Minisymposium 19: Mechanisms of Gene Regulation

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Abs # M1904: ABAP1 is an abscisic acid receptor modulating barley germination and dormancy

Presenter:	Kumar, Santosh       Contact Presenter
Authors	El-Kereamy, Ashraf  (A)   Razem, Fawzi A (A)   Kumar, Santosh  (A)   Hill, Robert D (A)
Affiliations:	(A): Plant Science, University of Manitoba

The plant hormone abscisic acid (ABA) mediates several aspects of seed development, including storage protein synthesis and germination. While there has been significant progress in our understanding of ABA function in seeds, no seed-specific ABA receptors have been identified, with the consequence that the events surrounding ABA perception and upstream signal transduction are not fully understood. Here we show that the barley caryopsis protein ABAP1 is an ABA receptor that specifically binds ABA and regulates genes involved in germination. ABAP1 downregulates genes activated by gibberellic acid and upregulates genes that promote dormancy. Furthermore, barley embryos overexpressing ABAP1 are more sensitive to germination inhibition by ABA, whereas suppression of ABAP1 expression in embryos results in ABA insensitivity and accelerates germination. This is the first description of an ABA receptor capable of modifying cereal germination and dormancy. The results have particular relevance to the problems of pre-harvest sprouting in cereals, barley malting, weed persistence and are of fundamental importance to our understanding of the processes involved in plant reproduction.