TRANSCRIPTION OF THE ZEA-MAYS HOMEOBOX (ZMHOX) GENES IS ACTIVATED EARLY IN EMBRYOGENESIS AND RESTRICTED TO MERISTEMS OF THE MAIZE PLANT

Four Zea mays homeobox (ZmHox) genes have been analyzed in their spatial expression pattern during development of the maize pla nt. The ZmHox1a or b and ZmHox2a or b gene pairs encode putative plant transcription factors; the mRNA transcripts belong to the rare class of mRNA molecules. Expression of the ZmHox1 and 2 genes is activated very early in embryonic development acid restricted to the embryo proper in the proembryo stage. After establishment of the root/shoot axis, transcripts are prevalent in the embryonic root and shoot apical meristems but later are also found in provascular tissues and young leaf primordia. In the vegetative plant body the transcription of the ZmHox genes marks several types of meristems of the shoot and root system, the descending proliferating regions and provascular strands. Expression persists in the developing reproductive organs, but results obtained in the male flower indicate that transcription of ZmHox genes here may become confined to specific cell types. The data obtained during this study show that these four ZmHox genes are expressed very specifically in cells where developmental decisions contribute to the ontogeny of the maize plant. The overall expression pattern suggests that the ZmHox class of maize homeobox genes will be involved in transcriptional control during maize development from the embryonic to the reproductive phase. (C) 1995 Wiley-Liss, Inc.