J Integr Plant Biol ›› 2019, Vol. 61 ›› Issue (9): 987-999.DOI: 10.1111/jipb.12729

Special Issue: Rice Genomics and Agriculture

• Cell and Developmental Biology • Previous Articles     Next Articles

Short Panicle 3 controls panicle architecture by upregulating APO2/RFL and increasing cytokinin content in rice

Yong Huang, Xufeng Bai, Meifang Luo and Yongzhong Xing*   

  1. National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China

    *Correspondence:
    Email: Yongzhong Xing (yzxing@mail.hzau.edu.cn)
  • Received:2018-05-27 Accepted:2018-10-07 Online:2018-10-10 Published:2019-09-01

Abstract:

Inflorescence architecture is a major determinant of spikelet numbers per panicle, a key component of grain yield in rice. In this study, Short Panicle 3 (SP3) was identified from a short panicle 3 (sp3) mutant in which T‐DNA was inserted in the promoter of SP3, resulting in a knockdown mutation. SP3 encodes a DNA binding with one finger (Dof) transcriptional activator. Quantitative real time (qRT)‐PCR and RNA in situ hybridization assays confirmed that SP3 is preferentially expressed in the young rice inflorescence, specifically in the branch primordial regions. SP3 acts as a negative regulator of inflorescence meristem abortion by upregulating APO2/RFL. SP3 both up‐ and downregulates expression of genes involved in cytokinin biosynthesis and catabolism, respectively. Consequently, cytokinin concentrations are decreased in young sp3 panicles, thereby leading to small panicles having fewer branches and spikelets. Our findings support a model in which SP3 regulates panicle architecture by modulating cytokinin homeostasis. Potential applications to rice breeding, through gene‐editing of the SP3 promoter are assessed.

In this study, a novel rice T-DNA insertion mutant with small panicles was obtained. Gene cloning and characterization demonstrated that LOC_Os03g55610 underlying SP3 encodes a DNA binding with one finger (Dof) transcriptional activator. SP3 controls panicle architecture by upregulating APO2/RFL and increasing the cytokinin content in rice.
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