Abstract: 【Objective】This study aimed to perform prokaryotic expression， purification， and subcellular localization of the lipid transfer protein （OsLTPL108） of rice grain shape regulation， providing theoretical reference for elucidating its biological functions and its molecular mechanism of grain shape regulation.【Method】The OsLTPL108 gene coding sequence （CDS） was obtained from the UniProt database， and primers were designed for PCR amplification. The amplification product was detected by electrophoresis and sequencing. Bioinformatic software were used to predict the physicochemical properties， transmembrane domains， signal peptides， hydrophilicity/hydrophobicity， and subcellular localization of the encoded protein. The OsLTPL108 gene was ligated into pGEX-2T to construct the prokaryotic expression vector pGEX-2T-OsLTPL108， which was then transformed into Escherichia coli BL21-CodonPlus（DE3）-RIPL for induced expression. The purified target protein was verified by immunoblotting. Concurrently， the subcellular localization vector pRHV-OsLTPL108-cGFP was constructed and transformed into rice protoplasts to observe its subcellular localization.【Result】Using cDNA of rice variety Dingxiang B as the template， the amplified OsLTPL108 gene was 477 bp in length and the sequence was completely consistent with japonica rice whose accession number was LOC_Os03g14654 from the RGAP database. The OsLTPL108 gene encoded 158 amino acid residues， with its relative protein molecular mass of 15.66 kD， and a theoretical isoelectric point of 8.7； amino acids 1-30 of N-terminal contained a transmembrane domain， and amino acids 31-158 constituted a soluble domain. Amino acids 1-24 of N-terminal formed a typical signal peptide sequence， suggesting the protein was a secretory one. The core region of OsLTPL108 protein （amino acids 30-120） harbored a complete non-specific LTP family domain （Pfam accession number of PF14368） composed of eight highly conserved cysteine residues. After the prokaryotic expression vector pGEX-2T-OsLTPL108 was transformed into the prokaryotic expression system， low temperature overnight induction at 18 °C with 0.1 mmol/L IPTG resulted in a high expression of OsLTPL108 protein. A GST-OsLTPL108 protein fusion protein with a molecular mass of approximately 39.64 kD was successfully obtained， showing single bands without obvious non-specific bands. Protein mass spectrometry identified three specific peptides matching OsLTPL108 protein， confirming that the sequence of exogenously expressed and purified protein OsLTPL108 was correct. After the subcellular localization vector pRHV-OsLTPL108-cGFP was transformed into rice protoplasts， the green fluorescence signal of the OsLTPL108-EGFP fusion protein displayed a reticular pattern and completely overlapped with the red fluorescence signal OsHLP1-mCherry of endoplasmic reticulum-localized protein， proving that the protein localized to the endoplasmic reticulum in rice protoplasts.【Conclusion】OsLTPL108 is a secretory protein. By utilizing the solubility-enhancing GST tag， highly pure soluble fusion protein can be obtained from the prokaryotic expression system， which can be used for subsequent protein antibody preparation. The OsLTPL108 protein localizes to the endoplasmic reticulum of rice cells， and as the endoplasmic reticulum is the main site of plant lipid synthesis， OsLTPL108 is speculated to function in lipid transport.