AbstractWUSCHEL(WUS) andWUSCHEL-RELATED HOMEOBOX(WOX) encode transcription factors and play important roles in regulating the formation and maintenance of shoot and floral meristems.OsWUShave distinct functions in meristem development with slightly tuned expression. However, the mechanisms regulating the specific expression ofOsWUSneed to be further explored. In this study, an abnormal expression mutant ofOsWUS, calledDwarf and aberrant panicle 1(Dap1) was used. In order to identify the causal gene inDap1, high-efficiency thermal asymmetric interlaced (hiTAIL)-PCR and co-segregation analysis were performed. We surveyed the growth and yield traits inDap1and wild type. Changes in gene expression betweenDap1and wild type were determined by RNA-seq. TheDap1mutant is due to the T-DNA inserted at 3,628-bp upstream of the translation start codon ofOsWUS. Plant height, tiller numbers, panicle length, the number of grains per main panicle, and the number of secondary branches was significantly reduced in theDap1mutant. The expression ofOsWUSwas markedly increased inDap1mutant plants compared to the wild type, which might be due to a disruption in the genomic sequence integrity. Simultaneously, the expression levels of gibberellic acid-related genes and genes involved in panicle development were significantly changed in theDap1mutant. Our results suggest thatOsWUSis a precise regulatory element, its specific spatio-temporal expression pattern is critical for its function, and both loss-of-function and gain-of-function mutations lead to abnormal plant growth.