A cDNA clone of zucchini yellow mosaic virus (ZYMV) RNA was mapped to the 3' terminal region. The nucleotide sequence revealed a single open reading frame of 1035 nucleotides followed by a 3' noncoding region of 215 nucleotides. The putative protease cleavage site for the release of coat protein (CP) was deduced to be between Glu-Ser (at amino acid position 66-67), which would result in a protein of 279 amino acids. This non-aphid-transmissible Singapore isolate of ZYMV showed a change of DAG to GAG triplet near the N-terminal of the CP. The CP gene was expressed as a protein fused to the beta-galactosidase in Escherichia coli and as an unfused protein in Saccharomyces cerevisiae.