Poster: Transcription Regulation

Abs # 1045: Two Transcription Factors, SUSIBA 1 and 2, Participate in Sugar Signaling of Starch Synthesis in Barley by Binding to the SURE Elements

Presenter:	Sun, Chuanxin , Chuanxin.Sun@vbsg.slu.se
Authors	Sun, Chuanxin  (A)   Ahlandsberg, Staffan  (A)   Palmqvist, Sara  (A)   Olsson, Helena  (A)   Borén, Mats  (A)   Baguma, Yona  (A)   Mutisya, Joel  (A)   Venkateshaiah, Laxmi  (A)   Ghebremedhin, Haile  (A)   Jansson, Christer  (A)
Affiliations:	(A): Dept. of Plant Biology and Forest Genetics

Sugar signaling cascades are important regulatory networks in bacteria, yeast, mammals and plants. Participants of the sugar signaling pathways in plants are poorly understood. During cereal seed development, starch is synthesized and deposited in the endosperm, processes regulated by sugar signaling. We have shown previously that two starch synthesis genes in barley, sbeIIb and iso1, are expressed exclusively in the endosperm, while another gene, sbeIIa, is expressed also in embryonic and vegetative tissues. Recently, we have isolated and characterized three related transcription factors, SUSIBA 1, 2 and 3. SUSIBA 1 and 2 bind to the iso1 promoter at a sugar responsive (SURE) cis element. A similar SURE element is also found in the sbeIIb but not sbeIIa gene. Expression of susiba2 is sugar-inducible and is confined to the endosperm, whereas expression of susiba1 is rather unaffected by sugar levels and is specific for source tissues. We will present a model how sugars regulate the starch synthesis genes by SUSIBA1, 2 and 3.