title: Ehd4 encodes a novel and Oryza-genus-specific regulator of photoperiodic flowering in rice.
abstract: Land plants have evolved increasingly complex regulatory modes of their flowering time (or heading date in crops). Rice (Oryza sativa L.) is a short-day plant that flowers more rapidly in short-day but delays under long-day conditions. Previous studies have shown that the CO-FT module initially identified in long-day plants (Arabidopsis) is evolutionary conserved in short-day plants (Hd1-Hd3a in rice). However, in rice, there is a unique Ehd1-dependent flowering pathway that is Hd1-independent. Here, we report isolation and characterization of a positive regulator of Ehd1, Early heading date 4 (Ehd4). ehd4 mutants showed a never flowering phenotype under natural long-day conditions. Map-based cloning revealed that Ehd4 encodes a novel CCCH-type zinc finger protein, which is localized to the nucleus and is able to bind to nucleic acids in vitro and transactivate transcription in yeast, suggesting that it likely functions as a transcriptional regulator. Ehd4 expression is most active in young leaves with a diurnal expression pattern similar to that of Ehd1 under both short-day and long-day conditions. We show that Ehd4 up-regulates the expression of the "florigen" genes Hd3a and RFT1 through Ehd1, but it acts independently of other known Ehd1 regulators. Strikingly, Ehd4 is highly conserved in the Oryza genus including wild and cultivated rice, but has no homologs in other species, suggesting that Ehd4 is originated along with the diversification of the Oryza genus from the grass family during evolution. We conclude that Ehd4 is a novel Oryza-genus-specific regulator of Ehd1, and it plays an essential role in photoperiodic control of flowering time in rice.
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, China.
authors: He
authors: H
authors: Gao
authors: Xiao-Ming
authors: XM
authors: Zheng
authors: Guilin
authors: G
authors: Fei
authors: Jun
authors: J
authors: Chen
authors: Mingna
authors: M
authors: Jin
authors: Yulong
authors: Y
authors: Ren
authors: Weixun
authors: W
authors: Wu
authors: Kunneng
authors: K
authors: Zhou
authors: Peike
authors: P
authors: Sheng
authors: Feng
authors: F
authors: Zhou
authors: Ling
authors: L
authors: Jiang
authors: Jie
authors: J
authors: Wang
authors: Xin
authors: X
authors: Zhang
authors: Xiuping
authors: X
authors: Guo
authors: Jiu-Lin
authors: JL
authors: Wang
authors: Zhijun
authors: Z
authors: Cheng
authors: Chuanyin
authors: C
authors: Wu
authors: Haiyang
authors: H
authors: Wang
authors: Jian-Min
authors: JM
authors: Wan
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000235:genetics / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D009687:Nuclear Proteins / Q000235:genetics*; D012275:Oryza / Q000235:genetics / Q000254:growth & development; D010641:Phenotype; D017440:Photoperiod; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D009687:Nuclear Proteins; D010940:Plant Proteins; D015534:Trans-Activators; D014157:Transcription Factors