Shibaya Taeko, Hori Kiyosumi, Ogiso-Tanaka Eri, Yamanouchi Utako, Shu Koka, Kitazawa Noriyuki, Shomura Ayahiko, Ando Tsuyu, Ebana Kaworu, Wu Jianzhong, Yamazaki Toshimasa, Yano Masahiro
National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan These authors contributed equally to this work.
National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan.
Plant Cell Physiol. 2016 Sep;57(9):1828-38. doi: 10.1093/pcp/pcw105. Epub 2016 Jun 18.
Flowering time is one of the most important agronomic traits in rice (Oryza sativa L.), because it defines harvest seasons and cultivation areas, and affects yields. We used a map-based strategy to clone Heading date 18 (Hd18). The difference in flowering time between the Japanese rice cultivars Koshihikari and Hayamasari was due to a single nucleotide polymorphism within the Hd18 gene, which encodes an amine oxidase domain-containing protein and is homologous to Arabidopsis FLOWERING LOCUS D (FLD). The Hayamasari Hd18 allele and knockdown of Hd18 gene expression delayed the flowering time of rice plants regardless of the day-length condition. Structural modeling of the Hd18 protein suggested that the non-synonymous substitution changed protein stability and function due to differences in interdomain hydrogen bond formation. Compared with those in Koshihikari, the expression levels of the flowering-time genes Early heading date 1 (Ehd1), Heading date 3a (Hd3a) and Rice flowering locus T1 (RFT1) were lower in a near-isogenic line with the Hayamasari Hd18 allele in a Koshihikari genetic background. We revealed that Hd18 acts as an accelerator in the rice flowering pathway under both short- and long-day conditions by elevating transcription levels of Ehd1 Gene expression analysis also suggested the involvement of MADS-box genes such as OsMADS50, OsMADS51 and OsMADS56 in the Hd18-associated regulation of Ehd1 These results suggest that, like FLD, its rice homolog accelerates flowering time but is involved in rice flowering pathways that differ from the autonomous pathways in Arabidopsis.
抽穗期是水稻（Oryza sativa L.）最重要的农艺性状之一，因为它决定收获季节和种植区域，并影响产量。我们采用基于图谱的策略克隆了抽穗期18（Hd18）基因。日本水稻品种越光和早生笹之间抽穗期的差异是由于Hd18基因内的一个单核苷酸多态性，该基因编码一种含胺氧化酶结构域的蛋白质，与拟南芥开花位点D（FLD）同源。无论日照长度条件如何，早生笹的Hd18等位基因和Hd18基因表达的敲低都会延迟水稻植株的抽穗期。Hd18蛋白的结构模型表明，非同义替换由于结构域间氢键形成的差异而改变了蛋白质的稳定性和功能。与越光相比，在越光遗传背景下携带早生笹Hd18等位基因的近等基因系中，抽穗期基因抽穗期提早1（Ehd1）、抽穗期3a（Hd3a）和水稻开花位点T1（RFT1）的表达水平较低。我们发现，在短日和长日条件下，Hd18通过提高Ehd1的转录水平，在水稻开花途径中起促进作用。基因表达分析还表明，MADS盒基因如OsMADS50、OsMADS51和OsMADS56参与了Hd18相关的Ehd1调控。这些结果表明，与FLD一样，其水稻同源物加速抽穗期，但参与了与拟南芥自主途径不同的水稻开花途径。
