Poster: Transcription Regulation
Abs #
1041: Novel Myb-like protein, CTMyb1, transactivates Rep1 gene in cooperation with OsGAMyb in rice aleurone
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Presenter: |
Sutoh, Keita , s-keita@comp.metro-u.ac.jp |
Authors | Sutoh, Keita (A) Wada, Masamitsu (A) Yamauchi, Daisuke (B) | | Affiliations: |
(A): Department of Biological Sciences. Tokyo Metropolitan University
(B): Department of Life Science. Himeji Institute of Technology
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In germinating rice seeds, a cysteine proteinase (REP-1) synthesized in aleurone layer cells is a key enzyme in the degradation of the major storage protein, glutelin. Rep1 (the gene for REP-1) expression is induced by gibberellins (GA). To identify GA response elements in the Rep1 promoter, we developed a transient expression system in rice aleurone cells. Analyses of deletion and point-mutation of the Rep1 promoter indicated that a complex for the GA-response is composed of TAACAGA, TAACGTA, and two copies of CAACTC. The former two sequences are identical to GAREs conserved in the promoter of genes for a-amylase and proteinases in cereals. The latter, termed CAREs (CAACTC regulatory elements), are novel GA-responsive elements. Gain of function experiments revealed that two pairs of GARE and CARE were necessary and sufficient to confer GA-inducibility. The sequences were also required for effective transactivation by the transcription factor OsGAMyb which binds to GARE, not CARE. Yeast one-hybrid screening with CARE as a bait identified a novel protein, termed CTMyb1, which contained one Myb domain in carboxy terminal region. Transient assays with rice aleurone cells suggested that CTMyb1 cooperated with OsGAMyb in transactivation of Rep1 gene promoter without GA.
CARE and GARE were also found in the promoter region of a rice a-amylase gene, RAmy1A, and a barley proteinase gene, EPB1, which are expressed in germinating seeds. Mutations of CARE in their promoters caused a loss of GA-inducibility and GAMyb-transactivation, suggesting that CARE is the regulatory element for GA-inducible expression of hydrolase genes in germinating seeds.
