Expression pattern of the Arabidopsis thaliana AtEP3/AtchitIV endochitinase gene

The carrot (Daucus carota L.) EP3 chitinase was shown to be essential for s omatic embryo formation in a carrot mutant cell line. We identified the Ara bidopsis thaliana (L.) Heynh. ortholog of the carrot EP3-3 chitinase gene, designated as AtEP3/AtchitIV and analyzed its expression in Arabidopsis by means of reverse transcription-polymerase chain reaction and promoter::beta -glucuronidase and luciferase fusions. As in carrot, the gene is expressed during somatic embryogenesis in "nursing" cells surrounding the embryos bu t not in embryos themselves. In plants, gene expression is found in mature pollen and growing pollen tubes until they enter the receptive synergid, bu t not in endosperm and integuments as in carrot, Post-embryonically, expres sion is found in hydathodes, stipules, root epidermis and emerging root hai rs, indicating that the Al Arabidopsis chitinase may have a function that i s not restricted to embryogenesis.