Poster: Transcription Regulation

Abs # 1050: The SUSIBA transcription factors are involved in starch biosynthesis, and are differentially expressed in barley

Presenter:	Olsson, Helena , Helena.Olsson@vbsg.slu.se
Authors	Olsson, Helena  (A)   Sun, Chuanxin  (A)   Palmqvist, Sara  (A)   Borén, Mats  (A)   Jansson, Christer  (A)
Affiliations:	(A): Swedish University of Agricultural Sciences

Starch is one of the most important biopolymers on earth. It is part of both human and animal diets, and it is used as a raw material for many industrial processes. Starch biosynthesis in plants is only partly understood. During cereal seed development, starch is synthesized and deposited in the endosperm, a process which is regulated by sugar signaling. We have isolated three WRKY transcription factor cDNAs from barley (Hordeum vulgare), susiba1, 2, and 3 (sugar signaling in barley) and purified two of the corresponding proteins, SUSIBA1 and 2. Both were shown to bind to the SURE (sugar responsive) element in the iso1 promoter, a cis element that has been reported to confer sugar responiveness to the patatin promoter in potato. Antibodies against SUSIBA2 have been produced and the expression pattern has been determined at RNA and protein level. The expression of SUSIBA2 was stronger in endosperm than in leaves. SUSIBA1 was detected in leaves but not in endosperm. Our data indicate that SUSIBA1 binds to the SURE element in the barley iso1 promoter as a repressor, and SUSIBA2 as an activator. How the two transcription factors bind to the same cis elements and regulate the expression of starch synthesis genes will be discussed.