Ito Yukihiro, Chujo Atsushi, Eiguchi Mitsugu, Kurata Nori
Plant Genetics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan.
Gene. 2004 Apr 28;331:9-15. doi: 10.1016/j.gene.2004.02.040.
Homeobox genes that encode transcription factors play important roles in development and differentiation of both plant and animal systems. From a cDNA library of 3-day after-pollination (DAP) rice embryos we cloned a HAZ1 cDNA that encodes a protein with a PHD-finger domain and a homeodomain. A database search showed that HAZ1 was most similar in its entire amino acid sequence to Zmhox1a (52% identity) and Zmhox1b (50%), PHD-finger family homeodomain proteins of maize. Differing from Zmhox1, overexpression of HAZ1 brought no morphological change either in tobacco or in rice. In situ hybridization showed that HAZ1 was expressed at a higher level in the outer layers of a developing embryo than in the inner parts of the embryo at 3 DAP. At 4 and 5 DAPs, the expression of HAZ1 was concentrated at the ventral part of an embryo. These results indicate that HAZ1 marks outer layer cells of a globular embryo before any morphological differentiation is discerned in it. Radial axis differentiation marked by HAZ1 is then collapsed dynamically along with embryo morphogenesis, and HAZ1 later marks the ventral surface of the embryo.
编码转录因子的同源异型框基因在植物和动物系统的发育与分化过程中发挥着重要作用。我们从授粉后3天（DAP）的水稻胚cDNA文库中克隆了一个HAZ1 cDNA，它编码一种含有植物同源结构域（PHD）和同源异型结构域的蛋白质。数据库搜索显示，HAZ1的整个氨基酸序列与玉米的Zmhox1a（一致性为52%）和Zmhox1b（一致性为50%）最为相似，它们都是PHD-指结构域家族的同源异型结构域蛋白。与Zmhox1不同，HAZ1在烟草和水稻中过表达均未引起形态变化。原位杂交显示，在授粉后3天，HAZ1在发育中的胚外层的表达水平高于胚内部。在授粉后4天和5天，HAZ1的表达集中在胚的腹侧部分。这些结果表明，在球形胚出现任何形态分化之前，HAZ1标记了其外层细胞。随后，由HAZ1标记的径向轴分化随着胚形态发生而动态瓦解，HAZ1随后标记了胚的腹面。
