Activation of the Oryza sativa non-symbiotic haemoglobin-2 promoter by the cytokinin-regulated transcription factor, ARR1

Authors

Emily Ross, University of Nebraska-Lincoln
Julie M. Stone, University of Nebraska-LincolnFollow
Christian Elowsky, University of Nebraska-LincolnFollow
Raul Arredondo-Peter, Universidad Auto´noma del Estado de Morelos, Avenida Universidad 1001, Colonia Chamilpa, 62210 Cuernavaca, Morelos, Me´xicoFollow
Robert V. Klucas, University of Nebraska-Lincoln
Gautam Sarath, University of Nebraska-LincolnFollow

ORCID IDs

Christian Elowsky

Date of this Version

8-1-2004

Comments

Published in Journal of Experimental Botany, Vol. 55, No. 403, pp. 1721–1731, August 2004.

Abstract

Using in silico methods, several putative phytohormoneresponsive cis-elements in the Oryza sativa nonsymbiotic haemoglobin (NSHB) 1-4 and Arabidopsis thaliana NSHB1-2 promoters have been identified. An OsNSHB2 promoter::GUS reporter gene fusion shows tissue-specific expression in A. thaliana. GUS expression was observed in roots, the vasculature of young leaves, in flowers, and in the pedicel/stem junction. In transient assays, activity of the OsNSHB2 promoter was significantly up-regulated in the presence of the cytokinin, 6-benzylaminopurine (BA). Deletion analyses indicated that the full-length promoter was required for maximal trans-activation in the presence of cytokinin. Mutation of the single cytokinin-regulated ARR1-binding element abolished promoter activation in response to cytokinin. Constitutive expression of ARR1 under the control of the 35S cauliflower mosaic virus promoter enhanced wild-type OsNSHB2 promoter activity, but had no effect on the activity of the mutated promoter in the absence of cytokinin. However, overexpression of ARR1 in the presence of cytokinin resulted in super-activation of the wild-type promoter. The mutated promoter was only moderately activated in the presence of cytokinin and ARR1, indicating that the OsNSHB2 promoter can be regulated by the ARR1 protein, but requires other cytokinin-induced factors for optimal activation. This is the first report that identifies a trans-acting factor involved in the activation of a NSHB gene.