Plants generally possess a strong ability to regenerate organs; for example, in tissue culture, shoots can regenerate from callus, a clump of actively proliferating, undifferentiated cells. Processing of pre-mRNA and ribosomal RNAs is important for callus formation and shoot regeneration. However, our knowledge of the roles of RNA quality control via the nonsense-mediated mRNA decay (NMD) pathway in shoot regeneration is limited. Here, we examined the shoot regeneration phenotypes of the low-beta-amylase1 (lba1)/upstream frame shift1-1 (upf1-1) and upf3-1 mutants, in which the core NMD components UPF1 and UPF3 are defective. These mutants formed callus from hypocotyl explants normally, but this callus behaved abnormally during shoot regeneration: the mutant callus generated numerous adventitious root structures instead of adventitious shoots in an auxin-dependent manner. Quantitative RT-PCR and microarray analyses showed that the upf mutations had widespread effects during culture on shoot-induction medium. In particular, the expression patterns of early auxin response genes, including those encoding AUXIN/INDOLE ACETIC ACID (AUX/IAA) family members, were significantly affected in the upf mutants. Also, the upregulation of shoot apical meristem-related transcription factor genes, such as CUP-SHAPED COTYLEDON1 (CUC1) and CUC2, was inhibited in the mutants. Taken together, these results indicate that NMD-mediated transcriptomic regulation modulates the auxin response in plants and thus plays crucial roles in the early stages of shoot regeneration.
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Specimen part
View SamplesTemporal and spatial regulation of cell division is central for generating multicellular organs with predictable sizes and shapes. However, it remains largely unclear how genes with mitotic functions are transcriptionally regulated during organogenesis in plants. Here, we showed that a group of R1R2R3-Myb transcription factors are responsible for developmentally controlled downregulation of variety of mitotic genes in Arabidopsis. Loss of their functions resulted in elevated expression of mitotic genes in quiescent cells including those underwent terminal differentiation. Concomitantly, their mutations enhanced cell division activities in various aspects of plant development, generating organs with increased sizes and irregular architectures. In addition, we showed that this type of R1R2R3-Myb proteins are required for oscillated expression of G2/M-specfiic genes, most likely by inhibiting transcription outside of G2/M in the cell cycle. Our finding uncovered a novel plant-specific mechanism in which scheduled expression of G2/M-specific genes may require their global repression both in the cell cycle and during development.
Transcriptional repression by MYB3R proteins regulates plant organ growth.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
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Specimen part
View SamplesSubfamily 2 of SNF1-related protein kinase (SnRK2) plays important roles in plant abiotic stress responses as a global positive regulator of abscisic acid signaling. In the genome of the model tree Populus trichocarpa, 12 SnRK2 genes have been identified, and some are upregulated by abiotic stresses. In this study, we heterologously overexpressed the PtSnRK2 genes in Arabidopsis thaliana and found that overexpression of PtSnRK2.5 and PtSnRK2.7 genes enhanced stress tolerance. In the PtSnRK2.5 and PtSnRK2.7 overexpressors, chlorophyll content and root elongation were maintained under salt stress conditions, leading to higher survival rates under salt stress compared with those in the wild type. Transcriptomic analysis revealed that PtSnRK2.7 overexpression affected stress-related metabolic genes, including lipid metabolism and flavonoid metabolism, even under normal growth conditions. However, the stress response genes reported to be upregulated in Arabidopsis SRK2C/SnRK2.6 and wheat SnRK2.8 overexpressors were not changed by PtSnRK2.7 overexpression. Instead, PtSnRK2.7 overexpression widely and largely influenced the transcriptome in response to salt stress; genes related to transport activity, including anion transport-related genes, were characteristically upregulated, and a variety of metabolic genes were specifically downregulated. We also found that the salt stress response genes were greatly upregulated in the PtSnRK2.7 overexpressor. Taken together, poplar subclass 2 PtSnRK2 genes can modulate salt stress tolerance in Arabidopsis, through the activation of cellular signaling pathways in a different manner from that by herbal subclass 2 SnRK2 genes.
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Specimen part, Treatment
View SamplesAuxin 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.
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Specimen part
View SamplesAuxin 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.
No associated publication
Specimen part
View SamplesDuring development of the mammalian central nervous system (CNS), neurons and glial cells (astrocytes and oligodendrocytes) are generated from common neural precursor cells (NPCs). However, neurogenesis precedes gliogenesis, which normally commences at later stages of fetal telencephalic development. Astrocyte differentiation of mouse NPCs at embryonic day (E) 14.5 (relatively late gestation) is induced by activation of the transcription factor STAT3, whereas at E11.5 (mid-gestation) NPCs do not differentiate into astrocytes even when stimulated by STAT3-activating cytokines such as leukemia inhibitory factor (LIF). This can be explained in part by the fact that astrocyte-specific gene promoters are highly methylated in NPCs at E11.5, but other mechanisms are also likely to play a role. We therefore sought to identify genes involved in the inhibition of astrocyte differentiation of NPCs at midgestation. We first examined gene expression profiles in E11.5 and E14.5 NPCs, using Affymetrix GeneChip analysis, applying the Percellome method to normalize gene expression level. We then conducted in situ hybridization analysis for selected genes found to be highly expressed in NPCs at midgestation. Among these genes, we found that N-myc and high mobility group AT-hook 2 (Hmga2) were highly expressed in the E11.5 but not the E14.5 ventricular zone of mouse brain, where NPCs reside. Transduction of N-myc and Hmga2 by retroviruses into E14.5 NPCs, which normally differentiate into astrocytes in response to LIF, resulted in suppression of astrocyte differentiation. However, sustained expression of N-myc and Hmga2 in E11.5 NPCs failed to maintain the hypermethylated status of an astrocyte-specific gene promoter. Taken together, our data suggest that astrocyte differentiation of NPCs is regulated not only by DNA methylation but also by genes whose expression is controlled spatio-temporally during brain development.
Identification of genes that restrict astrocyte differentiation of midgestational neural precursor cells.
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View SamplesWe used microarrays to compare global gene expression patterns between Arabidopsis wild type and css1, a mitochondria-related mutant (Nakagawa and Sakurai, Plant and Cell Physiol. 47(6): 772-783).
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Specimen part
View SamplesThe model plant Arabidopsis thaliana has five double-stranded RNA-binding proteins (DRB1-DRB5), two of which, DRB1 and DRB4, are well characterized. In contrast, the functions of DRB2, DRB3 and DRB5 have yet to be elucidated. In this study, we tried to uncover their functions using drb mutants and DRB-over-expressed lines. In over-expressed lines of all five DRB genes, the over-expression of DRB2 or DRB3 (DRB2ox or DRB3ox) conferred a downward-curled leaf phenotype, but the expression profiles of 10 small RNAs were similar to that of the wild-type (WT) plant. Phenotypes were examined in response to abiotic stresses. Both DRB2ox and DRB3ox plants exhibited salt-tolerance. When these plants were exposed to cold stress, drb2 and drb3 over-accumulated anthocyanin but DRB2ox and DRB3ox did not. Therefore, the over-expression of DRB2 or DRB3 had pleiotropic effects on host plants. Microarray and deep-sequencing analyses indicated that several genes encoding key enzymes for anthocyanin biosynthesis, including chalcone synthase (CHS), dihydroflavonol reductase (DFR) and anthocyanidin synthase (ANS), were down-regulated in DRB3ox plants. When DRB3ox was crossed with the pap1-D line, which is an activation-tagged transgenic line that over-expresses the key transcription factor PAP1 (Production of anthocyanin pigmentation1) for anthocyanin biosynthesis, over-expression of DRB3 suppressed the expression of PAP1, CHS, DFR and ANS genes. DRB3 negatively regulates anthocyanin biosynthesis by modulating the level of PAP1 transcript. Since two different small RNAs regulate PAP1 gene expression, a possible function of DRB3 for small RNA biogenesis is discussed.
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