The far-upstream regulatory region of RFL is required for its precise spatial-temporal expression for floral development in rice
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A rice mutant aberrant floral organ 1 (afo1) was identified, showing increased floral organ number, aberrant floral organ identity and loss of floral meristem determinacy. A disruption of sequence integrity at 6292-bp upstream of RFL by a T-DNA insertion led to varied RFL expression patterns in floral meristem and floret in afo1 and caused the mutant phenotype.
The LEAFY (LFY) transcription factor and its homologs affect many aspects of plant development, especially floral development. RICE FLORICAULA/LEAFY (RFL), the rice ortholog of LFY, has complicated expression patterns and different functions in floral development. However, the mechanisms regulating the spatial-temporal expression of RFL remain largely unknown. Here, we describe a rice aberrant floral organ 1 (afo1) mutant that was produced by a T-DNA insertion at 6292-bp upstream of the start codon of RFL. This insertion altered the expression of RFL in floral meristem (FM) and floret. The in situ hybridization result showed that, when florets appear, RFL was expressed almost exclusively at the palea/lemma adaxial base adjacent to lodicules in the wild-type panicle. However, in afo1 florets, RFL mRNA signals were detected in the region between lodicule and stamen, and strong signals persisted in FM. The altered pattern of RFL expression in afo1 resulted in enlarged FMs, more floral organs, aberrant floral organ identity, and loss of FM determinacy. Transformation of rice with an RFL construct driven by the 6292-bp upstream genomic sequence re-built the mutant phenotype similar to afo1. The results suggest that the far-upstream region of RFL may contain potential cis element(s) that are critical to define the precise spatial-temporal expression pattern of RFL for its function in floral development.
KeywordsFloral development RFL Far-upstream regulatory element Rice
aberrant floral organ 1
aberrant panicle organization 2
floral organ number
Hygromycin phosphotransferase gene
Polymerase chain reaction
Quantitative reverse transcription PCR
Thermal asymmetric interlaced PCR
TERMINAL FLOWER 1
We thank Drs. Da Luo (Sun Yat-Sen University) and Jun Yang (Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences) for technical assistance on in situ hybridization. We also thank Xinfang Chen (South China Agricultural University) for technical assistance on scanning electron microscopy, and Drs Shunxiang Ren and Xingmin Wang (South China Agricultural University) for providing help in stereoscopic observation. This work was supported by grants from the National Natural Science Foundation of China (31271301), and the Ministry of Science and Technology of China (2012AA10A303).
SL and SC performed most of the experiments, and contribute equally to this project; XZ conducted phenotyping and genetic analysis. LC gave advice to the project and participated in revising the manuscript. JZ identified T-DNA flanking sequences and participated in genetic analysis. HF participated in phenotyping and genetic analysis. YL designed and supervised the project and revised the manuscript. YC created the afo1 mutant, designed and supervised the project and wrote the manuscript. All of the authors discussed the results and commented on the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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