| Summary: | 碩士 === 國立中興大學 === 農業生物科技學研究所 === 89 === The control of this vegetative-to-reproductive transition (or flowering time) has been extensively studied in Arabidopsis. Many different early- and late-flowering genes involved in either promoting or delaying the timing of the rosette-to-inflorescence transition have been cloned and characterized. Late-flowering gene CONSTANS (CO), encoded a zinc finger protein, has been thought to act as 1a transcriptional factor to promote flowering. Based on sequence similarity, two genes, ACOZ1, and ACOZ2 (Arabidopsis CO-like Zinc finger gene 1 and 2), showed homology to CO in Arabidopsis genome were cloned and characterized in this study. ACOZ1 gene, contained three exons on chromosome 1, encodes a putative 299 amino acid protein. ACOZ2 gene, contained three exons on chromosome 2, encodes a putative 237 amino acid protein. ACOZ1 and ACOZ2 mRNA were detected early and were increased gradually after germination. ACOZ1 and ACOZ2 mRNA can be detected in rosette leaves, cauline leaves and flowers after flowering. The expression of ACOZ1 and ACOZ2 mRNA was upregulated in early-flowering mutants elf1, 2, 3 and was induced by cold, heat and salt treatments. The expression pattern for ACOZ1 and ACOZ2 was very similar to that observed for CO. To further explore if the sequence and expression likeness is coupled to the functional similarity between ACOZ1, ACOZ2 and CO, functional analysis of ACOZ1 and ACOZ2 through transgenic plants is performed. Sense or antisense cDNA or genomic DNA for ACOZ1 were ectopically expressed in wild-type and late-flowering mutant Arabidopsis plants. Further phenotypic analysis indicated that transgenic wild-type plants were phenotypically indistinguishable from untransformed wild-type plants whereas the flowering time was reduced in transgenic late-flowering gi mutant plants. Our result indicated that ACOZ1 gene was function similar to CO in regulating flower transition although in a relative weak manner. In addition to regulate flowering time, ectopic expression of ACOZ1 significantly increased the salt tolerance in transgenic plants. By contrast, ectopic expression of antisense of ACOZ1 significantly reduced the length of the roots in transgenic plants. Constructs contained sense and antisense ACOZ2 were also constructed for further functional analysis through transgenic approach..
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