| Summary: | 碩士 === 國立中興大學 === 生物科技學研究所 === 96 === NAC genes (for NAM, ATAF1, 2, and CUC2) are plant specific gene family. Most NAC proteins contain one highly conserved N-terminal DNA-binding domain, consisting of approximately 150 residues and a nuclear localization signal sequence. Some Arabidopsis NAC members involve a variety of plant growth and development processes, such as cell cycle control, growth hormone signaling, floral development, and apical meristem formation. To investigate the function of gene, the promoter of AtNACL14 in NAC2 subgroup was fused with GUS reporter gene, transformed into Arabidopsis and GUS activity analyzed. The results indicated that AtNACL14 were highly expressed in roots, cotyledon, shoot apical meristem and leaves. In addition, NAC family in Arabidopsis containing strong α-helical transmembrane motif (TM) in their C-terminal regions and are predicted to be membrane-associated. Transgenic plants ectopic expression of either full-length of AtNACL14 (35S::AtNACL14) or the truncated AtNACL14 construct (35S:: AtNACL14ΔC) were analyzed. The results indicated that 35S::AtNACL14 and 35S:: AtNACL14ΔC no show any detectable phenotypic changes. Surprisingly, the 35S::AtNACL14ΔTM transgenic plants exhibited severe phenotypic alterations such as dwarfism and curled leaves. This result revealed that membrane release is essential for the function of NAC MTFs (membrane-associated transcription factors). An Arabidopsis T-DNA insertional mutant caused circle and smooth rosette leaves was characterized in this research. Through inverse PCR (IPCR), it has been found that the T-DNA was inserted in 1572 bp of 5’ UTR from start codon of At5g24590. All the sa7 mutants are homozygotes for T-DNA insertion and At5g24590 mRNA were down-regulated in the sa7 mutants. This result revealed that the phenotype of sa7 mutant may be caused by the repression of At5g24590 after T-DNA insertion. To explore this possibility, sense and RNAi of At5g24590 cDNA driven by 35S promoter were transformed into Arabidopsis and phenotypic analyzed. Notably, we could not obtained 35S::At5g24590 transgenic plants by selected solid MS medium. The indicated that RNAi plants were phenotypically indistinguishable from wild-type plants. It implied that T-DNA insertion resulted in contain At5g24590 and other gene were affected.
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