ZMHOX - A NOVEL CLASS OF MAIZE HOMEOBOX GENES

Clones of two highly related genes, ZmHox2a and ZmHox2b (Zen mays home obox), were isolated from maize embryo cDNA libraries by screening wit h the ZmHox1a homeobox sequence. The genes map to chromosomes 3 and 8, respectively, and encode mRNA transcripts of 6 kb. The encoded protei ns, ZmHox2a and b, share 84% sequence identity and exhibit a modular s tructure with several novel plant-specific protein domains. Interestin gly, each ZmHox2 gene product contains two complete homeodomains which , for Zmhox2a, were both shown to be functional DNA-binding motifs in vitro. Not only probes encoding the homeobox but also DNA fragments co rresponding to other ZmHox2 domains hybridize to multiple bands in gen omic Southern blots, indicating that related protein domains may be co nserved in other maize genes. The ZmHox2a/b genes, therefore, are memb ers of a novel and large class of maize genes, some of which can be ex pected to encode new transcription factors.