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A gene network for long-day flowering activates RFT1 encoding a mobile flowering signal in rice
Reina Komiya1, Shuji Yokoi, Ko Shimamoto
1Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology (NAIST), Takayama, Ikoma, Japan.
Development (Cambridge, England)
|September 19, 2009
Summary
Rice flowering under long-day conditions is regulated by a gene network involving RICE FLOWERING LOCUS T 1 (RFT1) as a key floral activator. This study reveals the roles of OsMADS50 and Ehd1 in promoting flowering and OsMADS14
Area of Science:
- Plant biology
- Molecular genetics
- Agricultural science
Background:
- Photoperiodic flowering is crucial for crop yield in rice (Oryza sativa).
- While some flowering genes are conserved between long-day (LD) plants like Arabidopsis thaliana and short-day (SD) plants like rice, the specific gene networks controlling rice flowering, especially under LD conditions, remain unclear.
Purpose of the Study:
- To elucidate the gene network regulating flowering in rice under long-day conditions.
- To identify key floral activators and their upstream regulators in rice.
Main Methods:
- Utilized RICE FLOWERING LOCUS T 1 (RFT1) gene analysis, including RFT1:GFP fusion protein localization in the shoot apical meristem (SAM).
- Investigated mutants of OsMADS50, a rice ortholog of Arabidopsis SUPPRESOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1).
- Analyzed gene expression patterns in wild-type and RFT1 RNAi plants, including OsMADS14.
Main Results:
- RFT1 was identified as a major floral activator under LD conditions, with its protein localizing to the SAM.
- OsMADS50 acts upstream of RFT1 and is essential for promoting flowering under LD conditions; OsMADS50 mutants failed to flower.
- A regulatory network involving positive regulators (OsMADS50, Ehd1) and negative regulators (Hd1, phyB, Ghd7) of RFT1 was proposed. Ehd1, a rice-specific inducer, integrates multiple pathways to regulate RFT1.
- OsMADS14, a rice ortholog of Arabidopsis APETALA1, is activated by RFT1 downstream.
Conclusions:
- A comprehensive gene network regulating LD flowering in rice has been uncovered.
- RFT1 is a critical florigen gene in rice, functioning downstream of OsMADS50 and integrating signals through Ehd1.
- OsMADS14 acts as a downstream floral meristem identity gene activated by RFT1.
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