A cDNA encoding a polygalacturonase-inhibitor-like protein (PGIP) was isolated from cotton flower cDNA library. The cDNA, designated GhPS1 (GenBank acces-sion No. ABO47744), encodes a protein with 370 amino acids that shares high similarity with the known plant PGIPs. Fluorescent microscopy indicated that GhPS1protein localizes on the cell membranes as well as in cytoplasm. Real-time quantitative RT-PCR and north-e blot analyses showed that GhPSI was specifically expressed in cotton petals. Furthermore, the GhPS1 expression was gradually up-regulated in petal develop-ment, and its transcripts were accumulated to the highest level in the petals at anthesis. However, its expression level was declined rapidly in senesced petals after flowering. At low temperature, the GhPS1 gene expression was gradually decreased to very low level in petals. Collectively, our results suggest that GhPSI gene might be involved in cotton petal development and senescence, and in response to cold stress.