Radial axis differentiation in a globular embryo is marked by HAZ1, a PHD-finger homeobox gene of rice.
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.
Ito
Yukihiro
Y
Plant Genetics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan.
Chujo
Atsushi
A
Eiguchi
Mitsugu
M
Kurata
Nori
N
D000595:Amino Acid Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005801:Genes, Homeobox / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics*; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics*; D010802:Phylogeny; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics* / Q000254:growth & development; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*; D016335:Zinc Fingers / Q000235:genetics*
D018076:DNA, Complementary; D018744:DNA, Plant; D018398:Homeodomain Proteins; D014157:Transcription Factors