CLONING AND SEQUENCING OF A DEVELOPMENTALLY-REGULATED AVIAN MESSENGER-RNA CONTAINING THE LEA MOTIF FOUND IN PLANT SEED PROTEINS

We report the cloning of a bromodeoxyuridine (BrdU)-sensitive transcri pt of 918 bp from an immortalized quail heart cell line containing an open reading frame (ORF) of 215 amino acids (aa) (approximate to 23 kD a). Analysis of the secondary structure predicts two amphipathic alpha -helices with oppositely oriented amphipathic surfaces at the C-termin us of the protein. Each of the helices contains an LEA (late embryogen esis abundant) consensus sequence (A/TAEKAK/RETKD) which has been prev iously described only in a group of plant seed-specific proteins. Temp oral and spatial distribution patterns of the transcript during chick embryo development were examined by whole-mount in situ hybridization and Northern blot analysis. At H&H (Hamburger and Hamilton, 1951) stag es 11-14, the message was expressed strongly in blood islands in the a rea opaca. At day 5, strong signals were found in the liver primordia, mesonephrons, and nephric duet. Frozen sections of whole mount-staine d embryonic liver demonstrated that the message was restricted to deve loping blood cells. The expression pattern of this transcript suggests that its protein product may be involved in hematopoiesis during avia n development.