Map-based cloning of <i>Se14</i> and structural comparison of the proteins between Se14 and ELF6.

<p>A) Chromosomal location of <i>Se14</i> and marker positions on chromosome 3. B) High-resolution linkage map of <i>Se14</i> and genes annotated in the Rice Annotation Project Database (RAP-DB; <a href="http://rapdb.lab.nig.ac.jp" target="_blank">http://rapdb.lab.nig.ac.jp</a>). C) Genomic structure of the candidate region and the mutation in HS112. D) Schematic domain structure of two loci, Os03g0151300 and Os03g0151400, annotated at RAP-DB, and their combined cDNA.</p

Genetic interaction of the <i>Se14</i> locus with other flowering time genes loci.

<p>Comparison of flowering time among single mutant lines for flowering time: A) <i>hd1</i>, B) <i>ghd7</i>, C) ehd1 and D) <i>se13</i>, and their double mutant lines for <i>se14</i>. These lines were grown under ND.</p

Histone methylation levels at <i>Ehd1</i>, <i>Hd3a</i> and <i>RFT1.</i>

<p>A) The location of primer sets used for ChIP assay. A total of five primer sets named I to V were prepared on the promoter region every 500 bp from −2.0 kb to 0 kb at in the upstream region of TSS, and three sets named VI to VIII on 5′ UTR, exon 1 and intron 1, respectively. B∼J) Relative levels of H3K4me3 in <i>Ehd1, Hd3a</i> and <i>RFT1</i> chromatin. The amount of DNA fragments of the ChIP assay were quantified with three replications of real-time PCR. Concentrations of each sample were normalized to those manipulated with H3 universal antibody.</p

<i>Se14</i>, Encoding a JmjC Domain-Containing Protein, Plays Key Roles in Long-Day Suppression of Rice Flowering through the Demethylation of H3K4me3 of <i>RFT1</i>

<div><p>Floral transition from the vegetative to the reproductive growth phase is a major change in the plant life cycle and a key factor in reproductive success. In rice (<i>Oryza sativa</i> L.), a facultative short-day plant, numerous flowering time and flower formation genes that control floral transition have been identified and their physiological effects and biochemical functions have been clarified. In the present study, we used a <i>Se14</i>-deficient mutant line (HS112) and other flowering mutant lines to investigate the photoperiodic response, chromosomal location and function in the photoperiod sensitivity of the <i>Se14</i> gene. We also studied the interactive effects of this locus with other crucial flowering time genes. We found that <i>Se14</i> is independent of the known photoperiod-sensitive genes, such as <i>Hd1</i> and <i>Ghd7</i>, and is identical to Os03g0151300, which encodes a Jumonji C (JmjC) domain-containing protein. Expression analysis revealed that the expressions of <i>RFT1</i>, a floral initiator known as a “florigen-like gene”, and <i>Ehd1</i> were up-regulated in HS112, whereas this up-regulation was not observed in the original variety of ‘Gimbozu’. ChIP assays of the methylation states of histone H3 at lysine 4 (H3K4) revealed that the trimethylated H3K4 in the promoter region of the <i>RFT1</i> chromatin was significantly increased in HS112. We conclude that <i>Se14</i> is a novel photoperiod-sensitivity gene that has a suppressive effect on floral transition (flowering time) under long day-length conditions through the modification of chromatin structure by H3K4me3 demethylation in the promoter region of <i>RFT1</i>.</p></div

Diurnal expression of flowering time genes in the WT and HS112.

<p>Transcriptional level of the major flowering time genes were compared between HS112 (<i>se14</i>) and Gimbozu (WT) under 14.5 h day-length conditions. X axis means Zeitgeber time (ZT), and the black bars indicate the dark period, and the white bars indicate the light period. Thirty days after sowing, leaves of three plants were sampled at 4 h intervals (three replications). Expression analysis was performed by the standard curve method. For comparing expression levels among the genes, the relative expression level of each gene against the UBQ expression level was calculated.</p

Phenotype of early flowering mutant HS112.

<p>A) 100-day-old plants of the wild type Gimbozu (WT; left) and HS112 (right) grown under normal day-length conditions (ND) in Kyoto. B) Days to heading (DH;  =  flowering time) of HS112 and the WT under 10 h (SD: short day-length), 14.5 h (14.5 LD: 14.5 h long day-length) and ND conditions. C) DH of HS112, <i>hd1</i> and <i>ghd7</i> under 16 h (16 LD: 16 h long day-length) and 24 h (24 LD: continuous light) conditions. Error bars indicate standard deviations.</p