Abstract: 【Objective】The flap endonuclease 1(RcFEN1)gene was cloned from castor,and its tissue expression characteristics and spatial and temporal expression patterns under different stresses were detected,which provided a theoretical reference for revealing the function of the RcFEN1 gene in castor growth and development and response to abiotic stresses such as low-temperature stress.【Method】According to the transcriptome annotation information of castor cold stress,the coding region(CDS)of the RcFEN1 gene was cloned by RT-PCR,the sequence characteristics were analyzed by bioinformatics software,and the tissue expression characteristics and temporal and spatial expression patterns under different stresses were detected by quantitative real-time PCR(q RT-PCR).【Result】The cloned RcFEN1 gene(GenBank accession number∶OP205366)contained an open reading frame(ORF)of 1154 bp,encoding 383 amino acid residues,it contained the typical domains XPG-N and XPG-I of the RAD2/XPG nuclease protein family and belonged to the RAD2/XPG protein family. RcFEN1 protein contained multiple biologically active sites and functional areas but had no transmembrane region and signal peptide structure. It was a non-secretory hydrophilic protein located in the nucleus. The amino acid sequence identity of RcFEN1 protein with TsFEN1 protein was the highest,and the sequence identity with ZmFEN1 protein was the lowest,which were 90.28% and 84.32%,respectively. The RcFEN1 protein was closely related to the FEN1 protein of Salvia splendens and Dorcoceras hygrometricum. The relative expression of the RcFEN1 gene in cotyledons was significantly higher than that in roots,stems and true leaves(P<0.05,the same below),and the relative expression in true leaves was the lowest. The RcFEN1 gene was expressed under four abiotic stresses,but the expression patterns differed greatly. Among them,the RcFEN1 gene was the most sensitive to drought stress,and the relative expression levels at 2 and 4 h were significantly higher than that of the control group(0 h). The RcFEN1 gene showed the same response expression pattern under salt stress and ABA stress,which began to express at 4 h,and then the relative expression decreased. Under low-temperature stress,the presentation of the RcFEN1 gene was delayed under low-temperature stress,and it was activated after 12 h of treatment,and the relative expression level continued to increase.【Conclusion】The RcFEN1 gene cloned from castor belongs to the RAD2/XPG family. It is a differentially expressed gene under low temperature stress and participates in the response regulation of castor low-temperature stress.