ARS | Publication request: Loss-of-function of DELLA protein SLN1 activates GA signaling in barley aleurone

Submitted to: Acta Physiologiae Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 31, 2009
Publication Date: N/A

Interpretive Summary: Gibberellic acid (GA) is a plant hormone inducing degradation of seed storage starch, protein and other reserve in cereal grains during germination to provide nutrients for seedling growth. The malting industry takes advantage of the biological process of germination to mobilize barley seed storage reserves to provide the substrate for fermentation during the production of alcohol beverages. Understanding of how GA induces the degradation of seed storage reserves and the identification of the genes involved in the biological process of germination is important for the development of barley cultivars with superior malting qualities and to improve the malting process. The research applied a modern technology, GeneChip, to examine the expression of over 22,000 genes in a barley sln1c mutant whose SLN1 gene activity (a gene whose protein product negatively regulates the response of seeds to GA) is lost. The research demonstrated that the expression properties of 1448 genes changed significantly in response to inactivation of SLN1. The studies also provided evidence that SLN1 is a key regulatory gene and functions early in the GA response pathway. This research provides information that is a prerequisite for the development of novel strategies for the improvement of the malting qualities of U.S. barley cultivars.

Technical Abstract: Gibberellic acid (GA) is a key phytohormone regulating seed germination and seedling growth. In cereal species, GA is synthesized in embyros and then translocated to aleurone tissues where it induces production of hydrolytic enzymes for mobolization of seed storage reserve. De-embyronated barley aleurone is composed of a single cell type, and responds to GA treatment strongly, and therefore provides an excellent system to study transcriptional regulatory networks underlying GA response pathway. Barley SLN1 gene encodes a DELLA protein and functions as a negative regulator in GA response pathway. Barley sln1c, a mutant with loss-of-function of SLN1, constitutively expresses alpha-amylase activity in aleurone tissue without GA treatment. As part of the effort to delineate transcriptional regulatory networks underlying GA response, the research examined the transcript accumulation of over 22,000 genes in sln1c aleurone without GA treatment. Bioinformatic analysis identified 1448 SLN1 dependent genes. The transcriptomes of barley aleurone in response to GA treatment and inactivation of SLN1 activity are very similar, and provide strong evidence at system leveles that SLN1 is a key negative regulator in the GA response pathway, and is likely to function very upstream of the transcriptional regulatory cascade in the GA response pathway.