriate plant hormones. Recent studies demonstrated that callus resembles the tip of a root meristem, even if it is derived from aerial organs. However, the underlying mechanism that guides differentiated organs to form callus is unknown. Here we show that genome-wide reprogramming of histone H3 lysine 27 trimethylation (H3K27me3) is critical in callus formation. During culture of leaf explants, the H3K27me3 level was decreased first at certain auxin-pathway genes, and then increased at the leaf- but decreased at the root-preferentially expressed genes. In addition, only the root but not the leaf explants of the Polycomb group (PcG) mutants can normally form callus. Our data indicate that PcG and H3K27me3 demethylation pathways act separately in reprogramming of H2K27me3 distributions, and also suggest that this is a general mechanism leading to cell fate transition.
Project description:In dense stands,the earliest neighbor response is induced by touching,leading to shade avoidance. During light competion the R:FR distribution is not homogenous, leading to local differences in light quality (R:FR) within the same leaf. Hyponasty is induced by FR-signaling in the lamina tip, which then induces local cell growth in the petiole base. Likewise, local touching of the leaf tip induces a similar phenoype. We studied gene expression in Arabidopsis, exposed to supplemental-FR in the lamina tip and in whole rosette plant. We harvested the lamina tip and the petiole base after 5h of the treatments (white-light, supplemeted-FR in the lamina tip (local FR) and rossete plants exposed to low R:FR (whole plant FR))
Project description:Plants can regenerate from a variety of tissues on culturing in appropriate media. However, the metabolic shifts involved in callus formation and shoot regeneration are largely unknown. The metabolic profiles of callus generated from tomato (Solanum lycopersicum) cotyledons and that of shoot regenerated from callus were compared with the pct1-2 mutant that exhibits enhanced polar auxin transport and the shr mutant that exhibits elevated nitric oxide levels. The transformation from cotyledon to callus involved a major shift in metabolite profiles with denser metabolic networks in the callus. In contrast, the transformation from callus to shoot involved minor changes in the networks. The metabolic networks in pct1-2 and shr mutants were distinct from wild type and were rewired with shifts in endogenous hormones and metabolite interactions. The callus formation was accompanied by a reduction in the levels of metabolites involved in cell wall lignification and cellular immunity. On the contrary, the levels of monoamines were upregulated in the callus and regenerated shoot. The callus formation and shoot regeneration were accompanied by an increase in salicylic acid in wild type and mutants. The transformation to the callus and also to the shoot downregulated LST8 and upregulated TOR transcript levels indicating a putative linkage between metabolic shift and TOR signalling pathway. The network analysis indicates that shift in metabolite profiles during callus formation and shoot regeneration is governed by a complex interaction between metabolites and endogenous hormones.