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Abstract Detail

Mechanisms of Gene Regulation

Yu, Su-May [1], Hong, Ya-Fang [2].

GA and Sugar Signaling Interference in Germinating Cereal Grains: Mechanism of MYBGA and MYBS1 Interaction in the Regulation of α-Amylase Gene Expression.

During cereal grain germination, the expression of α-amylase genes is regulated negatively by sugar in embryos and positively by GA in endosperms, through the action of sugar response complex (SRC) and GA response complex (GARC) in their promoters, respectively. Transcription factors MYBGA and MYBS1 are known to bind to the GA response element (GARE, an important cis-acting element of GARC) and the TA box (a cis-acting element shared by SRC and GARC), respectively. Previously we showed that, in endosperms, MYBGA and GARE interaction interferes glucose repression on α-amylase expression, and MYBGA and MYBS1 cooperation is necessary for high-level GA-induced α-amylase expression. In the present study, mechanisms of GA and sugar signaling interference and MYBGA-MYBS1 interaction were further investigated. MYBS1 was fused with the reporter GFP, and the cellular localization of the fusion protein was studied using barley and rice aleurone transient expression systems. We observed that the nuclear localization of MYBS1-GFP fusion protein was promoted by glucose starvation and inhibited by glucose; however, application of GA or overexpression of MYBGA promoted the nuclear localization of MYBS1 even in the presence of glucose. The transactivation domain of MYBS1 was identified by yeast and aleurone cell one-hybrid assays. Additionally, functional domains of MYBGA and MYBS1 responsible for interaction and transactivation of α-amylase promoter activity were also defined by aleurone cell two-hybrid assays. Currently, a MYBGA knockout rice mutant and MYBGA overexpressed transgenic rice seeds are used for studying how MYBGA and MYBS1 interaction controls the nuclear localization of MYBS1 that might lead to interference of sugar repression on α-amylase expression in endosperms.

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1 - Academia Sinica, Institute of Molecular Biology, Nankang, Taipei, 115, Taiwan, R.O.C.
2 - Academia Sinica, Institute of Molecular Biology

Hormone signaling
sugar signaling
seed germination.

Presentation Type: ASPB Minisymposium
Session: M17
Location: Waldorf Room/Hilton
Date: Monday, July 9th, 2007
Time: 11:55 AM
Number: M17004
Abstract ID:680

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