Ginseng ESTs allowed us to identify an unknown transcript which is highly abundant in rhizomes and seeds. We called the cDNA ginseng-specific abundant protein (GSAP), and identified three homologues, GSAP1, GSAP2, and GSAP3. GSAP cDNAs encode a small polypeptide consisting of 121 or 117 amino acids, and GSAP3 shows 87.6% amino acid sequence homology with GSAP1. GSAP transcripts were detected in most plant tissues, but GSAP3 is highly expressed in seeds, and is up-regulated under stressed conditions, water deficit. GSAP3-GFP fusion protein is located in the cell wall when expressed in onion epidermis cells. The transgenic Arabidopsis seedlings which over-expressed GSAP3 grew faster than those of the wild-type plant on the medium containing 300 mM mannitol and 100 mM NaCl. GSAP3 may play a role in altering the characteristics of the cell wall to allow for more tolerance of water deficit stress under abiotic stress conditions.