Poster: Late and Moved Abstracts

Abs # 967: The first intron of PhADF1 gene enhances GUS expression and acts as a transcriptional enhancer in transgenic Arabidopsis

Presenter:	Jeong, Young-Min , supelta@snu.ac.kr
Authors	Jeong, Young-Min  (A)   Mun, Jeong-Hwan  (B)   Kim, Hoyeun  (A)   Kim, Sang-Gu  (A)
Affiliations:	(A): School of Biological Sciences, Seoul National University, Seoul, Korea (B): Dept. of Plant Pathology, UC Davis, CA 95616, USA

Actin-depolymerizing factor (ADF) is a small actin-binding protein which regulates cellular actin dynamics. We previously isolated the genomic clone of petunia ADF1 (PhADF1) and analyzed its expression pattern in transgenic Arabidopsis. Transgenic lines carrying PhADF1 promoter-GUS with its first intron showed 22-fold enhanced GUS expression when compared to promoter-GUS fusion construct without the intron. To elucidate how the first intron of PhADF1 enhances gene expression, several constructs were made and analyzed in transgenic Arabidopsis. The intron was placed in front of promoter region to test enhancer activity. Transgenic plants showed enhanced expression both transcripts and protein levels. Plants harboring construct that has a mutated 3' splice site to inhibit splicing showed very weak expression. Sequencing of RT-PCR products revealed that the splicing occurred at alternative splice site. To identify potential cis-regulatory sites in the intron, constructs carrying various deletions within the intron were generated and analyzed in transgenic Arabidopsis. Both RT-PCR and GUS assay results suggested that the 5' 600-bp region of the intron is important for its activity. These results suggest that the first intron contains enhancer-like elements. But the data also indicate that other mechanisms such as post-transcriptional regulation are involved. These are to be tested in further research.