Poster: Regulation of gene expression

Abs # 791: Carbon status of the plant modulates the expression of PSI genes during Pi starvation in Arabidopsis

Presenter:	Karthikeyan, Athikkattuvalasu S, karthik@purdue.edu
Authors	Karthikeyan, Athikkattuvalasu S (A)   Varadarajan, Deepa K (A)   Raghothama, Kashchandra G (A)
Affiliations:	(A): Purdue University

Phosphate (Pi) is the second most important plant nutrient that is responsible for dynamic changes in carbon fluxes. The interaction between Pi and carbon metabolism coordinates several crucial processes that control plant growth and development. In addition, plant Pi levels regulates the expression of genes involved in sugar metabolism/synthesis. This close relationship between carbon and Pi led to the current study of the effect of carbon supply on the regulation of expression of phosphate starvation induced (PSI) genes. Presence of sucrose in the medium was found to be essential for the expression of PSI genes under both Pi limiting as well as sufficient conditions. This influence on the gene expression was not confined to sucrose but also observed with other metabolizable sugars examined. Further a concurrent increase in the abundance of PSI genes transcript was observed with the increasing concentration of sucrose and glucose in the medium. The induction of PSI genes was much rapid and the transcripts were observed within three hours of re-supply of sucrose or glucose to the sugar and Pi starved seedlings. Interestingly addition of non-metabolizable sugar 3-O-methylglucose, a glucose analog, did not induce the expression of PSI genes. Further studies using HXK over-expressing (sense AtHXK1 and AtHXK2) and under-expressing (anti-sense AtHXK1 and AtHXK2, gin2) plants revealed a reduction in the level of expression PSI genes in anti-sense AtHXK2 and gin2 background. These studies point to a strong influence of carbon on phosphate mediated gene expression in plants.