In this study,a new gene encoding proline-rich protein was isolated from 12 days post anthesis(DPA) cotton fiber,and designated as GhPRP10.The ORF of the gene was 684bp encoding 228 amino acids,contained 34.6% proline.The bioinformatics analysis showed that the protein encoded by this gene belonged to the first class of PRPs,which has a signal peptide in N terminal and a proline rich conserved region.The quantitative RT-PCR results showed that GhPRP10 is preferentially expressed in cotton fiber.The transcript level increased along with fiber development and reached the highest abundance at 18DPA,after which time it gradually decreased.The plant over-expression vector was constructed using Gateway technology and then transformed into tobacco suspension BY-2 cells.The phenotype observation and cell length measurement found that the transgenic cells were significantly longer than that of the wild type.Based on the expression profile of GhPRP10 and phenotype analysis of transgenic cells,it is presumed that the gene plays an important role in the process of fiber elongation and secondary wall synthesis.