Ectopic Expression of the Homeobox Gene Disturbs the Developmental Program.

Abstract

The developmental program in animal is controlled by homeotic genes which share a unique and homologous sequence, the homeobox sequence. And the gene product of homeobox, the homeodomain protein, is thought to work as a gene regulator protein which binds to target DNA by its helix-turn-helix motif. And thus effect as regulators on developmental program. Whether homeobox genes control the development and differentiation of plants like in animals or not, is one of the interesting questions. To understand the effect of plant homeobox genes, we isolated a homeobox containing gene, OSH1 from rice and introduced it into several plant species including kiwifruit and tobacco. OSH1-transformed plant species exhibit similar morphological changes such as dwarfism, abnormal shaped leaves and loss of apical dominance. These observations suggest that the OSH1 gene product may regulate the expression of genes related to plant morphogenesis. However, the molecular mechanism(s) by which OSH1 regulates plant morphogenesis, such as the target gene(s) are still unknown. So, we analyzed the plant hormones which have distinct influences on plant growth and development. We discussed about the hormonal changes related to OSH1 expression and possible effect site of OSH1 in development.