National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
J Integr Plant Biol. 2019 Sep;61(9):987-999. doi: 10.1111/jipb.12729. Epub 2019 Jan 7.
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.
花序结构是每穗小穗数的主要决定因素，是水稻粒重的关键组成部分。本研究从一个短穗 3（sp3）突变体中鉴定出短穗 3（SP3），该突变体中 T-DNA 插入 SP3 的启动子中，导致敲低突变。SP3 编码一个 DNA 结合一个手指（Dof）转录激活因子。定量实时（qRT）-PCR 和 RNA 原位杂交分析证实，SP3 在幼嫩的水稻花序中特异性表达，特别是在分枝原基区域。SP3 通过上调 APO2/RFL 作为花序分生组织败育的负调节剂起作用。SP3 分别上调和下调参与细胞分裂素生物合成和分解代谢的基因的表达。因此，在幼穗 3 中细胞分裂素浓度降低，导致小穗具有较少的分支和小穗。我们的研究结果支持 SP3 通过调节细胞分裂素稳态来调节穗型结构的模型。通过 SP3 启动子的基因编辑评估了其在水稻育种中的潜在应用。
