| Summary: | 碩士 === 國立臺灣師範大學 === 生命科學研究所 === 98 === The majority of the chloroplastic proteins are encoded by nuclear genome and then imported into chloroplasts via Toc/Tic complex (translocon at the outer/inner envelope membrane of chloroplast). In Arabidopsis thaliana, Toc33 plays an important role in regulating chloroplast development because it predominantly recognizes and assists the translocation of the photosynthesis-related proteins on
chloroplast membranes. However, the regulatory mechanism of TOC33 expression remains unclear so far. We have previously characterized a transcription factor, CIA2 (chloroplast import apparatus 2), which specifically up-regulate the TOC33 in leaves. To further understand how CIA2 and other nuclear proteins regulate the expression of TOC33 gene, the function of TOC33 promoter sequence are analyzed in detail by stable and transient assays. Quantitative RT-PCR and activity assay of reporter gene suggest that the upregulatory efficiency of TOC33 gene expression by CIA2 is
affected by the 1st intron in the 5’UTR of TOC33. Furthermore, 5’ promoter deletion reveals that two regulatory regions in TOC33 promoter sequences, 33CAE1 (located on -710 to -616) and 33CAE2 (located on -616 to -517). 33CAE1 and 33CAE2 are putative nuclear proteins and CIA2 binding sites, respectively. These results not only
reveal the molecular mechanism how CIA2 and other nuclear proteins modulate TOC33 expression, but also provide more understanding of the regulatory processes during chloroplast development.
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