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The far-upstream regulatory region of RFL is required for its precise spatial-temporal expression for floral development in rice

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Abstract

Key message

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.

Abstract

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.

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Abbreviations

afo1 :

aberrant floral organ 1

AG :

AGAMOUS

AP3 :

APETALA3

apo2 :

aberrant panicle organization 2

CLV :

CLAVATA

FM:

Floral meristem

fon :

floral organ number

Hm:

Hygromycin

hpt :

Hygromycin phosphotransferase gene

LFY :

LEAFY

PCR:

Polymerase chain reaction

qRT-PCR:

Quantitative reverse transcription PCR

RFL :

RICE FLORICAULA/LEAFY

TAIL-PCR:

Thermal asymmetric interlaced PCR

TFL1 :

TERMINAL FLOWER 1

WUS :

WUSCHEL

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Acknowledgements

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).

Author contributions

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.

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    Authors and Affiliations

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, South China Agricultural University, Guangzhou, 510642, China

      Sulin Lou, Shuifu Chen, Xiucai Zhao, Letian Chen, Yao-Guang Liu & Yuanling Chen

    2. Key Laboratory of Plant Functional Genomics and Biotechnology of Guangdong Provincial Higher Education Institutions, South China Agricultural University, Guangzhou, 510642, China

      Xiucai Zhao, Letian Chen, Yao-Guang Liu & Yuanling Chen

    3. Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, South China Agricultural University, Guangzhou, 510642, China

      Letian Chen

    4. College of Life Sciences, South China Agricultural University, Guangzhou, 510642, China

      Sulin Lou, Shuifu Chen, Xiucai Zhao, Letian Chen, Jian Zhang, Hongxiang Fu, Yao-Guang Liu & Yuanling Chen

    5. Guangdong Engineering Research Centre for Marine Algal Biotechnology, Guangdong Key Laboratory of Plant Epigenetics, Shenzhen Key Laboratory of Marine Bioresource and Eco-Environmental Science, Shenzhen University, Shenzhen, 518060, China

      Sulin Lou

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    Sulin Lou and Shuifu Chen have contributed equally to this work and are regarded as co-first authors.

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    Lou, S., Chen, S., Zhao, X. et al. The far-upstream regulatory region of RFL is required for its precise spatial-temporal expression for floral development in rice. Plant Mol Biol 93, 185–195 (2017). https://doi.org/10.1007/s11103-016-0556-6

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