Functional studies of Arabidopsis polyubiquitin genes UBQ3 and UBQ4

• Main Authors: Hsin-Yen Chang, 張心嚴
• Other Authors: Chih-Wen Sun
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/jncxpz

碩士 === 國立臺灣師範大學 === 生命科學研究所 === 97 === Ubiquitin is a small protein existing in all eukaryotes with a conserved sequence and structure. It has been found to play important roles in controlling cellular signal transduction. In Arabidopsis, ubiquitins are primarily encoded by five polyubiquitin genes, including UBQ3, UBQ4, UBQ10, UBQ11, and UBQ14. UBQ3 and UBQ4 are the paralogous polyubiquitin genes, however, they express differentially through various developmental stages. Thus, in this study, we first investigated the spatial expression profile of UBQ3 and UBQ4, and the regulatory mechanisms of gene expression. GUS activity assay in transgenic plants revealed that UBQ3 and UBQ4 were expressed at the same locations in vegetative tissues, but the expression patterns varied in reproductive tissues. Therefore, we suggest that UBQ3 and UBQ4 are differentially expressed in reproductive tissues due to different regulatory pathways. Further studies indicated that intron sequence play an important role in regulating the expression of UBQ3 and UBQ4 in planta: it enhances the transcript level of UBQ3, but represses that of UBQ4. Nevertheless, sequence analyses and EMSA experiments revealed that intron sequences of UBQ3 and UBQ4 still share two conserved cis-acting elements. Finally, Arabidopsis seedlings were treated under different light wavelength and temperature conditions. We found that UBQ3 increases transcript levels in dark, red light, blue light, and ultraviolet rays, but UBQ4 remains similar transcript levels under these treatments. In conclusion, the differential expression of UBQ3 and UBQ4 is predominantly regulated at the transcriptional levels during reproductive development and under various environmental factors, such as light and temperature.