Cysteine proteinase gene expression in the endosperm of germinating carrot seeds.

A gene for carrot seed cysteine proteinase (CSCP; AB057371, AB057372) was cloned using PCR. The deduced amino acid sequence of CSCP had active sites for eukaryotic cysteine proteinases, putative signal sequences, and an endoplasmic reticulum targeting sequence. RNA gel blot analysis showed that CSCP transcripts appeared from dry seed, reached a maximum 3 days after imbibition (DAI), and disappeared by 5 DAI. In situ hybridization showed that CSCP transcripts accumulated in the endosperm of germinating seeds. This is the first report of the expression pattern of a cysteine proteinase gene in the endosperm of germinating dicotyledonous plants. The promoter of the CSCP gene had an endosperm motif and many other motifs also found in the promoters of endosperm-specific storage protein genes in monocotyledons. It is suggested that dicotyledons, like monocotyledons, have a temporal and spatial regulation system for endosperm-specific gene expression in germinating seeds.