水稻穗顶部退化导致穗子短小以及重要的产量指标穗粒数显著降低，造成水稻产量的大幅下降。目前对于水稻顶端穗退化的形成的分子机制了解十分有限。通过水稻穗发育表达谱的系统分析，我们筛选了一批在水稻穗发育过程中特异表达的转录因子作为重点研究对象。其中，RPD1编码一个DNA结合蛋白，其突变体呈现明显的顶端穗退化的表型。遗传互补实验表明突变体的顶端穗退化表型是由于RPD1突变所导致的。细胞学和生化分析显示rpd1突变体顶端小穗呈现明显的细胞程序化死亡（PCD）特征。本项目的主要目标是解析以RPD1为关键调控节点的水稻顶端穗退化以及细胞程序化死亡调控机制，鉴定RPD1所调控的下游靶点基因，并系统分析下游基因参与PCD发生和进程调节的细胞生物学过程及分子机制。研究将阐释水稻顶端穗退化抑制因子RPD1调控其下游基因的分子生化特性和调控模式，建立较为明确的水稻穗顶端退化的遗传和分子调控路径。

Panicle apical degeneration commonly results in short panicles and causes a dramatic reduction in grain number per panicle, which is a determinant trait for rice yield. Thus, panicle apical degeneration is a severe threat to rice production. However, our knowledge about the molecular mechanisms in regulation of panicle apical degeneration in rice is very limited. In order to characterize the transcriptional regulators during panicle development, we have selected the candidate transcription factors that are highly and specifically expressed during panicle development based on the analysis of expression profiles. One of candidate gene designated as RPD1, encoding a DNA-binding protein, has been focused on its role in panicle development because the rpd1 (repressor of panicle degeneration1) mutant showed a severe phenotype of panicle apical degeneration. Complementation experiments further confirm that panicle apical degeneration occurred in the rpd1 mutant is caused by the RPD1 mutation. Our cytological and biochemical analysis indicated that the tissue-specific programmed cell death was characterized in apical spikelets. In this study, we aim at dissecting the molecular mechanisms of RPD1 in regulation of panicle apical degeneration and the related programmed cell death processes. We will identify the downstream target genes of RPD1 and conduct the functional analysis of these target genes with respect to their roles in modulating programmed cell death occurred in apical spikelets. Our studies will reveal the molecular and biochemical patterns by which RPD1 regulates the activation of its downstream target genes. These results will provide insights into better understanding the genetic and molecular regulatory pathways about panicle apical degeneration in rice.