A chromo box gene from carrot ( Daucus carota L.): its cDNA structure and expression during somatic and zygotic embryogenesis

Abstract

A cDNA clone, designated DcDB1, was isolated from a cDNA library prepared from embryogenic cell clusters of carrot ( Daucus carota L.) and characterized. The cDNA (1416 bp) encoded for a protein of 392 amino acid residues that contained a conserved chromo domain. The chromo domain is a 37 aa region found in both the Polycomo gene product, which is a repressor of homeotic genes, and a heterochromatin protein 1 of Drosophila. This domain is postulated to function in the binding of proteins to chromatin. Genomic blot hybridization experiments suggested that the number of DcCB1 genes in the carrot genome is low. The level of DcCB1 mRNAs was high in somatic embryos at globular and heart-shaped stages but low in torpedo-shaped somatic embryos. The level of DcCB1 transcripts decreased during the formation of seeds. The existence of both homeo and chromo box genes in plants suggests that regulatory mechanisms of developmental genes in plants may resemble those in Drosophila.