Molecular Cloning and Characterization of the ATML1 Gene Homologues in Rice
| Autor: | Ching-Yu Tu, 涂景瑜 |
|---|---|
| Rok vydání: | 1999 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 87 Homeobox genes are master regulatory genes that specify the body plans and control development of many eukaryotic organisms. They share a common homeodomain (HD) which consists of 60 amino acids and is responsible for sequence-specific binding to target genes. HD proteins act as transcription factors that control gene expression in the precise spatial and temporal patterns. One HD-containing protein, ATML1 (Arabidopsis thaliana meristem L1 layer), was found to be expressed only in the L1 layer of apical meristem during embryogenesis and throughout plant development. Such observations indicated that ATML1 protein might provide positional information necessary for controlling cell specification. By analogy, we proposed that monocotyledonous rice might contain the ATML1 gene homologues. Where using tblastn program obtained by homology search of rice EST (expressed sequence tags) databank two ESTs, C91737 and C74009, which encode polypeptide with high sequence similarity (59% and 65%) to ATML1. The EST fragments were used as probes and various strategies were employed for isolation of their corresponding cDNA clones, designated as OSML1A (1699 bp) and OSML1B (2567 bp) for C91737 and C74009, respectively. Genomic Southern blot analyses indicated that both OSML1A and OSML1B are single-copy genes in rice. The cDNA of OSML1A is truncated and encode a polypeptide of 306 amino acid residues which shows 65% sequence similarity to ATML1. However, no OSML1A transcripts could be detected in northern blot analysis even by using 2 mg of poly(A)+ RNA isolated from various tissues. We reasoned that OSML1A might be expressed only in a very restricted area and only to a limited level. OSML1B encodes a putative transcription factor that can be classified as HD-GL2 homeobox protein. OSML1B was preferentially expressed in the spikelets after pollination, and was undetectable at early embryogenesis stages. Transcripts of OSML1B could also be detected in the upper parts of the spikelets (5DAP), indicated that OSML1B is not an embryo-specific gene. The amino acid sequence similarity between OSML1B and ATML1 is only 50% which suggested that OSML1B might not be the ATML1 gene homologue in rice. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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