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Song, Hae-Ryong,Song, Ju-Dong,Cho, Jung-Nam,Amasino, Richard M,Noh, Bosl,Noh, Yoo-Sun American Society of Plant Physiologists 2009 The Plant cell Vol.21 No.4
<P>SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1) is regulated by a complex transcriptional regulatory network that allows for the integration of multiple floral regulatory inputs from photoperiods, gibberellin, and FLOWERING LOCUS C. However, the posttranscriptional regulation of SOC1 has not been explored. Here, we report that EARLY FLOWERING9 (ELF9), an Arabidopsis thaliana RNA binding protein, directly targets the SOC1 transcript and reduces SOC1 mRNA levels, possibly through a nonsense-mediated mRNA decay (NMD) mechanism, which leads to the degradation of abnormal transcripts with premature translation termination codons (PTCs). The fully spliced SOC1 transcript is upregulated in elf9 mutants as well as in mutants of NMD core components. Furthermore, a partially spliced SOC1 transcript containing a PTC is upregulated more significantly than the fully spliced transcript in elf9 in an ecotype-dependent manner. A Myc-tagged ELF9 protein (MycELF9) directly binds to the partially spliced SOC1 transcript. Previously known NMD target transcripts of Arabidopsis are also upregulated in elf9 and recognized directly by MycELF9. SOC1 transcript levels are also increased by the inhibition of translational activity of the ribosome. Thus, the SOC1 transcript is one of the direct targets of ELF9, which appears to be involved in NMD-dependent mRNA quality control in Arabidopsis.</P>
Kim, Sang Yeol,He, Yuehui,Jacob, Yannick,Noh, Yoo-Sun,Michaels, Scott,Amasino, Richard American Society of Plant Physiologists 2005 The Plant cell Vol.17 No.12
<P>Winter-annual accessions of Arabidopsis thaliana are often characterized by a requirement for exposure to the cold of winter to initiate flowering in the spring. The block to flowering prior to cold exposure is due to high levels of the flowering repressor FLOWERING LOCUS C (FLC). Exposure to cold promotes flowering through a process known as vernalization that epigenetically represses FLC expression. Rapid-cycling accessions typically have low levels of FLC expression and therefore do not require vernalization. A screen for mutants in which a winter-annual Arabidopsis is converted to a rapid-cycling type has identified a putative histone H3 methyl transferase that is required for FLC expression. Lesions in this methyl transferase, EARLY FLOWERING IN SHORT DAYS (EFS), result in reduced levels of histone H3 Lys 4 trimethylation in FLC chromatin. EFS is also required for expression of other genes in the FLC clade, such as MADS AFFECTING FLOWERING2 and FLOWERING LOCUS M. The requirement for EFS to permit expression of several FLC clade genes accounts for the ability of efs lesions to suppress delayed flowering due to the presence of FRIGIDA, autonomous pathway mutations, or growth in noninductive photoperiods. efs mutants exhibit pleiotropic phenotypes, indicating that the role of EFS is not limited to the regulation of flowering time.</P>
Eun-Hye Hong,정영민,Jee-Youn Ryu,Richard M. Amasino,오보슬,Yoo-Sun Noh 한국분자세포생물학회 2009 Molecules and cells Vol.27 No.4
Diverse posttranslational modifications of histones, such as acetylation and methylation, play important roles in controlling gene expression. Histone methylation in particular is involved in a broad range of biological processes, including heterochromatin formation, X-chromosome inactivation, genomic imprinting, and transcriptional regulation. Recently, it has been demonstrated that proteins containing the Jumonji (Jmj) C domain can demethylate histones. In Arabidopsis, twenty-one genes encode JmjC domain-containing proteins, which can be clustered into five clades. To address the biological roles of the Arabidopsis genes encoding JmjC-domain proteins, we analyzed the temporal and spatial expression patterns of nine genes. RT-PCR analyses indicate all nine Arabidopsis thaliana Jmj (AtJmj) genes studied are actively expressed in various tissues. Furthermore, studies of transgenic plants harboring AtJmj::β-glucuronidase fusion constructs reveal that these nine AtJmj genes are expressed in a developmentally and spatially regulated manner.
Control of Seed Germination by Light-Induced Histone Arginine Demethylation Activity
Cho, J.N.,Ryu, J.Y.,Jeong, Y.M.,Park, J.,Song, J.J.,Amasino, Richard M.,Noh, B.,Noh, Y.S. Cell Press 2012 DEVELOPMENTAL CELL Vol.22 No.4
For optimal survival, various environmental and endogenous factors should be monitored to determine the appropriate timing for seed germination. Light is a major environmental factor affecting seed germination, which is perceived by phytochromes. The light-dependent activation of phytochrome B (PHYB) modulates abscisic acid and gibberellic acid signaling and metabolism. Thus far, several negative regulators of seed germination that act when PHYB is inactive have been reported. However, neither positive regulators of seed germination downstream of PHYB nor a direct mechanism for regulation of the hormone levels has been elucidated. Here, we show that the histone arginine demethylases, JMJ20 and JMJ22, act redundantly as positive regulators of seed germination. When PHYB is inactive, JMJ20/JMJ22 are directly repressed by the zinc-finger protein SOMNUS. However, upon PHYB activation, JMJ20/JMJ22 are derepressed, resulting in increased gibberellic acid levels through the removal of repressive histone arginine methylations at GA3ox1/GA3ox2, which in turn promotes seed germination.
Choi, Jean,Hyun, Youbong,Kang, Min-Jeong,In Yun, Hye,Yun, Jae-Young,Lister, Clare,Dean, Caroline,Amasino, Richard M.,Noh, Bosl,Noh, Yoo-Sun,Choi, Yeonhee Blackwell Publishing Ltd 2009 The Plant journal Vol.57 No.5
<P>Summary</P><P>The epigenetic regulation of the floral repressor <I>FLOWERING LOCUS C</I> (<I>FLC</I>) is one of the critical factors that determine flowering time in <I>Arabidopsis thaliana</I>. Although many <I>FLC</I> regulators, and their effects on <I>FLC</I> chromatin, have been extensively studied, the epigenetic resetting of <I>FLC</I> has not yet been thoroughly characterized. Here, we investigate the <I>FLC</I> expression during gametogenesis and embryogenesis using <I>FLC::GUS</I> transgenic plants and RNA analysis. Regardless of the epigenetic state in adult plants, <I>FLC</I> expression disappeared in gametophytes. Subsequently, <I>FLC</I> expression was reactivated after fertilization in embryos, but not in the endosperm. Both parental alleles contributed equally to the expression of <I>FLC</I> in embryos. Surprisingly, the reactivation of <I>FLC</I> in early embryos was independent of FRIGIDA (FRI) and SUPPRESSOR OF FRIGIDA 4 (SUF4) activities. Instead, <I>FRI</I>, <I>SUF4</I> and autonomous-pathway genes determined the level of <I>FLC</I> expression only in late embryogenesis. Many <I>FLC</I> regulators exhibited expression patterns similar to that of <I>FLC</I>, indicating potential roles in <I>FLC</I> reprogramming. An <I>FVE</I> mutation caused ectopic expression of <I>FLC</I> in the endosperm. A mutation in <I>PHOTOPERIOD-INDEPENDENT EARLY FLOWERING 1</I> caused defects in <I>FLC</I> reactivation in early embryogenesis, and maintenance of full <I>FLC</I> expression in late embryogenesis. We also show that the polycomb group complex components, Fertilization-Independent endosperm and MEDEA, which mediate epigenetic regulation in seeds, are not relevant for <I>FLC</I> reprogramming. Based on our results, we propose that <I>FLC</I> reprogramming is composed of three phases: (i) repression in gametogenesis, (ii) reactivation in early embryogenesis and (iii) maintenance in late embryogenesis.</P>